JP2005247672A - Fuel reformer and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reformer capable of precisely setting an air-fuel ratio of a hydrocarbon fuel and air of a reforming catalyst at a desired value and its operation method. <P>SOLUTION: An internal combustion engine 1 is equipped with a fuel reformer 20 where a gaseous mixture of a hydrocarbon fuel and air is reformed by a reforming catalyst, and ECU (electronic control unit) 30. The fuel reformer 20 has a reforming reaction part 23 in which a reforming catalyst is placed and a CO<SB>2</SB>sensor Sc detecting CO<SB>2</SB>concentration contained in a fluid flowing out from the reforming reaction part 23. ECU 30 controls a ratio of oxygen atom in air vs. carbon atom in the hydrocarbon fuel fed into the reforming reaction part 23, i.e. O/C, to be within a range from about 1 to a value slightly more than 1 by correcting the feeding amount of the hydrocarbon fuel to the reforming reaction part 23 so that the CO<SB>2</SB>concentration detected by the CO<SB>2</SB>sensor Sc is within a specified range. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel reformer having a reforming catalyst and reforming a mixture of hydrocarbon fuel and air by the reforming catalyst, and an operation method thereof.

2. Description of the Related Art Conventionally, an internal combustion engine having a reformer that reforms a mixture of a hydrocarbon fuel and air to generate a reformed gas containing a predetermined fuel component (for example, CO or H ₂ ) is known. (For example, refer to Patent Document 1). In this internal combustion engine, in order to increase the yield of fuel components (CO and H ₂ ) in the reformed gas, reforming is performed when the temperature of the reforming catalyst of the reformer reaches a predetermined temperature (600 ° C.). The air-fuel ratio of fuel and air in the catalyst is set to around 5. In addition, in a reformer applied to this type of internal combustion engine, deterioration of the reforming performance due to catalyst deterioration is prevented, generation of by-products is suppressed, and the influence of heat around the reformer is reduced. Therefore, it is also important to appropriately manage the temperature of the reforming catalyst (catalyst bed temperature). Therefore, as a method for controlling the temperature of the reforming catalyst, the air-fuel ratio in the reforming catalyst is controlled using the correlation between the air-fuel ratio of the fuel and air supplied to the reforming catalyst and the temperature reached by the reforming catalyst. Thus, a technique for appropriately setting the temperature of the reforming catalyst is also known (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 9-21362 JP 2002-1790405 A

  As described above, in order to increase the yield of the fuel component in the reformed gas, it is preferable to set the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst around 5 which is the theoretical air-fuel ratio. It is not always easy to accurately set the air-fuel ratio in the reforming catalyst to a desired value. In this case, it is conceivable to set the air-fuel ratio in the reforming catalyst based on the temperature of the reforming catalyst using the correlation between the air-fuel ratio in the reforming catalyst and the temperature reached by the reforming catalyst.

  However, the temperature of the reforming catalyst is affected by the temperature of the supplied air and fuel and the components of the supplied fuel. Further, when the air-fuel ratio in the reforming catalyst is in the vicinity of the stoichiometric air-fuel ratio (approximately 5), the reforming catalyst once activated, although the temperature of the reforming catalyst dynamically changes nonlinearly with respect to the air-fuel ratio. Because the temperature does not change much even if the air-fuel ratio of fuel and air deviates from the stoichiometric air-fuel ratio, the air-fuel ratio of fuel and air in the reforming catalyst is dynamically set based on the temperature of the reforming catalyst. Have difficulty.

  Accordingly, an object of the present invention is to provide a fuel reforming apparatus and an operating method thereof capable of accurately setting the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst to desired values.

A fuel reforming apparatus according to the present invention includes a reforming catalyst, and the reforming catalyst includes a reforming catalyst, and the reforming catalyst includes a fluid that flows out of the reforming catalyst. Concentration detecting means for detecting the concentration of at least one of CO ₂ and H ₂ O, and control means for setting the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst based on the detection value of the concentration detecting means; It is characterized by providing.

In general, when hydrocarbon fuel and air are reacted with a reforming catalyst and a partial oxidation reaction proceeds to obtain a fuel component, in the air with respect to carbon atoms in the hydrocarbon fuel supplied to the reforming catalyst When the oxygen atom ratio O / C is close to an appropriate value (approximately 1), the concentration of CO ₂ and H ₂ O in the fluid flowing out of the reforming catalyst changes almost linearly with respect to the O / C. To do. On the other hand, since the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst slightly exceeds 1, oxygen is excessive and a complete oxidation reaction proceeds. The concentration of CO ₂ and H ₂ O in the fluid flowing out of the reforming catalyst is significantly increased.

In view of these points, in the fuel reformer of the present invention, the concentration of at least one of CO ₂ and H ₂ O contained in the fluid flowing out of the reforming catalyst is detected, and reforming is performed based on the concentration. The air-fuel ratio of the hydrocarbon fuel and air in the catalyst is set (corrected). That is, based on the above characteristics, the O / C is appropriately adjusted by correcting the amount of hydrocarbon fuel and air supplied to the reforming catalyst so that the concentration detected by the concentration detecting means is within a predetermined range. It can be kept near 1 which is a small value. Since the concentration of CO ₂ or H ₂ O contained in the fluid that has flowed out of the reforming catalyst immediately reflects the reaction status in the reforming catalyst, if the concentration is used, it depends on the reaction status in the reforming catalyst. In addition, appropriate air-fuel ratio control can be executed. As a result, in the fuel reformer of the present invention, it is possible to accurately set the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst to desired values.

  In this case, the control unit corrects at least one of the supply amount of the hydrocarbon-based fuel and air to the reforming catalyst so that the concentration detected by the concentration detection unit is within the predetermined range, and the predetermined range is When the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is determined to fall within a range from about 1 to a value slightly higher than 1. preferable.

  Thus, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is included in a range from approximately 1 to a value slightly exceeding 1. By doing so, it becomes possible to reduce the unreformed fuel in the fuel reformer.

  Further, the control means increases the supply amount of hydrocarbon fuel to the reforming catalyst or supplies air to the reforming catalyst when the concentration detected by the concentration detection means falls within the predetermined range. It is preferable to reduce the amount.

  That is, when the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is included in a range from about 1 to a value slightly higher than 1, Furthermore, by slightly increasing the amount of hydrocarbon fuel supplied to the reforming catalyst or slightly decreasing the amount of air supplied to the reforming catalyst, the O / C in the reforming catalyst is further increased by 1. It becomes possible to approach. Thereby, the amount of fuel supplied to the fuel reformer can be made appropriate.

  Furthermore, the fuel reforming apparatus according to the present invention preferably further comprises means for determining that some abnormality has occurred in the apparatus when the concentration detected by the concentration detecting means is equal to or greater than a predetermined value.

An operation method of a fuel reformer according to the present invention includes a reforming catalyst, and the reforming catalyst is an operation method of a fuel reformer that reforms a mixture of hydrocarbon-based fuel and air by the reforming catalyst. And detecting the concentration of at least one of CO ₂ and H ₂ O contained in the fluid flowing out of the fuel, and setting the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst based on the concentration .

  According to the present invention, it is possible to realize a fuel reforming apparatus and an operation method thereof capable of accurately setting the air-fuel ratio of hydrocarbon fuel and air in a reforming catalyst to desired values.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing an internal combustion engine provided with a fuel reformer according to a first embodiment of the present invention. The internal combustion engine 1 shown in the figure is preferably used as a driving source for driving a vehicle, for example. The internal combustion engine 1 generates power by burning an air-fuel mixture containing a fuel component inside a combustion chamber 3 formed in the cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Although only one cylinder is shown in FIG. 1, the internal combustion engine 1 of the present embodiment is configured as a multi-cylinder engine.

The intake port of each combustion chamber 3 is connected to an intake pipe 5 a constituting the intake manifold 5, and the exhaust port of each combustion chamber 3 is connected to an exhaust pipe 6 a constituting the exhaust manifold 6. In addition, an intake valve Vi that opens and closes the intake port and an exhaust valve Ve that opens and closes the exhaust port are disposed in the cylinder head of the internal combustion engine 1 for each combustion chamber 3. Each intake valve Vi and each exhaust valve Ve are opened and closed by, for example, a valve mechanism 7 having a variable valve timing function or the like. Further, a spark plug 8 is provided for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. The exhaust manifold 6 is provided with an exhaust air-fuel ratio sensor (O ₂ sensor) SAF for detecting the air-fuel ratio of the exhaust gas from each combustion chamber 3. The exhaust manifold 6 is connected to a front catalyst device 9a and a rear catalyst device 9b as exhaust gas purification devices each including an exhaust gas purification catalyst.

  As shown in FIG. 1, each intake pipe 5 a constituting the intake manifold 5 is connected to a surge tank 10, and an air supply pipe L <b> 1 is connected to the surge tank 10. The intake manifold 5 (each intake pipe 5a), the surge tank 10, and the supply pipe L1 constitute an intake path of the internal combustion engine 1. The air supply pipe L1 is connected to an air intake port (not shown) via the air cleaner 11, and a throttle valve (in the present embodiment, electronic control) is provided in the middle of the air supply pipe L1 (between the surge tank 10 and the air cleaner 11). Type throttle valve) 12 is incorporated. The surge tank 10 is provided with a pressure sensor SP, and the pressure sensor SP detects the internal pressure of the surge tank 10.

  Further, a first air flow meter AFM1 is installed in the supply pipe L1 so as to be positioned between the air cleaner 11 and the throttle valve 12. A bypass pipe (reformed air supply path) L2 is branched from the supply pipe L1 at a branching portion BP defined between the throttle valve 12 and the first air flow meter AFM1 (upstream side of the throttle valve 12). Yes. The bypass pipe L2 includes an air pump AP, a second air flow meter AFM2, a flow rate adjustment valve 14 and an on-off valve 15 in this order from the branching part BP side, and its tip (on the side opposite to the end part on the branching part BP side). The end portion is connected to the fuel reformer 20. The arrangement order of the air pump AP, the second air flow meter AFM2, the flow rate adjustment valve 14 and the on-off valve 15 is not limited to this order, and the air pump AP is arranged upstream of the flow rate adjustment valve 14 and the on-off valve 15. If so, the other orders can be determined arbitrarily.

  The fuel reformer 20 has a substantially cylindrical main body 21 whose both ends are closed. Inside the main body 21, an air / fuel mixing unit 22 to which the above-described bypass pipe L2 is connected, and an air / fuel mixing unit 22 are provided. And a reforming reaction section 23 adjacent to. In addition to the bypass pipe L2, the reforming fuel injection valve 16 is connected to the air-fuel mixing unit 22. The reforming fuel injection valve 16 is connected to a fuel tank 18 via a fuel pump 17 and can inject hydrocarbon-based fuel (liquid fuel) such as gasoline into the air-fuel mixing unit 22. In the reforming reaction section 23, for example, a reforming catalyst in which rhodium is supported on zirconia is disposed, and an electric preheater 24 for preheating the reforming catalyst is disposed.

Further, a reformed fuel distribution chamber 25 is defined in the main body 21 on the downstream side of the reforming reaction section 23. A base end of a reformed fuel supply pipe 26 is connected to the reformed fuel distribution chamber 25, and a tip end side of the reformed fuel supply pipe 26 is branched toward each combustion chamber 3. A reformed fuel supply nozzle 27 is attached to each tip of the reformed fuel supply pipe 26, and each reformed fuel supply nozzle 27 is disposed in the vicinity of the corresponding intake port of the combustion chamber 3. A plurality of reformed fuel supply pipes 26 may be provided for each combustion chamber 3 so as to communicate each reformed fuel supply nozzle 27 and the reformed fuel distribution chamber 25 individually. The internal combustion engine 1 also has a heat exchanger 28 for cooling the reformed fuel in the reformed fuel supply pipe 26. As the cooling medium of the heat exchanger 28, for example, engine cooling water is used. Further, the reformed fuel distribution chamber 25 of the fuel reformer 20 is provided with a CO ₂ sensor Sc for detecting the CO ₂ concentration of the fluid inside. As the CO ₂ sensor Sc, an infrared light sensor, a semiconductor sensor, or the like can be employed.

  In addition, the internal combustion engine 1 has a normal fuel injection valve 160 provided in each intake pipe 5a (each intake port), and the fuel reformer 20 is operated, or the fuel reformer 20 In a state where the supply of air and fuel to the engine is stopped, hydrocarbon fuel such as gasoline pumped by the fuel pump 17 from each normal fuel injection valve 160 is injected into each intake pipe 5a (intake port). It is possible to obtain The normal fuel injection valve 160 may directly inject hydrocarbon-based fuel into the corresponding combustion chamber 3.

  FIG. 2 is a control block diagram of the internal combustion engine 1 described above. As shown in the figure, the internal combustion engine 1 has an electronic control unit (hereinafter referred to as “ECU”) 30 that functions as a control means. The ECU 30 includes a CPU, a ROM, a RAM, an input / output port, and a memory in which various information and maps are stored. The input / output port of the ECU 30 includes the valve operating mechanism 7, the ignition plug (igniter) 8, the throttle valve 12, the flow rate adjusting valve 14, the on-off valve 15, the reforming fuel injection valve 16, and the normal fuel injection valve. 160, an electric preheater 24, an air pump AP, and a starter 19 and the like are appropriately connected via a control circuit or the like.

Further, the input and output ports of the ECU 30, various sensors, namely an air flow meter AFM1 and AFM2 above, CO ₂ sensor Sc, a pressure sensor SP, form exhaust air-fuel ratio sensor SAF and the like are connected. The first air flow meter AFM1 detects the total flow rate of air taken into the supply pipe L1 from the air intake port (total amount of air supplied to all the combustion chambers 3), and gives a signal indicating the detected value to the ECU 30. The second air flow meter AFM2 detects the flow rate of the air flowing through the bypass pipe L2, and gives a signal indicating the detected value to the ECU 30. The CO ₂ sensor Sc, the pressure sensor SP, and the exhaust air / fuel ratio sensor SAF also each provide a signal indicating the detected value to the ECU 30.

  Further, an ignition switch 31, an accelerator position sensor 32, a crank angle sensor 33, a water temperature sensor SW, a shift position sensor SSP, and the like are connected to an input / output port of the ECU 30. The accelerator position sensor 32 gives a signal indicating the amount of depression of an accelerator pedal (not shown) to the ECU 30, the crank angle sensor 33 gives a signal showing the crank angle of the internal combustion engine 1 to the ECU 30, and the water temperature sensor SW is used for the internal combustion engine 1. A signal indicating the temperature of the cooling water flowing through the cooling system is provided to the ECU 30, and the shift position sensor SSP provides the ECU 30 with a signal indicating the shift position of the transmission (not shown). The ECU 30 determines the degree of opening of the throttle valve 12 and the flow rate adjustment valve 14 and the reforming fuel injection valve based on signals from the air flow meters AFM1, AFM2, the accelerator position sensor 32, the crank angle sensor 33, the shift position sensor SSP, and the like. 16, the fuel injection amount by the normal fuel injection valve 160, the ignition timing by the spark plug 8, the opening / closing timing of the intake valve Vi and the exhaust valve Ve, and the like are controlled.

When the internal combustion engine 1 described above is operated under predetermined conditions, such as when the engine is started or when the load is low, for example, an air pump AP controlled by the ECU 30 with respect to the air / fuel mixing unit 22 of the fuel reformer 20 Air is introduced through the bypass pipe L2 including the flow rate adjusting valve 14 and the like, and a hydrocarbon-based fuel such as gasoline is injected from the reforming fuel injection valve 16 controlled by the ECU 30. A hydrocarbon-based fuel such as gasoline is vaporized in the air-fuel mixing unit 22, mixed with air from the bypass pipe L 2, and flows into the reforming reaction unit 23. In the reforming reaction section 23, the hydrocarbon-based fuel and air are reacted by the reforming catalyst, and a partial oxidation reaction represented by the following formula (1) proceeds.
C _m H _n + (m / 2) O ₂ → mCO + (n / 2) H ₂ (1)

Then, as the reaction of the above formula (1) proceeds, a reformed gas (reformed fuel) containing CO and H ₂ as fuel components is generated, and the obtained reformed gas is supplied to the fuel reformer 20. To the intake port of each combustion chamber 3 through the reformed fuel supply pipe 26 and the reformed fuel supply nozzle 27. Air is introduced into the intake port of each combustion chamber 3 via the throttle valve 12 of the supply pipe L1 whose opening is adjusted by the ECU 30. Therefore, the reformed gas introduced from the fuel reformer 20 into each intake port is further mixed with air and then sucked into each combustion chamber 3. When each spark plug 8 is ignited at a predetermined timing, the fuel components CO and H ₂ burn in each combustion chamber 3 to reciprocate the piston 4. Power can be obtained.

By the way, as described above, when the internal combustion engine 1 is operated using the reformed gas, the reforming reaction is performed so that the reforming reaction in the fuel reformer 20 proceeds well and a desired fuel component is obtained. It is necessary to keep the reforming efficiency in the section 23 high. Further, the reforming efficiency in the reforming reaction section 23 has a correlation with the air-fuel ratio of the hydrocarbon fuel and air in the reforming reaction section 23 (reforming catalyst), and CO and H in the reformed gas are correlated. _In order to increase the yield (reforming efficiency) of the fuel component such as _2, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel in the reforming reaction section 23 should be set to around 1. Is preferred.

On the other hand, when a fuel component is obtained by reacting a hydrocarbon-based fuel and air with a reforming catalyst and advancing the partial oxidation reaction of the above formula (1), in the hydrocarbon-based fuel supplied to the reforming catalyst When the ratio O / C of oxygen atoms in the air to carbon atoms is in the vicinity of 1 which is an appropriate value (for example, in the range from 1.0 to the value a in FIG. 3), in the fluid that has flowed out of the reforming catalyst As shown in FIG. 3, the concentrations of CO ₂ and H ₂ O vary substantially linearly with respect to O / C. In addition, since the O / C slightly exceeds 1 (for example, from O / C = 1.05), oxygen is excessive and, for example, the following complete oxidation reaction (2) proceeds, and FIG. As shown, the concentration of CO ₂ and H ₂ O in the fluid flowing out of the reforming catalyst is significantly increased.
CH _{1.869 +} 1.467 · O ₂ → CO ₂ + 0.935 · H ₂ O +596.5 [kJ] (2)

  In view of these points, in the fuel reformer 20 of the present embodiment, the reforming control shown in FIG. 4 is performed by the ECU 30 as the control means in order to set the O / C in the reforming reaction unit 23 to around 1. The routine is executed. In this case, the ECU 30 first checks the value of the operating condition flag (S10), and if the operating condition flag is “0”, the operating condition of the internal combustion engine 1 (for example, based on the detected value of the accelerator position sensor 32 or the like) , Target torque) is read (S12). Further, the ECU 30 obtains an air supply amount (hereinafter referred to as “reformed air supply amount” as appropriate) to the fuel reformer 20 corresponding to the engine operating condition read in S12 using a predetermined map, The fuel injection amount from the reforming fuel injection valve 16 is calculated so that the O / C of the air-fuel mixture in the reforming reaction section 23 (reforming catalyst) becomes 1 in relation to the obtained reformed air supply amount. (S14).

  When the reformed air supply amount and the fuel injection amount are set in S14, the ECU 30 supplies the fuel reformer 20 with the amount of air determined in S14 and the amount of hydrocarbon fuel determined in S14. Thus, the flow rate adjusting valve 14 and the reforming fuel injection valve 16 are controlled (S16). Prior to the processing of S16, the ECU 30 sets the air-fuel ratio of the air-fuel mixture sucked into each combustion chamber 3 to a desired value in consideration of the reformed air supply amount and the fuel injection amount determined in S14. Is calculated according to the engine operating conditions read in S12. In S16, in addition to the flow rate adjustment valve 14 and the reforming fuel injection valve 16, the throttle valve 12 is opened. Also control the degree.

After the process of S16, the ECU 30 is included in the reformed gas that has flowed out of the reforming catalyst, that is, from the reforming reaction section 23 to the reformed fuel distribution chamber 25, based on the signal from the CO ₂ sensor Sc. get the concentration V of CO ₂ that is (S18), first, it is determined whether the CO ₂ concentration V is smaller than the threshold value _{V HH} predetermined (S20). The threshold value V _HH is the CO ₂ concentration in the reformed gas when O / C is sufficiently larger than 1 (see FIG. 3), and it is determined in S20 that the CO ₂ concentration V is _{equal to} or higher than the threshold value V _HH. In such a case, it is assumed that some trouble has occurred in the fuel reformer 20. For this reason, if the ECU 30 makes a negative determination in S20, the ECU 30 regards the fuel reformer 20 as having some sort of failure and generates an alarm by turning on a predetermined warning lamp (not shown). (S21), the reforming control routine is temporarily terminated. In this way, if the characteristics shown in FIG. 3 are used, the failure determination of the fuel reformer 20 can be executed based on the CO ₂ concentration V in the reformed gas.

When it is determined in S20 that the CO ₂ concentration V is lower than the threshold value V _HH (when an affirmative determination is made in S20), the ECU 30 further determines the CO ₂ concentration V acquired in S18 as a predetermined threshold value. It is determined whether or not it is equal to or higher than _VL (S22). In the present embodiment, as shown in FIG. 3, the threshold value V _L has a ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst of 1. The concentration of CO ₂ in the reformed gas in the case of 0.0. When it is determined in S22 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , the ECU 30 determines whether or not the CO ₂ concentration V acquired in S18 exceeds a predetermined threshold value V _H ( S24). In the present embodiment, the value of the threshold value V _H is the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst, as shown in FIG. The concentration of CO _{2 in} the reformed gas when a (a> 1.0, for example, a = 1.02 to 1.03) is used.

Here, when it is determined in S22 that the CO ₂ concentration V is lower than the threshold _VL , the fuel injection amount to the reforming reaction unit 23 is excessive or the reformed air supply amount is insufficient. As a result, O / C in the reforming reaction section 23 is less than 1.0 (the interior of the reforming reaction section 23 is rich). Therefore, when the ECU 30 makes a negative determination in S22, the ECU 30 corrects the fuel injection amount from the reforming fuel injection valve 16 to be decreased by a predetermined amount ΔF (where ΔF is a positive predetermined value). An amount (−ΔF) is set (S26). In S26, the correction amount may be set so as to decrease the reformed air supply amount by a predetermined amount.

If it is determined in S22 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , and if it is determined in S24 that the CO ₂ concentration V exceeds a predetermined threshold value V _H , the reforming reaction is performed. O / C in the reforming reaction unit 23 exceeds the value a because the fuel injection amount to the unit 23 is insufficient or the reforming air supply amount is excessive (inside the reforming reaction unit 23) Is too lean). Therefore, when an affirmative determination is made in S24, the ECU 30 sets a correction amount (+ ΔF) so as to increase the fuel injection amount from the reforming fuel injection valve 16 by a predetermined amount ΔF (S28). In S28, the correction amount may be set so that the reformed air supply amount is increased by a predetermined amount.

On the other hand, if it is determined in S22 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , and it is determined in S24 that the CO ₂ concentration V is equal to or lower than the predetermined threshold value V _H , the reforming reaction unit 23 is performed. The fuel injection amount and the reformed air supply amount are generally appropriate, and the O / C in the reforming reaction section 23 is included in the range from 1.0 to the value a. In this case, basically, the O / C in the reforming reaction section 23 is kept near 1 which increases the yield (reforming efficiency) of the fuel component in the reformed gas. Is in the range of 1.0 to the value a, it becomes a slight oxygen excess state (lean state).

  Therefore, in this embodiment, when the ECU 30 makes a negative determination in S24, the ECU 30 sets a correction amount (ΔFm) for making the O / C in the reforming reaction unit 23 closer to 1.0 (S30). . In the present embodiment, for example, a map that defines the amount of increase in the fuel injection amount as the correction amount (ΔFm) according to the rotational speed of the internal combustion engine 1 and the intake air amount (detected value of the first air flow meter AFM1) is stored in the ECU 30. The ECU 30 reads the correction amount (ΔFm) from this map at S30.

  Note that the map used in S30 may define the ratio of the fuel increase amount to the fuel injection amount at that time according to, for example, the rotational speed of the internal combustion engine 1 and the intake air amount. In addition, the map used in S30 specifies a reduction amount of the reformed air supply amount or a ratio of the reduction amount to the reformed air supply amount at that time according to, for example, the rotational speed of the internal combustion engine 1 and the intake air amount. It may be.

  After the process of S26, S28 or S30 described above, the ECU 30 determines whether or not the engine operating conditions such as the target torque have changed based on signals from various sensors (S32). Then, only when it is determined in S32 that the engine operating condition has not changed, the ECU 30 sets the above-described operating condition flag to “1” (S34), and executes the above-described processing after S10 again. .

  When the process after S10 is executed again, if the switching start flag is “1” (when it is determined that the operation condition flag is not “0” in S10), the processes of S12 and S14 are skipped. Is done. When the processing after S10 is executed again, if the correction amount (−ΔF) is set in S26, in the next S16, the amount obtained by subtracting ΔF from the set fuel injection amount. When the hydrocarbon fuel is injected from the reforming fuel injection valve 16 and the correction amount (+ ΔF) is set in S28, in the next S16, an amount obtained by adding ΔF to the set fuel injection amount. Hydrocarbon fuel is injected from the reforming fuel injection valve 16.

That is, in the fuel reforming apparatus 20 according to the present invention, in light of the characteristics described in connection with FIG. 3, CO ₂ concentration V detected by the CO ₂ sensor Sc is included in the range from V _L to V _H Thus, the amount of hydrocarbon fuel supplied to the reforming reaction section 23 is corrected. Thereby, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is accurately within a range from about 1 to a value a slightly exceeding 1. It becomes possible to set.

As a result, in the fuel reformer 20, it is possible to maintain the reforming efficiency in the reforming reaction unit 23 well and to reduce the unreformed fuel in the fuel reformer 20. The concentration of CO ₂ or H ₂ contained in the reformed gas that has flowed out of the reforming catalyst, since it immediately reflects the reaction conditions in the reforming catalyst, the use of the CO ₂ concentration V, the reaction of the reforming catalyst Appropriate air-fuel ratio control according to the situation can be executed. Furthermore, since the temperature of the reforming catalyst rises abruptly when the O / C exceeds about 1.05, for example, as described above, the value of the reforming catalyst is slightly higher than about 1 to 1. By keeping within the range up to a, it is possible to suppress an excessive temperature rise of the reforming catalyst.

In the present embodiment, when it is determined that the CO ₂ concentration V is included in the range from _VL to _VH, and the correction amount (ΔFm) is set in S30, it is set in the next S16. An amount of hydrocarbon fuel obtained by adding ΔFm to the fuel injection amount is injected from the reforming fuel injection valve 16. As described above, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is included in a range from approximately 1 to a value a slightly exceeding 1. If so, the O / C in the reforming reaction section 23 can be made closer to 1.0 by slightly increasing the amount of hydrocarbon fuel supplied to the reforming reaction section 23. Thereby, the fuel supply amount with respect to the fuel reformer 20 can be made appropriate.

Instead of providing the CO ₂ sensor Sc in the reformed fuel distribution chamber 25, an H ₂ O sensor may be installed. In other words, if use of the connection with the described characteristics in FIG. 3, to detect the concentration of H _{2 O} contained in the reformed gas that has flowed out of the reforming catalyst by H 2 _O sensors, based in H 2 _O concentration It is also possible to set (correct) the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst. The method of setting the thresholds V _L and V _H is not limited to the above example, and can be arbitrarily determined within a range where O / C in the reforming reaction unit 23 is in the vicinity of 1.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

FIG. 5 is a flowchart for explaining another reforming control routine that can be executed in the fuel reforming apparatus 20 described above. Even when the reforming control routine shown in FIG. 5 is executed, the ECU 30 first checks the value of the operating condition flag (S40). If the operating condition flag is “0”, the ECU 30 detects the accelerator position sensor 32 or the like. Based on the value, the operating condition (for example, target torque) of the internal combustion engine 1 is read, and the value ΔF _TOT obtained by integrating the correction amount ΔF of the fuel injection amount from the reforming fuel injection valve 16 is reset (S42).

  Further, the ECU 30 obtains the reformed air supply amount corresponding to the engine operating condition read in S42 by using a predetermined map, and the reforming reaction unit 23 ( The fuel injection amount from the reforming fuel injection valve 16 is calculated so that the O / C of the air-fuel mixture in the reforming catalyst) becomes 1 (S44). Then, the ECU 30 controls the flow rate adjusting valve 14 and the reforming fuel injection valve so that the amount of air determined in S44 and the amount of hydrocarbon fuel determined in S44 are supplied to the fuel reformer 20. 16 is controlled (S46). In S46, the ECU 30 also controls the opening of the throttle valve 12 so that the air-fuel ratio of the air-fuel mixture sucked into each combustion chamber 3 becomes a desired value.

After the processing of S46, the ECU 30 is included in the reformed gas flowing out from the reforming catalyst, that is, from the reforming reaction section 23 to the reformed fuel distribution chamber 25, based on the signal from the CO ₂ sensor Sc. The obtained CO ₂ concentration V is acquired (S48), and it is determined whether or not the acquired CO ₂ concentration V is equal to or higher than a predetermined threshold _VL (S50). Also in the present embodiment, as shown in FIG. 3, the value of the threshold value V _L is the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst. The concentration of CO ₂ in the reformed gas is 1.0.

Further, when it is determined in S50 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , the ECU 30 determines whether or not the CO ₂ concentration V acquired in S48 exceeds a predetermined threshold value V _H ( S52). Also in the present embodiment, as shown in FIG. 3, the value of the threshold value V _H is equal to the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst. The value a (a> 1.0, for example, a = 1.02 to 1.03) is used as the concentration of CO _{2 in} the reformed gas.

In this embodiment, when it is determined in S50 that the CO ₂ concentration V is lower than the threshold value _VL , the fuel injection amount to the reforming reaction unit 23 is excessive, or the reformed air supply amount is Due to the shortage, O / C in the reforming reaction section 23 is less than 1.0 (the interior of the reforming reaction section 23 is rich). Therefore, if the ECU 30 makes a negative determination in S50, the ECU 30 corrects the fuel injection amount from the reforming fuel injection valve 16 so as to decrease by a predetermined amount ΔF (where ΔF is a positive predetermined value). The amount (−ΔF) is set, and the integration process of the correction amount ΔF such that ΔF _TOT = ΔF _TOT −ΔF is executed (S54).

Further, if it is determined in S50 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , and it is determined in S52 that the CO ₂ concentration V exceeds the predetermined threshold value V _H , the reforming reaction is performed. O / C in the reforming reaction unit 23 exceeds the value a because the fuel injection amount to the unit 23 is insufficient or the reforming air supply amount is excessive (inside the reforming reaction unit 23) Is too lean). Therefore, when the ECU 30 makes an affirmative determination in S52, the ECU 30 sets the correction amount (+ ΔF) so as to increase the fuel injection amount from the reforming fuel injection valve 16 by a predetermined amount ΔF, and ΔF _TOT = Integration processing of the correction amount ΔF, which is ΔF _TOT + ΔF, is executed (S56).

Further, when it is determined in S50 that the CO ₂ concentration V is equal to or higher than the threshold value _VL , and in S52, when it is determined that the CO ₂ concentration V is equal to or lower than the predetermined threshold value V _H , the ECU 30 A correction amount (ΔFm) for setting the O / C at 23 closer to 1.0 is set (S58). Also in the present embodiment, for example, a map that defines the amount of increase in the fuel injection amount as the correction amount (ΔFm) according to the rotational speed of the internal combustion engine 1 and the intake air amount is stored in the storage device of the ECU 30, and in S30 The ECU 30 reads the correction amount (ΔFm) from this map.

In the present embodiment, when the process of S54 or S56 is executed, the ECU 30 determines whether or not the absolute value of the integrated value ΔF _TOT of the correction amount ΔF exceeds a predetermined value α (S58). Here, the fact that the absolute value of ΔF _TOT exceeds the predetermined value α means that the O / C in the reforming reaction section 23 is predetermined even if either increase correction or decrease correction of hydrocarbon fuel is performed to some extent. This means that it does not fall within the range (in this embodiment, the range from 1.0 to the value a), so it is assumed that there is a high possibility that some trouble has occurred in the fuel reformer 20. . For this reason, if the ECU 30 makes an affirmative determination in S60, the ECU 30 considers that a failure has occurred in the fuel reformer 20, and generates an alarm by turning on a predetermined warning lamp (not shown). (S62), the reforming control routine is temporarily terminated. As described above, the failure determination of the fuel reformer 20 is executed based on the integrated value ΔF _TOT of the correction amount ΔF for setting the air-fuel ratio (O / C) of the hydrocarbon fuel and air in the reforming catalyst. May be.

  When a negative determination is made in S60, or after the processing of S30, the ECU 30 determines whether or not the engine operating conditions such as the target torque have changed based on signals from various sensors (S64). The ECU 30 sets the above-mentioned operating condition flag to “1” only when it is determined in S64 that the engine operating condition has not changed (S66), and executes the processes after S40 described above again. .

  When the process after S40 is executed again, if the switching start flag is set to “1”, the processes of S42 and S44 are skipped. When the processing after S40 is executed again, if the correction amount (−ΔF) is set in S54, in the next S46, the amount obtained by subtracting ΔF from the set fuel injection amount. When the hydrocarbon fuel is injected from the reforming fuel injection valve 16 and the correction amount (+ ΔF) is set in S56, in the next S46, an amount obtained by adding ΔF to the set fuel injection amount. Hydrocarbon fuel is injected from the reforming fuel injection valve 16. Thereby, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is accurately within a range from about 1 to a value a slightly exceeding 1. The reforming reaction unit 23 can maintain good reforming efficiency, suppress excessive temperature rise of the reforming catalyst, and reduce unreformed fuel in the fuel reformer 20. it can.

  Further, in the present embodiment, when the correction amount (ΔFm) is set in S58, in the next S46, an amount of hydrocarbon fuel obtained by adding ΔFm to the set fuel injection amount is the reforming fuel. The fuel is injected from the injection valve 16. As a result, the O / C in the reforming reaction section 23 can be made closer to 1.0, and the amount of fuel supplied to the fuel reformer 20 can be made appropriate. In this embodiment, the correction amount may be set to decrease the reformed air supply amount by a predetermined amount in S54, and the correction amount is set to increase the reformed air supply amount by a predetermined amount in S56. May be. Then, the correction amount of the reformed air supply amount may be integrated in S54 or S56, and the failure determination of the fuel reformer 20 may be executed based on the integrated value.

Further, the integrated value ΔF _TOT of the correction amount ΔF used in S42, S54, S56 and S60 in FIG. 5 is the air-fuel ratio (O / C) of the hydrocarbon-based fuel and air in the reforming catalyst, as shown in FIG. ) May be replaced with the integrated value n of the set number of times. That is, in the reforming control routine of FIG. 6, when the ECU 30 sets the correction amount (−ΔF) so as to decrease the fuel injection amount from the reforming fuel injection valve 16 by the predetermined amount ΔF in S55, At the same time, the correction value integrated value n is decremented by one. In S57, the ECU 30 sets the correction amount (+ ΔF) so as to increase the fuel injection amount from the reforming fuel injection valve 16 by a predetermined amount ΔF. Increment.

  Then, after the process of S55 or S57, the ECU 30 determines in S61 whether or not the absolute value of the integrated value n of the number of corrections exceeds a predetermined value β. Here, that the integrated value n of the number of corrections exceeds the predetermined value β means that the O / O in the reforming reaction unit 23 is maintained even if the increase or decrease of the hydrocarbon-based fuel is performed a certain number of times. This means that C does not fall within a predetermined range (in the present embodiment, a range from 1.0 to value a), and therefore it is highly likely that some trouble has occurred in the fuel reformer 20. is assumed. For this reason, if the ECU 30 makes an affirmative determination in S61, the ECU 30 considers that a failure has occurred in the fuel reformer 20, and generates an alarm by turning on a predetermined warning lamp (not shown). (S62), the reforming control routine is temporarily terminated.

  Even if such a reforming control routine of FIG. 6 is employed, the same operation and effect as when the reforming control routine of FIG. 5 is employed can be obtained. In the reforming control routine of FIG. 6, when it is determined in S40 that the operating condition flag is “0”, the correction value integrated value n is reset along with the reading of the engine operating condition. (S43).

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 7 is a flowchart for explaining yet another reforming control routine that can be executed in the fuel reforming apparatus 20 described above. When the reforming control routine shown in FIG. 7 is executed, the ECU 30 first checks the value of the operating condition flag (S100), and if the operating condition flag is “0”, the detected value of the accelerator position sensor 32 or the like. Based on the operation condition (for example, target torque) of the internal combustion engine 1 is read (S102). Further, the ECU 30 obtains the reformed air supply amount corresponding to the engine operating condition read in S102 by using a predetermined map, and the reforming reaction unit 23 ( The fuel injection amount from the reforming fuel injection valve 16 is calculated so that the O / C of the air-fuel mixture in the reforming catalyst) becomes 1 (S104).

Then, the ECU 30 controls the flow rate adjusting valve 14 and the reforming fuel injection valve so that the amount of air determined in S104 and the amount of hydrocarbon fuel determined in S104 are supplied to the fuel reformer 20. 16 is controlled (S106). In S106, the ECU 30 also controls the opening degree of the throttle valve 12 so that the air-fuel ratio of the air-fuel mixture sucked into each combustion chamber 3 becomes a desired value. After the process of S106, the ECU 30 is included in the reformed gas that has flowed out of the reforming catalyst, that is, from the reforming reaction section 23 to the reformed fuel distribution chamber 25, based on the signal from the CO ₂ sensor Sc. get the concentration V of CO ₂ that (S108), and determines whether the obtained CO ₂ concentration V is smaller than the threshold value _{V R} to a predetermined (S110). In the present embodiment, the threshold value V _R is, for example, when the ratio O / C of oxygen atoms in the air to carbon atoms of the hydrocarbon-based fuel supplied to the reforming catalyst is 1.0 The CO ₂ concentration in the reformed gas is used.

If S110 in CO ₂ concentration V is determined to be below the threshold value V _R, or the amount of fuel injected into the reformer 23 is excessive, or that the reforming air supply quantity is insufficient Thus, the O / C in the reforming reaction section 23 is less than 1.0 (the interior of the reforming reaction section 23 is rich). Therefore, when the ECU 30 makes an affirmative determination in S110, the ECU 30 corrects the fuel injection amount from the reforming fuel injection valve 16 so as to decrease by a predetermined amount ΔFS (where ΔFS is a positive predetermined value). An amount (−ΔFS) is set (S112).

On the other hand it, if the CO ₂ concentration V in S110 is determined to be equal to or larger than the threshold value V _R, or the amount of fuel injected into the reformer 23 is insufficient, or reforming air supply amount is excessive As a result, the O / C in the reforming reaction section 23 is 1.0 or more (the interior of the reforming reaction section 23 is lean). Therefore, if the ECU 30 makes a negative determination in S110, the ECU 30 corrects the fuel injection amount from the reforming fuel injection valve 16 to increase by a predetermined amount ΔFL (where ΔFL is a positive predetermined value). An amount (−ΔFL) is set (S114). Here, the correction amount ΔFS set in S112 to decrease the fuel injection amount from the reforming fuel injection valve 16 is set in S114 to increase the fuel injection amount from the reforming fuel injection valve 16. In this embodiment, for example, ΔFS = 3 × ΔFL.

  After the process of S112 or S114, the ECU 30 determines whether or not the engine operating conditions such as the target torque have changed based on signals from various sensors (S116). The ECU 30 sets the above-described operating condition flag to “1” only when it is determined in S11 that the engine operating condition has not fluctuated (S118), and again executes the processes after S100 described above. .

  When the processing after S100 is executed again, if the switching start flag is set to “1”, the processing of S102 and S104 is skipped. When the processing after S100 is executed again, if the correction amount (−ΔFS) is set in S112, in the next S106, an amount obtained by subtracting ΔFS from the set fuel injection amount. When the hydrocarbon fuel is injected from the reforming fuel injection valve 16 and the correction amount (+ ΔFL) is set in S114, in the next S106, an amount obtained by adding ΔFL to the set fuel injection amount. Hydrocarbon fuel is injected from the reforming fuel injection valve 16.

  In this case, since the correction amount ΔFS set in S112 is larger (the absolute value) than the correction amount ΔFL set in S114, the reforming reaction unit 23 is rich (O / C <1). In this case, the supply amount of the hydrocarbon-based fuel to the reforming reaction unit 23 is sufficiently increased, and it is reliably suppressed that the inside of the reforming reaction unit 23 remains in a rich state. Further, when the reforming reaction section 23 is lean (O / C> 1), the decrease in the amount of the hydrocarbon-based fuel supplied to the reforming reaction section 23 is relatively small. Is reliably suppressed from being made rich.

  Therefore, even if the reforming control routine of FIG. 7 is adopted, the ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is set to about 1 to 1. It is possible to accurately set within a range up to a value a slightly higher (a range in which the reforming reaction section 23 becomes slightly lean), maintaining a good reforming efficiency in the reforming reaction section 23, and reforming While suppressing an excessive temperature rise of the catalyst, the unreformed fuel in the fuel reformer 20 can be reduced.

1 is a schematic configuration diagram showing an internal combustion engine to which a fuel reformer according to a first embodiment of the present invention is applied. FIG. 2 is a control block diagram of the internal combustion engine of FIG. 1. It is a graph which shows the relationship between ratio O / C of the oxygen atom in the air with respect to the carbon atom in the hydrocarbon fuel supplied with respect to a reforming catalyst, and the density | concentration of each component in reformed gas. 3 is a flowchart for explaining a reforming control routine in the fuel reformer according to the first embodiment of the present invention. It is a flowchart for demonstrating the reforming control routine in the fuel reformer which concerns on 2nd Embodiment of this invention. 7 is a flowchart for explaining a modification of a reforming control routine in a fuel reformer according to a second embodiment of the present invention. It is a flowchart for demonstrating the reforming control routine in the fuel reformer which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Combustion chamber 12 Throttle valve 14 Flow control valve 15 On-off valve 16 Reforming fuel injection valve 160 Normal fuel injection valve 17 Fuel pump 18 Fuel tank 20 Fuel reformer 21 Main body 22 Air-fuel mixing part 23 Reforming reaction Unit 24 Electric preheater 25 Reformed fuel distribution chamber 26 Reformed fuel supply pipe 27 Reformed fuel supply nozzle Sc CO ₂ sensor

Claims (5)

In a fuel reformer having a reforming catalyst and reforming a mixture of hydrocarbon fuel and air with the reforming catalyst,
Concentration detecting means for detecting the concentration of at least one of CO ₂ and H ₂ O contained in the fluid flowing out of the reforming catalyst;
A fuel reformer comprising: control means for setting an air-fuel ratio of hydrocarbon-based fuel and air in the reforming catalyst based on a detection value of the concentration detection means.   The control means corrects at least one of the supply amount of hydrocarbon-based fuel and air to the reforming catalyst so that the concentration detected by the concentration detection means falls within a predetermined range, and the predetermined range is The ratio O / C of oxygen atoms in the air to carbon atoms in the hydrocarbon-based fuel supplied to the reforming catalyst is determined to be within a range of approximately 1 to a value slightly exceeding 1. The fuel reformer according to claim 1.   The control means increases the supply amount of hydrocarbon-based fuel to the reforming catalyst or the air to the reforming catalyst when the concentration detected by the concentration detection means falls within the predetermined range. The fuel reformer according to claim 2, wherein the supply amount of the fuel is reduced.   The apparatus according to any one of claims 1 to 3, further comprising means for determining that some abnormality has occurred in the apparatus when the concentration detected by the concentration detection means is a predetermined value or more. Fuel reformer. In a method for operating a fuel reformer having a reforming catalyst and reforming a mixture of hydrocarbon fuel and air with the reforming catalyst,
The concentration of at least one of CO ₂ and H ₂ O contained in the fluid flowing out of the reforming catalyst is detected, and the air-fuel ratio of the hydrocarbon fuel and air in the reforming catalyst is set based on the concentration. A method for operating a fuel reforming apparatus.

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