JP2018076798A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent inflow of HC from a heat and hydrogen generation device into an exhaust treatment catalyst.SOLUTION: An exhaust emission control device for an internal combustion engine includes an exhaust treatment catalyst (13) arranged in an engine exhaust passage, a heat and hydrogen generation device (50) capable of supplying heat only or heat and hydrogen into the exhaust treatment catalyst (13) for warming up the exhaust treatment catalyst (13), and a hydrocarbon adsorption device (82) capable of adsorbing hydrocarbon in combustion gas to be supplied from the heat and hydrogen generation device (50) into the exhaust treatment catalyst (13). At the time of the combustion of the hydrocarbon adsorbed to the hydrocarbon adsorption device (82), the combustion gas generated in the heat and hydrogen generation device (50) by complete oxidation reaction based on a lean air-fuel ratio is supplied to the hydrocarbon adsorption device (82).SELECTED DRAWING: Figure 1

Description

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

  A fuel gas supply device, a reforming catalyst for reforming the fuel gas supplied from the fuel gas supply device, and a reformed gas passage for supplying the reformed gas flowing out from the reforming catalyst into the exhaust pipe. A fuel reforming apparatus is known in which the exhaust treatment catalyst is warmed up by the reformed gas supplied into the exhaust pipe when the engine is started (see Patent Document 1). However, in such a fuel reformer, a large amount of unburned HC is contained in the reformed gas until the reforming catalyst is activated, and this large amount of unburned HC is released into the atmosphere. There is a risk. Therefore, in this fuel reformer, an adsorption passage in which the HC adsorbent is arranged is provided in the reformed gas passage, and the reformed gas flowing out from the reforming catalyst is sent into the adsorption passage until the reforming catalyst is activated. Thus, unburned HC contained in the reformed gas is adsorbed on the HC adsorbent.

JP 2009-137818 A

  On the other hand, in this HC adsorbent, when the temperature of the HC adsorbent reaches the adsorption HC desorption temperature, the adsorbed HC desorbs from the HC adsorbent. Therefore, in this fuel reformer, when the temperature of the HC adsorbent reaches the desorption temperature of the adsorbed HC, a part of the reformed gas flowing out of the reforming catalyst and flowing in the reformed gas passage is The reformed gas containing the separated HC is recirculated upstream of the reforming catalyst through the recirculation passage and the negative pressure control valve. Next, the detached HC contained in the reformed gas is combusted in the reforming catalyst and reused as fuel. As described above, this fuel reformer has an advantage that the HC released from the HC adsorbent can be reused as fuel, but the piping and flow path control device for reusing the HC released from the HC adsorbent. Is complicated and unsuitable for practical use.

  In order to solve the above problems, according to the present invention, it is possible to supply only heat or heat and hydrogen to the exhaust treatment catalyst disposed in the engine exhaust passage and to warm up the exhaust treatment catalyst. A heat and hydrogen generator, and the heat and hydrogen generator includes a reforming catalyst into which fuel and air combustion gas is sent. The heat and hydrogen generator performs a partial oxidation reaction. As a result, combustion gas containing hydrogen or combustion gas not containing hydrogen is generated by performing a complete oxidation reaction device under a lean air-fuel ratio, and further supplied from the hydrogen generator to the exhaust treatment catalyst. A hydrocarbon adsorbing device capable of adsorbing hydrocarbons in the combustion gas is provided, and when the hydrocarbon adsorbed or deposited on the hydrocarbon adsorbing device is burned, in the heat and hydrogen generating device, the lean air-fuel ratio is reduced. Supplying the generated combustion gas to hydrocarbon adsorber by complete oxidation reaction at.

  When the hydrocarbon adsorbed or deposited on the hydrocarbon adsorbing device is separated and burned, the heat and hydrogen generator need only perform a complete oxidation reaction with a lean air-fuel ratio. Without use, hydrocarbons can be released from the hydrocarbon adsorber and burned.

FIG. 1 is an overall view of an internal combustion engine. FIG. 2 is an overall view of the heat and hydrogen generator. FIG. 3 is a diagram for explaining a light oil reforming reaction. FIG. 4 is a graph showing the relationship between the reaction equilibrium temperature TB and the O ₂ / C molar ratio. FIG. 5 is a graph showing the relationship between the number of generated molecules per carbon atom and the O ₂ / C molar ratio. FIG. 6 is a view showing a temperature distribution in the reforming catalyst. FIG. 7 is a diagram showing the relationship between the reaction equilibrium temperature TB and the O ₂ / C molar ratio when the supplied air temperature TA changes. 8A and 8B are diagrams showing changes in the temperature TD of the exhaust treatment catalyst. FIG. 9 is a time chart showing heat and hydrogen generation control. 10A and 10B are diagrams showing an operation region in which secondary warm-up is performed. FIG. 11 is a time chart showing heat and hydrogen generation control. FIG. 12 is a diagram showing a change in the HC accumulation amount. FIG. 13 is a diagram showing the amount of generated HC. FIG. 14 is a diagram showing the combustion HC amount. FIG. 15 is a flowchart for performing the deposited HC combustion control. FIG. 16 is a flowchart for performing the deposited HC combustion control. FIG. 17 is a flowchart for performing heat and hydrogen generation control. FIG. 18 is a flowchart for performing heat and hydrogen generation control. FIG. 19 is a flowchart for performing heat and hydrogen generation control. FIG. 20 is a flowchart for performing heat and hydrogen generation control. FIG. 21 is a flowchart for performing catalyst temperature increase restriction control.

FIG. 1 shows an overall view of a compression ignition type internal combustion engine.
Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 via the intake air amount detector 8. A throttle valve 10 driven by an actuator is disposed in the intake duct 6, and a cooling device 11 for cooling intake air flowing through the intake duct 6 is disposed around the intake duct 6. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 11, and the intake air is cooled by the engine cooling water.

On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the inlet of the exhaust treatment catalyst 13 via the exhaust pipe 12. In the example shown in FIG. 1, the exhaust treatment catalyst 13 is composed of a NO _X storage catalyst. The outlet of the exhaust treatment catalyst 13 is connected to a particulate filter 14 carrying a NO _X selective reduction catalyst, and a sweeper catalyst 15 made of, for example, an oxidation catalyst is disposed downstream of the particulate filter 14. A fuel supply valve 16 for supplying light oil, for example, is arranged in the exhaust pipe 12 upstream of the exhaust treatment catalyst 13, and urea water is supplied between the exhaust treatment catalyst 13 and the particulate filter 14. A urea supply valve 17 is arranged for this purpose.

  On the other hand, the exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 18, and an electronically controlled EGR control valve 19 is disposed in the EGR passage 18. A cooling device 20 for cooling the EGR gas flowing in the EGR passage 18 is disposed around the EGR passage 18. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 20, and the EGR gas is cooled by the engine cooling water. Each fuel injection valve 3 is connected to a common rail 22 via a fuel supply pipe 21, and this common rail 22 is connected to a fuel tank 24 via an electronically controlled fuel pump 23 having a variable discharge amount. The fuel stored in the fuel tank 24 is supplied into the common rail 22 by the fuel pump 23, and the fuel supplied into the common rail 22 is supplied to the fuel injection valve 3 through each fuel supply pipe 21.

The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. As shown in FIG. 1, temperature sensors 25a, 25b, and 25c are arranged on the upstream side of the exhaust treatment catalyst 13, the downstream side of the exhaust treatment catalyst 13, and the downstream side of the particulate filter 14, respectively. upstream and exhaust treatment respectively NO _X sensor 26a on the downstream side of the catalyst 13 of the catalyst 13, 26b are arranged. Further, a differential pressure sensor 27 for detecting the differential pressure across the particulate filter 14 is attached to the particulate filter 14, and an air-fuel ratio sensor 28 is disposed downstream of the particulate filter 14. These temperature sensors 25a, 25b, 25c, NO _X sensor 26a, 26b, a differential pressure sensor 27, the air-fuel ratio sensor 28 and the output signal is the input port 35 via an AD converter 37 respectively corresponding to the intake air amount detector 8 Entered.

  A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is connected to the input port 35 via the corresponding AD converter 37. Entered. The input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. Further, the operation signal of the engine starter switch 43 is input to the input port 35. On the other hand, the output port 36 is connected to the fuel injection valve 3, the actuator for driving the throttle valve 10, the fuel supply valve 16, the urea supply valve 17, the EGR control valve 19, and the fuel pump 23 through corresponding drive circuits 38.

Referring to FIG. 1, heat and hydrogen, or heat that can generate only heat, a hydrogen generator 50 is provided, and this heat and hydrogen generator 50 is disposed in the exhaust pipe 12 via a passage switching device 51. It is connected to. The heat and hydrogen generation device 50 is started, for example, when the engine is started, and the heat, the heat and hydrogen generated in the hydrogen generation device 50, or the heat is passed through the passage switching device 51, or the exhaust treatment catalyst 13 or It is supplied to the particulate filter 14 carrying the NO _X selective reduction catalyst. Thereby, the warming-up action of the exhaust treatment catalyst 13 is performed by these heat and hydrogen, or heat. This heat and hydrogen generator 50 is disposed, for example, in an engine room of a vehicle.

FIG. 2 shows an overall view of the heat and hydrogen generator 50. The heat and hydrogen generator 50 is generally cylindrical.
Referring to FIG. 2, 52 is heat, a cylindrical housing of the hydrogen generator 50, 53 is a burner combustion chamber formed in the housing 52, 54 is a reforming catalyst disposed in the housing 52, and 55 is a housing 52. The gas outflow chamber formed in each is shown. In the embodiment shown in FIG. 2, the reforming catalyst 54 is disposed at the longitudinal center of the housing 52, and the burner combustion chamber 53 is disposed at one longitudinal end of the housing 52. A gas outflow chamber 55 is disposed at the other end in the direction. As shown in FIG. 2, in this embodiment, the entire outer periphery of the housing 52 is covered with a heat insulating material 56.

  As shown in FIG. 2, a burner 57 having a fuel injection valve 58 is disposed at one end of the burner combustion chamber 53. The tip of the fuel injection valve 58 is disposed in the burner combustion chamber 53, and a fuel injection port 59 is formed at the tip of the fuel injection valve 58. An air chamber 60 is formed around the fuel injection valve 58, and an air supply port 61 for ejecting air in the air chamber 60 toward the burner combustion chamber 53 around the tip of the fuel injection valve 58. Is formed. In the embodiment shown in FIG. 2, the fuel injection valve 58 is connected to the fuel tank 24 as shown in FIG. 1, and the fuel in the fuel tank 24 is injected from the fuel injection port 59 of the fuel injection valve 58. Is done. In the embodiment shown in FIGS. 1 and 2, this fuel consists of light oil.

  On the other hand, the air chamber 60 is connected to an air pump 64 whose discharge amount can be controlled via a high-temperature air flow passage 62 on the one hand and to an air pump 64 whose discharge amount can be controlled via a low-temperature air flow passage 63 on the other hand. It is connected. As shown in FIG. 2, a hot air valve 65 and a cold air valve 66 are disposed in the hot air flow passage 62 and the cold air flow passage 63, respectively. Further, as shown in FIG. 2, the high-temperature air flow passage 62 includes a heat exchanging portion disposed in the gas outflow chamber 55, and this heat exchanging portion is schematically shown in FIG. Is shown in The heat exchanging portion 62 a can also be formed around the housing 52 that defines the gas outflow chamber 55 downstream of the reforming catalyst 54. That is, the heat exchanging portion 62a is preferably arranged or formed in a place where the heat exchanging action is performed using the high-temperature gas heat flowing out from the gas outflow chamber 55. On the other hand, the low-temperature air flow passage 63 does not have a heat exchanging portion that performs heat exchange using the high-temperature gas heat that has flowed out of the gas outflow chamber 55 in this way.

  When the high-temperature air valve 65 is opened and the low-temperature air valve 66 is closed, the outside air passes through the air cleaner 67, the air pump 64, the high-temperature air flow passage 62, and the air chamber 60 from the air supply port 61 to the burner combustion chamber 53. Supplied in. At this time, outside air, that is, air is circulated in the heat exchanging portion 62a. On the other hand, when the low-temperature air valve 66 is opened and the high-temperature air valve 65 is closed, the outside air, that is, the air is passed through the air cleaner 67, the air pump 64, the low-temperature air flow passage 63 and the air chamber 60. Supplied from the supply port 61. Therefore, the high temperature air valve 65 and the low temperature air valve 66 can switch the air flow path for supplying air to the air supply port 61 via the air chamber 60 between the high temperature air flow path 62 and the low temperature air flow path 63. A simple switching device.

  On the other hand, an ignition device 68 is disposed in the burner combustion chamber 53. In the embodiment shown in FIG. 2, the ignition device 68 is formed of a glow plug. The glow plug 68 is connected to a power source 70 via a switch 69. On the other hand, in the embodiment shown in FIG. 2, the reforming catalyst 54 is composed of an oxidizing portion 54a and a reforming portion 54b. In the embodiment shown in FIG. 2, the base of the reforming catalyst 54 is made of zeolite, and palladium Pd is mainly supported in the oxidation part 54a on this base, and rhodium Rh is mainly supported in the reforming part 54b. It is supported. In the burner combustion chamber 53, a temperature sensor 71 for detecting the temperature of the upstream end surface of the oxidation portion 54a of the reforming catalyst 54 is disposed. A temperature sensor 72 for detecting the temperature of the downstream end face of the reforming portion 54b of the catalyst 54 is disposed. Furthermore, a temperature sensor 73 for detecting the temperature of the air flowing through the low temperature air flow passage 63 is disposed in the low temperature air flow passage 63 located outside the heat insulating material 56.

  The output signals of these temperature sensors 71, 72 and 73 are input to the input port 35 via the corresponding AD converters 37 shown in FIG. An output signal indicating the resistance value of the glow plug 68 is also input to the input port 35 via the corresponding AD converter 37 shown in FIG. On the other hand, the output port 36 shown in FIG. 1 is connected to a fuel injection valve 58, a high temperature air valve 65, a low temperature air valve 66, and a switch 69 via corresponding drive circuits 38. Further, as shown in FIG. 1, the output port 36 is connected to a pump drive circuit 44 that controls the discharge amount of the air pump 64, and the discharge amount of the air pump 64 is output by the pump drive circuit 44. The drive is controlled so as to be the command value of the discharge amount output to

  At the start of operation of the heat and hydrogen generator 50, the fuel injected from the burner 57 is ignited by the glow plug 68, whereby the fuel and air supplied from the burner 57 react in the burner combustion chamber 53. Burner combustion is started. When the burner combustion is started, the temperature of the reforming catalyst 54 gradually increases. At this time, burner combustion is performed under a lean air-fuel ratio. Next, when the temperature of the reforming catalyst 44 reaches a temperature at which the fuel can be reformed, the air-fuel ratio is normally switched from the lean air-fuel ratio to the rich air-fuel ratio, and the fuel reforming action in the reforming catalyst 44 is achieved. Is started. When the reforming action of the fuel is started, hydrogen is generated, and a high-temperature gas containing the generated hydrogen is caused to flow out from the gas outlet 74 of the gas outlet chamber 55. The hot gas flowing out from the gas outlet 74 is supplied into the exhaust pipe 12 via the passage switching device 51 as shown in FIG.

  Thus, in the embodiment of the present invention, the heat and hydrogen generator 50 includes the burner combustion chamber 53, the burner 57 disposed in the burner combustion chamber 53 for performing the burner combustion, and the burner 57 to the burner combustion chamber. The fuel supply device that can control the supply amount of the fuel supplied into 53, the air supply device that can control the temperature and supply amount of the air supplied from the burner 57 into the burner combustion chamber 53, and the fuel are ignited. And a reforming catalyst 54 into which the burner combustion gas is sent. The air supply device heats the air supplied from the burner 57 into the burner combustion chamber 53 with the burner combustion gas. The heat exchange part 62a for this is comprised. In this case, in the embodiment of the present invention, the fuel injection valve 58 constitutes the above-described fuel supply device, and the air chamber 60, the air supply port 61, the high temperature air flow passage 62, the heat exchange section 62a, and the low temperature air flow passage. 63, the air pump 64, the high temperature air valve 65, and the low temperature air valve 66 constitute the above-described air supply device.

  Next, the passage switching device 51 will be described with reference to FIG. Referring to FIG. 1, the passage switching device 51 includes a main flow passage 80 connected to a heat and gas outlet 74 (FIG. 2) of the hydrogen generator 50, a main flow passage valve 81 disposed in the main flow passage 80, and a carbonization. A hydrogen adsorption device 82 (hereinafter referred to as HC adsorption device 82) is connected to the main flow passage 80 upstream of the main flow passage valve 81 and the main flow passage 80 downstream of the HC adsorption device 82. A bypass passage 83 that bypasses the passage valve 81 and the HC adsorption device 82 and a bypass valve 84 disposed in the bypass passage 83 are provided. Note that the HC adsorption device 82 has a built-in HC adsorbent made of zeolite, for example.

Further, the passage switching device 51 includes a flow passage switching valve 85 disposed at the downstream end of the main flow passage 80 and a first passage 86 connected from the flow passage switching valve 85 into the exhaust pipe 12 upstream of the exhaust treatment catalyst 13. And a second passage 87 connected from the flow path switching valve 85 to the exhaust pipe 12 upstream of the particulate filter 14 carrying the NO _X selective reduction catalyst. The outlet of the main flow passage 80 is connected to one of the first passage 86 and the first passage 87 by a flow path switching valve 85. During the engine warm-up operation, the outlet of the main flow passage 80 is normally connected to the first passage 86 via the flow path switching valve 85. Therefore, hereinafter, the outlet of the main flow path 80 is connected to the flow path switching valve 85. A case where the first passage 86 is connected to the first passage 86 will be described as an example.

  In the embodiment of the present invention, the heat and hydrogen generator 1 generates hydrogen by reforming the fuel. First, the reforming reaction when light oil is used as the fuel will be described with reference to FIG.

3 (a) to 3 (c) show a reaction formula and a partial oxidation reforming reaction when a complete oxidation reaction is performed, taking an example of using light oil generally used as a fuel. The reaction equation when the steam is reformed and the reaction equation when the steam reforming reaction is performed are shown. In addition, the calorific value ΔH ⁰ in each reaction formula is indicated by the lower calorific value (LHV). As can be seen from FIGS. 3B and 3C, in order to generate hydrogen from light oil, there are two methods: a method of performing a partial oxidation reforming reaction and a method of performing a steam reforming reaction. There is. The steam reforming reaction is a method of adding steam to light oil. As can be seen from FIG. 3C, the steam reforming reaction is an endothermic reaction. Therefore, it is necessary to apply heat from the outside in order to cause the steam reforming reaction. In large hydrogen generation plants, in addition to the partial oxidation reforming reaction, a steam reforming reaction that uses the generated heat to generate hydrogen without increasing the generated heat in order to increase the efficiency of hydrogen generation. Is used.

On the other hand, in the present invention, in order to generate both hydrogen and heat, the steam reforming reaction using the generated heat for generating hydrogen is not used. In the present invention, the partial oxidation reforming reaction is not used. Hydrogen is generated using only. As can be seen from FIG. 3B, this partial oxidation reforming reaction is an exothermic reaction, and therefore the reforming reaction proceeds with the heat generated by itself without applying heat from the outside, and hydrogen is generated. The As shown in the reaction formula of the partial oxidation reforming reaction in FIG. 3B, the partial oxidation reforming reaction has an O ₂ / C molar ratio indicating the ratio of air to fuel to be reacted is 0.5. At a rich air / fuel ratio, CO and H ₂ are produced at this time.

FIG. 4 shows the relationship between the reaction equilibrium temperature TB when air and fuel are reacted in the reforming catalyst to reach equilibrium, and the O ₂ / C molar ratio of air and fuel. In addition, the continuous line of FIG. 4 has shown the theoretical value when air temperature is 25 degreeC. As shown by the solid line in FIG. 4, when the partial oxidation reforming reaction is performed with a rich air-fuel ratio of O ₂ / C molar ratio = 0.5, the equilibrium reaction temperature TB is approximately 830 ° C. Note that the actual equilibrium reaction temperature TB at this time is slightly lower than 830 ° C., but the embodiment according to the present invention will be described below assuming that the equilibrium reaction temperature TB is a value shown by the solid line in FIG.

On the other hand, as can be seen from the reaction formula of the complete oxidation reaction in FIG. 3A, the ratio of air to fuel becomes the stoichiometric air-fuel ratio when the O ₂ / C molar ratio = 1.4575, as shown in FIG. Moreover, the reaction equilibrium temperature TB becomes the highest when the ratio of air to fuel becomes the stoichiometric air-fuel ratio. When the O ₂ / C molar ratio is between 0.5 and 1.4575, a partial oxidation reforming reaction is performed in part, and a complete oxidation reaction is performed in part. In this case, as the O ₂ / C molar ratio increases, the rate at which the complete oxidation reaction is performed is higher than the rate at which the partial oxidation reforming reaction is performed. Therefore, the reaction equilibrium temperature increases as the O ₂ / C molar ratio increases. TB becomes high.

On the other hand, FIG. 5 shows the relationship between the number of generated molecules (H ₂ and CO) per carbon atom and the O ₂ / C molar ratio. As described above, as the O ₂ / C molar ratio becomes larger than 0.5, the rate at which the partial oxidation reforming reaction is performed decreases. Therefore, as shown in FIG. 5, the amount of H ₂ and CO generated decreases as the O ₂ / C molar ratio is greater than 0.5. Although not shown in FIG. 5, when the O ₂ / C molar ratio is larger than 0.5, the production amounts of CO ₂ and H ₂ O are increased by the complete oxidation reaction shown in FIG. Increase. Incidentally, FIG. 5 shows the production amounts of H ₂ and CO when it is assumed that the water gas shift reaction shown in FIG. However, in reality, the water gas shift reaction shown in FIG. 3D is caused by CO generated by the partial oxidation reforming reaction and H ₂ O generated for the complete oxidation reaction. Is generated.

As described above, the amount of H ₂ and CO produced decreases as the O ₂ / C molar ratio is greater than 0.5. On the other hand, as shown in FIG. 5, when the O ₂ / C molar ratio is smaller than 0.5, surplus carbon C that cannot be reacted increases. This surplus carbon C accumulates in the pores of the base of the reforming catalyst and causes so-called coking. When coking occurs, the reforming ability of the reforming catalyst is significantly reduced. Therefore, in order to avoid causing coking, the O ₂ / C molar ratio should not be made smaller than 0.5. Further, as can be seen from FIG. 5, the generation amount of hydrogen is maximized when the O ₂ / C molar ratio is 0.5 within the range where no surplus carbon C is generated. Therefore, in the embodiment of the present invention, when a partial oxidation reforming reaction is performed to generate hydrogen, O ₂ / C mole is generated so that hydrogen can be generated most efficiently while avoiding coking. The ratio is in principle 0.5.

Meanwhile, O ₂ / C molar ratio, is a stoichiometric air-fuel ratio O ₂ / C molar ratio = 1.4575 even complete oxidation reaction is greater than can be performed, O ₂ / C as the molar ratio increases heating The amount of air that should be increased. Therefore, as shown in FIG. 4, when the O ₂ / C molar ratio is greater than the O ₂ / C molar ratio indicating the theoretical air-fuel ratio = 1.4575, the larger the O ₂ / C molar ratio is, The reaction equilibrium temperature TB decreases. In this case, for example, when the lean air-fuel ratio is 2.6 with an O ₂ / C molar ratio, the reaction equilibrium temperature TB is approximately 920 ° C. when the air temperature is 25 ° C.

  Now, as described above, when the operation of the heat and hydrogen generator 50 shown in FIG. 1 is started, burner combustion is performed under a lean air-fuel ratio, whereby the temperature of the reforming catalyst 54 gradually increases. To rise. Next, when the temperature of the reforming catalyst 54 reaches a temperature at which the fuel can be reformed, the air-fuel ratio is normally switched from the lean air-fuel ratio to the rich air-fuel ratio, and the fuel reforming action in the reforming catalyst 54 is achieved. Is started. When the reforming action of the fuel is started, hydrogen is generated. FIG. 6 shows the temperature distribution in the oxidizing portion 54a and the reforming portion 54b of the reforming catalyst 54 when the reaction in the reforming catalyst 54 reaches an equilibrium state. 6 shows the temperature distribution when the outside air is supplied from the burner 57 into the burner combustion chamber 53 via the low-temperature air flow passage 63 shown in FIG. 2 when the outside air temperature is 25 ° C. Show.

The solid line in FIG. 6 shows the temperature distribution in the reforming catalyst 54 when the O ₂ / C molar ratio of air and fuel supplied from the burner 57 is 0.5. As shown in FIG. 6, in this case, in the oxidation portion 54a of the reforming catalyst 54, the temperature in the reforming catalyst 54 rises toward the downstream side due to the heat of oxidation reaction due to residual oxygen. When the combustion gas advances from the oxidizing portion 54a of the reforming catalyst 54 into the reforming portion 54b, the remaining oxygen in the combustion gas disappears, and the reforming portion 54b of the reforming catalyst 54 reforms the fuel. The action is performed. This reforming reaction is an endothermic reaction, and therefore the temperature in the reforming catalyst 54 decreases as the reforming action proceeds, that is, toward the downstream side of the reforming catalyst 54. At this time, the temperature of the downstream end face of the reforming catalyst 54 is 830 ° C., which corresponds to the reaction equilibrium temperature TB when the O ₂ / C molar ratio = 0.5 shown in FIG.

On the other hand, in FIG. 6, the temperature distribution in the reforming catalyst 54 when the O ₂ / C molar ratio of the air and fuel supplied from the burner 57 is 2.6 is indicated by a broken line. ing. Also in this case, the temperature in the reforming catalyst 54 rises toward the downstream side in the oxidation portion 54a of the reforming catalyst 54 due to the oxidation reaction heat of the fuel. On the other hand, in this case, since the reforming action is not performed in the reforming part 54b of the reforming catalyst 54, the temperature in the reforming catalyst 54 is kept constant in the reforming part 54b. At this time, the temperature of the downstream end face of the reforming catalyst 54 is 920 ° C., which matches the reaction equilibrium temperature TB when the O ₂ / C molar ratio shown in FIG. 4 is 2.6. That is, the reaction equilibrium temperature TB in FIG. 4 is obtained when the outside air is supplied from the burner 57 into the burner combustion chamber 53 via the low temperature air flow passage 63 shown in FIG. This indicates the temperature of the downstream end face of the reforming catalyst 54.

Next, the reaction equilibrium temperature TB when the temperature of the air that reacts with the fuel in the reforming catalyst is changed will be described with reference to FIG. FIG. 7 shows the relationship between the reaction equilibrium temperature TB when air and fuel are reacted in the reforming catalyst to reach equilibrium, and the O ₂ / C molar ratio of air and fuel, as in FIG. Yes. In FIG. 7, TA indicates the air temperature. In FIG. 7, the relationship between the reaction equilibrium temperature TB and the O ₂ / C molar ratio indicated by the solid line in FIG. 4 is again shown by the solid line. Further, in FIG. 7, the relationship between the reaction equilibrium temperature TB and the O ₂ / C molar ratio when the air temperature TA is changed to 225 ° C., 425 ° C., and 625 ° C. is indicated by a broken line. FIG. 7 shows that when the air temperature TA rises, the reaction equilibrium temperature TB increases as a whole regardless of the O ₂ / C molar ratio.

On the other hand, it has been confirmed that the reforming catalyst 54 used in the examples of the present invention does not cause large thermal degradation when the catalyst temperature is 950 ° C. or lower. Therefore, in the embodiment of the present invention, 950 ° C. is the allowable catalyst temperature TX that can avoid the thermal deterioration of the reforming catalyst 54, and this allowable catalyst temperature TX is shown in FIGS. 4, 6, and 7. Has been. As can be seen from FIG. 6, when the air temperature TA is 25 ° C., even when the O ₂ / C molar ratio is 0.5 or when the O ₂ / C molar ratio is 2.6, The temperature of the reforming catalyst 54 when the reaction reaches an equilibrium state is equal to or lower than the allowable catalyst temperature TX at any location of the reforming catalyst 54. Therefore, in this case, the reforming catalyst 54 can be continuously used without causing a problem of thermal degradation in practice.

On the other hand, as can be seen from FIG. 4, when the O ₂ / C molar ratio is slightly larger than 0.5 even when the air temperature TA is 25 ° C., the reaction in the reforming catalyst 54 is in an equilibrium state. When the temperature of the downstream end face of the reforming catalyst 54, that is, the reaction equilibrium temperature TB exceeds the allowable catalyst temperature TX and the O ₂ / C molar ratio is slightly smaller than 2.6, the reforming catalyst 54 The temperature of the downstream end face of the reforming catalyst 54 when the reaction reaches an equilibrium state exceeds the allowable catalyst temperature TX. Thus, for example, it may give rise to partial oxidation reforming reaction when the reaction in the reforming catalyst 54 is in equilibrium, although the O ₂ / C molar ratio may be greater than 0.5, O ₂ / The range in which the C molar ratio can be increased is limited.

On the other hand, as can be seen from FIG. 7, when the air temperature TA increases, the reforming catalyst 54 is in an equilibrium state, and even if the O ₂ / C molar ratio is 0.5, the reforming is performed. The temperature of the downstream end face of the reforming catalyst 54 when the reaction in the reforming catalyst 54 reaches an equilibrium state becomes higher than the allowable catalyst temperature TX, and thus the reforming catalyst 54 is thermally deteriorated. Therefore, when the air temperature TA becomes high, the O ₂ / C molar ratio cannot be made 0.5 when the reaction in the reforming catalyst 54 is in an equilibrium state. Therefore, in the embodiment of the present invention, when the reaction in the reforming catalyst 54 reaches an equilibrium state, the air temperature TA is set to a low temperature of about 25 ° C., and the air temperature TA is maintained at a low temperature of about 25 ° C. In the state, the O ₂ / C molar ratio is set to 0.5.

  As described above, in the embodiment of the present invention, when the operation of the heat and hydrogen generator 50 is started, burner combustion is started under the lean air-fuel ratio, and the burner under this lean air-fuel ratio is started. Combustion is performed until the reforming action by the reforming catalyst 54 becomes possible. In other words, in the embodiment of the present invention, after the heat and hydrogen generator 50 is started, the heat and hydrogen generator 50 under a lean air-fuel ratio until the reforming action by the reforming catalyst 54 becomes possible. Is warmed up. In this case, when the temperature of the reforming catalyst 54 reaches about 700 ° C., the reforming action by the reforming catalyst 54 becomes possible. Therefore, in the embodiment of the present invention, after the heat and the hydrogen generator 50 are started, the reforming is performed. Until the temperature of the catalyst 54 reaches 700 ° C., the warm-up operation of the heat and hydrogen generator 50 is performed under the lean air-fuel ratio. During this time, heat and heat generated in the hydrogen generator 50 are discharged from the gas outlet 74 of the gas outlet chamber 55, and then pass through the main flow passage 80 or the bypass passage 83 as shown in FIG. The exhaust pipe 12 is supplied through the first passage 86. Next, when the reforming action by the reforming catalyst becomes possible, that is, when the temperature of the reforming catalyst 54 reaches 700 ° C., the air-fuel ratio is normally switched from the lean air-fuel ratio to the rich air-fuel ratio, and the partial oxidation reforming is performed. A quality reaction takes place. When the partial oxidation reforming reaction is performed, heat and hydrogen are generated in the reforming catalyst 44. These heat and hydrogen are discharged from the gas outlet 74 of the gas outlet chamber 55, and then supplied to the exhaust pipe 12 through the main flow passage 80 or the bypass passage 83 and then through the first passage 86. .

Next, the exhaust gas purification action by the exhaust treatment catalyst 13 disposed in the engine exhaust passage will be described. As described above, in the example shown in FIG. 1, the exhaust treatment catalyst 13 is composed of a NO _X storage catalyst. The NO _X storage catalyst 13 is composed of a noble metal such as platinum Pt, palladium Pd, rhodium Rh, It carries an alkali metal such as potassium K, sodium Na and cesium Cs, or an alkaline earth metal such as barium Ba and calcium Ca. This the NO _X storing catalyst 13, NO _X when the air-fuel ratio of the inflowing exhaust gas lean in storing catalyst 13 occludes NO _X contained in the exhaust gas, the air-fuel ratio of the exhaust gas flowing into the NO _X storing catalyst 13 There have the absorption and release function of the NO _X that emits NO _X occluded when made rich from the NO _X storing catalyst 13. Further, in the NO _X storage catalyst 13, HC discharged from the engine is oxidized by the noble metal supported on the NO _X storage catalyst 13, and therefore the NO _X storage catalyst 13 also has an HC purification function. Yes.

Meanwhile _the NO _X storage rate to the the NO _X storing catalyst 13, i.e., HC purification rate by the NO _X purification rate and the NO _X storing catalyst 13 by the NO _X storing catalyst 13, the NO _X storing catalyst 13, i.e., the exhaust treatment catalyst 13 If the temperature does not turn about 200 ° C. not sufficiently high, therefore, at the time of engine starting, in order to obtain a high nO _X purification rate and high HC purification rate by the nO _X storing catalyst 13, the nO _X storing catalyst 13, i.e. It is necessary to raise the temperature of the exhaust treatment catalyst 13 to a target warm-up temperature of about 200 ° C. By the way, in the embodiment of the present invention, when the engine is started, the warming-up action of the exhaust treatment catalyst 13 is started by the exhaust gas discharged from the engine. However, it takes a long time to raise the temperature of the exhaust treatment catalyst 13 to the target warm-up temperature by the exhaust gas. Therefore, in the embodiment of the present invention, in order to quickly increase the temperature of the exhaust treatment catalyst 13 to the target warm-up temperature, the operation of the heat and hydrogen generator 50 is started simultaneously with the start of the engine, and the heat, hydrogen, The warm-up action of the exhaust treatment catalyst 13 is promoted by heat and hydrogen supplied to the exhaust treatment catalyst 13 from the generation device 50 or heat. Next, with reference to FIG. 8A and FIG. 8B, the heat and warming promotion action of the exhaust treatment catalyst 13 by the hydrogen generator 50 will be described.

  8A and 8B show that the exhaust treatment catalyst 13 is warmed up by the heat and hydrogen generator 50 when the exhaust treatment catalyst 13 carries a noble metal such as platinum Pt, palladium Pd, and rhodium Rh. The change of the temperature TD of the exhaust treatment catalyst 13 is shown. In FIGS. 8A and 8B, the horizontal axis indicates the passage of time. In FIG. 8A and FIG. 8B, the warm-up action of the exhaust treatment catalyst 13 by the exhaust gas discharged from the engine is ignored for easy understanding. In FIG. 8B, TK indicates a temperature at which the noble metal is activated. In the example shown in FIG. 8B, the temperature TK at which the noble metal is activated is 110 ° C. Hereinafter, the temperature TK at which the noble metal is activated is referred to as the activation temperature TK of the exhaust treatment catalyst 13.

Now, as can be seen from FIG. 3, when the complete oxidation reaction and the partial oxidation reforming reaction are compared, the complete oxidation reaction has a much larger calorific value than the partial oxidation reforming reaction, and therefore, the fuel used. When the amounts are the same, the amount of heat supplied to the exhaust treatment catalyst 13 is equal to that when the complete oxidation reaction is performed in the heat and hydrogen generator 50. Much greater than when quality reactions are taking place. FIG. 8A shows the exhaust when the exhaust treatment catalyst 13 is warmed up by the generated heat when the complete oxidation reaction is performed with the O ₂ / C molar ratio = 2.6 in the case where the amount of fuel used is the same. The temperature change of the treatment catalyst 13 is indicated by a solid line A, and the exhaust treatment catalyst 13 is warmed up only by the heat generated when the partial oxidation reforming reaction is performed with an O ₂ / C molar ratio = 0.5. The temperature change of the exhaust treatment catalyst 13 is shown by a broken line a. As can be seen by comparing the solid line A and the broken line a, the rate of increase in the temperature TD of the exhaust treatment catalyst 13 when the exhaust treatment catalyst 13 is warmed up only by heat and heat generated in the hydrogen generator 50 is completely It can be seen that the oxidation reaction is higher than the partial oxidation reforming reaction.

On the other hand, when the exhaust treatment catalyst 13 is warmed up, when hydrogen is supplied to the exhaust treatment catalyst 13 and an oxidation reaction of hydrogen is performed on the noble metal, the temperature TD of the exhaust treatment catalyst 13 is rapidly increased due to the oxidation reaction heat of hydrogen. To rise. The broken line b in FIG. 8A shows that the exhaust treatment catalyst 13 is warmed only by the generated hydrogen when the partial oxidation reforming reaction is performed with the O ₂ / C molar ratio = 0.5 under the same amount of fuel used. FIG. 8A shows the change in temperature of the exhaust treatment catalyst 13 when it is operated, and the solid line B in FIG. 8A shows the partial oxidation reforming with the O ₂ / C molar ratio = 0.5 under the same amount of fuel used. A temperature change of the exhaust treatment catalyst 13 when the exhaust treatment catalyst 13 is warmed up by generated heat and produced hydrogen when the reaction is performed is shown. As can be seen by comparing the solid line A and the solid line B in FIG. 8A, when the warming-up action of the exhaust treatment catalyst 13 by hydrogen is also performed, the rate of increase in the temperature TD of the exhaust treatment catalyst 13 is the partial oxidation modification. It can be seen that the quality reaction is much higher than the complete oxidation reaction.

  That is, a part of heat and combustion gas heat generated in the hydrogen generator 50 escapes to the outside while the combustion gas flows in the passage switching device 51, and the combustion gas heat is exhausted by heat transfer. Since it is only supplied to the catalyst 13, the amount of heat actually used for heating the exhaust treatment catalyst 13 is not so much. On the other hand, the heat and hydrogen generated in the hydrogen generator 50 are not consumed until reaching the exhaust treatment catalyst 13, and the exhaust treatment catalyst 13 itself is directly heated by the oxidation reaction heat of hydrogen. The temperature of the exhaust treatment catalyst 13 is rapidly raised by the oxidation reaction heat.

  By the way, when the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK of the exhaust treatment catalyst 13 shown in FIG. 8B, even if hydrogen is supplied to the exhaust treatment catalyst 13, the oxidation reaction of hydrogen on the noble metal Therefore, at this time, no heat of oxidation reaction is generated by the oxidation reaction of hydrogen. Therefore, when the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK of the exhaust treatment catalyst 13, as shown in FIG. 8A, the direction when the complete oxidation reaction is performed in the heat and hydrogen generator 50. However, the temperature increase rate of the exhaust treatment catalyst 13 is much higher than when the partial oxidation reforming reaction is performed in the heat and hydrogen generator 50.

  On the other hand, when the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK of the exhaust treatment catalyst 13, a partial oxidation reforming reaction is performed in the heat and hydrogen generator 50, thereby the exhaust treatment catalyst 13. When hydrogen is supplied to the exhaust gas, the temperature of the exhaust treatment catalyst 13 is rapidly raised by the heat of oxidation reaction of hydrogen. Therefore, in order to raise the temperature of the exhaust treatment catalyst 13 as soon as possible, when the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK of the exhaust treatment catalyst 13, as shown by a solid line A in FIG. When only the heat is supplied to the exhaust treatment catalyst 13 by performing a complete oxidation reaction in the heat and hydrogen generator 50, and the temperature TD of the exhaust treatment catalyst 13 becomes higher than the activation temperature TK of the exhaust treatment catalyst 13. 8B, it is understood that heat and hydrogen are preferably supplied to the exhaust treatment catalyst 13 by performing a partial oxidation reforming reaction in the heat and hydrogen generator 50, as indicated by a solid line B in FIG.

  However, in practice, as shown in FIG. 8B, when the temperature TD of the exhaust treatment catalyst 13 reaches the activation temperature TK, the reaction in the heat and the hydrogen generator 50 is always changed from the complete oxidation reaction to the partial oxidation. It is difficult to switch to the reforming reaction. Therefore, in the embodiment of the present invention, the temperature TD of the exhaust treatment catalyst 13 is shown in FIG. 8B when the reforming action by the reforming catalyst 54 becomes possible after the heat and hydrogen generator 50 is started. When the temperature is higher than the activation temperature TK of the exhaust treatment catalyst 13, basically, the reaction in the heat and hydrogen generator 50 is immediately switched from the complete oxidation reaction to the partial oxidation reforming reaction. After the start-up, when the reforming action by the reforming catalyst 54 becomes possible, if the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK, the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK. When the temperature TD of the exhaust treatment catalyst 13 becomes higher than the activation temperature TK, basically, the heat and hydrogen generation device 50 is continued. In The reaction, and to switch to the partial oxidation reforming reaction from complete oxidation reaction. By doing so, warming up of the exhaust treatment catalyst 13 can be accelerated most.

Note that the relationship shown in FIGS. 8A and 8B occurs not only when the NO _X storage catalyst is used as the exhaust treatment catalyst 13, but as the exhaust treatment catalyst 13, such as platinum Pt, palladium Pd, and rhodium Rh. The relationship shown in FIGS. 8A and 8B similarly occurs when a catalyst supporting a noble metal, for example, an oxidation catalyst is used. Therefore, the present invention can be applied even when an oxidation catalyst is used as the exhaust treatment catalyst 13.

Next, the outline of the heat shown in FIG. 2, the heat generated by the hydrogen generator 50, and the hydrogen generation method will be described with reference to FIG. In FIG. 9, the temperature TD of the exhaust treatment catalyst 13 is set in advance when the warming-up operation of the heat and hydrogen generator 50 is completed and the reforming action by the reforming catalyst 54 becomes possible. The case where it is more than the activation temperature TK is shown. Further, in FIG. 9, the operating state of the glow plug 68, the amount of air supplied from the burner 57, the amount of fuel supplied from the burner 57, the O ₂ / C molar ratio of the reacted air and fuel, supplied from the burner 57. The air supply air temperature, the temperature TC of the downstream end face of the reforming catalyst 54, and the temperature TD of the exhaust treatment catalyst 13 are shown. Note that each target temperature with respect to the temperature TC of the downstream end face of the reforming catalyst 54 and each target temperature with respect to the temperature of the reforming catalyst 54 shown in FIG. 9 and the like are theoretical values, and in the embodiment according to the present invention, As described above, for example, the actual equilibrium reaction temperature TB is slightly lower than the target temperature of 830 ° C. Each of these target temperatures varies depending on heat, the structure of the hydrogen generator 50, etc. Therefore, in practice, an optimum target temperature corresponding to the structure of the heat, the hydrogen generator 50 is determined in advance. There is a need.

When the engine is started, the heat and hydrogen generator 50 is started simultaneously. When the heat and hydrogen generator 50 is started, the glow plug 68 is turned on, and then air is supplied into the burner combustion chamber 53 via the hot air flow passage 62. In this case, as shown by a broken line in FIG. 9, after the air is supplied into the burner combustion chamber 53 via the high-temperature air flow passage 62, the glow plug 68 can be turned on. Next, fuel is injected from the burner 57. When the fuel injected from the burner 57 is ignited by the glow plug 68, the amount of fuel is increased and the O ₂ / C molar ratio of air to fuel to be reacted is reduced from 4.0 to 3.0, Burner combustion is started in the burner combustion chamber 53. In the period from the start of fuel supply until the fuel is ignited, the air-fuel ratio is set to the lean air-fuel ratio in order to suppress the amount of HC generated as much as possible.

  Next, burner combustion, that is, a complete oxidation reaction with a lean air-fuel ratio is continued, whereby the temperature of the reforming catalyst 54 is gradually raised. On the other hand, when the burner combustion is started, the temperature of the gas flowing out into the gas outflow chamber 55 through the reforming catalyst 54 gradually increases. Therefore, the temperature of the air heated in the heat exchanging portion 62a by this gas also gradually increases, and as a result, the temperature of the air supplied from the high temperature air flow passage 62 into the burner combustion chamber 53 gradually increases. As a result, warm-up of the reforming catalyst 54 is promoted. As described above, in the embodiment of the present invention, the warming-up of the reforming catalyst 54 performed under the lean air-fuel ratio is performed as shown in FIG. This is called warm-up. In the example shown in FIG. 9, the supply air amount and the fuel amount are increased during the primary warm-up operation.

This primary warm-up operation, that is, the warm-up operation of the heat and hydrogen generator 50 is continued until the reforming of the fuel in the reforming catalyst 54 becomes possible. In the example shown in FIG. 9, when the temperature TC at the downstream end face of the reforming catalyst 54 reaches 700 ° C., it is determined that the reforming catalyst 54 can reform the fuel. In this example, the primary warm-up operation, that is, the warm-up operation of the heat and hydrogen generator 50 is continued until the temperature TC of the downstream end face of the reforming catalyst 54 reaches 700 ° C. In the example shown in FIG. 9, the operation until the primary warm-up of the reforming catalyst 54 is completed after the operation of the hydrogen generator 50 is started, that is, after the operation of the hydrogen generator 50 is started. Until the warming-up of the hydrogen generator 50 is completed, as shown in FIG. 9, the O ₂ / C molar ratio of the air to be reacted and the fuel is changed from 3.0 to 4.0. An oxidation reaction is taking place. Of course, since the temperature of the reforming catalyst 54 is considerably lower than the allowable catalyst temperature TX at this time, the O ₂ / C molar ratio of air and fuel to be reacted is set to, for example, 2.0 to 3.0. An O ₂ / C molar ratio close to the theoretical air-fuel ratio can also be set.

  On the other hand, as shown in FIG. 9, when the engine is started, the temperature TD of the exhaust treatment catalyst 13 immediately rises slightly. Next, in the example shown in FIG. 9, the temperature TD of the exhaust treatment catalyst 13 gradually increases during the primary warm-up operation, that is, the warm-up operation of the heat and hydrogen generator 50, and the exhaust treatment is performed. The temperature TD of the catalyst 13 exceeds the preset activation temperature TK during the primary warm-up operation, that is, the heat and hydrogen generation device 50 warm-up operation. Thus, even if the temperature TD of the exhaust treatment catalyst 13 exceeds the preset activation temperature TK, the heat and hydrogen generator 50 continues the complete oxidation reaction with the lean air-fuel ratio. Next, the temperature TD of the exhaust treatment catalyst 13 further increases little by little. In the example shown in FIG. 9, when the temperature TC of the downstream end face of the reforming catalyst 54 reaches 700 ° C., the temperature of the exhaust treatment catalyst 13 is increased. TD is equal to or higher than a preset activation temperature TK.

  Next, when the temperature TC at the downstream end face of the reforming catalyst 54 reaches 700 ° C., it is determined that the reforming catalyst 54 can reform the fuel. At this time, since the temperature TD of the exhaust treatment catalyst 13 is equal to or higher than a preset activation temperature TK, a partial oxidation reforming reaction for generating hydrogen is started. In the embodiment of the present invention, as shown in FIG. 9, the secondary warm-up operation is first performed, and the normal operation is performed when the secondary warm-up operation is completed. This secondary warm-up operation is performed to further raise the temperature of the reforming catalyst 54 while generating hydrogen. When the secondary warm-up operation is started, the heat, the heat generated in the hydrogen generator 50 and hydrogen are supplied to the exhaust treatment catalyst 13, and as a result, as shown in FIG. TD rises rapidly.

  On the other hand, the secondary warm-up operation is continued until the temperature TC of the downstream end face of the reforming catalyst 54 reaches the reaction equilibrium temperature TB, and the temperature TC of the downstream end face of the reforming catalyst 54 is changed to the reaction equilibrium. When the temperature TB is reached, normal operation is started. When the secondary warm-up operation is started, the required value for the heat required to raise the temperature TD of the exhaust treatment catalyst 13 to the target warm-up temperature and the output heat amount (kW) of the hydrogen generator 50 are calculated. The In this case, the required value of the output heat quantity (kW) is basically the difference between the target warm-up temperature of the exhaust treatment catalyst 13 and the current exhaust gas temperature, and the exhaust gas quantity exhausted from the engine. Calculated based on the product. When the required value of the heat and the output calorie (kW) of the hydrogen generator 50 is calculated, the target fuel supply amount required to generate the required output calorie of this output calorie (kW) is calculated, as shown in FIG. As described above, when shifting from the secondary warm-up operation to the normal operation, the amount of fuel supplied from the burner 57 is increased to this target fuel supply amount.

In the case where the exhaust treatment catalyst 13 is comprised of _the NO _X storage catalyst, the target warm-up temperature of the exhaust treatment catalyst 13 described above, are as described above, for example, 200 ° C.. Therefore, in the example shown in FIG. 9, the heat required to raise the temperature TD of the exhaust treatment catalyst 13 to 200 ° C. and the output heat amount (kW) of the hydrogen generator 50 are set as required values. On the other hand, in FIG. 10A, the heat in which the secondary warm-up operation is performed and the operation region GG of the hydrogen generator 1 are indicated by hatching regions surrounded by solid lines GL, GU, and GS. In FIG. 10A, the vertical axis indicates the O ₂ / C molar ratio of air and fuel to be reacted, and the horizontal axis indicates the temperature TC of the downstream end face of the reforming catalyst 54.

As described with reference to FIG. 5, coking occurs when the O ₂ / C molar ratio of air and fuel to be reacted is smaller than 0.5. A solid line GL in FIG. 10A indicates a boundary of the O ₂ / C molar ratio with respect to the occurrence of coking, and coking occurs in a region where the O ₂ / C molar ratio is smaller than the boundary GL. When the temperature of the reforming catalyst 54 is lowered, even if the O ₂ / C molar ratio increases, that is, even if the degree of richness in the air-fuel ratio decreases, the reforming without carbon C being oxidized. It becomes deposited in the pores of the catalyst substrate and causes coking. Accordingly, as shown in FIG. 10A, the O ₂ / C molar ratio boundary GL causing coking increases as the temperature of the reforming catalyst 54 decreases. Therefore, in order to avoid the occurrence of coking, the partial oxidation reforming reaction, that is, the heat, the secondary warm-up operation and the normal operation of the hydrogen generator 50 are performed on the O ₂ / C molar ratio boundary GL, or It is performed on the upper side of the boundary GL.

On the other hand, in FIG. 10A, a solid line GU indicates O ₂ / C mol for preventing the temperature of the reforming catalyst 54 from exceeding the allowable catalyst temperature TX during the secondary warm-up operation of the heat and hydrogen generator 50. The upper limit guard value of the ratio is shown, and the solid line GS is a modified value for preventing the temperature of the reforming catalyst 54 from exceeding the allowable catalyst temperature TX during the secondary warm-up operation of the heat and hydrogen generator 50. The upper limit guard value of the temperature TC of the downstream end face of the quality catalyst 54 is shown. After the secondary warm-up operation is started, the O ₂ / C molar ratio is set to 0.5, and the temperature TC of the downstream end face of the reforming catalyst 54 is O ₂ / C molar ratio = 0.5 When the reaction equilibrium temperature TB is reached, normal operation is started, and hydrogen continues to be produced while maintaining the temperature TC of the downstream end face of the reforming catalyst 54 at the reaction equilibrium temperature TB.

FIG. 10B shows an example of secondary warm-up operation control until transition to normal operation. In the example shown in FIG. 10B, as indicated by the arrow, when the temperature of the downstream end face of the reforming catalyst 54 reaches 700 ° C., O ₂ is used to promote secondary warm-up of the reforming catalyst 54. The partial oxidation reforming reaction is started with a / C molar ratio = 0.56, and then the O ₂ / C molar ratio = 0.56 until the temperature TC of the downstream end face of the reforming catalyst 54 reaches 830 ° C. Thus, the partial oxidation reforming reaction is continued. Next, when the temperature on the downstream end face of the reforming catalyst 54 reaches 830 ° C., the O ₂ / C molar ratio is decreased until the O ₂ / C molar ratio = 0.5. Next, when the O ₂ / C molar ratio is 0.5, the reforming reaction in the reforming catalyst 54 is in an equilibrium state. Then, the O ₂ / C molar ratio is maintained at 0.5, and the normal operation is started.

As described above with reference to FIG. 7, if the temperature TA of the air reacted with the fuel is high when the reforming reaction in the reforming catalyst 54 is in an equilibrium state, as described with reference to FIG. The temperature TB increases. As a result, since the temperature of the reforming catalyst 54 becomes higher than the allowable catalyst temperature TX, the reforming catalyst 54 undergoes thermal deterioration. Therefore, in the embodiment of the present invention, when the O ₂ / C molar ratio is maintained at 0.5 and the reforming reaction in the reforming catalyst 54 is in an equilibrium state, the burner combustion chamber 53 is connected from the high-temperature air flow passage 62. The supply of high-temperature air to the inside is stopped, and low-temperature air is supplied from the low-temperature air flow passage 63 into the burner combustion chamber 53. At this time, the temperature TC of the downstream end face of the reforming catalyst 54 is maintained at 830 ° C. Therefore, the temperature of the reforming catalyst 54 is maintained below the allowable catalyst temperature TX. Therefore, hydrogen can be generated by the partial oxidation reforming reaction while avoiding thermal degradation of the reforming catalyst 54.

  When the secondary warm-up operation is performed in the operation region GG shown in FIGS. 10A and 10B, the reforming reaction in the reforming catalyst 54 is not in an equilibrium state, so the air temperature TA is high. However, as shown in FIG. 7, the temperature of the reforming catalyst 54 does not increase. However, since the secondary warm-up operation is performed in a state where the temperature of the reforming catalyst 54 is high, there is a risk that the temperature of the reforming catalyst 54 becomes higher than the allowable catalyst temperature TX for some reason. There is. Therefore, in the embodiment of the present invention, the secondary warm-up operation is started simultaneously with the burner from the high-temperature air flow passage 62 so that the temperature of the reforming catalyst 54 does not become higher than the allowable catalyst temperature TX. The supply of high-temperature air into the combustion chamber 53 is stopped, and low-temperature air is supplied into the burner combustion chamber 53 from the low-temperature air flow passage 63. That is, as shown in FIG. 9, the supply air temperature is lowered. Thereafter, the low temperature air continues to be supplied from the low temperature air flow passage 63 into the burner combustion chamber 53 until the normal operation is completed.

As described above, when the temperature TA of the air reacted with the fuel is 25 ° C., the equilibrium reaction temperature TB when the O ₂ / C molar ratio = 0.5 is 830 ° C. Therefore, generally speaking, when the temperature of the air reacted with the fuel is TA ° C., the equilibrium reaction temperature TB when the O ₂ / C molar ratio = 0.5 is (TA + 805 ° C.). Therefore, in the embodiment of the present invention, when the temperature of the air reacted with the fuel is TA, when the secondary warm-up operation is started, the temperature TC of the downstream end face of the reforming catalyst 4 is (TA + 805 ° C.). in until, _{O 2} / C molar ratio = with 0.56 partial oxidation reforming reaction continues, then, when the temperature TC of the downstream end face of the reforming catalyst 54 is _{(TA + 805 ℃), O} 2 / The C molar ratio is decreased until O ₂ / C molar ratio = 0.5. Then, when the O ₂ / C molar ratio = 0.5, the O ₂ / C molar ratio is maintained at 0.5.

  The temperature TA of the air reacted with the fuel described above is the temperature of the air used when calculating the equilibrium reaction temperature TB as shown in FIG. 4, and the burner combustion reaction in the burner combustion chamber 53. It is the temperature of air that is not affected by heat. For example, the air supplied from the air supply port 61 or the air in the air chamber 60 is affected by the reaction heat of the burner combustion, and absorbs the reaction heat energy of the burner combustion to increase the temperature. Therefore, these air temperatures indicate the temperature of air that is already in the process of reaction, and thus are not the temperature of air when calculating the equilibrium reaction temperature TB.

  Incidentally, it is necessary to calculate the equilibrium reaction temperature TB when the partial oxidation reforming reaction is performed, that is, when low-temperature air is supplied from the low-temperature air flow passage 63 into the burner combustion chamber 53. It is. Therefore, in the embodiment of the present invention, in order to detect the temperature of the air that is not influenced by the reaction heat of the burner combustion in the burner combustion chamber 53, as shown in FIG. The temperature detected by the temperature sensor 73 is used as the air temperature TA when calculating the equilibrium reaction temperature TB.

  On the other hand, when a stop command is issued, the fuel supply is stopped as shown in FIG. At this time, if the supply of air is stopped, there is a risk that the reforming catalyst 54 may coke due to heat and fuel remaining in the hydrogen generator 50. Therefore, in the embodiment of the present invention, in order to burn and remove the heat and the fuel remaining in the hydrogen generator 50, as shown in FIG. 9, the air is sent for a while after the stop command is issued. Continue to supply.

  Thus, in the embodiment of the present invention, at the same time as the start of the secondary warm-up operation, the burner from the high-temperature air flow passage 62 is prevented so that the temperature of the reforming catalyst 54 does not become higher than the allowable catalyst temperature TX. The supply of high-temperature air into the combustion chamber 53 is stopped, and low-temperature air is supplied into the burner combustion chamber 53 from the low-temperature air flow passage 63. In other words, at this time, the air flow path for sending air into the burner combustion chamber 53 is switched from the high-temperature air flow path for sending high-temperature air to the low-temperature air flow path for sending low-temperature air. In this embodiment of the present invention, the air flow path for sending air into the burner combustion chamber 53 can be switched between the high-temperature air flow path and the low-temperature air flow path. A switching device comprising a low temperature air valve 66 is provided. In this case, in the embodiment of the present invention, the air flow path from the air cleaner 67 to the air supply port 61 via the high temperature air flow path 62 corresponds to the high temperature air flow path. The air flow path leading to the air supply port 61 via the low temperature air flow path corresponds to the low temperature air flow path.

  Next, referring to FIG. 11, when the warming-up operation of the heat and hydrogen generator 50 is completed and the reforming action by the reforming catalyst 54 becomes possible, the temperature TD of the exhaust treatment catalyst 13 is set in advance. A case where the temperature is lower than the set activation temperature TK will be described. In FIG. 11, as in FIG. 9, the operating state of the glow plug 68, the amount of air supplied from the burner 57, the amount of fuel supplied from the burner 57, the O 2 / C molar ratio of air to fuel reacted, the burner The supply air temperature of the air supplied from 57, the temperature TC of the downstream end face of the reforming catalyst 54, and the temperature TD of the exhaust treatment catalyst 13 are shown.

  Referring to FIG. 11, even in the case shown in FIG. 11, when the engine is started, the heat and hydrogen generator 50 are started simultaneously. When the engine is started, the temperature TD of the exhaust treatment catalyst 13 immediately increases slightly. Next, while the primary warm-up operation, that is, the heat and warm-up operation of the hydrogen generator 50 is performed, that is, while the complete oxidation reaction by the lean air-fuel ratio is continued in the heat and hydrogen generator 50, The temperature TD of the exhaust treatment catalyst 13 increases little by little. However, in the example shown in FIG. 11, unlike the case shown in FIG. 9, when the reforming action by the reforming catalyst 54 becomes possible, that is, the temperature of the downstream end face of the reforming catalyst 54. When TC reaches 700 ° C., the temperature TD of the exhaust treatment catalyst 13 is still maintained below the preset activation temperature TK.

  In FIG. 11, the operation state of the glow plug 68 from the start of the heat and hydrogen generator 50 to the end of the primary warm-up operation, that is, the heat and warm-up operation of the hydrogen generator 50, Change in supply air amount from burner 57, change in fuel supply amount from burner 57, change in O2 / C molar ratio, change in supply air temperature from burner 57, and temperature of downstream end face of reforming catalyst 54 The change in TC is the same as that shown in FIG. Accordingly, the operation of the glow plug 68 shown in FIG. 11 during the period from the start of the heat and hydrogen generator 50 to the end of the primary warm-up operation, that is, the warm-up operation of the heat and hydrogen generator 50 is completed. State, change in supply air amount from burner 57, change in fuel supply amount from burner 57, change in O2 / C molar ratio, change in supply air temperature from burner 57, and downstream end face of reforming catalyst 54 Description of the change in temperature TC is omitted.

  As shown in FIG. 11, when the reforming action by the reforming catalyst 54 becomes possible, that is, when the temperature TC of the downstream end face of the reforming catalyst 54 becomes 700 ° C., When the temperature TD of the exhaust treatment catalyst 13 is lower than the preset activation temperature TK, the complete oxidation reaction with the lean air-fuel ratio is continued. Accordingly, at this time, only heat is supplied from the heat and hydrogen generator 50 to the exhaust treatment catalyst 13, thereby increasing the temperature TD of the exhaust treatment catalyst 13 little by little. This complete oxidation reaction by the lean air-fuel ratio is continued until the temperature TD of the exhaust treatment catalyst 13 reaches a preset activation temperature TK. In the embodiment of the present invention, the temperature from the downstream end face TC of the reforming catalyst 54 reaches 700 ° C. until the temperature TD of the exhaust treatment catalyst 13 reaches the preset activation temperature TK. The operation mode when the complete oxidation reaction with the lean air-fuel ratio is performed is referred to as a heat generation mode as shown in FIG.

  As shown in FIG. 11, when the operation mode is the heat generation mode, the complete oxidation reaction is performed with a lean air-fuel ratio of O2 / C molar ratio = 2.6. Even in the case shown in FIG. 11, when the operation mode is set to the heat generation mode, the heat necessary for raising the temperature TD of the exhaust treatment catalyst 13 to the target warm-up temperature, the output heat amount of the hydrogen generator 50. A required value of (kW) is calculated, and then a target supply fuel amount necessary to generate the required output heat amount of this output heat amount (kW) is calculated. In the example shown in FIG. 11, as shown in FIG. 11, when the operation mode is set to the heat generation mode, the amount of fuel supplied from the burner 57 is increased to this target supply fuel amount.

  On the other hand, when the operation mode is changed to the heat generation mode, as can be seen from FIG. 11, the reforming reaction in the reforming catalyst 54 is not in an equilibrium state. As shown, the temperature of the reforming catalyst 54 does not increase. However, in this heat generation mode, the complete oxidation reaction is performed with the lean air-fuel ratio while the temperature of the reforming catalyst 54 is high. For some reason, the temperature of the reforming catalyst 54 is higher than the allowable catalyst temperature TX. There is a risk of becoming higher. Therefore, in the embodiment of the present invention, the operation mode is changed to the heat generation mode so that the temperature of the reforming catalyst 54 does not become higher than the allowable catalyst temperature TX. The supply of high-temperature air into the burner combustion chamber 53 is stopped, and low-temperature air is supplied into the burner combustion chamber 53 from the low-temperature air flow passage 63. That is, as shown in FIG. 11, the supply air temperature is lowered. Thereafter, low-temperature air continues to be supplied from the low-temperature air flow passage 63 into the burner combustion chamber 53.

  On the other hand, when the operation mode is the heat generation mode and the temperature TD of the exhaust treatment catalyst 13 reaches the preset activation temperature TK, the O2 / C molar ratio is changed from 2.6 to 0.5. And normal operation is started. At this time, the partial oxidation reforming reaction is performed with an O 2 / C molar ratio = 0.5, and heat, heat generated in the hydrogen generator 50 and hydrogen are supplied to the exhaust treatment catalyst 13. As a result, as shown in FIG. 11, the temperature TD of the exhaust treatment catalyst 13 is rapidly raised to the target warm-up temperature. Next, when a stop command is issued, the fuel supply is stopped as shown in FIG. 11, and then after a while. Air supply is stopped.

As described above, in the heat and hydrogen generator 50, the air-fuel ratio is set to the lean air-fuel ratio in order to suppress the generation amount of HC as much as possible during the period from the start of the fuel supply until the fuel is ignited. Has been. However, in practice, a large amount of HC is generated at this time. Also, a large amount of HC is generated during the primary warm-up operation, that is, during the heat-up operation of the heat and hydrogen generator 50. In this case, when these HCs are supplied into the exhaust pipe 12, the HCs adhere to the noble metal on the exhaust treatment catalyst 13 to cover the surface of the noble metal, and as a result, the activation temperature of the exhaust treatment catalyst 13 becomes high. Cause the problem of Further, when HC is supplied into the exhaust pipe 12, there arises a problem that the performance of the NO _X selective reduction catalyst supported on the particulate filter 14 is deteriorated. That is, when the acid sites on _the NO _X selective reducing catalyst to the HC flow into _the NO _X selective reducing catalyst is covered by the HC, urea feed valve ammonia produced from the feed urine hydrophobic from 17 on _the NO _X selective reducing catalyst The acid point cannot be reached. As a result, the selective reduction reaction of NO _X by ammonia is not performed well, and the performance of the NO _X selective reduction catalyst is lowered. In addition, it is widely known that the performance of the NO _X selective reduction catalyst is reduced by HC poisoning in this way.

Therefore, in order to prevent the activation temperature of the exhaust treatment catalyst 13 from becoming high, and further to prevent the occurrence of HC poisoning of the NO _X selective reduction catalyst, in the embodiment of the present invention, the heat and hydrogen generator 50 When the operation of is started, the bypass valve 84 is closed and the main flow passage valve 81 is opened, and the combustion gas discharged from the heat and hydrogen generator 50 is led to the HC adsorption device 82, so that the combustion gas The HC contained in the HC is adsorbed or deposited on the HC adsorption device 82. In this way, the HC contained in the combustion gas is adsorbed or deposited on the HC adsorption device 82, whereby the combustion gas not containing HC is supplied into the exhaust pipe 12, and as a result, the exhaust treatment catalyst 13 is activated. It is possible to prevent the temperature from becoming high, and furthermore, it is possible to prevent a decrease in the performance of the NO _X selective reduction catalyst due to HC poisoning.

  FIG. 12 shows a change in the amount of HC adsorbed or deposited on the HC adsorption device 82 during the warm-up operation of the heat and hydrogen generator 50. As shown in FIG. 12, a part of the HC adsorbed or deposited on the HC adsorbing device 82 is adsorbed or burned while it is being deposited, so that the amount of HC deposition increases gradually while increasing or decreasing. I will go. In the embodiment of the present invention, when the amount of HC deposition increases, the combustion gas containing a large amount of oxygen is supplied to the HC adsorption device 82, and thereby the HC adsorbed or deposited on the HC adsorption device 82. Is trying to burn. At this time, if the amount of accumulated HC is large, the amount of heat generated during combustion increases, and there is a risk that the HC adsorbent of the HC adsorption device 82 is thermally deteriorated.

  Therefore, in the embodiment of the present invention, the upper limit value of the HC deposition amount that does not cause thermal degradation of the HC adsorbent of the HC adsorption device 82 even if the HC adsorbed on the HC adsorption device 82 is burned is set to the allowable HC. When the amount of HC deposition exceeds the allowable amount of HC deposition, the combustion gas containing a large amount of oxygen is supplied to the HC adsorption device 82 and is adsorbed by the HC adsorption device 82, or The accumulated HC is burned. This allowable HC deposition amount is indicated by MAX in FIG. 12. Therefore, as shown in FIG. 12, in the embodiment of the present invention, when the HC deposition amount exceeds this allowable HC deposition amount MAX, deposition was performed. Accumulated HC combustion control for burning HC is started. In the embodiment of the present invention, a combustion gas containing a large amount of oxygen can be generated by causing the heat and hydrogen generator 50 to perform a complete oxidation reaction with a lean air-fuel ratio. Therefore, in the embodiment of the present invention, when the HC deposition amount exceeds the allowable HC deposition amount MAX, the HC adsorption device 82 is caused to perform a complete oxidation reaction by the lean air-fuel ratio in the heat and hydrogen generator 50. The adsorbed HC is burned.

  When the combustion of HC is started, as shown in FIG. 12, the amount of HC deposition is rapidly reduced, and when the amount of HC deposition is less than or equal to the minimum value MIN considered to be almost zero, the accumulation HC combustion control is stopped. Is done. That is, at this time, the complete oxidation reaction by the lean air-fuel ratio for burning the HC adsorbed by the HC adsorption device 82 is stopped.

  Thus, in the embodiment of the present invention, only the heat or heat and hydrogen can be supplied to the exhaust treatment catalyst 13 to warm up the exhaust treatment catalyst 13 disposed in the engine exhaust passage. The heat and hydrogen generator 50 includes a reforming catalyst 54 into which fuel and air combustion gas is fed. In the heat and hydrogen generator 50, A combustion gas containing hydrogen is generated by performing an oxidation reaction, or a combustion gas not containing hydrogen is generated by performing a complete oxidation reaction apparatus under a lean air-fuel ratio. Further, a hydrocarbon adsorbing device 82 capable of adsorbing hydrocarbons in the combustion gas supplied from the heat and hydrogen generating device 30 to the exhaust treatment catalyst 13 is provided, and adsorbed or deposited on the hydrocarbon adsorbing device 82. When the hydrocarbon is combusted, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied to the hydrocarbon adsorption device 50 in the heat and hydrogen generation device 50.

  As described above, in the embodiment of the present invention, when the HC deposition amount exceeds the allowable HC deposition amount MAX during the warm-up operation of the heat and hydrogen generator 50, the complete oxidation reaction under the lean air-fuel ratio is performed. The generated combustion gas is sent to the HC adsorption device 82, whereby the regeneration action of the HC adsorption device 82 is performed. Therefore, in the embodiment of the present invention, the heat and hydrogen generating device 50 can be used to perform a complete oxidation reaction with a lean air-fuel ratio without requiring special piping or the like for regeneration of the HC adsorption device 82. The HC adsorption device 82 can be regenerated.

  On the other hand, in the embodiment of the present invention, during the warm-up operation of the heat and hydrogen generator 50, even if the HC deposition amount exceeds the allowable HC deposition amount MAX, the exhaust treatment catalyst 13 is not activated, that is, When the temperature TD of the exhaust treatment catalyst 13 is lower than a preset activation temperature TK, warming up of the exhaust treatment catalyst 13 is prioritized over regeneration of the HC adsorption device 82. Therefore, at this time, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied into the exhaust pipe 12 through the bypass passage 83 without passing through the HC adsorbing device 82, and thereby the exhaust treatment. The catalyst 13 is quickly warmed up. Next, when the warming-up of the exhaust treatment catalyst 13 is completed, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied to the HC adsorption device 82, and the regeneration operation of the HC adsorption device 82 is performed.

In the embodiment of the present invention, the HC accumulation amount is calculated based on the numerical values shown in the tables of FIGS. Note that the numerical values shown in the respective columns of the table of FIG. 13 indicate the amount of HC generated per second MG (generated when 0.1 (g) of fuel per second is supplied to the heat and hydrogen generator 50 ( mg / s). As shown in FIG. 13, the generated HC amount MG includes the heat, the O ₂ / C molar ratio of air and fuel reacted in the hydrogen generator 50, and the reforming catalyst 54 of the heat, hydrogen generator 50. Is a function of the temperature TBC. In the example shown in FIG. 13, the temperature TBC of the reforming catalyst 54 is an average value of the temperature TB of the upstream end face of the reforming catalyst 54 and the temperature TC of the downstream end face of the reforming catalyst 54. Has been. As can be seen from FIG. 13, the generated HC amount MG decreases as the temperature TBC of the reforming catalyst 54 increases and the O ₂ / C molar ratio increases.

  On the other hand, the numerical values shown in each column of the table of FIG. 14 indicate the combustion HC amount MB (mg / s) per second in the HC adsorption device 82. As shown in FIG. 14, the combustion HC amount MG includes heat, supply air amount (g / s) per second supplied to the hydrogen generation device 50, and heat, hydrogen generation device 50 to HC adsorption device. It is a function of the combustion gas temperature supplied to 82. As the combustion gas temperature, for example, the temperature TC of the downstream end face of the reforming catalyst 54 is used. As can be seen from FIG. 14, the combustion HC amount MB increases as the combustion gas temperature increases and as the amount of heat and air supplied to the hydrogen generator 50 increases.

  As described above, HC is generated by the amount of HC generated MG per second and burned by the amount of combustion HC MB per second. Therefore, assuming that the current HC accumulation amount is ΣHC, the HC accumulation amount after one second. Is represented by ΣHC + MG-MB. In the embodiment of the present invention, it is determined whether or not the HC deposition amount exceeds the allowable HC deposition amount MAX using the HC deposition amount calculated in this way.

  Next, referring to FIG. 15 and FIG. 16, the amount of HC accumulation is calculated, the opening and closing of the main flow passage valve 81 and the bypass valve 84 are controlled, and the combustion of HC adsorbed or deposited on the HC adsorption device 82 is controlled. A deposition HC combustion control routine for this purpose will be described. This accumulated HC combustion control routine is executed by interruption every predetermined time. On the other hand, in this accumulated HC combustion control routine, an HC combustion flag is used. When this HC combustion flag is set, heat is generated by a complete oxidation reaction in the hydrogen generator 50 under a lean air-fuel ratio. The combusted gas is supplied to the HC adsorption device 82. Control of the heat and hydrogen generator 50 based on the HC combustion flag is performed in a heat and hydrogen generation control routine shown in FIGS.

  Referring to FIG. 15, first, at step 100, it is determined whether or not the heat and hydrogen generator 50 is in operation. When the operation of the heat and hydrogen generator 50 is stopped, the routine proceeds to step 125 where the main flow passage valve 81 is opened in order to avoid the main flow passage valve 81 from sticking. Next, at step 126, the bypass valve 84 is opened to avoid sticking of the bypass valve 84. The processing cycle is then completed. On the other hand, when it is determined in step 100 that the heat and hydrogen generator 50 is in operation, the routine proceeds to step 101 where it is determined whether or not the main flow passage valve 81 is open. When the main flow passage valve 81 is open, that is, when the combustion gas is flowing into the HC adsorbing device 82, the routine proceeds to step 102. From step 102 to step 110, the amount of HC accumulation on the HC adsorbing device 82 is calculated. Is done. On the other hand, when the main flow passage valve 81 is closed, that is, when the combustion gas is not flowing into the HC adsorption device 82, the routine jumps to step 111. At this time, the amount of HC accumulation is not calculated.

In step 102, the temperature TBC of the reforming catalyst 54 is calculated from the detection signals of the temperature sensor 71 and the temperature sensor 72 shown in FIG. Next, in step 103, heat, the current O ₂ / C molar ratio in the hydrogen generator 50 (see FIGS. 9 and 11) is read. Next, in step 104, the amount of HC generated (mg / s) generated when 0.1 (g) of fuel per second is supplied to the heat and hydrogen generator 50 from the table shown in FIG. The Next, in step 105, heat and the current fuel supply amount (see FIGS. 9 and 11) in the hydrogen generator 50 are read. Next, at step 106, the generated HC amount MG (mg) per interrupt time Δt is calculated using the current fuel supply amount and the interrupt time Δt.

Next, at step 107, for example, the temperature of the combustion gas flowing into the HC adsorption device 82 is obtained based on the detection signal of the temperature sensor 72. Next, in step 108, heat and the current supply air amount in the hydrogen generator 50 (see FIGS. 9 and 11) are read. Next, at step 109, the amount of combustion HC per second (mg / s) is calculated from the table shown in FIG. 14, and then the amount of combustion HC MB per interruption time Δt (mg) using the interruption time Δt. ) Is calculated. Next, at step 110, an HC accumulation amount ΣHC per interruption time Δt is calculated based on the following equation.
HC accumulation amount ΣHC ← ΣHC + MG-MB
Next, the process proceeds to step 111.

  In step 111, it is determined whether or not the HC combustion flag is set. When the HC combustion flag is not set, the routine proceeds to step 112, where it is determined from the table shown in FIG. 13 whether or not the current generated HC amount (mg / s) is zero. When the current generated HC amount (mg / s) is zero, the routine jumps to step 117 to effectively use the heat and heat generated in the hydrogen generator 50 for warming up the exhaust treatment catalyst 13. The main flow passage valve 81 is closed, and then in step 118, the bypass valve 84 is opened. The processing cycle is then completed. On the other hand, when it is determined in step 112 that the current generated HC amount (mg / s) is not zero, the routine proceeds to step 113, where it is determined whether or not the HC accumulation amount ΣHC exceeds the allowable HC accumulation amount MAX. Determined. When the HC accumulation amount ΣHC does not exceed the allowable HC accumulation amount MAX, the routine proceeds to step 123, where the main flow passage valve 81 is opened, and then, at step 124, the bypass valve 84 is closed. The processing cycle is then completed. At this time, HC contained in the combustion gas is adsorbed or deposited on the HC adsorption device 82.

  On the other hand, when it is determined at step 113 that the HC accumulation amount ΣHC has exceeded the allowable HC accumulation amount MAX, the routine proceeds to step 114 where it is determined whether or not the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK. Determined. When the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK, the routine proceeds to step 115, where the HC combustion flag is set. The processing cycle is then completed. When the HC combustion flag is set, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied to the HC adsorption device 82. Once the HC combustion flag is set, in the next processing cycle, the routine proceeds from step 111 to step 119, where the main flow passage valve 81 is opened, and then in step 120, the bypass valve 84 is closed. Next, at step 121, it is judged if the HC accumulation amount ΣHC has become smaller than the minimum value MIN. When the HC accumulation amount ΣHC is larger than the minimum value MIN, the processing cycle is completed. On the other hand, when it is determined at step 121 that the HC accumulation amount ΣHC has become smaller than the minimum value MIN, the routine proceeds to step 122 where the HC combustion flag is reset. The processing cycle is then completed.

  On the other hand, when it is determined at step 114 that the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK, the routine proceeds to step 116, where a waiting flag is set. This waiting flag continues to be set until the temperature TD of the exhaust treatment catalyst 13 becomes higher than the activation temperature TK. When the wait flag is set at step 116, the routine proceeds to step 117, where the main flow passage valve 81 is closed, and then at step 118, the bypass valve 84 is opened. Thus, even if it is determined that the HC accumulation amount ΣHC exceeds the allowable HC accumulation amount MAX, when the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK, a waiting flag is set and the main flow passage valve 81 is set. Is closed and the bypass valve 84 is opened.

  Next, the heat and hydrogen generation control routine shown in FIGS. 17 to 20 will be described. This heat and hydrogen generation control routine is performed when the starter switch 43 of the engine shown in FIG. 1 is turned on or during the operation of the engine, for example, when the temperature of the exhaust treatment catalyst 13 is higher than the target warm-up temperature. Run when dropped. The starter switch 43 of the engine may be turned on manually by a driver, or may be automatically turned on as in a hybrid vehicle that uses an engine and an electric motor as drive sources.

  When the heat and hydrogen generation control routine is executed, first, in step 200 of FIG. 17, the temperature TD of the upstream end face of the reforming catalyst 54 is determined based on the output signal of the temperature sensor 71. It is determined whether or not the temperature at which the oxidation reaction can be performed on the upstream end face of the catalyst 54 is, for example, 300 ° C. or higher. When the temperature TD on the upstream end face of the reforming catalyst 54 is 300 ° C. or lower, the routine proceeds to step 201 where the glow plug 68 is turned on. Next, at step 202, it is determined whether or not a certain time has elapsed since the glow plug 68 was turned on. When the certain time has elapsed, the routine proceeds to step 203.

In step 203, the air pump 64 is operated, and air is supplied to the burner combustion chamber 53 via the high-temperature air flow passage 62. When the operation of the heat and hydrogen generation device 50 is stopped, the high temperature air valve 65 is opened and the low temperature air valve 66 is closed, so that the heat and hydrogen generation device 50 is operated. The air is supplied to the burner combustion chamber 53 via the high-temperature air flow passage 62. Next, at step 204, the temperature TG of the glow plug 68 is calculated from the resistance value of the glow plug 68. Next, at step 205, it is judged if the temperature TG of the glow plug 68 has exceeded 700.degree. When it is determined that the temperature TG of the glow plug 68 does not exceed 700 ° C., the process returns to step 203. On the other hand, when it is determined that the temperature TG of the glow plug 68 has exceeded 700 ° C., it is determined that ignition is possible, and the routine proceeds to step 206.

  In step 206, fuel is injected from the burner 57 into the burner combustion chamber 53. Next, in step 207, the temperature TD of the upstream end face of the reforming catalyst 54 is detected based on the output signal of the temperature sensor 71. Next, at step 208, it is determined from the output signal of the temperature sensor 71 whether or not the fuel has ignited. When the fuel is ignited, the temperature TD of the upstream end face of the reforming catalyst 54 is instantaneously increased. Therefore, it can be determined from the output signal of the temperature sensor 71 whether or not the fuel has ignited. When it is determined at step 208 that the fuel has not ignited, the routine returns to step 106, and when it is determined at step 108 that the fuel has ignited, the routine proceeds to step 209, where the glow plug 68 is turned off. Next, the process proceeds to step 210 in FIG. When the fuel is ignited, the temperature TD at the upstream end face of the reforming catalyst 54 immediately becomes a temperature at which an oxidation reaction can be performed on the upstream end face of the reforming catalyst 54, for example, 300 ° C. or more. . On the other hand, when it is determined in step 200 that the temperature TD of the upstream end face of the reforming catalyst 54 is 300 ° C. or higher, the process proceeds to step 210.

In step 210 and step 211, the primary warm-up operation is performed. That is, the discharge amount of the air pump 65 is controlled in step 210 so that the O ₂ / C molar ratio is 3.0, and the fuel amount supplied from the burner 57 is controlled in step 211. In the embodiment of the present invention, when the primary warm-up operation is performed, the supply air amount and the supply fuel amount are increased stepwise as shown in FIGS. 9 and 11. Next, at step 212, based on the output signal of the temperature sensor 72, it is determined whether or not the temperature TC of the downstream end face of the reforming catalyst 54 has exceeded 700 ° C. When it is determined that the temperature TC of the downstream end face of the reforming catalyst 4 does not exceed 700 ° C., the process returns to step 210, and the primary warm-up operation, that is, the heat and hydrogen generator 50 warm-up operation continues. Done. On the other hand, when it is determined that the temperature TC of the downstream end face of the reforming catalyst 54 has exceeded 700 ° C., the routine proceeds to step 213.

  In step 213, the low temperature air valve 66 is opened, and in step 214, the high temperature air valve 65 is closed. Accordingly, at this time, air is supplied to the burner combustion chamber 53 via the low-temperature air flow passage 63. Next, at step 215, a required value for the heat required to raise the temperature TD of the exhaust treatment catalyst 13 to the target warm-up temperature and the output heat quantity (kW) of the hydrogen generator 50 is calculated. Next, at step 216, a target supply fuel amount necessary to generate the required output heat amount of the output heat amount (kW) is calculated. Next, at step 217, the activation temperature TK of the exhaust treatment catalyst 13 is determined. The activation temperature TK is set to 110 ° C., for example. Next, at step 218, it is determined whether or not the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK.

When it is determined at step 218 that the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK, the routine proceeds to step 219, where the HC controlled in the accumulated HC combustion control routine shown in FIGS. It is determined whether or not a combustion flag is set. When the HC combustion flag is not set, the routine proceeds to step 221, and the secondary warm-up operation is started as shown in FIG. That is, in step 221, while maintaining the amount of fuel supplied from the burner 57, the discharge amount of the air pump 64 is reduced so that the O ₂ / C molar ratio becomes 0.56. At this time, the partial oxidation reforming reaction is started, and heat and hydrogen are supplied to the exhaust treatment catalyst 13. Next, at step 222, it is determined whether or not the temperature TC of the downstream end face of the reforming catalyst 54 has reached the sum (TA + 805 ° C.) of the air temperature TA detected by the temperature sensor 73 and 805 ° C. . As described above, this temperature (TA + 805 ° C.) is the reaction equilibrium temperature TB when the partial oxidation reforming reaction is performed with an O ₂ / C molar ratio = 0.5 when the air temperature is TA ° C. Show. Therefore, in step 222, it is determined whether or not the temperature TC of the downstream end face of the reforming catalyst 54 has reached the reaction equilibrium temperature (TA + 805 ° C.).

When it is determined that the temperature TC at the downstream end face of the reforming catalyst 54 has not reached the reaction equilibrium temperature (TA + 805 ° C.), the process returns to step 219 so that the O ₂ / C molar ratio becomes 0.56. In addition, the discharge amount of the air pump 64 continues to be controlled. On the other hand, when it is determined at step 222 that the temperature TC of the downstream end face of the reforming catalyst 54 has reached the reaction equilibrium temperature (TA + 805 ° C.), the routine proceeds to step 223 where the discharge amount of the air pump 15 is reduced. While maintaining a constant value, the fuel injection amount is gradually increased to the amount of fuel supplied calculated in step 216. As a result, the O ₂ / C molar ratio gradually decreases. Next, at step 224, it is judged if the O ₂ / C molar ratio has become 0.5. When it is determined that the O ₂ / C molar ratio is not 0.5, the process returns to step 223. In contrast, when it is determined in step 224 that the O ₂ / C molar ratio has become 0.5, it is determined that the secondary warm-up operation has been completed. When it is determined that the secondary warm-up operation has been completed, the routine proceeds to step 231 where normal operation is performed.

On the other hand, when it is determined at step 219 that the HC combustion flag is set, the routine proceeds to step 220 where the fuel injection amount is set to the supply fuel amount calculated at step 216 and the O ₂ / C mole. The discharge amount of the air pump 64 is controlled so that the ratio is 2.6. Accordingly, at this time, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied to the HC adsorption device 82. Then, the process returns to step 219. Therefore, while the HC combustion flag continues to be set, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio continues to be supplied to the HC adsorption device 82 and is adsorbed or deposited on the HC adsorption device 82. Burning HC is burned quickly. Next, when the HC combustion flag is reset, the routine proceeds to step 221.

  On the other hand, when it is determined in step 218 that the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK, the process proceeds to step 225 and the operation mode is set to the heat generation mode as shown in FIG. . That is, in step 225, fuel is injected from the burner 57 with the amount of fuel supplied calculated in step 216, and the discharge amount of the air pump 64 is controlled so that the O2 / C molar ratio is 2.6. At this time, the complete oxidation reaction under a lean air-fuel ratio is continued, and only heat is supplied to the exhaust treatment catalyst 13. Next, at step 226, it is determined whether or not the temperature TD of the exhaust treatment catalyst 13 has reached the activation temperature TK. When the temperature TD of the exhaust treatment catalyst 13 has not reached the activation temperature TK, the process returns to step 225.

On the other hand, when it is determined at step 226 that the temperature TD of the exhaust treatment catalyst 13 has reached the activation temperature TK, the routine proceeds to step 227, where it is controlled in the accumulated HC combustion control routine shown in FIGS. It is determined whether the waiting flag is set. When the wait flag is not set, the routine proceeds to step 228, and the discharge amount of the air pump 64 is set so that the O ₂ / C molar ratio becomes 0.5 while maintaining the amount of fuel supplied from the burner 57 as it is. It can be reduced. At this time, the partial oxidation reforming reaction is started, and heat and hydrogen are supplied to the exhaust treatment catalyst 13. Next, the routine proceeds to step 231 where normal operation is performed. On the other hand, when it is determined at step 227 that the wait flag is set, the routine proceeds to step 229, where the HC combustion flag is set, and then at step 230, the wait flag is reset. Next, the routine proceeds to step 231 where normal operation is performed.

In step 231, it is determined whether or not the HC combustion flag is set. When the HC combustion flag is not set, the process proceeds to step 232, and the O ₂ / C molar ratio is adjusted by adjusting the supply air amount in a state where the supply fuel amount is fixed to the supply fuel amount calculated in step 216. The partial oxidation reforming reaction is performed with = 0.5. At this time, heat and hydrogen are generated, and the heat and hydrogen are supplied to the exhaust treatment catalyst 13. Next, the process proceeds to step 234. On the other hand, when it is determined in step 231 that the HC combustion flag is set, the process proceeds to step 233, and the supply air amount is adjusted in a state where the supply fuel amount is fixed to the supply fuel amount calculated in step 216. By doing so, the complete oxidation reaction is carried out with an O ₂ / C molar ratio = 2.6. At this time, the combustion gas generated by the complete oxidation reaction under the lean air-fuel ratio is supplied to the HC adsorbing device 82, and adsorbed by the HC adsorbing device 82 or accumulated HC is rapidly burned. Next, the process proceeds to step 234.

  As described above, when the HC combustion flag is set and the temperature TD of the exhaust treatment catalyst 13 is higher than the activation temperature TK, complete oxidation by the lean air-fuel ratio is performed during the secondary warm-up operation or during the normal operation. The combustion gas generated by the reaction is supplied to the HC adsorption device 82, and the HC adsorbed or deposited on the HC adsorption device 82 is rapidly burned. On the other hand, when the temperature TD of the exhaust treatment catalyst 13 is lower than the activation temperature TK when the HC combustion flag is set, after the temperature TD of the exhaust treatment catalyst 13 becomes higher than the activation temperature TK, During normal operation, combustion gas generated by performing a complete oxidation reaction with a lean air-fuel ratio is supplied to the HC adsorption device 82, and the HC adsorbed or deposited on the HC adsorption device 82 is rapidly burned.

  In step 234, it is determined whether or not the operation of the heat and hydrogen generator 50 should be stopped. In this case, in the embodiment of the present invention, when the normal operation is continued for a certain period, or when the temperature TD of the exhaust treatment catalyst 13 reaches the target warm-up temperature, or for other reasons, the heat and hydrogen generator When a command to stop the operation of 50 is issued, it is determined that the operation of the heat and hydrogen generator 50 should be stopped. If it is determined in step 234 that the operation of the heat and hydrogen generator 50 should not be stopped, the process returns to step 231. On the other hand, when it is determined in step 234 that the operation of the heat and hydrogen generator 50 should be stopped, the routine proceeds to step 235, where fuel injection from the burner 57 is stopped.

  Next, in step 236, air continues to be supplied from the air pump 64 to burn off the remaining fuel. Next, in step 237, it is determined whether or not a certain time has elapsed. If it is determined that the fixed time has not elapsed, the process returns to step 236. On the other hand, when it is determined in step 237 that the predetermined time has elapsed, the process proceeds to step 238, where the operation of the air pump 65 is stopped and the supply of air into the burner combustion chamber 53 is stopped. Next, at step 239, the low temperature air valve 66 is closed, and at step 240, the high temperature air valve 65 is opened. Next, while the operation of the heat and hydrogen generator 50 is stopped, the low temperature air valve 66 is kept closed and the high temperature air valve 65 is kept opened.

Next, the catalyst temperature increase restriction control routine will be described with reference to FIG. This routine is executed by interruption every predetermined time.
Referring to FIG. 21, first, in step 300, the temperature TC of the downstream end face of the reforming catalyst 54 detected by the temperature sensor 72 is read. Next, at step 301, it is judged if the temperature TC of the downstream end face of the reforming catalyst 54 has exceeded the allowable catalyst temperature TX. When it is determined that the temperature TC at the downstream end face of the reforming catalyst 54 does not exceed the allowable catalyst temperature TX, the processing cycle is completed.

  On the other hand, when it is determined at step 301 that the temperature TC of the downstream end face of the reforming catalyst 54 has exceeded the allowable catalyst temperature TX, the routine proceeds to step 302 where the low temperature air valve 66 is opened, and then In step 303, the hot air valve 65 is closed. The processing cycle is then completed. That is, when the temperature TC of the downstream end face of the reforming catalyst 54 exceeds the allowable catalyst temperature TX during the operation of the heat and hydrogen generator 50, the air flow path for sending air into the burner combustion chamber 53 has a high temperature. Is switched from a high-temperature air flow path for feeding the air to a low-temperature air flow path for sending low-temperature air, and the temperature of the burner combustion air supplied into the burner combustion chamber 53 is lowered.

DESCRIPTION OF SYMBOLS 1 Engine main body 12 Exhaust pipe 13 Exhaust treatment catalyst 14 Particulate filter 50 Heat, hydrogen production | generation apparatus 51 Passage switching device 53 Burner combustion chamber 54 Reforming catalyst 57 Burner 80 Main flow passage 81 Main flow passage valve 82 HC adsorption device 83 Bypass passage 84 Bypass valve

Claims (1)

  An exhaust treatment catalyst disposed in the engine exhaust passage, and a heat and hydrogen generator that can supply only heat or heat and hydrogen to the exhaust treatment catalyst in order to warm up the exhaust treatment catalyst. The heat and hydrogen generator includes a reforming catalyst into which a combustion gas of fuel and air is sent. In the heat and hydrogen generator, a combustion gas containing hydrogen or a lean gas is generated by performing a partial oxidation reaction. Combustion gas that does not contain hydrogen is generated by performing a complete oxidation reactor under an air-fuel ratio, and furthermore, hydrocarbons in the combustion gas supplied from the hydrogen generator to the exhaust treatment catalyst can be adsorbed. When the hydrocarbon adsorbed or deposited on the hydrocarbon adsorbing device is burned, the heat and hydrogen generating device are subjected to a complete oxidation reaction under a lean air-fuel ratio. Generation An exhaust purification system of an internal combustion engine which is adapted to supply combustion gases to the hydrocarbon adsorber.

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