JP2007032398A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology to suitably increase the temperature of an exhaust gas purifying catalyst and suppress fuel consumption accompanied by the increase. <P>SOLUTION: In a configuration having the exhaust gas purifying catalyst and a catalyst temperature increase means for increasing the temperature of the catalyst, the catalyst temperature increase means is provided with an air supply means supplying fresh air, a fuel supply means, a premixed space where fresh air supplied by the air supply means and fuel supplied by the fuel supply means are mixed and air fuel mixture is formed, an ignition means igniting air fuel mixture formed in the premixed space, and a combustion catalyst. The combustion catalyst is formed by applying a wash coat on a Fe-Cr-Al stainless structure called a metal honeycomb and dispersing and carrying noble metal particles, and is provided between the air supply means, fuel supply means, premixed space, ignition means and the exhaust gas purifying catalyst. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to a technique for increasing the temperature of an exhaust gas purification catalyst.

  As an exhaust gas purification apparatus for an internal combustion engine, a catalytic converter that is activated with a HC (hydrocarbon) component as a reducing agent in the middle of an exhaust passage to reduce and decompose NOx (nitrogen oxide), and an exhaust gas introduction side of the catalytic converter Has been proposed in which a burner for heating the catalytic converter and means for detecting the temperature of the exhaust gas led to the catalytic converter are provided in the vicinity (see, for example, Patent Document 1).

In this exhaust purification device, when the temperature of the exhaust gas led to the catalytic converter is equal to or lower than the activation lower limit temperature of the catalyst, the burner is controlled to generate a flame to heat the catalyst. On the other hand, when the temperature is equal to or higher than the activation lower limit temperature, misfire occurs and HC, which is a burner fuel, is added to the catalyst so that the catalyst is always activated.
Utility Model Registration No. 2500050 JP 2000-282920 A Japanese Patent No. 2752114 JP-A-5-184875

  However, since the flame temperature of the burner is high and the distance between the burner and the catalytic converter is short, the temperature of the catalyst becomes excessively high and the catalyst may be thermally deteriorated. On the other hand, if the burner and the catalytic converter are moved away from each other, the heat transfer efficiency is deteriorated, and the fuel efficiency is deteriorated.

  Further, the flame temperature of the burner is high, and there is a possibility that a large amount of NOx exists in the exhaust gas of the burner itself, and that NOx is discharged into the atmosphere.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique for appropriately raising the temperature of the exhaust purification catalyst and suppressing fuel consumption associated therewith. .

  In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention is provided in an exhaust passage of the internal combustion engine and purifies exhaust gas, and raises the temperature of the exhaust gas purification catalyst. In the exhaust gas purification apparatus for an internal combustion engine comprising a catalyst temperature raising means, the catalyst temperature raising means is supplied by an air supply means for supplying fresh air, a fuel supply means for supplying fuel, and the air supply means. Premixed space in which fresh air and fuel supplied by the fuel supply means are mixed to form a mixture, ignition means for igniting the mixture formed in the premixed space, and the air supply Means, a fuel supply means, the premixing space and the ignition means, and a combustion catalyst provided between the exhaust purification catalyst.

  Here, the exhaust purification catalyst is a ceramic carrier catalyst. On the other hand, the combustion catalyst is a catalyst in which noble metal fine particles are dispersed and supported on a Fe-Cr-Al stainless steel structure called a metal honeycomb by applying a wash coat.

  The combustion catalyst configured as described above has a noble metal catalyst component finely divided and has high dispersibility, and can oxidize and decompose organic components at a low temperature. Moreover, since this combustion catalyst is a stainless steel substrate, it has high thermal conductivity and low heat capacity. Therefore, the rise to the catalyst operating temperature (activation temperature) is much faster than the ceramic carrier catalyst. Furthermore, since the substrate is made of stainless steel, it has a very high heat resistance and is hardly damaged even when exposed to high-temperature exhaust gas.

  In the exhaust gas purification apparatus for an internal combustion engine thus configured, when the temperature of the exhaust gas purification catalyst has not reached the activation temperature, such as during a cold start of the internal combustion engine, fresh air is generated by the air supply means. In addition to supplying the fuel with the fuel supply means, a fresh air / fuel mixture is formed in the premix space. Thereafter, combustion gas can be generated by igniting the air-fuel mixture with an ignition means. The combustion gas and the exhaust purification catalyst can be heated by the combustion gas.

  As described above, since the combustion catalyst has high thermal conductivity and low heat capacity, it rises early to the activation temperature. When the combustion catalyst reaches the activation temperature, the combustion gas generated by ignition of the ignition means, fresh air supplied by the air supply means, and oxygen and HC (hydrocarbon in the fuel supplied by the fuel supply means) ) Reacts on the catalyst. Then, the combustion gas is further warmed by the reaction heat and the temperature of the gas reaching the exhaust purification catalyst is increased, so that the temperature of the exhaust purification catalyst rises. As a result, since the temperature of the exhaust purification catalyst can be raised early, exhaust emission can be improved.

  Further, since the reaction at the combustion catalyst is HC oxidative decomposition (low temperature combustion) and lean combustion (flameless combustion) at 1500 ° C. or less, the temperature of the exhaust purification catalyst does not become excessively high. The burner flame has a high temperature of 2000 ° C. or higher. Compared with heating the exhaust purification catalyst directly with this burner flame, the thermal effect on the exhaust purification catalyst can be reduced and the thermal deterioration of the catalyst can be suppressed. it can.

  In addition, in the catalyst temperature raising means according to the present invention, a combustion catalyst is provided between the air supply means, the fuel supply means, the premixing space and the ignition means, and the exhaust purification catalyst. Therefore, the combustion gas generated by ignition by the ignition means does not directly reach the exhaust purification catalyst but passes through the combustion catalyst, so that the temperature is lowered before reaching the exhaust purification catalyst. Therefore, thermal deterioration of the exhaust purification catalyst can be suppressed. Further, since the distance between the catalyst temperature raising means and the exhaust purification catalyst can be reduced, the thermal efficiency can be improved, and the deterioration of fuel consumption caused by raising the temperature of the exhaust purification catalyst can be suppressed. As described above, since the base of the combustion catalyst is stainless steel, it has very high heat resistance and is hardly damaged even when exposed to high-temperature combustion gas.

  Further, in the catalyst temperature raising apparatus according to the present invention, after the start of the internal combustion engine, even after the exhaust purification catalyst has once reached the activation temperature, the low load operation of the internal combustion engine is continued. Even when the temperature of the exhaust gas to reach is lowered and the exhaust purification catalyst may be out of the active temperature range, the exhaust temperature is increased by increasing the temperature of the exhaust purification catalyst by the catalyst temperature raising means, as in the above-mentioned start. The temperature of the purification catalyst can be maintained in the activation temperature region.

  When there is no need to raise the temperature of the exhaust purification catalyst so much, the air-fuel mixture in the premixing space is not ignited by the ignition means, fresh air is supplied by the air supply means, and fuel is supplied by the fuel addition means. You may just add. Even in such a case, fresh air supplied by the air supply means and oxygen or HC (hydrocarbon) in the fuel added by the fuel addition means react on the combustion catalyst, and the exhaust heat purification catalyst is generated by the reaction heat. Can warm up.

  Further, when there is a possibility that the temperature of the exhaust purification catalyst will rise excessively, the exhaust purification catalyst is cooled by supplying fresh air by the air supply means without adding fuel by the fuel addition means, and the exhaust purification catalyst is supplied. Thermal deterioration of the catalyst can be suppressed.

  In the exhaust purification device described above, a branch passage that branches from the exhaust passage upstream of the exhaust purification catalyst and communicates with the exhaust purification catalyst, and a flow rate adjusting means that adjusts the flow rate of the exhaust gas flowing through the branch passage. Furthermore, it is preferable that the catalyst temperature raising means is provided in the branch passage.

  In the exhaust gas purification apparatus for an internal combustion engine configured in this way, the flow rate of the exhaust gas flowing through the branch passage can be adjusted by the flow rate adjusting means, and when the exhaust gas passes through the combustion catalyst, the heat As a result, the temperature of the combustion catalyst can be increased. As a result, the reaction at the combustion catalyst can be promoted, and the temperature of the exhaust purification catalyst can be raised at an early stage as the reaction is promoted.

  Further, when the combustion catalyst has reached the activation temperature, in addition to the combustion gas generated by ignition of the ignition means, the fresh air supplied by the air supply means, and the fuel supplied by the fuel supply means, the internal combustion engine Oxygen and HC (hydrocarbon) in the exhaust discharged from the reactor react on the catalyst.

  The amount of fresh air supplied by the air supply means and the amount of fuel supplied by the fuel supply means can be adjusted according to the flow rate of the exhaust gas passing through the combustion catalyst and the air-fuel ratio thereof. Thus, assuming that the amount of heat generated in the combustion catalyst is the same, the driving of the air supply means and the fuel supply means can be reduced as oxygen and HC in the exhaust gas increase. As a result, power for driving the air supply means and the fuel supply means can be minimized, so that fuel consumption can be suppressed in order to raise the temperature of the catalyst.

  As described above, according to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, it is possible to suitably increase the temperature of the exhaust gas purification catalyst and to suppress fuel consumption associated therewith.

  The best mode for carrying out the present invention will be exemplarily described in detail below based on the following embodiments with reference to the drawings.

  As shown in FIG. 1, an exhaust purification catalyst 3 is provided in the middle of the exhaust passage 2 of the internal combustion engine 1.

  A branch passage 4 is formed on the upstream side of the exhaust purification catalyst 3 so as to branch from the exhaust passage 2 and communicate with the exhaust purification catalyst 3. The branch passage 4 is used to increase the temperature of the exhaust purification catalyst 3. A catalyst temperature raising device 5 as an apparatus is provided. The branch passage 4 upstream of the catalyst temperature raising device 5 is provided with a flow rate control valve 6 for controlling the flow rate of the exhaust gas from the internal combustion engine 1 flowing through the branch passage 4.

  The catalyst temperature raising device 5 is formed in a combustion catalyst 51 having an electric heater (glow plug) 50 therein and a branch passage 4 upstream of the combustion catalyst 51 and downstream of the flow control valve 6. The fuel addition valve 52 that supplies fuel to the premixing space 55, the air pump 53 that supplies fresh air to the premixing space 55, and the air-fuel mixture in the branch passage 4 upstream of the combustion catalyst 51 and downstream of the air pump 53. And an ignition plug 54 for igniting the battery.

  The combustion catalyst 51 in this embodiment is obtained by applying a wash coat on a Fe—Cr—Al stainless steel structure called a metal honeycomb to disperse and carry precious metal fine particles. The combustion catalyst 51 configured as described above has a noble metal catalyst component finely divided and has high dispersibility, and can oxidize and decompose organic components at a low temperature.

  Moreover, since this catalyst 51 is a stainless steel base, its thermal conductivity is high and its heat capacity is low. Therefore, the rise to the catalyst operating temperature (activation temperature) is much faster than the ceramic carrier catalyst. Furthermore, since the substrate is made of stainless steel, it has a very high heat resistance and is hardly damaged even when exposed to high-temperature exhaust gas.

  The electric heater 50, the fuel addition valve 52, the air pump 53, the spark plug 54, and the flow rate control valve 6 of the exhaust purification apparatus according to the present embodiment are from an electronic control unit (ECU) 10 provided in the internal combustion engine 1. Is controlled based on the command signal.

  In the exhaust gas purification apparatus configured as described above, when the temperature of the exhaust gas purification catalyst 3 is low and has not reached its activation temperature, for example, when the internal combustion engine 1 is started, the exhaust gas discharged from the internal combustion engine 1 is exhausted. In some cases, it cannot be sufficiently purified. If it does so, the exhaust_gas | exhaustion discharged | emitted from the internal combustion engine 1 may be diffused outside a vehicle, without being fully purified, and there exists a possibility that emission may deteriorate.

  Therefore, in this embodiment, when the temperature of the exhaust purification catalyst 3 is low, such as when the internal combustion engine 1 is started, the amount of exhaust that passes through the branch passage 4 by driving the flow control valve 6 to the valve opening side. Increase. Then, fresh air is supplied to the premixing space 55 by the air pump 53 and fuel is added from the fuel addition valve 52 to form a mixture in the premixing space 55 and then ignited by the spark plug 54. As a result, the combustion gas reaches the combustion catalyst 51 and the exhaust purification catalyst 3, and these catalysts are warmed.

  As described above, the combustion catalyst 51 has a high thermal conductivity and a low heat capacity, so that it quickly rises to the activation temperature. When the combustion catalyst 51 reaches the activation temperature, the exhaust gas from the internal combustion engine 1 and oxygen or HC (hydrocarbon) in the combustion gas caused by ignition at the spark plug 54 react on the catalyst 51. Then, the temperature of the combustion catalyst 51 rises due to the reaction heat, the temperature of the gas reaching the exhaust purification catalyst 3 is increased, and the temperature of the exhaust purification catalyst 3 rises. Further, the exhaust from the internal combustion engine 1 can be purified by the combustion catalyst 51.

  However, since the reaction at the combustion catalyst 51 is oxidative decomposition (low temperature combustion) of HC and lean combustion (flameless combustion) at 1500 ° C. or less, the temperature of the exhaust purification catalyst 3 does not become excessively high. The burner flame is at a high temperature of 2000 ° C. or higher, and compared with the case where the exhaust purification catalyst 3 is directly warmed by this burner flame, the heat effect on the exhaust purification catalyst 3 is small and the thermal degradation of the exhaust purification catalyst 3 is suppressed. Can do.

  Further, in the catalyst temperature raising device 5 in the present embodiment, the combustion catalyst 51 is provided between the exhaust purification catalyst 3 and the spark plug 54, and between the exhaust purification catalyst 3 and the spark plug 54 is sufficient. Space is provided. Therefore, since the temperature of the combustion gas resulting from ignition by the spark plug 54 decreases before reaching the exhaust purification catalyst 3, thermal deterioration of the exhaust purification catalyst 3 can be suppressed.

  As a result, the distance between the catalyst temperature raising device 5 and the exhaust purification catalyst 3 can be reduced, so that the thermal efficiency can be improved and the deterioration of fuel consumption caused by raising the temperature of the exhaust purification catalyst 3 can be suppressed. it can. Since the base of the combustion catalyst 51 is stainless steel, it has extremely high heat resistance and is not easily damaged even when exposed to high-temperature exhaust gas.

  Further, an electrothermal heater 50 is provided inside the combustion catalyst 51, and the combustion catalyst 51 can be brought to the activation temperature at an early stage when the internal combustion engine 1 is cold started. The reaction at 51 can be promoted. As a result, the exhaust purification catalyst 3 can also be brought to the activation temperature at an early stage.

  Further, in the catalyst temperature raising device 5 in this embodiment, after the internal combustion engine 1 is started, the low-load operation of the internal combustion engine 1 is continued even after the exhaust purification catalyst 3 once reaches the activation temperature. When the temperature of the exhaust gas reaching the exhaust purification catalyst 3 is lowered and the exhaust purification catalyst 3 may be out of the active temperature range, the catalyst temperature raising device 5 can be controlled in the same manner as the control at the time of starting. Is preferred.

  That is, the amount of exhaust gas passing through the branch passage 4 is increased by driving the flow control valve 6 to the valve opening side. Then, fresh air is supplied to the premixing space 55 by the air pump 53 and fuel is added from the fuel addition valve 52 to form a mixture in the premixing space 55 and then ignited by the spark plug 54. As a result, when the internal combustion engine 1 is in operation, the exhaust purification catalyst 3 can always be kept at the activation temperature, so that exhaust emission can be improved.

  When it is not necessary to raise the temperature of the exhaust purification catalyst 3 so much, the flow control valve 6 is opened without igniting the air-fuel mixture in the premixing space 55 and the branch passage 4 downstream thereof with the spark plug 54. It is also possible to drive to the side, supply fresh air from the air pump 53 and add fuel from the fuel addition valve 52.

  Even in such a case, the exhaust gas from the internal combustion engine 1, the fresh air supplied from the air pump 53, and the oxygen and HC (hydrocarbon) in the fuel added from the fuel addition valve 52 react on the catalyst 51, and the reaction heat. Thus, the temperature of the gas reaching the exhaust purification catalyst 3 can be increased, and the temperature of the exhaust purification catalyst 3 can be raised.

  Further, it is preferable to control the opening degree of the flow control valve 6 and the driving of the air pump 53 and the fuel addition valve 52 based on the detection value of the oxygen concentration sensor 7 provided in the exhaust passage 2. For example, when the lean value of the air-fuel ratio of the exhaust gas is high according to the detection value of the oxygen concentration sensor 7, the driving of the air pump 53 is stopped, or when the lean degree of the air-fuel ratio of the exhaust gas is low, the valve opening degree of the flow control valve 6 is set. Control is made to reduce the flow rate of the exhaust gas flowing through the branch passage 4 and drive the air pump 53. Further, when the air-fuel ratio of the exhaust is rich, the fuel addition valve 52 performs control so that fuel is not added.

  As a result, assuming that the amount of heat generated in the combustion catalyst 51 is the same, the drive of the air pump 53 and the fuel addition valve 52 can be reduced as oxygen and HC in the exhaust gas increase. Further, it is possible to suppress the deterioration of the fuel consumption accompanying the increase in the temperature of the exhaust purification catalyst 3.

  Further, when there is a possibility that the temperature of the exhaust purification catalyst 3 will rise excessively, the exhaust purification catalyst 3 is cooled by supplying fresh air with the air pump 53 without adding fuel with the fuel addition valve 52, Thermal deterioration of the exhaust purification catalyst 3 can be suppressed.

  FIG. 2 shows a schematic configuration of the exhaust purification apparatus according to the present embodiment. As shown in the figure, the exhaust purification apparatus according to the present embodiment differs from the exhaust purification apparatus according to the first embodiment only in the following points.

  The catalyst temperature raising device 5 is not installed on the passage branched from the exhaust passage 2 but on the combustion gas passage 8 independent of the exhaust passage 2. Then, one end of the combustion gas passage 8 is formed so that the combustion gas flowing through the combustion gas passage 8 directly hits the exhaust purification catalyst 3.

  In the exhaust purification device configured as described above, when the temperature of the exhaust purification catalyst 3 is low, such as when the internal combustion engine 1 is started, fresh air is supplied to the combustion gas passage 8 by the air pump 53 and from the fuel addition valve 52. After adding fuel and forming an air-fuel mixture in the premixing space 55, ignition is performed with a spark plug 54. As a result, the combustion gas reaches the combustion catalyst 51 and the exhaust purification catalyst 3, and these catalysts are warmed.

  As described above, the combustion catalyst 51 has a high thermal conductivity and a low heat capacity, so that it quickly rises to the activation temperature. When the combustion catalyst 51 reaches the activation temperature, oxygen and HC (hydrocarbon) in the combustion gas react on the catalyst 51. Then, the temperature of the combustion catalyst 51 rises due to the reaction heat, the temperature of the gas reaching the exhaust purification catalyst 3 is increased, and the temperature of the exhaust purification catalyst 3 rises.

  Further, by using the electric heater 50 provided inside the combustion catalyst 51, the combustion catalyst 51 can be heated to the activation temperature at an early stage when the internal combustion engine 1 is cold started. Therefore, the reaction in the combustion catalyst 51 can be promoted, and the exhaust purification catalyst 3 can be brought to the activation temperature at an early stage.

  Further, as described above, since the reaction at the combustion catalyst 51 is low-temperature combustion, it is possible to prevent the exhaust purification catalyst 3 from being thermally deteriorated by the combustion gas generated by ignition of the spark plug 54. Further, in the catalyst temperature raising device 5 in this embodiment, the combustion catalyst 51 is provided between the exhaust purification catalyst 3 and the ignition plug 54, so that the combustion gas generated by ignition at the ignition plug 54 is exhausted. Since the temperature decreases before reaching 3, the thermal deterioration of the exhaust purification catalyst 3 can be suppressed.

  Then, the catalyst temperature raising device 5 and the exhaust purification catalyst 3 can be brought close to each other, so that the thermal efficiency can be increased. As a result, it is possible to suppress the deterioration of fuel consumption as the exhaust purification catalyst 3 is heated using the catalyst temperature raising device 5.

  Further, in the catalyst temperature raising apparatus 5 in the present embodiment as well, when the exhaust purification catalyst 3 is likely to be out of the activation temperature range even after the warm-up of the internal combustion engine 1 is completed, the above-described control at the time of starting is performed. It is preferable to control the catalyst temperature raising device 5 similarly to the above.

  That is, fresh air is supplied to the branch passage 4 by the air pump 53 and fuel is added from the fuel addition valve 52 to form an air-fuel mixture in the premixing space 55, and then ignition is performed by the spark plug 54. As a result, when the internal combustion engine 1 is in operation, the exhaust purification catalyst 3 can always be kept at the activation temperature, so that exhaust emission can be improved.

  When it is not necessary to raise the temperature of the exhaust purification catalyst 3 so much, fresh air is supplied from the air pump 53 and the fuel addition valve 52 is not ignited by the spark plug 54. It is only necessary to add fuel.

  Even in such a case, fresh air supplied from the air pump 53 and oxygen or HC (hydrocarbon) in the fuel added from the fuel addition valve 52 react on the catalyst 51 and warm the exhaust purification catalyst 3 by the reaction heat. be able to.

  As described above, in the exhaust purification device according to the present embodiment, the temperature of the exhaust purification catalyst 3 can be quickly raised by controlling the catalyst temperature raising device 5 during a cold start of the internal combustion engine. In addition, after the warm-up is completed, the temperature of the exhaust purification catalyst 3 can be kept at the activation temperature during the operation of the internal combustion engine.

  Therefore, according to the exhaust gas purification apparatus of the present embodiment, exhaust emission can be improved and the accompanying fuel consumption can be suppressed.

  FIG. 3 shows a schematic configuration of the exhaust purification apparatus according to the present embodiment. As shown in the figure, the exhaust gas purification apparatus according to the present embodiment is provided with a catalyst temperature raising device 5 in the exhaust passage 2 upstream of the exhaust purification catalyst 3.

  That is, the combustion catalyst 51 is provided in the exhaust passage 2 upstream of the exhaust purification catalyst 3, and the fuel addition valve 52 for supplying fuel, the air pump 53 for supplying fresh air, and the spark plug 54 are provided in the exhaust passage 2 upstream thereof. Provide.

  In the exhaust gas purification apparatus configured as described above, after supplying fresh air to the exhaust gas from the internal combustion engine 1 by the air pump 53 and adding fuel from the fuel addition valve 52, such as when the internal combustion engine 1 is started, Ignite with spark plug 54. Exhaust gas whose temperature has been increased by the combustion reaches the combustion catalyst 51 and the exhaust gas purification catalyst 3, and these catalysts are warmed.

  Further, when the combustion catalyst 51 reaches the activation temperature, the exhaust gas from the internal combustion engine 1 and oxygen and HC (hydrocarbon) in the combustion gas caused by ignition at the spark plug 54 react on the catalyst 51. Then, the temperature of the combustion catalyst 51 rises due to the reaction heat, the temperature of the exhaust gas reaching the exhaust purification catalyst 3 is increased, and the temperature of the exhaust purification catalyst 3 rises.

  Further, as described above, since the reaction at the combustion catalyst 51 is low-temperature combustion, it is possible to prevent the exhaust purification catalyst 3 from being thermally deteriorated by the combustion gas generated by ignition of the spark plug 54. Further, in the catalyst temperature raising device 5 in this embodiment, the combustion catalyst 51 is provided between the exhaust purification catalyst 3 and the ignition plug 54, so that the combustion gas generated by ignition at the ignition plug 54 is exhausted. Since the temperature decreases before reaching 3, the thermal deterioration of the exhaust purification catalyst 3 can be suppressed.

  As a result, the catalyst temperature raising device 5 and the exhaust purification catalyst 3 can be brought closer to each other, so that the thermal efficiency can be increased. As the temperature of the exhaust purification catalyst 3 is raised using the catalyst temperature raising device 5, the fuel efficiency is increased. Can be prevented from deteriorating.

  Further, in the catalyst temperature raising apparatus 5 in the present embodiment as well, when the exhaust purification catalyst 3 is likely to be out of the activation temperature range even after the warm-up of the internal combustion engine 1 is completed, the above-described control at the time of starting is performed. It is preferable to control the catalyst temperature raising device 5 similarly to the above.

  In other words, fresh air is supplied to the exhaust gas by the air pump 53 and fuel is added from the fuel addition valve 52 to form an air-fuel mixture, which is then ignited by the spark plug 54. As a result, when the internal combustion engine 1 is in operation, the exhaust purification catalyst 3 can always be kept at the activation temperature, so that exhaust emission can be improved.

Further, when it is not necessary to raise the temperature of the exhaust purification catalyst 3 so much, it is sufficient to supply fresh air from the air pump 53 and / or add fuel from the fuel addition valve 52. Even in such a case, oxygen and HC (hydrocarbon) in the exhaust gas from the internal combustion engine 1, fresh air supplied from the air pump 53 and / or fuel added from the fuel addition valve 52 react on the combustion catalyst 51. The exhaust purification catalyst 3 can be warmed by the reaction heat.

  As described above, in the exhaust gas purification apparatus according to the present embodiment, the temperature of the exhaust gas purification catalyst 3 can be quickly raised by controlling the catalyst temperature raising device 5 when the internal combustion engine is cold started. After the warm-up is completed, the temperature of the exhaust purification catalyst 3 can be kept at the activation temperature during the operation of the internal combustion engine.

  Therefore, according to the exhaust gas purification apparatus of the present embodiment, exhaust emission can be improved and the accompanying fuel consumption can be suppressed.

  FIG. 4 shows a schematic configuration of the exhaust purification apparatus according to the present embodiment. As shown in the figure, the exhaust gas purification apparatus according to the present embodiment differs from the exhaust gas purification apparatus according to the first embodiment in a catalyst temperature raising device 5.

  In the catalyst temperature raising apparatus 5 according to this embodiment, a metal fiber burner 56 is provided on the branch passage 4 in a cylindrical shape, and the exhaust gas passes through the space inside the metal fiber burner 56. A spark plug 54 is provided so that the electrode exists in the space inside the metal fiber burner 56.

  The metal fiber burner 56 uses a metal fiber mat as a breathable material. This metal fiber mat is drawn, fiberized, and randomly laminated with a heat-resistant alloy containing iron, chromium, aluminum, and yttrium as components. After being layered, it is sintered at a thickness of 2 to 4 mm.

  A premix space 55 is formed outside the metal fiber burner 56 so as to wrap the metal fiber burner 56, and fuel is added into the premix space 55 from the fuel addition valve 52 and the air pump 53. Fresh air is supplied from. An electrothermal heater 50 is provided outside the outer periphery of the metal fiber burner 56.

  In the catalyst temperature raising apparatus 5 configured as described above, when fuel is added from the fuel addition valve 52 into the premixing space 55 and fresh air is supplied from the air pump 53, the fuel is heated in the premixing space 55. Fresh air is mixed. Thereafter, the air-fuel mixture permeates the metal fiber burner 56 and gets into the branch passage 4. When penetrating through the metal fiber burner 56, the fuel becomes uniform and a uniform air-fuel mixture leaks into the branch passage 4.

  Then, the air-fuel mixture that has oozed into the branch passage 4 is ignited by the spark plug 54 and burned. Then, the temperature of the exhaust gas from the internal combustion engine 1 can be raised by the combustion heat, and the temperature of the exhaust gas purification catalyst 3 can be raised by the exhaust gas having a high temperature. As described above, since the ignition mixture is ignited by the spark plug 54, its combustion temperature is low, and even if the combustion gas reaches the exhaust purification catalyst 3, it does not reach an excessively high temperature. Thermal degradation of the catalyst 3 can be suppressed.

  Further, when combustion gas is generated inside the metal fiber burner 56, evaporation of fuel added into the premixing space 55 is promoted by the heat, and a more uniform mixture is easily formed. Furthermore, by using the electric heater 50, evaporation of fuel can be promoted, and a more uniform air-fuel mixture can be formed.

In the exhaust purification device configured as described above, when the temperature of the exhaust purification catalyst 3 is low, such as when the internal combustion engine 1 is started, the flow control valve 6 is driven to the valve opening side to pass through the branch passage 4. Increase the amount of exhaust. Then, fresh air is supplied into the premixing space 55 by the air pump 53 and fuel is added from the fuel addition valve 52.

  Then, the air-fuel mixture blotted in the branch passage 4 is ignited by the spark plug 54 and burned. As a result, the temperature of the exhaust from the internal combustion engine 1 is raised by the combustion heat, the exhaust reaches the exhaust purification catalyst 3, and the catalyst 3 is warmed.

  Further, in the catalyst temperature raising apparatus 5 in the present embodiment, after the completion of warming-up of the internal combustion engine 1, when there is a possibility that the temperature of the exhaust purification catalyst 3 may deviate from the activation temperature range, it is the same as the control at the time of starting described above. It is preferable to control the catalyst temperature raising device 5. As a result, when the internal combustion engine 1 is in operation, the exhaust purification catalyst 3 can always be kept at the activation temperature, so that exhaust emission can be improved.

  As described above, in the exhaust gas purification apparatus according to the present embodiment, the temperature of the exhaust gas purification catalyst 3 is quickly increased by controlling the catalyst temperature raising device 5 and the flow rate control valve 6 when the internal combustion engine is cold started. In addition, after the warm-up is completed, the temperature of the exhaust purification catalyst 3 can be kept at the activation temperature during the operation of the internal combustion engine. Thereby, exhaust emission can be improved.

  Further, since the combustion in the catalyst temperature raising device 5 is an air-fuel mixture that is uniformly mixed, the temperature of the exhaust purification catalyst 3 can be increased with a minimum amount of fuel, so the temperature of the exhaust purification catalyst 3 is increased. It is possible to suppress deterioration in fuel consumption associated with the operation.

1 is a diagram illustrating a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment. FIG. 5 is a diagram illustrating a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to a second embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to a third embodiment. FIG. 10 is a diagram illustrating a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to a fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Exhaust purification catalyst 4 Branch passage 5 Catalyst temperature rising device 6 Flow control valve 7 Oxygen concentration sensor 8 Combustion gas passage 10 ECU
50 Electric heater (Glow plug)
51 Combustion Catalyst 52 Fuel Addition Valve 53 Air Pump 54 Spark Plug 55 Premixing Space 56 Metal Fiber Burner

Claims (2)

An exhaust purification catalyst that is provided in an exhaust passage of the internal combustion engine and purifies exhaust;
Catalyst temperature raising means for raising the temperature of the exhaust purification catalyst;
An exhaust gas purification apparatus for an internal combustion engine comprising:
The catalyst temperature raising means
Air supply means for supplying fresh air;
Fuel supply means for supplying fuel;
A premixing space in which fresh air supplied by the air supply means and fuel supplied by the fuel supply means are mixed to form an air-fuel mixture;
Ignition means for igniting the air-fuel mixture formed in the premixing space;
A combustion catalyst provided between the air supply means, the fuel supply means, the premixing space and the ignition means, and the exhaust purification catalyst;
An exhaust emission control device for an internal combustion engine, comprising: A branch passage branched from the exhaust passage on the upstream side of the exhaust purification catalyst and leading to the exhaust purification catalyst;
Flow rate adjusting means for adjusting the flow rate of the exhaust gas flowing through the branch passage;
Further comprising
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the catalyst temperature raising means is provided in the branch passage.

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