JP5979643B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for an internal combustion engine (hereinafter referred to as “engine”) provided with a reformer that oxidizes and reforms a hydrocarbon-based fuel to produce alcohol.

  In a gasoline engine that burns a premixed fuel / air mixture by spark ignition with an ignition plug, it is known that knocking occurs when the unburned mixture (end gas) separated from the ignition plug self-ignites. Yes. Since knocking is likely to occur when the compression ratio of the engine is increased, suppression of knocking is strongly demanded in recent high compression ratio engines.

  As a method for suppressing knocking, there is a method of retarding the ignition timing. However, if the ignition timing is retarded, the thermal efficiency of the engine decreases. Therefore, it is desired to develop a technology capable of obtaining high thermal efficiency while suppressing knocking even in a high compression ratio engine.

  By the way, since knocking can be suppressed by increasing the octane number of the fuel, an alcohol-containing fuel in which alcohol such as ethanol is mixed in advance with gasoline is widely used as a fuel having a high octane number in some areas. In addition, with the spread of such alcohol-containing fuel, a technique for separating the alcohol-containing fuel supplied from the outside into a high gasoline concentration fuel and a high alcohol concentration fuel on the vehicle has been proposed (for example, Patent Document 1). According to this technology, since the octane number of the fuel supplied to the engine can be optimally controlled by changing the supply ratio of the separated high gasoline concentration fuel and high alcohol concentration fuel according to the engine load condition, knocking is prevented. It is said that the operating state of the engine can be optimized by suppressing it.

  On the other hand, a synthesis method has been proposed in which a hydrocarbon is oxidized and reformed into an alcohol by using a carbon radical generating catalyst such as N-hydroxyphthalimide (NHPI) (for example, see Non-Patent Document 1). If this synthesis method can be used on a vehicle, it is considered that hydrocarbons contained in gasoline can be converted into alcohol having a high octane number and alcohol having a high octane number can be supplied to the engine according to the load state of the engine.

JP 2008-248840 A

S. Sakaguchi, S. Kato, T. Iwahama, Y. Ishii, Bull. Chem. Soc. Jpn. 71 (1998) p. 1237-1240

  However, the technique of Patent Document 1 cannot be applied to an area where alcohol-containing fuel is not widespread because alcohol cannot be separated from 100% gasoline fuel. Further, when the alcohol is a low-concentration alcohol-containing fuel, a sufficient amount of alcohol cannot be separated, so that the effect can be obtained only for a short time when a high load state requiring a high octane number fuel continues. Furthermore, since it takes time to separate the alcohol-containing fuel, it is difficult to separate the alcohol-containing fuel according to the engine load state.

  Moreover, the present condition is not made about examination which applies the synthesis method of a nonpatent literature 1 to fuels, such as gasoline. Therefore, if the reformer that oxidizes and reforms hydrocarbon-based fuel to produce alcohol can be optimized and controlled, high-octane alcohol can be supplied according to the engine load state, and the engine operating state Is extremely useful.

  The present invention has been made in view of the above, and an object of the present invention is to provide a control device for an internal combustion engine that can optimize and control a reforming device that generates alcohol by oxidizing and reforming fuel mainly composed of hydrocarbons. There is.

  In order to achieve the above object, the present invention provides a reforming method in which a hydrocarbon-based fuel is oxidized and reformed with air and a reforming catalyst to generate alcohol, and the reformed fuel containing the generated alcohol is injected into an internal combustion engine. A control apparatus for an internal combustion engine, comprising: a combustion fluctuation detection means for detecting a combustion fluctuation of the internal combustion engine; an air-fuel ratio detection means for detecting an exhaust air-fuel ratio of the internal combustion engine; and a detection by the combustion fluctuation detection means An octane number estimating means for estimating an octane number of the reformed fuel based on the combustion fluctuation, an exhaust air / fuel ratio detected by the air / fuel ratio detecting means, and an injection amount of the reformed fuel, Oxidation reaction progress estimation means for estimating the oxidation reaction progress of the fuel, octane number estimated by the octane number estimation means, and oxidation reaction estimated by the oxidation reaction progress estimation means Based on Gyodo, to provide a control apparatus for an internal combustion engine, characterized in that it comprises a modified control means for controlling the reformer.

In the present invention, an internal combustion engine provided with a reforming device that oxidizes and reforms a hydrocarbon-based fuel with air and a reforming catalyst to generate alcohol, and injects the reformed fuel containing the generated alcohol into the internal combustion engine. , The octane number of the reformed fuel is estimated based on the combustion fluctuation of the internal combustion engine, and the progress of the oxidation reaction of the reformed fuel is estimated based on the exhaust air / fuel ratio and the injection amount of the reformed fuel. Further, the reformer is controlled based on the estimated octane number of the reformed fuel and the progress of the oxidation reaction.
As described above, knocking can be suppressed by increasing the octane number of the fuel. Therefore, according to the present invention, the internal combustion engine is controlled while reliably suppressing knocking by controlling the reforming device based on the octane number of the reformed fuel. Can optimize the operating conditions. In addition, according to the present invention, since the reformer is controlled based on the degree of progress of the oxidation reaction, it is possible to optimize the operating state of the internal combustion engine while more reliably suppressing knocking.

  The reforming control means increases the flow rate of the fuel supplied to the reforming device when the oxidation reaction progress degree estimated by the oxidation reaction progress degree estimating means is larger than a predetermined target oxidation reaction progress degree. When the oxidation reaction progress estimated by the oxidation reaction progress estimation means is smaller than the target oxidation reaction progress, it is preferable to reduce the flow rate of the fuel supplied to the reformer.

In this invention, when the oxidation reaction progress is larger than the predetermined target oxidation reaction progress, the flow rate of the fuel supplied to the reformer is increased. Further, when the oxidation reaction progress is smaller than a predetermined target oxidation reaction progress, the flow rate of the fuel supplied to the reformer is decreased.
According to this invention, when the oxidation reaction progress is larger than the predetermined target oxidation reaction progress, the contact time between the fuel and the reforming catalyst is reduced by increasing the flow rate of the fuel supplied to the reformer. Since it can be reduced, oxidation reforming can be suppressed. Further, when the oxidation reaction progress is smaller than the predetermined target oxidation reaction progress, the contact time between the fuel and the reforming catalyst can be increased by decreasing the flow rate of the fuel supplied to the reformer, Oxidative reforming can be promoted. Therefore, according to the present invention, the reformer can be controlled more optimally.

  The reforming control means lowers the temperature of the reformer when the oxidation reaction progress estimated by the oxidation reaction progress estimation means is larger than a predetermined target oxidation reaction progress, and the oxidation reaction When the progress of the oxidation reaction estimated by the progress estimation means is smaller than the target progress of the oxidation reaction, it is preferable to raise the temperature of the reformer.

In the present invention, when the oxidation reaction progress is larger than a predetermined target oxidation reaction progress, the temperature of the reformer is lowered. Further, when the oxidation reaction progress is smaller than the predetermined target oxidation reaction progress, the temperature of the reformer is increased.
According to this invention, when the degree of progress of the oxidation reaction is larger than the predetermined degree of progress of the target oxidation reaction, the oxidation reforming can be suppressed by lowering the temperature of the reformer. Further, when the oxidation reaction progress is smaller than a predetermined target oxidation reaction progress, the oxidation reforming can be promoted by increasing the temperature of the reformer. Therefore, according to the present invention, the reformer can be controlled more optimally.

  The reforming control means, when the oxidation reaction progress estimated by the oxidation reaction progress estimation means is within a predetermined range and the octane number estimated by the octane number estimation means is smaller than a predetermined optimum octane number Preferably, it is determined that the reformer is out of order and the reformer is stopped.

In the present invention, if the octane number is smaller than the predetermined optimum octane number even though the oxidation reaction progress is within the predetermined optimum range, it is determined that the reformer has failed and the reformer Stop.
According to the present invention, since it is possible to determine the failure of the reformer, the reformer can be further optimized and controlled.

  Preferably, the combustion fluctuation detecting means is a knock sensor, and the air-fuel ratio detecting means is an air-fuel ratio sensor.

In the present invention, a knock sensor is used as the combustion fluctuation detecting means, and an air-fuel ratio sensor is used as the air-fuel ratio detecting means.
According to this invention, the reforming state of the fuel by the reformer can be estimated by the knock sensor and the air-fuel ratio (A / F) sensor that are widely used in gasoline engines. Therefore, an increase in the number of parts can be suppressed without adding a special sensor such as an alcohol sensor.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can optimize-control the reformer which produces | generates alcohol by oxidizing and reforming the fuel which mainly has a hydrocarbon can be provided.

It is a figure which shows the control apparatus of an internal combustion engine provided with the reformer which concerns on one Embodiment of this invention. It is a figure which shows the structure of the reformer which concerns on the said embodiment. It is a flowchart which shows the procedure of the reforming control which concerns on the said embodiment. It is a figure which shows the relationship between the oxidation reaction progress in the reformer which concerns on the said embodiment, and the density | concentration of a product. It is a figure which shows the relationship between the stoichiometric fuel-air ratio of a fuel, and an octane number. It is a flowchart which shows the procedure of the octane number estimation which concerns on the said embodiment.

An embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a control device for an internal combustion engine (hereinafter referred to as “engine”) including a reforming device according to an embodiment of the present invention. As shown in FIG. 1, the engine 51 includes an intake pipe 56 through which intake air flows, an exhaust pipe 57 through which exhaust flows, a reformer 1 that supplies reformed fuel to the engine 51, the engine 51, and the reformer. An electronic control unit (hereinafter referred to as “ECU”) 50 for controlling the apparatus 1 is provided.

  The engine 51 is a multi-cylinder engine, and FIG. 1 shows only one cylinder for convenience. The engine 51 includes a plurality of cylinders 52 and a piston 53 that slides in the cylinders 52. A combustion chamber 55 of the engine 51 is formed by the top surface of the piston 53 and the inner wall surface of the cylinder head 54. The piston 53 is connected to a crankshaft (not shown) via a connecting rod, and the crankshaft rotates according to the reciprocating motion of the piston 53.

  The cylinder head 54 is provided with a spark plug 58 that faces the combustion chamber 55. Further, the cylinder head 54 is provided with an intake port 56 a that connects the combustion chamber 55 and the intake pipe 56, and an exhaust port 57 a that connects the combustion chamber 55 and the exhaust pipe 57. An intake valve 59 for opening and closing the opening is provided at the opening of the intake port 56a facing the combustion chamber 55. An exhaust valve 60 for opening and closing the opening is provided at an opening facing the combustion chamber 55 of the exhaust port 57a.

  The intake pipe 56 is provided with a first injector 61 and a second injector 62 that inject fuel. The injectors 61 and 62 have their injection amounts and injection timing controlled by the ECU 50. Further, on the upstream side of these injectors 61 and 62, a throttle valve 63 for controlling the flow rate of the air mixed with the fuel is provided.

The first injector 61 is stored in a fuel tank provided in the reformer 1 described later, and gasoline supplied through a fuel pump and a fuel supply pipe 172 can be injected into the intake port 56a.
Further, the second injector 62 stores a reformed fuel containing alcohol stored in a reformed fuel tank provided in the reformer 1 to be described later and supplied via a reformed fuel pump and a reformed fuel supply pipe 192. Injection into the intake port 56a is possible. In addition, the reformed fuel containing alcohol is produced | generated by oxidizing and reforming gasoline with the reformer 1 mentioned later.

  Here, FIG. 2 is a diagram showing a configuration of the reformer 1 according to the present embodiment. The reformer 1 oxidizes and reforms hydrocarbons contained in gasoline into alcohol with air and a reforming catalyst in response to a request of the engine 51 on a vehicle (not shown) and supplies the reformed gas to the engine 51. That is, since the reformer 1 reforms gasoline using an oxidation reaction by oxygen in the air, reforming is possible under mild conditions at a lower temperature than reforming using a decomposition reaction, for example. Therefore, the device configuration can be simplified and is suitable for on-demand driving on a vehicle.

  As shown in FIG. 2, the reformer 1 according to this embodiment includes an air introduction unit 11, a fuel tank 12, a fuel introduction unit 13, a mixer 14, a reformer 15, and a condenser 16. The fuel supply unit 17, the reformed fuel tank 18, the reformed fuel supply unit 19, and the gas phase supply unit 20 are included.

  The air introduction unit 11 is provided upstream of the mixer 14 described later, and introduces air as an oxidant into the mixer 14. The air introduction unit 11 includes an air filter 111, an air pump 112, an air flow meter 113, and an air valve 114 in order from the upstream side of the air introduction pipe 110. The air introduction unit 11 takes in air from the outside air via the air filter 111 by driving the air pump 112. The air introduction unit 11 opens the air valve 114 to introduce the taken-in air into the mixer 14. The amount of air introduced into the mixer 14 is controlled by adjusting the opening of the air valve 114 by the ECU 50 based on the air flow rate detected by the air flow meter 113.

  The fuel tank 12 stores gasoline mainly containing hydrocarbons as fuel. That is, the fuel tank 12 is a fuel tank provided in a normal vehicle, and stores gasoline before reforming.

  The fuel supply unit 17 includes a fuel pump 171, a fuel supply pipe 172, and the above-described first injector 61 (see FIG. 1). The fuel supply unit 17 drives the fuel pump 171 to supply gasoline stored in the fuel tank 12 into the intake port 56 a of the engine 51 via the fuel supply pipe 172 and the first injector 61. The gasoline supply amount is controlled by adjusting the injection amount of the first injector 61 by the ECU 50.

  The fuel introduction unit 13 is provided upstream of a mixer 14 described later, and introduces fuel gasoline into the mixer 14. The fuel introduction unit 13 includes a reforming pump 131, a fuel flow meter 132, and a fuel valve 133 in order from the upstream side of the fuel introduction pipe 130. The fuel introduction unit 13 drives the reforming pump 131 and opens the fuel valve 133 to introduce the gasoline stored in the fuel tank 12 into the mixer 14. The amount of gasoline introduced into the mixer 14 is controlled by adjusting the opening of the fuel valve 133 by the ECU 50 based on the fuel flow rate detected by the fuel flow meter 132.

  The mixer 14 is provided upstream of the reformer 15 described later, and mixes gasoline and air as fuel and supplies the mixture into the reformer 15. The mixer 14 has a configuration capable of uniformly mixing the air introduced by the air introduction unit 11 and the liquid gasoline introduced by the fuel introduction unit 13. Specifically, for example, the mixer 14 may be configured to generate small air bubbles by forming a connection portion between the air introduction pipe 110 and the mixer 14 in a small hole. Moreover, the mixer 14 may be comprised so that a vortex may be generated with the strong flow of air. The mixer 14 includes a heater (not shown), and generates a mixture of gasoline and air by mixing gasoline and air while raising the temperature to a predetermined temperature.

  The reformer 15 reforms the hydrocarbon, which is the main component of gasoline in the gas mixture supplied from the mixer 14, using the air in the gas mixture to generate alcohol. Specifically, the reformer 15 may be either a flow reactor or a complete mixing reactor.

Here, the flow reactor is a mixture of gasoline and air introduced from the mixer 14 while being swept away like a piston without being mixed with the mixture supplied before and after the mixture in the reactor. It means a reactor that is reformed and flows out. Therefore, in the flow reactor, the composition of the fluid flowing out from the reactor and the composition of the fluid inside the reactor are different, and the variation in the residence time of the air-fuel mixture in the reactor is small.
On the other hand, the complete mixing reactor means a reactor in which a mixture of gasoline and air introduced from the mixer 14 is uniformly mixed with a reactant in the reformer and reformed. Therefore, in the complete mixing reactor, the composition of the fluid flowing out from the reactor and the composition of the fluid inside the reactor are the same, and the residence time inside the reactor of the mixer has a large variation.

  As shown in FIG. 2, the reformer 15 is provided with a temperature sensor (not shown) and a cooling unit 153 for cooling the interior of the reformer 15. The cooling unit 153 is controlled by the ECU 50 based on the temperature detected by the temperature sensor, and cools the reformer 15 by supplying cooling water of the engine 51 to the reformer 15. The temperature of the engine cooling water is preferably 70 ° C to 100 ° C. If the temperature of the engine cooling water is less than 70 ° C., the reforming reaction rate is small, and if it exceeds 100 ° C., it becomes difficult to use the engine cooling water. The cooling unit 153 cools the reformer 15 with engine cooling water when the reforming reaction proceeds and the temperature in the reformer 15 is high, but at the initial stage of the reforming reaction, the reformer 15 When the temperature in 15 is low, the reformer 15 is warmed with engine cooling water.

  The reformer 15 also includes a reforming catalyst 152 that reforms hydrocarbons mainly contained in gasoline using air as an oxidant to generate alcohol. Specifically, the reformer 15 includes a cylindrical casing 151 and a solid reforming catalyst 152 filled in the casing 151.

  The solid reforming catalyst 152 includes a small spherical porous carrier, and a main catalyst and a co-catalyst supported on the surface of the porous carrier. The main catalyst and the cocatalyst are supported on the surface of a small spherical porous support in a uniformly mixed state. As described above, the reforming catalyst 152 of the present embodiment has a small spherical porous carrier, which increases the surface area of the main catalyst and the promoter supported on the surface of the reforming catalyst 152. The contact area increases.

  As the small spherical porous carrier, for example, silica beads, alumina beads, silica alumina beads and the like are used. Of these, silica beads are preferably used. The particle size of the porous carrier is preferably 3 μm to 500 μm.

  The main catalyst has the ability to extract alkyl atoms from hydrocarbons in gasoline to generate alkyl radicals. Specifically, an N-hydroxyimide group-containing compound having an N-hydroxyimide group is used as the main catalyst. Among these, N-hydroxyphthalimide (hereinafter referred to as “NHPI”) or an NHPI derivative is preferably used.

  The cocatalyst has the ability to reduce an alkyl hydroperoxide generated from an alkyl radical to produce an alcohol. Specifically, a transition metal compound is used as the promoter. Among these, a compound selected from the group consisting of a cobalt compound, a manganese compound, and a copper compound is preferably used. Cobalt acetate (II) or the like is used as the cobalt compound, manganese (II) acetate or the like is used as the manganese compound, and copper (I) chloride or the like is used as the copper compound.

  As a method for supporting the main catalyst and the cocatalyst on the porous carrier, a conventionally known impregnation method or the like is employed. For example, after preparing a slurry containing a main catalyst and a promoter in a predetermined mixing ratio, a small spherical porous carrier is immersed in the prepared slurry. Next, the porous carrier is pulled up from the slurry to remove excess slurry adhering to the surface of the porous carrier, and then dried under predetermined conditions. Thereby, the reforming catalyst 152 in which the main catalyst and the promoter are uniformly supported on the surface of the porous carrier is obtained.

Here, the reforming reaction that proceeds in the reformer 15 will be described in detail below.
First, as shown in the following reaction formula (1), the reforming reaction of the present embodiment is initiated by a hydrogen abstraction reaction in which hydrogen atoms are extracted from hydrocarbons in gasoline to generate alkyl radicals. This hydrogen abstraction reaction proceeds by the action of the main catalyst, radicals, oxygen molecules and the like.
[Chemical 1]

RH → R ... Reaction formula (1)

[In Reaction Formula (1), RH represents a hydrocarbon, and R. represents an alkyl radical. ]

Next, as shown in the following reaction formula (2), the alkyl radical generated by the hydrogen abstraction reaction is combined with oxygen molecules to generate an alkyl peroxy radical.
[Chemical formula 2]

R · + O ₂ → ROO · ... Reaction formula (2)

[In Reaction Formula (2), O ₂ represents an oxygen molecule, and ROO · represents an alkyl peroxy radical. ]

Next, as shown in the following reaction formula (3), the alkyl peroxy radical generated by the reaction formula (2) pulls out hydrogen atoms from hydrocarbons contained in gasoline to generate an alkyl hydroperoxide.
[Chemical formula 3]

ROO ・ + RH → ROOH + R ・ ・ ・ ・ Reaction formula (3)

[In reaction formula (3), ROOH represents alkyl hydroperoxide. ]

Next, as shown in the following reaction formula (4), the alkyl hydroperoxide produced by the reaction formula (3) is reduced to an alcohol by the action of a promoter.
[Chemical formula 4]

ROOH → ROH ... Reaction formula (4)

[In the reaction formula (4), ROH represents an alcohol. ]

Moreover, the alkyl hydroperoxide produced | generated by Reaction formula (3) decomposes | disassembles into an alkoxy radical and a hydroxy radical by the effect | action of a promoter or a heat | fever, as shown in following Reaction formula (5).
[Chemical formula 5]

ROOH → RO ・ + ・ OH ・ ・ ・ Reaction formula (5)

[In the reaction formula (5), RO · represents an alkoxy radical, and · OH represents a hydroxy radical. ]

Subsequently, the alkoxy radical produced | generated by Reaction formula (5) draws out a hydrogen atom from the hydrocarbon contained in gasoline, and produces | generates alcohol.
[Chemical 6]

RO ・ + RH → ROH + R ・ ・ ・ ・ Reaction formula (6)

  As described above, hydrocarbons mainly contained in gasoline are oxidized and reformed and converted to alcohol. More specifically, since hydrocarbons contained in gasoline are hydrocarbons having 4 to 10 carbon atoms, these hydrocarbons are converted into alcohols having 4 to 10 carbon atoms. Thus, in the reformer 1 of this embodiment, the octane number of gasoline can be improved.

  Next, the condenser 16 is provided downstream of the reformer 15 and separates the produced gas generated by the reformer 15 into a condensed phase mainly composed of reformed fuel and a gas phase. The condenser 16 has a heat exchanger (not shown) inside, and by cooling the product gas flowing out from the outlet of the reformer 15, it is converted into a condensed phase mainly composed of reformed fuel and a gas phase. To separate. The condensed phase contains by-product water and the like in addition to the reformed fuel mainly composed of alcohol, and the gas phase contains nitrogen, oxygen, and other by-product gas components. .

  The reformed fuel tank 18 stores the reformed fuel in the condensed phase separated by the condenser 16. The reformed fuel tank 18 functions as a buffer tank that temporarily stores the reformed fuel alcohol generated by reforming gasoline by the reformer 15.

  The reformed fuel supply unit 19 supplies the reformed fuel stored in the reformed fuel tank 18 into the intake port 56 a of the engine 51. The reformed fuel supply unit 19 includes a reformed fuel pump 191, a reformed fuel supply pipe 192, and the above-described second injector 62 (see FIG. 1). The reformed fuel supply unit 19 drives the reformed fuel pump 191 to convert the reformed fuel stored in the reformed fuel tank 18 through the reformed fuel supply pipe 192 and the second injector 62 into the engine. 51 is supplied into the intake port 56a. The supply amount of the reformed fuel is controlled by adjusting the injection amount of the second injector 62 by the ECU 50.

  The gas phase supply unit 20 supplies the gas phase separated by the condenser 16 into the intake port 56 a of the engine 51. The gas phase supply unit 20 includes a gas phase supply pipe 201 connected to the intake port 56 a of the engine 51. The gas phase separated by the condenser 16 is supplied into the intake port 56a of the engine 51 through the gas phase supply pipe 201 (in FIG. 1, the description of the gas phase supply pipe 201 is omitted).

The reformer 1 is controlled by the ECU 50 and operates as follows.
First, when it is determined that gasoline reforming is necessary according to the operating state of the engine 51, it is determined whether or not the temperature of the engine cooling water is equal to or higher than a predetermined temperature. Immediately after the engine is started, when the temperature of the engine cooling water is lower than a predetermined temperature, the reformed fuel stored in the reformed fuel tank 18 at the previous reforming is put into the intake port 56a of the engine 51 by the reformed fuel pump 191. Supply.

  On the other hand, when the engine coolant temperature is equal to or higher than the predetermined temperature, the fuel valve 133 and the air valve 114 are opened. Next, the reforming pump 131 pumps gasoline from the fuel tank 12 and introduces it into the mixer 14. At the same time, air that has passed through the air filter 111 is introduced into the mixer 14 by the air pump 112.

  At this time, the gasoline flow rate and the air flow rate meter 113 monitored by the fuel flow rate meter 132 are set so as to obtain a desired proper gasoline flow rate / air flow rate ratio and to obtain a desired proper reforming reaction time. Feedback control of the opening degree of the fuel valve 133 and the air valve 114 is performed on the basis of the air flow rate monitored in (1). Thereby, the gasoline flow rate and the air flow rate are controlled.

  Next, the gasoline and air introduced into the mixer 14 are uniformly mixed while being heated to a predetermined temperature to form an air-fuel mixture, and then supplied into the reformer 15. The hydrocarbons, which are the main components of gasoline in the air-fuel mixture supplied into the reformer 15, are converted into alcohol as the above reaction formulas (1) to (6) proceed due to the action of the reforming catalyst 152. Is done. At this time, supply of engine cooling water is controlled based on the temperature monitored by the temperature sensor. Thereby, the temperature in the reformer 15 is maintained at a desired appropriate temperature.

  Next, the product gas generated in the reformer 15 is cooled by a heat exchanger in the condenser 16 to be separated into a condensed phase and a gas phase. The separated condensed phase mainly contains reformed fuel alcohol, and the reformed fuel is introduced into the reformed fuel tank 18 and stored. The reformed fuel in the reformed fuel tank 18 is supplied into the intake port 56 a of the engine 51 by the reformed fuel pump 191. On the other hand, the separated gas phase is introduced into the intake port 56 a of the engine 51 to be used for combustion in the cylinder of the engine 51.

  When it is determined that the reforming of gasoline is unnecessary according to the operating state of the engine 51, first, the air pump 112 is stopped, the air valve is closed, and the air is supplied into the mixer 14 To stop. Next, after the inside of the reformer 15 is filled with gasoline and all the air flows out, the reforming pump 131 is stopped, the fuel valve 133 is closed, and the supply of gasoline into the mixer 14 is stopped. This avoids a situation in which the reforming reaction proceeds due to oxygen remaining in the reformer 15 while the apparatus is stopped.

Returning to FIG. 1, the cylinder 52 is provided with a knock sensor 71 that detects combustion fluctuations of the engine 51. Knock sensor 71 detects knocking by detecting vibration. A detection signal of knock sensor 71 is output to ECU 50.
Further, an air-fuel ratio sensor for detecting the air-fuel ratio (A / F) of the exhaust is provided on the downstream side of the exhaust pipe 57. A detection signal from the air-fuel ratio sensor is output to the ECU 50.

Further, the engine 51 is provided with a crank angle position sensor 73 and an accelerator opening degree sensor 74.
The crank angle position sensor 73 detects the rotation angle of the crankshaft of the engine 51, generates a pulse at every predetermined crank angle, and outputs the pulse signal to the ECU 50. The engine speed is calculated by the ECU 50 based on this pulse signal.
The accelerator opening sensor 74 detects the amount of depression of the accelerator pedal of the vehicle, and outputs a detection signal to the ECU 50. The engine load is calculated by the ECU 50 based on the fuel injection amount calculated based on this detection signal.

  The ECU 50 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, converts an analog signal value into a digital signal value, and a central processing unit (hereinafter, referred to as a central processing unit). CPU). The ECU 50 also includes a storage circuit that stores various arithmetic programs executed by the CPU, arithmetic results, and the like, and an output circuit that outputs control signals to the engine 51 and the reformer 1.

Next, reforming control by the ECU 50 according to the present embodiment will be described.
FIG. 3 is a flowchart showing the procedure of reforming control according to the present embodiment. The reforming control process is executed at a predetermined cycle by the ECU 50 while the vehicle is traveling.

  In step S1, after estimating the octane number of the reformed fuel, the process proceeds to step S2. The procedure for estimating the octane number of the reformed fuel will be described in detail later with reference to FIG.

Here, the principle of estimating the octane number of the reformed fuel will be described.
Normally, a gasoline engine is more likely to knock when the engine load is higher and the engine speed is lower. Under such operating conditions where knocking is likely to occur, knocking does not occur at the ignition timing (MBT) with the highest efficiency, and the octane number of gasoline that can be combusted (hereinafter referred to as “required octane number”) increases.
Therefore, in this embodiment, when the reformed fuel is injected into the intake port 56a and used for combustion, if the octane number of the reformed fuel is lower than the required octane number, knocking is detected by the knock sensor. The knocking is suppressed by igniting the spark ignition timing later than MBT. At this time, the relationship between the required octane number at a certain engine load / engine speed and the octane number at a lower octane number and the spark ignition timing necessary for knocking suppression is mapped in advance. As a result, when the octane number of the reformed fuel is lower than the required octane number, the octane number of the reformed fuel can be estimated from the ignition timing value necessary for suppressing knocking.

In step S2, it is determined whether or not the octane number of the reformed fuel estimated in step S1 matches a predetermined required octane number A. If this determination is NO, the process proceeds to step S3, where it is determined that the reforming state is good, and this process ends. On the other hand, if this determination is NO, the process proceeds to step S4.
The required octane number A is calculated by searching a preset map based on the engine speed and the engine load. In this map, the required octane number A is set higher as the engine load is higher, and the required octane number A is set higher as the engine speed is lower.

Next, in the processing after step S4, the reformer is controlled on the basis of the stoichiometric fuel-air ratio of the reformed fuel (synonymous with the meaning based on the degree of progress of the oxidation reaction as will be described later). Before explaining, the reason will be described below.
FIG. 4 is a diagram showing the relationship between the oxidation reaction progress and the product concentration in the reformer. As shown in FIG. 4, when the oxidation reaction proceeds, first, gasoline mainly composed of hydrocarbons is oxidized to produce alcohol. Next, when the oxidation reaction further proceeds, the produced alcohol is oxidized to produce an aldehyde and a ketone. As the oxidation reaction further proceeds, the aldehyde and ketone are oxidized to produce CO and CO ₂ . Here, among these products, since the one having the highest octane number is alcohol, it can be seen that the octane number decreases when the degree of progress of the oxidation reaction becomes too large. Therefore, in order to increase the octane number, it is necessary to control the degree of progress of the oxidation reaction to be optimal.

FIG. 5 is a graph showing the relationship between the stoichiometric fuel-air ratio of fuel and the octane number.
By the way, normally, when the oxidation reaction proceeds, oxygen atoms are introduced into the fuel, so that the stoichiometric fuel-air ratio (the fuel when the amount of air is necessary to convert all the fuel into CO ₂ and H ₂ O). And the ratio of air) increases. That is, the stoichiometric fuel / air ratio has a correlation with the progress of the oxidation reaction.
On the other hand, since the octane number of the reformed fuel becomes maximum when the maximum amount of alcohol is generated as described above, the stoichiometric fuel-air ratio at this time can be said to be the optimum reforming state in the reformer. . Therefore, the maximum value of the octane number is the required octane number A, and by specifying the target stoichiometric fuel-air ratio B that provides this required octane number A, the reforming state of the reformer can be determined. Furthermore, the stoichiometric fuel-air ratio is within a predetermined range (for example, in the vicinity of the target stoichiometric fuel-air ratio B), and the octane number of the reformed fuel is smaller than the predetermined octane number calculated from the relationship shown in FIG. In this case, it can be determined that the reformer is out of order.

Returning to FIG. 4, in step S4, it is determined whether or not the stoichiometric fuel-air ratio of the reformed fuel is larger than the target stoichiometric fuel-air ratio B. If this determination is YES, the process proceeds to step S5, the fuel supply flow rate to the reformer is increased, and the present process is terminated. As a result, the contact time between the reforming catalyst and the fuel decreases, so that the degree of progress of the oxidation reaction decreases, and the target stoichiometric fuel / air ratio approaches the target stoichiometric fuel / air ratio B. It approaches the required octane number A. On the other hand, if this determination is NO, the process proceeds to step S6.
The stoichiometric fuel-air ratio of the reformed fuel, that is, the oxidation reaction progress, is estimated based on the exhaust air-fuel ratio and the fuel injection amount of the reformed fuel.

  In step S6, it is determined whether or not the stoichiometric fuel-air ratio of the reformed fuel is smaller than the target stoichiometric fuel-air ratio B. If this determination is YES, the process proceeds to step S7, the fuel supply flow rate to the reformer is decreased, and this process is terminated. As a result, the contact time between the reforming catalyst and the fuel increases, so that the degree of progress of the oxidation reaction increases, and the target stoichiometric fuel-air ratio approaches the target stoichiometric fuel-air ratio B. It approaches the required octane number A.

  On the other hand, when the determination in step S6 is NO, the octane number of the reformed fuel is not the required octane number A even though the stoichiometric fuel / air ratio of the reformed fuel is the target stoichiometric fuel / air ratio B. Therefore, the process proceeds to step S8, where it is determined that the reformer is out of order and this process is terminated.

Next, a procedure for estimating the octane number of the reformed fuel will be described.
FIG. 6 is a flowchart showing a procedure of octane number estimation according to the present embodiment. This octane number estimation procedure is based on the principle described above.

  In step S11, the reformed fuel is injected into the intake port 56a under the operating condition of the required octane number A. Thereafter, the process proceeds to step S12.

  In step S12, it is determined whether or not knocking has occurred in the engine. If this determination is NO, the process proceeds to step S13, where it is determined that the octane number of the reformed fuel matches the required octane number A, and this process is terminated. On the other hand, if this determination is YES, the process proceeds to step S14.

  In step S14, it is determined that the octane number of the reformed fuel is less than the required octane number A, and the process proceeds to step S15. In step S15, the spark ignition timing is delayed and the process proceeds to step S16.

  In step S16, it is determined whether or not knocking has occurred in the engine. If this determination is YES, the process moves to step S17 to further delay the spark ignition timing, and then returns to step S16 to determine again whether or not knocking has occurred in the engine. That is, this process is repeated until knocking does not occur in the engine. On the other hand, if this determination is NO, the process proceeds to step S18.

  In step S18, since knocking does not occur in the engine, the octane number of the reformed fuel is estimated by searching the map based on the spark ignition timing at that time, and this process is terminated.

According to this embodiment, the following effects are produced.
In the present embodiment, an internal combustion engine provided with a reformer that oxidizes and reforms a hydrocarbon-based fuel with air and a reforming catalyst to generate alcohol, and injects the reformed fuel containing the generated alcohol into the internal combustion engine. In the engine, the octane number of the reformed fuel was estimated based on the combustion fluctuation of the internal combustion engine, and the progress of the oxidation reaction of the reformed fuel was estimated based on the exhaust air-fuel ratio and the injection amount of the reformed fuel. The reformer was controlled based on the estimated octane number of reformed fuel and the progress of oxidation reaction.
As described above, since knocking can be suppressed by increasing the octane number of the fuel, according to the present embodiment, the internal combustion engine is controlled while reliably suppressing knocking by controlling the reforming device based on the octane number of the reformed fuel. The engine operating condition can be optimized. In addition, according to the present embodiment, since the reformer is controlled based on the degree of progress of the oxidation reaction, the operating state of the internal combustion engine can be optimized while more reliably suppressing knocking.

In the present embodiment, when the progress of the oxidation reaction is larger than the predetermined target progress of the oxidation reaction, the flow rate of the fuel supplied to the reformer is increased. Further, when the oxidation reaction progress is smaller than a predetermined target oxidation reaction progress, the flow rate of the fuel supplied to the reformer is decreased.
According to this embodiment, when the oxidation reaction progress is larger than the predetermined target oxidation reaction progress, the contact time between the fuel and the reforming catalyst is increased by increasing the flow rate of the fuel supplied to the reformer. Therefore, oxidation reforming can be suppressed. Further, when the oxidation reaction progress is smaller than the predetermined target oxidation reaction progress, the contact time between the fuel and the reforming catalyst can be increased by decreasing the flow rate of the fuel supplied to the reformer, Oxidative reforming can be promoted. Therefore, according to this embodiment, the reformer can be controlled more optimally.

In this embodiment, when the oxidation reaction progress is within a predetermined optimum range, but the octane number is smaller than the predetermined optimum octane number, it is determined that the reformer has failed and reforming is performed. The device was stopped.
According to the present embodiment, since it is possible to determine the failure of the reformer, the reformer can be further optimized and controlled.

In this embodiment, a knock sensor is used as the combustion fluctuation detection means, and an air-fuel ratio sensor is used as the air-fuel ratio detection means.
According to this embodiment, the reforming state of the fuel by the reformer can be estimated by a knock sensor and an air-fuel ratio (A / F) sensor that are widely used in gasoline engines. Therefore, an increase in the number of parts can be suppressed without adding a special sensor such as an alcohol sensor.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
In the said embodiment, although gasoline is used as a fuel, it is not limited to this. For example, even when alcohol-containing gasoline containing alcohol such as ethanol is used, the same effects as those of the above-described embodiment can be obtained.
Moreover, in the said embodiment, although gasoline was injected in the intake port, it is not limited to this, You may inject directly in a cylinder.

In the above embodiment, when the stoichiometric fuel-air ratio of the reformed fuel is larger than the target stoichiometric fuel-air ratio B, the amount of fuel supplied to the reformer is increased (step S5 in FIG. 3). When the stoichiometric fuel-air ratio of the reformed fuel is smaller than the target stoichiometric fuel-air ratio B, the amount of fuel supplied to the reformer is decreased (step S7 in FIG. 3). It is not limited.
For example, when the stoichiometric fuel / air ratio of the reformed fuel is larger than the target stoichiometric fuel / air ratio B, the temperature of the reformer is decreased, and the stoichiometric fuel / air ratio of the reformed fuel becomes equal to the target chemistry. When it is smaller than the stoichiometric fuel-air ratio B, the temperature of the reformer may be increased. Thereby, when the oxidation reaction progress is larger than the predetermined target oxidation reaction progress, the oxidation reforming can be suppressed by lowering the temperature of the reformer. Further, when the oxidation reaction progress is smaller than a predetermined target oxidation reaction progress, the oxidation reforming can be promoted by increasing the temperature of the reformer. Therefore, the reformer can be controlled more optimally.
In this case, the temperature of the reformer can be controlled by controlling the temperature and flow rate of the cooling water supplied to the reformer.

DESCRIPTION OF SYMBOLS 1 ... Reforming apparatus 50 ... ECU (control apparatus, octane number estimation means, oxidation reaction progress degree estimation means, reforming control means)
51. Engine (internal combustion engine)
71 ... Knock sensor (combustion fluctuation detecting means)
72: Air-fuel ratio sensor (air-fuel ratio detection means)
152 ... Reforming catalyst

Claims (5)

A control device for an internal combustion engine comprising a reformer that oxidizes and reforms a hydrocarbon-based fuel with air and a reforming catalyst to produce alcohol, and injects the reformed fuel containing the produced alcohol into the internal combustion engine. And
Combustion fluctuation detecting means for detecting combustion fluctuation of the internal combustion engine;
Air-fuel ratio detection means for detecting the exhaust air-fuel ratio of the internal combustion engine;
Octane number estimation means for estimating the octane number of the reformed fuel based on the combustion fluctuation detected by the combustion fluctuation detection means;
An oxidation reaction progress degree estimating means for estimating an oxidation reaction progress degree of the reformed fuel based on an exhaust air / fuel ratio detected by the air / fuel ratio detecting means and an injection amount of the reformed fuel;
And a reforming control means for controlling the reforming apparatus based on the octane number estimated by the octane number estimating means and the oxidation reaction progress estimated by the oxidation reaction progress estimating means. Control device for internal combustion engine. The reforming control means includes
When the oxidation reaction progress estimated by the oxidation reaction progress estimation means is larger than a predetermined target oxidation reaction progress, the flow rate of fuel supplied to the reformer is increased,
2. The flow rate of fuel supplied to the reformer is reduced when the oxidation reaction progress estimated by the oxidation reaction progress estimation means is smaller than the target oxidation reaction progress. The control apparatus of the internal combustion engine described in 1. The reforming control means includes
When the oxidation reaction progress estimated by the oxidation reaction progress estimation means is larger than a predetermined target oxidation reaction progress, the temperature of the reformer is decreased,
2. The internal combustion engine according to claim 1, wherein when the oxidation reaction progress degree estimated by the oxidation reaction progress degree estimation means is smaller than the target oxidation reaction progress degree, the temperature of the reformer is increased. Engine control device. The reforming control means includes
When the oxidation reaction progress degree estimated by the oxidation reaction progress degree estimation means is within a predetermined range and the octane number estimated by the octane number estimation means is smaller than a predetermined optimum octane number, the reformer fails. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the reformer is stopped when it is determined that the engine is operating. The combustion fluctuation detecting means is a knock sensor,
5. The control apparatus for an internal combustion engine according to claim 1, wherein the air-fuel ratio detection means is an air-fuel ratio sensor.

Images