JP2009138527A - Controller of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an internal combustion engine capable of accurately controlling an ignition timing to a proper timing during a reforming operation for reforming a fuel. <P>SOLUTION: Fuel reforming catalysts 26 are installed in the EGR passages 32, 36 of the internal combustion engine 10, respectively. A fuel for reforming is jetted into an EGR gas by a fuel injection device 34 for reforming. The fuel reforming catalyst 26 generates a reformed gas including flammable components by reforming and reacting the EGR gas on the fuel for reforming. A hydrogen concentration sensor 58 for detecting a hydrogen concentration in the reformed gas is installed in the EGR passage 36. An ECU 50 calculates a hydrogen amount flowing into a combustion chamber based on the hydrogen concentration detected by the hydrogen concentration sensor 58. The larger the hydrogen amount is, the more the ignition timing is delayed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  There is known an internal combustion engine including a fuel reforming catalyst that performs a reforming reaction between a fuel such as gasoline or biofuel and EGR gas. In this internal combustion engine, fuel and EGR gas are reacted in a fuel reforming catalyst heated by the heat of exhaust gas or the like to convert them into reformed gas. In the reformed gas, hydrogen gas and carbon monoxide gas are generated by the reforming reaction. This reformed gas is returned to the intake passage. Then, hydrogen and carbon monoxide in the reformed gas burn in the combustion chamber.

  In an internal combustion engine equipped with a fuel reforming catalyst, a reforming operation in which fuel reforming as described above is performed, and fuel injected into an intake port or cylinder without performing fuel reforming in the same manner as in a normal internal combustion engine. The non-reforming operation in which only the combustion is performed is switched according to the operation state.

  Only the fuel burns during the non-reforming operation, whereas hydrogen and carbon monoxide in the reformed gas burn together with the fuel during the reforming operation. Hydrogen has a very fast burning rate. Therefore, during the reforming operation, the overall combustion rate is also faster than during the non-reforming operation. As a result, the proper ignition timing is delayed during the reforming operation compared to the non-reforming operation. For this reason, when switching from the non-reforming operation to the reforming operation, the ignition timing becomes too advanced, and abnormal combustion such as knocking or pre-ignition tends to occur. In an internal combustion engine, when knocking is detected by a knock sensor, knock control control that retards the ignition timing is usually executed. However, since the proper ignition timing changes greatly during the reforming operation, the correction of the ignition timing is not in time in knock control control, and it is difficult to avoid abnormal combustion.

  Japanese Patent Laid-Open No. 2006-291775 discloses that reformed gas reaches the combustion chamber after injecting reforming fuel in order to prevent abnormal combustion from occurring when switching from non-reforming operation to reforming operation. Disclosed is a technology that delays the ignition timing before the reformed gas arrives when it is determined that the reformed gas has reached the combustion chamber by estimating the estimated arrival time required until Has been.

JP 2006-291775 A JP 2004-92520 A

  However, as described in paragraph 0059 of the above publication, it is difficult to accurately predict the arrival time of the reformed gas from the engine operating state or the like. For this reason, even if the technique described in the above publication is implemented, it is extremely difficult to retard the ignition timing at the exact timing when the reformed gas flows into the combustion chamber. Therefore, with the conventional technology, it is difficult to reliably prevent abnormal combustion such as knocking and preignition at the start of the reforming operation.

  Further, the proper ignition timing during the reforming operation varies depending on the amount of hydrogen flowing into the combustion chamber. Therefore, if the ignition timing retardation amount during the reforming operation is set to a constant value, the ignition timing cannot be made appropriate. That is, in order to accurately control the ignition timing at an appropriate timing, it is desirable to correct the ignition timing according to the amount of hydrogen flowing into the combustion chamber. However, the amount of hydrogen flowing into the combustion chamber varies depending on the EGR flow rate, the reforming reaction amount, and the like. Further, the reforming reaction amount varies according to the temperature of the fuel reforming catalyst, the fuel properties, and the like. For this reason, it may be difficult to accurately estimate the amount of hydrogen flowing into the combustion chamber. In particular, immediately after the start of the reforming operation, the reforming reaction amount is unstable, and it is extremely difficult to accurately estimate the amount of hydrogen flowing into the combustion chamber.

  For this reason, it has been difficult for the conventional technology to accurately control the ignition timing at an appropriate timing during the reforming operation.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine capable of accurately controlling an ignition timing at an appropriate timing during a reforming operation in which fuel reforming is performed. For the purpose.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An EGR passage that recirculates EGR gas extracted from the exhaust passage of the internal combustion engine to the intake passage;
Fuel reforming means for injecting reforming fuel into the EGR gas;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
A combustible component concentration detecting means for detecting a combustible component concentration in the reformed gas;
Ignition timing correction means for correcting the ignition timing based on the combustible component concentration;
It is characterized by providing.

The second invention is a control device for an internal combustion engine,
An EGR passage that recirculates EGR gas extracted from the exhaust passage of the internal combustion engine to the intake passage;
Fuel reforming means for injecting reforming fuel into the EGR gas;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
A combustible component concentration detecting means for detecting a combustible component concentration in the reformed gas;
Ignition timing correction means for correcting the ignition timing in advance before the combustible component reaches the combustion chamber of the internal combustion engine based on the signal detected by the combustible component concentration detection means;
It is characterized by providing.

The third invention is the first or second invention, wherein
The ignition timing correction means delays the ignition timing as the combustible component concentration is higher.

According to a fourth invention, in any one of the first to third inventions,
Combustible component amount calculating means for calculating the amount of combustible component recirculated to the internal combustion engine based on the combustible component concentration and the reformed gas flow rate flowing through the EGR passage;
The ignition timing correction means delays the ignition timing as the combustible component amount increases.

According to a fifth invention, in any one of the first to fourth inventions,
Operation switching for switching between a reforming operation in which the reformed gas is recirculated to the intake passage while fuel is supplied by the reforming fuel injection means and a non-reforming operation in which no fuel is injected from the reforming fuel injection means. Means,
Non-reforming operation ignition timing calculating means for calculating the ignition timing based on the non-reforming operation ignition timing map during non-reforming operation;
A reforming operation ignition timing calculating means for calculating the ignition timing based on the reforming operation ignition timing map during the reforming operation;
With
The ignition timing correction means corrects the ignition timing in a transition period between a state where the non-reforming operation ignition timing map is used and a state where the reforming operation ignition timing map is used. And

According to a sixth invention, in any one of the first to fifth inventions,
The heat supply means is constituted by a heat exchanger that transfers heat of exhaust gas of the internal combustion engine to the fuel reforming catalyst.

  According to the first invention, the combustible component concentration in the reformed gas can be detected by the combustible component concentration detecting means, and the ignition timing can be corrected based on the combustible component concentration. The combustible component in the reformed gas has a very fast burning rate. For this reason, the more the amount of combustible components in the reformed gas recirculated to the internal combustion engine, the later the proper ignition timing becomes. According to the first invention, the actual combustible component concentration in the reformed gas can be detected, and the ignition timing can be corrected according to the combustible component concentration. For this reason, even in a state where it is difficult to estimate the amount of combustible components recirculated to the internal combustion engine (for example, when switching between non-reforming operation and reforming operation), it can be accurately controlled to an appropriate ignition timing, It is possible to reliably prevent combustion abnormality such as knocking or pre-ignition.

  According to the second invention, based on the signal of the combustible component concentration detecting means for detecting the combustible component concentration in the reformed gas, the combustible component (reformed gas) can be accurately measured before reaching the combustion chamber of the internal combustion engine. The ignition timing can be corrected in advance at the timing. For this reason, when the reforming operation is started, the timing for correcting the ignition timing is too late with respect to the timing when the reformed gas flows into the combustion chamber, causing abnormal combustion such as knocking or preignition, In addition, it is possible to reliably prevent the torque of the internal combustion engine from being lowered due to the timing at which the ignition timing is corrected to be retarded too early relative to the timing at which the reformed gas flows into the combustion chamber. .

  According to the third aspect of the invention, the ignition timing can be delayed as the combustible component concentration in the reformed gas increases. For this reason, the ignition timing can be accurately controlled at an appropriate timing.

  According to the fourth aspect of the invention, the ignition timing can be delayed as the amount of combustible component calculated based on the combustible component concentration and the reformed gas flow rate increases. For this reason, the ignition timing can be controlled to an appropriate timing with higher accuracy.

  According to the fifth aspect of the invention, the ignition timing is corrected to an appropriate timing in the transition period between the state where the non-reforming operation ignition timing map is used and the state where the reforming operation ignition timing map is used. be able to. Therefore, it is possible to more reliably prevent combustion abnormalities such as knocking and preignition from occurring when switching between the non-reforming operation and the reforming operation.

  According to the sixth aspect of the invention, the heat of the exhaust gas of the internal combustion engine can be transferred to the fuel reforming catalyst and absorbed by the fuel reforming reaction. For this reason, the waste heat of an internal combustion engine can be collect | recovered and thermal efficiency can fully be improved.

Embodiment 1 FIG.
FIG. 1 shows an overall configuration diagram for explaining the system configuration of the first embodiment. The system of this embodiment includes a multi-cylinder type (four cylinders in the illustrated configuration) internal combustion engine 10. The fuel used in the present system is not particularly limited, and a biofuel containing a biomass-derived component such as alcohol (for example, ethanol) can be used in addition to a hydrocarbon fuel such as gasoline.

  An intake passage 12 of the internal combustion engine 10 is connected to an intake port of each cylinder via an intake manifold 14. In the middle of the intake passage 12, an electric throttle valve 16 for adjusting the amount of intake air is installed. A main fuel injection device 18 including an electromagnetic valve or the like for injecting fuel is provided in each intake port of each cylinder. The main fuel injection device 18 may be provided so as to inject fuel directly into the cylinder instead of in the intake port.

  An exhaust passage 20 of the internal combustion engine 10 is connected to an exhaust port of each cylinder via an exhaust manifold 22. A fuel reformer 24 is provided in the middle of the exhaust passage 20. Inside the fuel reformer 24, a fuel reforming catalyst 26 and an exhaust passage 28 are provided. In the fuel reforming catalyst 26, a metal (for example, Rh, Pt, Co, Ni, etc.) having an action of catalyzing a reforming reaction to be described later is installed on a carrier.

  The fuel reforming catalyst 26 and the exhaust passage 28 are separated from each other by a partition wall and blocked. The fuel reforming catalyst 26 can receive the heat of the exhaust gas passing through the exhaust passage 28. The fuel reforming catalyst 26 can cause a reforming reaction to be described later by using the received heat as reaction heat. That is, the fuel reformer 24 has a function as a heat exchanger that transfers the heat of the exhaust gas passing through the exhaust passage 28 to the fuel reforming catalyst 26. In the illustrated configuration, the exhaust passage 28 includes a plurality of parallel passages. The inlet of the exhaust passage 28 is connected to the exhaust passage 20, and the outlet of the exhaust passage 28 is connected to the exhaust passage 30.

  An EGR passage 32 is branched from the exhaust passage 20 upstream of the fuel reformer 24. According to the EGR passage 32, a part of the exhaust gas passing through the exhaust passage 20 can be taken out as EGR gas. The EGR passage 32 is connected to the fuel reforming catalyst 26. In the middle of the EGR passage 32, a reforming fuel injection device 34 for injecting fuel for use in the reforming reaction (hereinafter also referred to as reforming fuel) into the EGR gas is provided. The fuel injected from the reforming fuel injection device 34 flows into the fuel reforming catalyst 26 together with the EGR gas, and causes a reforming reaction by the action of the fuel reforming catalyst 26.

  One end of an EGR passage 36 is further connected to the fuel reforming catalyst 26. The other end of the EGR passage 36 is connected to the intake passage 12. Through this EGR passage 36, a reformed gas, which will be described later, or a simple EGR gas can be recirculated into the intake passage 12 and mixed with the intake air. In the middle of the EGR passage 36, an EGR cooler 38 that cools the gas passing through the EGR passage 36, and an EGR valve 40 that includes an electromagnetic valve that can open and close the EGR passage 36 are provided.

  Of the exhaust gas flowing through the exhaust passage 20, the remaining exhaust gas that has not flowed into the EGR passage 32 sequentially passes through the exhaust passages 28 and 30 and is released into the atmosphere. In the middle of the exhaust passage 30 on the downstream side of the fuel reformer 24, an exhaust purification catalyst 42 carrying a three-way catalyst for purifying harmful components and a muffler (not shown) are arranged. The exhaust passage 28 may carry a catalyst for purifying harmful components. By carrying the exhaust purification catalyst in the exhaust passage 28, reaction heat of the purification reaction can be generated in the exhaust passage 28, so that the amount of heat received by the fuel reforming catalyst 26 (heat recovery amount) can be further increased. The reforming efficiency can be further improved.

  The fuel used by the internal combustion engine 10 is stored in the fuel tank 44. The fuel tank 44 is provided with a fuel pump (not shown) for sending the fuel in the tank to the outside in a pressurized state. Connected to the discharge side of the fuel pump is a fuel pipe 46 for supplying the fuel discharged from the pump to the main fuel injection device 18 and the reforming fuel injection device 34, respectively.

  Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is constituted by a microcomputer provided with a storage circuit such as a ROM and a RAM. A sensor system including a catalyst temperature sensor 54, an exhaust gas sensor 56, a hydrogen concentration sensor 58, a knock sensor 60, and the like is connected to the input side of the ECU 50.

The catalyst temperature sensor 54 is provided in the fuel reforming catalyst 26 and detects the temperature of the fuel reforming catalyst 26. The exhaust gas sensor 56 is provided in the exhaust passage 20 and outputs a detection signal corresponding to the oxygen concentration in the exhaust gas. The hydrogen concentration sensor 58 is provided in the middle of the EGR passage 36, and outputs a detection signal corresponding to the hydrogen concentration (H ₂ concentration) in the reformed gas passing through the EGR passage 36. Knock sensor 60 is fixed to the cylinder block of internal combustion engine 10 and detects vibration generated in the cylinder block.

  The sensor system includes, for example, a rotation sensor that detects the engine speed, an air flow meter that detects the intake air amount, a water temperature sensor that detects the cooling water temperature, an accelerator opening sensor that detects the accelerator opening, and a throttle valve 16. A general sensor used for operation control of the internal combustion engine 10 is included, such as a throttle opening sensor for detecting the opening.

  On the other hand, on the output side of the ECU 50, various actuators including the throttle valve 16, the main fuel injection device 18, the reforming fuel injection device 34, the EGR valve 40, the fuel pump and the like are connected. The ECU 50 controls the operation by driving the actuators while detecting the operation state of the internal combustion engine 10 using the sensor system.

  In this operation control, the fuel injection amount is calculated according to the intake air amount and the like, and the fuel corresponding to the injection amount is injected from the main fuel injection device 18. Further, by performing air-fuel ratio feedback control using the detection signal of the exhaust gas sensor 56, the fuel injection amount of the main fuel injection device 18 so that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst 42 becomes the target air-fuel ratio. To control.

(Reforming operation)
The internal combustion engine 10 as described above can perform a reforming operation in which the reformed gas generated by the reforming reaction between the exhaust gas (EGR gas) and the reforming fuel is recirculated into the intake passage 12. . During the reforming operation, the reforming fuel is supplied from the reforming fuel injection device 34 to the EGR gas flowing in the EGR passage 32, thereby supplying the reforming fuel to the fuel reforming catalyst 26. At this time, the ECU 50 determines an appropriate injection amount (supply amount) of the reforming fuel according to, for example, the operating state of the internal combustion engine 10, the EGR flow rate, the temperature of the fuel reforming catalyst 26, and the like.

  In the fuel reforming catalyst 26, the reforming fuel and the components in the EGR gas cause a reforming reaction (steam reforming reaction) by the action of the above-described type of metal having catalytic action. The chemical reaction formula of the main reforming reaction occurring in the fuel reforming catalyst 26 is the following formula (1) when the reforming fuel is gasoline, for example, and when the reforming fuel is ethanol, for example, Each can be represented by formula (2).

1.56 (7.6CO ₂ + 6.8H ₂ O + 40.8N ₂ ) + 3C _7.6 H _13.6 + Q1
→ 31H ₂ + 34.7CO + 63.6N ₂ (1)
C ₂ H ₅ OH + 0.4CO ₂ + 0.6H ₂ O + 2.3N ₂ + Q2 → 3.6H ₂ + 2.4CO + 2.3N ₂ (2)

As shown in the above formula, according to the reforming reaction, the EGR gas and the reforming fuel can be converted into a reformed gas containing hydrogen (H ₂ ) and carbon monoxide (CO). In the following description, hydrogen and carbon monoxide are also collectively referred to as “flammable components”.

  The amount of heat Q1 in the above equation (1) and the amount of heat Q2 in the equation (2) are reaction heat absorbed by the reforming reaction. That is, since these reforming reactions are endothermic reactions, the calorific value of the combustible component on the right side in the above formulas (1) and (2) is the calorific value of the substance before the reaction described on the left side of each formula. Bigger than.

  Therefore, according to the fuel reformer 24, the heat received by the fuel reforming catalyst 26 from the exhaust passage 28 can be absorbed by the reforming reaction. That is, in the system of the present embodiment, the heat of exhaust gas can be recovered and used to convert the reforming fuel into a combustible component having a larger amount of heat.

  The reformed gas containing the combustible component generated by the above reforming reaction flows into the intake passage 12 through the EGR passage 36, is mixed with the intake air, and then flows into the combustion chamber of the internal combustion engine 10. The combustible component in the reformed gas is combusted in the combustion chamber together with the fuel injected from the main fuel injection device 18. The ECU 50 stores a map for determining a required combustible component amount to be flown into the combustion chamber of the internal combustion engine 10 during the reforming operation based on the operating conditions and the like. The ECU 50 controls the reformed gas flow rate by the EGR valve 40 so that the amount of combustible components flowing into the combustion chamber becomes the required amount of combustible components, and the total fuel amount necessary for setting the air-fuel ratio to the target air-fuel ratio. Then, the remaining fuel after subtracting the amount of the combustible component that has flowed in is injected into the main fuel injection means 18.

  As described above, the amount of heat of the reformed gas is greater than that of the original fuel by the amount of heat recovered from the exhaust gas by the fuel reformer 24. Therefore, during the reforming operation, the reformed gas is recirculated to the intake system and burned in the internal combustion engine 10 as a part of the fuel, so that the thermal efficiency of the entire system is improved, so that the fuel efficiency performance of the internal combustion engine 10 is improved. be able to.

  In addition, refluxing the reformed gas to the intake system is also a kind of EGR (Exhaust Gas Recirculation). Therefore, according to the reforming operation, it is possible to obtain a general effect of EGR, that is, a fuel efficiency improvement effect by reducing pump loss, a NOx generation amount reducing effect by reducing combustion temperature, and the like. In this connection, the reforming operation has the following advantages. In the case of normal EGR operation, if the EGR rate is increased, combustion becomes unstable, and therefore there is a limit to the EGR rate. On the other hand, in the reforming operation, hydrogen having high combustibility (high combustion speed) is contained in the reformed gas, and this hydrogen is combusted together with the fuel in the combustion chamber. For this reason, even if the EGR rate is increased, combustion is not likely to become unstable, and the limit of the EGR rate can be increased. Therefore, during the reforming operation, a large amount of EGR is possible, so that the fuel efficiency improvement effect due to the pump loss reduction and the NOx generation amount reduction effect due to the reduction in the combustion temperature can be exhibited more greatly.

(Non-reforming operation)
The internal combustion engine 10 of the present embodiment can be operated by burning only the fuel injected from the main fuel injection device 18 without using the fuel reforming as described above. Such operation is hereinafter referred to as “non-reforming operation”. In the non-reforming operation, EGR operation with normal EGR for returning EGR gas to the intake passage 12 through the EGR passages 32 and 36 and EGR gas is allowed to flow through the EGR passages 32 and 36 by closing the EGR valve 40. And non-EGR operation to prevent it from being included.

(Knock control control)
In an internal combustion engine, knocking occurs when the ignition timing is too early. On the other hand, the ignition timing (MBT) that provides the best fuel efficiency exists on the advance side. For this reason, in order to improve fuel consumption, it is desirable to advance the ignition timing as much as possible within a range in which knocking does not occur. Thus, in the present embodiment, the ECU 50 gradually advances the ignition timing until knocking is detected by the knock sensor 60, and retards the ignition timing when knocking is detected. Control for preventing knocking (hereinafter referred to as “knock control control”) can be executed.

(Ignition timing control)
In an internal combustion engine, in general, an appropriate ignition timing changes according to operating conditions such as engine speed and engine load. For this reason, conventionally, an ignition timing map for calculating an appropriate basic ignition timing in accordance with operating conditions such as engine speed and engine load is stored in the ECU 50 in advance, and the ignition timing is controlled using the ignition timing map. To be done.

  Furthermore, in the internal combustion engine 10 of the present embodiment, the proper ignition timing differs between the reforming operation and the non-reforming operation. During the non-reforming operation, only the fuel injected from the main fuel injector 18 burns in the combustion chamber. On the other hand, during the reforming operation, in addition to the fuel injected from the main fuel injection device 18, combustible components in the reformed gas burn in the combustion chamber. A combustible component in the reformed gas, particularly hydrogen, has an extremely high burning rate compared to liquid fuel. Therefore, during the reforming operation, the combustion speed as a whole is increased and the combustion period is shortened, so that the appropriate ignition timing is delayed as compared with the non-reforming operation.

  Therefore, in this embodiment, the ECU 50 stores two types of maps, the non-reforming operation ignition timing map used during non-reforming operation and the reforming operation ignition timing map used during reforming operation. . When the operating conditions such as engine speed and engine load are the same, the ignition timing calculated by the reforming operation ignition timing map is larger than the ignition timing calculated by the non-reforming operation ignition timing map. It is set so as to be delayed by the amount of retardation corresponding to the expected amount of hydrogen flowing into the gas.

  As described above, in order to make the ignition timing appropriate during the reforming operation, it is necessary to retard the ignition timing as compared with the non-reforming operation. The ignition timing retardation amount changes in accordance with the amount of hydrogen flowing into the combustion chamber. FIG. 2 is a diagram showing the relationship, that is, the relationship between the ignition timing retard amount necessary for obtaining the proper ignition timing during the reforming operation and the amount of hydrogen flowing into the combustion chamber. As the amount of hydrogen flowing into the combustion chamber increases, the combustion speed increases, so the proper ignition timing becomes later. For this reason, as shown in FIG. 2, the ignition timing retardation amount required during the reforming operation becomes larger as the amount of hydrogen flowing into the combustion chamber increases.

  During the reforming operation, as described above, the ECU 50 controls the amount of combustible components flowing into the combustion chamber to a required amount corresponding to the engine speed, the engine load, and the like. The combustible components in the reformed gas, that is, hydrogen and carbon monoxide are generated at a certain ratio as shown in the chemical reaction formula described above. For this reason, if the amount of combustible components flowing into the combustion chamber matches the required amount, the amount of hydrogen flowing into the combustion chamber is determined, and the required ignition timing retardation is determined based on the amount of hydrogen and the relationship shown in FIG. The amount is also determined. The reforming ignition timing map is set so as to calculate an ignition timing later than the non-reforming ignition timing map by the necessary ignition timing retard amount determined in this way. Therefore, when the amount of combustible components flowing into the combustion chamber is accurately controlled to the required amount, an appropriate basic ignition timing can be calculated by using the reforming ignition timing map.

  However, even if the injection of reforming fuel is started, the amount of hydrogen flowing into the combustion chamber does not rise from zero to the required amount at once, and it takes time to reach the required amount of hydrogen. That is, immediately after switching from the non-reforming operation to the reforming operation, the amount of hydrogen flowing into the combustion chamber has not yet reached the required amount, and therefore the required ignition timing retardation amount is small. For this reason, if the ignition timing map is switched to that for the reforming operation immediately after switching from the non-reforming operation to the reforming operation, the ignition timing retardation amount becomes too large.

  On the other hand, immediately after switching from the non-reforming operation to the reforming operation, if the basic ignition timing calculated from the ignition timing map for non-reforming operation is used as it is, the ignition timing becomes too early. Since the correction range by the knock control control is small, in such a case, the retard correction of the ignition timing is not in time, and abnormal combustion such as knocking or pre-ignition occurs.

  Therefore, in order to prevent abnormal combustion after switching to the reforming operation, the ignition timing should be retarded in advance after the reforming operation starts and before the reformed gas containing combustible components reaches the combustion chamber. Is desirable. On the other hand, if the time until the reformed gas reaches the combustion chamber after the ignition timing is corrected to be retarded is too long, the torque of the internal combustion engine 10 decreases during that time. This adversely affects drivability. That is, when switching from non-reforming operation to reforming operation, it is possible to accurately match the timing for correcting the ignition timing with the timing immediately before the reformed gas containing the combustible component reaches the combustion chamber. desirable.

  However, there is a delay required for the injected reforming fuel to reach the fuel reforming catalyst 26 from when the reforming fuel is injected until the reformed gas (combustible component) reaches the combustion chamber. The delay required for the reforming reaction to occur in the fuel reforming catalyst 26 to generate combustible components and the delay required for the reformed gas containing the combustible components to reach the combustion chamber from the fuel reforming catalyst 26. Three delays occur. Therefore, it is extremely difficult to accurately predict the time for the reformed gas to reach the combustion chamber only from the operating state of the internal combustion engine 10.

  There are also the following problems. The amount of reforming reaction occurring in the fuel reforming catalyst 26 not only depends on the injection amount of reforming fuel but also depends on various conditions such as the temperature of the fuel reforming catalyst 26. For this reason, immediately after the start of the injection of the reforming fuel, the reforming reaction amount generated in the fuel reforming catalyst 26 is unstable, and the amount of hydrogen flowing into the combustion chamber is also unstable. The proper ignition timing also changes. Therefore, if the retard amount when the ignition timing is retarded in advance before the reformed gas reaches the combustion chamber after the reforming operation is started, the ignition timing can be made to coincide with the appropriate ignition timing with high accuracy. Can not.

  Therefore, in the system of the present embodiment, by providing the hydrogen concentration sensor 58, the timing at which the reformed gas flows into the combustion chamber and the amount of hydrogen that flows in are directly detected, and the detected combustion chamber is detected. The ignition timing was controlled based on the actual inflow of hydrogen.

  That is, in the system of the present embodiment, when the reforming reaction starts in the fuel reforming catalyst 26 and hydrogen starts to be generated, this can be detected by the hydrogen concentration sensor 58. The delay time required for the reformed gas (hydrogen) to reach the combustion chamber from the hydrogen concentration sensor 58 includes the reformed gas flow rate (that is, the EGR flow rate), the passage volume from the hydrogen concentration sensor 58 to the combustion chamber, and the engine speed. It is possible to calculate with high accuracy based on the number. Therefore, if the generation of hydrogen is detected by the hydrogen concentration sensor 58, the timing at which the reformed gas (hydrogen) flows into the combustion chamber can be accurately known. For this reason, the ignition timing can be retarded at the optimum timing, that is, immediately before the reformed gas flows into the combustion chamber.

  Further, the ignition timing retard amount at that time can be controlled to be an optimum retard amount based on the hydrogen concentration detected by the hydrogen concentration sensor 58. That is, first, the amount of hydrogen flowing through the EGR passage 36 is calculated by multiplying the detected hydrogen concentration by the reformed gas flow rate. Next, the actual amount of hydrogen flowing into the combustion chamber is calculated based on the hydrogen flow rate and the arrival delay time from the hydrogen concentration sensor 58 to the combustion chamber. Based on the actual amount of hydrogen flowing into the combustion chamber, the ignition timing is executed according to the relationship shown in FIG. In this way, according to the present embodiment, the actual amount of hydrogen flowing into the fuel reforming catalyst 26 can be detected, and the ignition timing retardation can be corrected based on the amount of hydrogen. As a result, even when the reforming reaction amount is unstable immediately after switching from non-reforming operation to reforming operation, the ignition timing can be accurately controlled at an appropriate time, and combustion such as knocking and pre-ignition can be performed. Abnormality can be reliably prevented.

[Specific Processing in Embodiment 1]
3 and 4 are flowcharts of routines executed by the ECU 50 in the present embodiment in order to realize the above functions. When switching from the non-reforming operation to the reforming operation, a reforming retardation control routine shown in FIG. 3 is first executed. During execution of the routine shown in FIG. 3, the non-reforming ignition timing map is continuously used.

  According to the routine shown in FIG. 3, first, reforming fuel injection is started by the reforming fuel injection device 34 (step 100). Next, the hydrogen concentration detected by the hydrogen concentration sensor 58 is read (step 102), and further operating conditions such as the engine speed, the engine load, and the opening degree of the EGR valve 40 are read (step 104).

  Subsequently, the ignition timing retardation amount is determined as follows (step 106). First, the flow rate of the reformed gas flowing through the EGR passage 36 is calculated based on the operating condition read in step 104 above. The calculation of the reformed gas flow rate is the same as the EGR flow rate calculation method. That is, the reformed gas flow rate can be calculated by a known method based on the engine speed, the engine load, the opening degree of the EGR valve 40, and the like. Next, by multiplying the hydrogen concentration read in step 102 by the reformed gas flow rate, the amount of hydrogen flowing through the EGR passage 58 (hydrogen flow rate in the EGR passage 36) is calculated. Further, the arrival delay time required for the reformed gas to reach the combustion chamber from the hydrogen concentration sensor 58 is calculated based on the reformed gas flow rate, the passage volume from the hydrogen concentration sensor 58 to the combustion chamber, the engine speed, and the like. The Based on the hydrogen flow rate in the EGR passage 36 and the reformed gas arrival delay time calculated as described above, the actual amount of hydrogen currently flowing into the combustion chamber can be calculated. The ECU 50 stores a map shown in FIG. 2 in advance, and is necessary for setting the ignition timing to an appropriate timing based on the map and the amount of hydrogen flow into the combustion chamber calculated as described above. The ignition timing retard amount is calculated. When the necessary ignition timing retard amount is calculated in this way, processing for actually retarding the ignition timing is executed (step 108).

  According to the control of the present embodiment as described above, by detecting the generation of hydrogen by the hydrogen concentration sensor 58, the ignition timing is set at an accurate timing immediately before the reformed gas (hydrogen) flows into the combustion chamber. The retardation can be corrected. For this reason, the timing to correct the ignition timing is too late relative to the timing at which the reformed gas flows into the combustion chamber, causing abnormal combustion such as knocking or pre-ignition, or conversely, retarding the ignition timing. It is possible to reliably prevent the torque of the internal combustion engine 10 from being lowered due to the correction timing being too early with respect to the timing at which the reformed gas flows into the combustion chamber.

  Further, according to the present embodiment, the amount of hydrogen actually flowing into the combustion chamber can be detected, and an appropriate ignition timing retardation amount corresponding to the amount of hydrogen can be realized. For this reason, immediately after the start of reforming fuel injection, even when the reforming reaction amount is unstable and difficult to predict, it is accurately controlled to the optimal ignition timing according to the amount of hydrogen flowing into the combustion chamber. can do. For this reason, it can prevent more reliably that abnormal combustion, such as knocking and preignition, arises.

  In the present embodiment, the reforming delay angle control as described above is performed in such a manner that the amount of reforming reaction in the fuel reforming catalyst 26 is stable and it can be determined that the amount of combustible component produced matches the required amount with high accuracy. Until the above condition is satisfied (for example, until a predetermined time elapses).

  FIG. 4 is a routine for switching the ignition timing map to that for reforming operation and executing knock control control after the end of the reforming delay angle control represented by the routine of FIG. That is, according to the routine shown in FIG. 4, after the above-described reforming delay angle control is completed (step 110), switching from the non-reforming operation ignition timing map to the reforming operation ignition timing map is executed. In addition, knock control control is started (step 112). After execution of this step 112, the basic ignition timing is calculated from the reforming operation ignition timing map. For this reason, since the basic ignition timing can be set to a late timing suitable for the reforming operation, abnormal combustion such as knocking or pre-ignition can be reliably prevented. Further, by executing the knock control, the ignition timing can be advanced as much as possible within a range where knocking does not occur, so that the ignition timing can be made sufficiently close to MBT. For this reason, the outstanding thermal efficiency is obtained.

  In the first embodiment described above, the hydrogen concentration sensor 58 is provided in the EGR passage 36. However, in the present invention, instead of the hydrogen concentration sensor 58, a CO concentration sensor for detecting the carbon monoxide concentration, hydrogen, A hydrogen / CO concentration sensor that detects the concentration of the combustible component combined with carbon monoxide may be used. As shown in the chemical reaction equation described above, hydrogen and carbon monoxide are generated at a constant rate, so the hydrogen concentration is calculated from the concentration of carbon monoxide or the total concentration of hydrogen and carbon monoxide. It is possible. Therefore, even when a CO concentration sensor or a hydrogen / CO concentration sensor is used, the same control as in this embodiment can be executed.

  In the present embodiment, the ignition timing is corrected according to the amount of hydrogen obtained by multiplying the hydrogen concentration detected by the hydrogen concentration sensor 58 by the reformed gas flow rate. However, in the present invention, the ignition timing is based only on the hydrogen concentration. Thus, the ignition timing may be corrected.

  Further, in this embodiment, when switching from non-reforming operation to reforming operation, the ignition timing map for non-reforming operation is used as a basis, and as the amount of hydrogen flowing into the combustion chamber or the hydrogen concentration increases, the ignition is delayed. Although described as correcting the timing, in the present invention, based on the ignition timing map for reforming operation, the ignition timing is corrected in the advance direction as the amount of hydrogen flowing into the combustion chamber or the hydrogen concentration decreases. Also good.

  In this embodiment, the ignition timing control when switching from non-reforming operation to reforming operation has been described. However, the present invention is also applicable to ignition timing control when switching from reforming operation to non-reforming operation. It is.

  In the present embodiment, the case where the ignition timing correction based on the hydrogen concentration detected by the hydrogen concentration sensor 58 is executed in the transition period between the non-reforming operation and the reforming operation has been described. The ignition timing correction based on the concentration may always be executed during the reforming operation.

  In the present embodiment, in the fuel reformer 24, the heat of the exhaust gas of the internal combustion engine 10 is transferred to the fuel reforming catalyst 26 and absorbed in the reforming reaction. The configuration is not limited to the configuration in which the heat applied to the reforming catalyst 26 is covered by the heat of the exhaust gas. That is, in the present invention, the fuel reforming catalyst 26 may be configured to be heated by a heater, a combustor, or the like.

  In the first embodiment described above, the reforming fuel injection device 34 is the “reforming fuel injection means” in the first and second inventions, and the fuel reformer 24 is the first and second reforming fuel injection devices. The hydrogen concentration sensor 58 corresponds to the “combustible component concentration detecting means” in the first and second inventions, respectively. Further, when the ECU 50 executes the processing of the above steps 102 to 108, the “ignition timing correction means” in the first and second inventions is based on the engine speed, the engine load, the EGR valve 40 opening degree, and the like. By calculating a value obtained by multiplying the calculated reformed gas flow rate and the hydrogen concentration detected by the hydrogen concentration sensor 58 as the hydrogen amount, the “combustible component amount calculating means” in the fourth aspect of the present invention is realized. Yes.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the relationship between the ignition timing retard amount required in order to set it as an appropriate ignition timing at the time of a reforming operation, and the amount of hydrogen which flows into a combustion chamber. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Intake manifold 16 Throttle valve 18 Main fuel injection device 20, 28, 30 Exhaust passage 24 Fuel reformer 26 Fuel reforming catalyst 32, 36 EGR passage 34 Reforming fuel injection device 38 EGR cooler 40 EGR valve 42 Exhaust gas purification catalyst 44 Fuel tank 46 Fuel piping 50 ECU
54 catalyst temperature sensor 56 exhaust gas sensor 58 hydrogen concentration sensor 60 knock sensor

Claims (6)

An EGR passage that recirculates EGR gas extracted from the exhaust passage of the internal combustion engine to the intake passage;
Fuel reforming means for injecting reforming fuel into the EGR gas;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
A combustible component concentration detecting means for detecting a combustible component concentration in the reformed gas;
Ignition timing correction means for correcting the ignition timing based on the combustible component concentration;
A control device for an internal combustion engine, comprising: An EGR passage that recirculates EGR gas extracted from the exhaust passage of the internal combustion engine to the intake passage;
Fuel reforming means for injecting reforming fuel into the EGR gas;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
A combustible component concentration detecting means for detecting a combustible component concentration in the reformed gas;
Ignition timing correction means for correcting the ignition timing in advance before the combustible component reaches the combustion chamber of the internal combustion engine based on the signal detected by the combustible component concentration detection means;
A control device for an internal combustion engine, comprising:   3. The control device for an internal combustion engine according to claim 1, wherein the ignition timing correction means delays the ignition timing as the combustible component concentration is higher. Combustible component amount calculating means for calculating the amount of combustible component recirculated to the internal combustion engine based on the combustible component concentration and the reformed gas flow rate flowing through the EGR passage;
4. The control apparatus for an internal combustion engine according to claim 1, wherein the ignition timing correction means delays the ignition timing as the amount of the combustible component increases. Operation switching for switching between a reforming operation in which the reformed gas is recirculated to the intake passage while fuel is supplied by the reforming fuel injection means and a non-reforming operation in which no fuel is injected from the reforming fuel injection means. Means,
Non-reforming operation ignition timing calculating means for calculating the ignition timing based on the non-reforming operation ignition timing map during non-reforming operation;
A reforming operation ignition timing calculating means for calculating the ignition timing based on the reforming operation ignition timing map during the reforming operation;
With
The ignition timing correction means corrects the ignition timing in a transition period between a state where the non-reforming operation ignition timing map is used and a state where the reforming operation ignition timing map is used. The control device for an internal combustion engine according to any one of claims 1 to 4.   The internal combustion engine according to any one of claims 1 to 5, wherein the heat supply means includes a heat exchanger that transfers heat of exhaust gas of the internal combustion engine to the fuel reforming catalyst. Engine control device.

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