JP2010127151A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, achieving early activation of a catalyst while suppressing fuel consumption. <P>SOLUTION: This exhaust emission control device for the internal combustion engine includes: an oxidation catalyst 25 arranged in an exhaust passage of the internal combustion engine 10; a heat storage material 50 temporarily storing heat and releasing stored heat for activating the oxidation catalyst 25; and a burner 60 supplying combustion gas with fuel burnt for activating the oxidation catalyst 25 to the exhaust passage 15. The exhaust passage 15 is formed with first and second branch passages 15A, 15B provided upstream of the oxidation catalyst 25, branched into two and rejoined. A selector valve selectively changing over an exhaust gas flow to one of the first and second branch passages is provided in a branch portion for the first and second branch passages 15A, 15B. The heat storage material 50 is provided in the first branch passage 15A, and the burner 60 is provided in the second branch passage 15B. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  For example, Patent Document 1 discloses a cold start by disposing a heat storage material in a bypass passage bypassing from a main passage in order to quickly activate a catalyst for purifying exhaust gas provided in an exhaust passage of an internal combustion engine. A technique for giving heat stored in a heat storage material to a relatively low temperature exhaust gas at times is disclosed.

  Further, as another method for activating the catalyst provided in the exhaust passage at an early stage, a burner is provided in the middle of the exhaust passage, and the fuel is burned in the combustion chamber communicating with the exhaust passage of the burner so that the exhaust gas is discharged. A technique for increasing the temperature and increasing the temperature of the catalyst at an early stage is also known.

Japanese Patent Laid-Open No. 06-207281

  By the way, in order to promote early activation of the catalyst and improve fuel efficiency, a heat storage material and a burner are used in combination, and when heat is not stored in the heat storage material, the temperature of the exhaust gas is increased by using the burner, and the heat storage material In the state where heat has already been stored, it is conceivable to increase the temperature of the exhaust gas by using a heat storage material without using a burner.

  However, when the heat storage material and the burner are used in combination, if the heat storage material and the burner are arranged in series in the exhaust passage, the heat released from the burner is absorbed by the heat storage material or the heat released from the heat storage material. May be released to the outside through the burner, which may cause an increase in energy (fuel) consumption.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine capable of early activation of a catalyst while suppressing fuel consumption.

  An exhaust gas purification apparatus for an internal combustion engine according to the present invention releases a catalyst provided in an exhaust passage of the internal combustion engine and heat stored in the exhaust passage for temporarily activating the catalyst. An exhaust purification device for an internal combustion engine, comprising: a possible heat storage means; and a burner provided in the exhaust passage and capable of supplying a combustion gas obtained by burning fuel for activating the catalyst to the exhaust passage. The exhaust passage has first and second branch passages that are branched into two and merge again on the upstream side of the catalyst, and an exhaust gas is provided at a branch portion of the first and second branch passages. A switching valve capable of selectively switching the gas flow to one of the first and second branch passages is provided, the heat storage means is provided in the first branch passage, and the burner is provided with the switching valve. Is switched to the second branch passage side, the fuel Characterized in that provided directly that can be supplied to the catalyst positioned gases without passing through the heat storage means.

  In the above configuration, preferably, the burner may employ a configuration provided in the second branch passage.

  The said structure WHEREIN: It is also possible to employ | adopt the structure by which the said burner is provided in the upstream from the branch part of the said 1st and 2nd branch channel.

  In the above configuration, the burner is supplied to the combustion chamber, the fuel supply unit that supplies fuel to the combustion chamber, the air supply unit that supplies air to the combustion chamber, and the combustion chamber. A configuration including ignition means for igniting the fuel can be employed.

  In the above configuration, the catalyst is an oxidation catalyst, and further includes a filter for collecting particulates contained in exhaust gas downstream of the catalyst, and the oxidation catalyst oxidizes fuel and flows into the filter. A configuration provided to raise the temperature of the exhaust gas can be employed.

  According to the present invention, it is possible to obtain an exhaust gas purification apparatus for an internal combustion engine capable of early activation of a catalyst particularly during cold start while suppressing fuel consumption.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of an exhaust emission control device for an internal combustion engine according to an embodiment of the present invention.

  In FIG. 1, the internal combustion engine 10 is, for example, a diesel engine. The exhaust passage 15 of the internal combustion engine 10 has a first branch passage 15A and a second branch passage 15B that branch into two in the middle and merge again. Further, the exhaust passage 15 is covered with a heat insulating material in order to suppress the release of heat energy to the outside as much as possible and promote activation of various catalysts described later.

  A switching valve 20 that can selectively switch the flow of exhaust gas to one of the first and second branch passages 15A and 15B is provided at the branch portion of the first branch passage 15A and the second branch passage 15B. ing. For example, a well-known electric or electromagnetic two-way switching valve can be used as the switching valve 20 and is controlled by an electronic control unit (ECU) 100 described later.

  A burner 60 is provided in the second branch passage 15B. An air supply path 61 for supplying air and a fuel supply path 62 for supplying fuel are connected to the burner 60 from the internal combustion engine 10 side. The burner 60 combusts the fuel supplied from the fuel supply path 62 and supplies the combustion gas to the second branch passage 15B.

  Specifically, for example, as shown in FIG. 2, the burner 60 includes a combustion chamber 63, a spark plug 64, a fuel supply unit 65, and an air supply unit 66 connected to communicate with the branch passage 15 </ b> B.

  The air supply unit 66 communicates with the air supply path 61 and guides the air A supplied from the air supply path 61 to the combustion chamber 63.

  The fuel supply unit 65 communicates with the fuel supply path 63 and supplies the fuel FL supplied from the fuel supply path 63 to the combustion chamber 63.

  The spark plug 64 is controlled by the ECU 100 and ignites the fuel supplied to the combustion chamber 63.

  The fuel FL supplied to the combustion chamber 63 of the burner 60 can be mixed with the air A and ignited by the discharge between the electrodes 64, or the fuel vaporized and burned by the glow plug. The combustion gas is discharged to the second branch passage 15B, that is, the exhaust passage 15. As a result, the temperature of the exhaust gas EG flowing through the exhaust passage 15 increases. Note that the combustion gas discharged from the burner 60 may be discharged to the exhaust passage 15 in a completely burned state, or may be discharged to the exhaust passage 15 in a state containing unburned fuel. By including unburned fuel in the combustion gas discharged from the burner 60, the unburned fuel can be supplied to the downstream oxidation catalyst 25.

  The heat storage material 50 is a latent heat storage material, and absorbs or releases thermal energy with a phase change between a liquid and a solid. For example, as shown in FIG. 3, this heat storage material acts to absorb heat energy of the exhaust gas and store heat when the ambient temperature, that is, the temperature of the exhaust gas is higher than the melting latent heat temperature T 0. When the temperature of the exhaust gas is lower than the melting latent heat temperature T0, the stored energy is released and the temperature of the exhaust gas is raised. The material of the heat storage material 50 is selected according to the required melting latent heat temperature. For example, if the melting latent heat is about 90 ° C., a paraffin-based material, and if about 260 ° C., lithium chloride or the like is used. Materials.

  The exhaust passage 15 includes an oxidation catalytic converter 25, a DPF (diesel particulate filter) 30, a selective catalytic reduction converter 35, and an oxidation catalytic converter 40 on the downstream side of the first branch passage 15A and the second branch passage 15B. Are provided in order. A urea water addition valve 70 is provided between the DPF 30 in the exhaust passage 15 and the selective catalytic reduction converter 35.

  In the exhaust passage 15, exhaust temperature sensors 90 A and 90 B for detecting the temperature of the exhaust gas EG are provided before and after the DPF 30, and a NOx sensor 95 for detecting the concentration of nitrogen oxides is provided downstream of the oxidation catalyst 40. The detection signals of these sensors are input to the ECU 100.

  Further, in the exhaust passage 15, a urea water addition valve 70 for adding a urea aqueous solution to the exhaust passage 15 and a downstream of the urea water addition valve 70 are provided between the DPF 30 and the selective reduction catalytic converter 40. An addition valve downstream mixer 80 for mixing the exhaust gas EG and the urea aqueous solution is provided.

  The oxidation catalyst converter 25 carries an oxidation catalyst that oxidizes unburned fuel and the like in the exhaust gas EG in order to raise the temperature of the exhaust gas EG supplied to the DPF 30 and the like at the subsequent stage. Specifically, for example, when the temperature rises to about 200 ° C. or higher, it is activated and its oxidation function works. That is, the oxidation catalytic converter 25 oxidizes unburned fuel or the like in the exhaust gas EG to increase the temperature of the exhaust gas EG and supply it to the DPF 30 at the subsequent stage.

  The oxidation catalytic converter 25 also has a NOx adsorption function capable of temporarily adsorbing and holding nitrogen oxides (NOx). The oxidation catalyst converter 25 temporarily adsorbs and holds NOx in a relatively low temperature state where the oxidation function is not activated. However, if the temperature rises to some extent, the adsorbed NOx is desorbed. As the oxidation catalyst converter 25, for example, an adsorbing material made of a material such as zeolite can be supported on a known oxidation catalyst structure. In order to desorb NOx from the oxidation catalyst converter 25, the burner 60 is activated to raise the temperature of the oxidation catalyst converter 25.

  The DPF 30 is a filter that collects particulate matter (PM) contained in the exhaust gas EG. As is well known, the structure of the DPF 30 is composed of, for example, a honeycomb body made of metal or ceramics. The DPF 30 needs to be regenerated when a predetermined amount of PM is deposited. Specifically, for example, the oxidation catalyst converter 25 is activated by raising the temperature, and the exhaust gas EG heated by the oxidation action of the oxidation catalyst converter 35 is supplied to the DPF 30. As a result, the collected PM is burned and the filter function is regenerated. The temperature of the DPF 30 in this regeneration process is, for example, about 600 to 700 ° C. Note that the determination of whether a predetermined amount of PM has accumulated on the DPF 30 is a well-known technique, and a description thereof will be omitted. Further, the DPF 30 may be configured to carry an oxidation catalyst made of a noble metal.

  The urea water addition valve 70 is supplied with urea water from a tank 75 that stores a urea aqueous solution, and adds an amount of urea water according to a control signal from the ECU 100 to the exhaust passage 15.

The selective reduction catalytic converter 35 selectively reduces NOx contained in the exhaust gas EG into nitrogen gas and water using the urea aqueous solution added from the urea addition valve 70 as a reducing agent. Specifically, the urea aqueous solution added to the exhaust gas EG is hydrolyzed by the heat of the exhaust gas EG to change to ammonia, and this ammonia reacts with NOx in the catalytic converter 35 to form water and harmless nitrogen. Reduced. This selective reduction catalytic converter 35 has a well-known structure, for example, a material composed of zeolite containing Si, O, Al as main components and containing Fe ions, or a surface of a base material made of, for example, aluminum oxide alumina. And the like, on which a vanadium catalyst (V ₂ O ₅ ) is supported, can be used, and the present invention is not particularly limited thereto. The selective reduction catalytic converter 35 has an activation temperature that functions as a catalyst, for example, about 200 ° C. or higher.

  The oxidation catalytic converter 40 serves to oxidize unburned fuel and ammonium that pass through the selective catalytic reduction converter 30. The oxidation catalytic converter 40 has a known structure.

  The ECU 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a backup memory such as an EEPROM (Electronically Erasable and Programmable Read Only Memory), an A / D converter, a buffer, and the like. It comprises hardware including an output interface circuit including an input interface circuit, a drive circuit, etc., and necessary software. The ECU 100 controls the switching valve 20, the burner 60, the urea water addition valve 70, and the like based on signals from the exhaust temperature sensors 90A and 90B, the NOx sensor 95, and the like.

  In the exhaust purification device having the above configuration, in the state where heat is already stored in the heat storage material 50, the switching valve 20 is switched to the first branch passage 15A side in order to use the heat of the heat storage material 50. The exhaust gas EG discharged from the internal combustion engine 10 is heated by passing through the heat storage material 23 of the first branch passage 15A, and is supplied to the oxidation catalytic converter 30. Thereby, the catalyst of the oxidation catalytic converter 25 can be activated. It is possible to determine whether or not the heat storage material 50 is stored by, for example, providing a temperature sensor in the heat storage material 50 and detecting the temperature. It is also possible to estimate and determine the amount of heat accumulated so far from the operating status of the internal combustion engine 10 or the like.

  In a state where heat is already stored in the heat storage material 50, the exhaust gas EG discharged from the internal combustion engine 10 passes only through the first branch passage 15A and does not pass through the second branch passage 15B. The burner 60 provided in the second branch passage 15B has a structure in which heat energy is easily released to the outside due to its structure, but the exhaust gas EG does not pass through the second branch passage 15B, so the heat storage material 50 When the temperature of the exhaust gas EG is raised using the heat, no thermal energy is released to the outside through the burner 60.

  If the heat storage material 50 is not storing heat or the amount of stored heat is not sufficient, such as during cold start, the switching valve 20 is switched to the second branch passage 15B side as shown in FIG. In addition, the burner 60 is activated, the combustion gas is supplied to the second branch passage 15B, and the exhaust gas EG is heated and supplied directly to the oxidation catalytic converter 25. At this time, since the exhaust gas EG does not pass through the heat storage material 50, the thermal energy supplied from the burner 60 is effectively used to raise the temperature of the oxidation catalytic converter 50 without being taken away by the heat storage material 50.

  After the oxidation catalytic converter 50 is heated to a necessary temperature and the oxidation function is exhibited, the burner 50 is stopped and the switching valve 20 is switched to the first branch passage 15A side. Thereby, the heat storage to the heat storage material 50 is performed.

  FIG. 5 is a block diagram of an exhaust emission control device for an internal combustion engine according to another embodiment of the present invention. In FIG. 5, the same reference numerals are used for the same components as those in the exhaust gas purification apparatus of FIG.

  The exhaust purification device shown in FIG. 5 is different from the exhaust purification device of FIG. 1 in that the burner 60 is provided in the exhaust passage 15 upstream of the switching valve 20, and the other configuration is the same.

  In the exhaust emission control device according to the present embodiment, in the state where heat is already stored in the heat storage material 50, the switching valve 20 is used as the first branch passage in order to use the heat of the heat storage material 50 as in the above embodiment. It is switched to the 15A side.

  When the heat storage material 50 is not storing heat or the amount of stored heat is not sufficient, such as during cold start, the switching valve 20 is switched to the second branch passage 15B side as shown in FIG. In addition, the burner 60 is activated, the combustion gas is supplied to the second branch passage 15B, and the exhaust gas EG is heated and supplied directly to the oxidation catalytic converter 25. At this time, since the exhaust gas EG does not pass through the heat storage material 50, the thermal energy supplied from the burner 60 is effectively used to raise the temperature of the oxidation catalytic converter 50 without being taken away by the heat storage material 50.

  FIG. 7 is a view showing another arrangement example of the burner, and shows a configuration in which the burner 60 is provided downstream of the first and second branch passages 15A and 15B. In FIG. 7, the same reference numerals are used for the same components as those in the exhaust gas purification apparatus of FIG.

  In this configuration, since the burner 60 is disposed in the immediate vicinity of the oxidation catalyst 25, it is advantageous in that the oxidation catalyst 25 is heated.

  However, when the temperature of the exhaust gas EG is raised using the thermal energy stored in the heat storage material 50, the exhaust gas EG heated by the heat storage material 50 always passes through the burner 60. For this reason, when raising the temperature of the oxidation catalyst 25 using the heat storage material 50, the loss of thermal energy becomes relatively large.

  The present invention can be applied not only to a diesel engine but also to a gasoline engine. Further, the catalyst to be activated is not limited to the oxidation catalyst but can be applied to other catalysts.

1 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. It is the side view and sectional drawing which show an example of the structure of a burner. It is a graph for demonstrating the thermal characteristic of a thermal storage material. It is a figure which shows the state of the switching valve at the time of heating up an oxidation catalyst using a burner. 1 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the state of the switching valve at the time of heating up an oxidation catalyst using a burner. It is a figure which shows the other example of arrangement | positioning of a burner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 15 ... Exhaust passage 15A ... First branch passage 15B ... Second branch passage 20 ... Switching valve 25 ... Oxidation catalytic converter 30 ... DPF
35 ... selective reduction catalytic converter 40 ... oxidation catalyst 60 ... burner 70 ... urea water addition valve 100 ... ECU

Claims (5)

A catalyst provided in an exhaust passage of the internal combustion engine; heat storage means provided in the exhaust passage, which is capable of temporarily storing heat and storing the heat for activation of the catalyst; and provided in the exhaust passage. An exhaust gas purification apparatus for an internal combustion engine, comprising: a burner capable of supplying a combustion gas obtained by burning fuel to activate the catalyst to the exhaust passage,
The exhaust passage has first and second branch passages branched into two and joined again on the upstream side of the catalyst,
A switching valve capable of selectively switching the flow of exhaust gas to one of the first and second branch passages is provided at a branch portion of the first and second branch passages,
The heat storage means is provided in the first branch passage,
The burner is provided at a position where combustion gas can be directly supplied to the catalyst without passing through the heat storage means when the switching valve is switched to the second branch passage side. An exhaust purification device for an internal combustion engine.   The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the burner is provided in the second branch passage.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the burner is provided on an upstream side of a branch portion of the first and second branch passages.   The burner ignites the combustion chamber communicating with the exhaust passage, a fuel supply section for supplying fuel to the combustion chamber, an air supply section for supplying air to the combustion chamber, and fuel supplied to the combustion chamber An exhaust purification device for an internal combustion engine according to any one of claims 1 to 3, further comprising ignition means for performing the operation. The catalyst is an oxidation catalyst;
Further comprising a filter on the downstream side of the catalyst for collecting particulates contained in the exhaust gas;
The exhaust purification device for an internal combustion engine according to any one of claims 1 to 4, wherein the oxidation catalyst is provided to oxidize fuel and raise a temperature of exhaust gas flowing into the filter. .

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