JP2013238145A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device which can achieve securement of purification performance in cold staring, or the like, and to control increase of a channel resistance and deterioration of purification performance due to clogging, or the like.SOLUTION: An exhaust emission control device 21 includes: a main catalyst converter 26 which has a plurality of cells 33 communicating from an inflow surface 31 to an exhaust surface 32 of exhaust gas and in which the inflow surface 31 is disposed over the whole area of an opening surface inside a housing 25; and an auxiliary catalyst converter 27 which is arranged apart from the main catalyst converter 26 at a direct upstream inside the housing 25 and which has a smaller thermal capacity than the main catalyst converter 26. A projected area of the auxiliary catalyst converter 27 is set smaller than the opening surface of the housing 25, and an inflow surface 37 is formed to be a convex surface.

Description

  The present invention relates to an exhaust gas purification device that purifies exhaust gas using a catalyst.

  Conventionally, in exhaust gas purification devices, in order to ensure purification performance at the cold start of the engine, etc., in addition to the main catalytic converter, an auxiliary catalytic converter that has a small heat capacity and can be activated early is used in combination What has been proposed.

  For example, in Patent Document 1, a main catalyst converter having a large heat capacity in which a catalyst metal is supported on the surface of a ceramic sintered in a honeycomb-like cylindrical body is disposed over the entire exhaust gas passage, and this main catalyst The upstream side of the converter is branched into a first passage in which a metal catalyst converter with a small heat capacity formed of a refractory metal in a honeycomb shape is arranged, and a second passage that bypasses the metal catalyst converter. An exhaust gas purification device is disclosed that selectively communicates either the first passage or the second passage to the main catalyst carrier by a provided valve. In this exhaust gas purifying device, the first passage is basically opened, and a metal catalytic converter with a small heat capacity is activated early at the time of cold start or the like, so that the main catalytic converter is activated. It is also possible to demonstrate purification performance. On the other hand, at the time of engine fuel cut, the purification of exhaust gas is continued by the main catalytic converter having a large heat capacity while closing the first passage and opening the second passage to prevent the temperature reduction of the metal catalytic converter. Is possible.

JP-A-6-346724

  By the way, in recent years, particularly in emerging countries and the like, inferior fuel mixed with additives in order to increase impurities and octane formation may be used.

  However, if the bad fuel is continuously used, the bad fuel component adheres to the inflow surface of the exhaust gas of the catalytic converter, and the deposit of the bad fuel component may cause clogging of the catalytic converter. For example, in the exhaust gas purification device disclosed in the above-mentioned Patent Document 1, clogging due to deposits of bad fuel components occurs particularly on the inflow surface of the metal catalytic converter. There is a possibility of causing an increase in purification and a decrease in purification performance.

  The present invention has been made in view of the above circumstances, and can achieve purification performance at the time of cold start and the like, and increase in flow resistance and suppression of degradation in purification performance due to clogging and the like. An object is to provide an exhaust gas purification device.

  An exhaust gas purification apparatus according to an aspect of the present invention includes a housing interposed in an exhaust passage, and a plurality of cells communicating from an exhaust gas inflow surface to an exhaust surface, and the inflow surface is in the middle of the housing. A main catalytic converter disposed over the entire opening surface, and a sub-catalytic converter having a smaller heat capacity than the main catalytic converter disposed in the housing and immediately upstream of the main catalytic converter, The sub-catalytic converter has a projected area smaller than the opening area of the housing, and the inflow surface of the exhaust gas is formed as a convex curved surface.

  According to the exhaust gas purifying apparatus of the present invention, it is possible to ensure purification performance at the time of cold start or the like and to suppress increase in flow path resistance or reduction in purification performance due to clogging or the like.

Schematic configuration diagram of the engine A perspective view showing a main catalyst carrier and a sub catalyst carrier arranged in a housing Cross-sectional view of essential parts along the line III-III in FIG. Cross-sectional view of essential parts along line IV-IV in FIG. FIG. 3 is a cross-sectional view of an essential part taken along line VV in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings relate to an embodiment of the present invention, FIG. 1 is a schematic configuration diagram of an engine, FIG. 2 is a perspective view showing a main catalyst carrier and a sub catalyst carrier arranged in a housing, and FIG. FIG. 4 is a cross-sectional view of a main part taken along line IV-IV in FIG. 3, and FIG. 5 is a cross-sectional view of a main part taken along line V-V in FIG.

  An engine 1 shown in FIG. 1 is, for example, a horizontally opposed four-cylinder engine, and cylinder heads 3 are provided in both the left and right banks of the cylinder block 2 of the engine 1. A combustion chamber 5 for each cylinder is formed between the cylinder block 2 and each cylinder head 3, and an intake port 6 and an exhaust port 7 that open to the cylinder head 3 are communicated with the combustion chamber 5. Yes.

  An intake manifold 10 communicates with the intake port 6 of the cylinder head 3, and the intake manifold 10 communicates with a throttle chamber 13 via an air chamber 12 in which intake passages of the respective cylinders gather. A throttle valve 14 a driven by a throttle actuator 14 is interposed in the throttle chamber 13. Further, an air cleaner 16 is attached upstream of the throttle chamber 13 via an intake pipe 15, and a chamber 17 is communicated with an air intake passage connected to the air cleaner 16.

  On the other hand, an exhaust manifold 20 is communicated with each exhaust port 7 of the cylinder head 3. An exhaust pipe 22 communicates with the exhaust manifold 20, and an exhaust gas purification device 21 is interposed in the exhaust pipe 22. Further, a muffler 23 communicates with the downstream of the exhaust pipe 22.

  As shown in FIGS. 2 to 5, the exhaust gas purifying device 21 includes, for example, a main catalyst converter 26 and a main catalyst converter 26 in a housing 25 having a substantially cylindrical shape interposed in the exhaust pipe 22. The sub catalyst converter 27 having a small heat capacity is accommodated to constitute a main part.

  More specifically, the main catalytic converter 26 includes, for example, a ceramic catalyst carrier 30. The catalyst carrier 30 has a cylindrical shape having an outer diameter that is substantially the same as the inner diameter of the housing 25, and has one end surface set as an exhaust gas inflow surface 31 and the other end surface set as an exhaust gas discharge surface 32. Yes. The catalyst carrier 30 has a plurality of honeycomb-shaped cells 33 communicating from the inflow surface 31 to the discharge surface 32. And this catalyst carrier 30 comprises the main catalyst converter 26 by carrying | supporting catalyst bodies, such as Pt, Pd, Rh, for example. The main catalytic converter 26 configured in this way is disposed on the downstream side in the housing 25 and is held by being fitted to the inner peripheral surface of the housing 25, for example.

  The sub-catalytic converter 27 includes a metal catalyst carrier 35, for example. The catalyst carrier 35 is configured by, for example, superimposing a plurality of (for example, about 10 to 20) rectangular mesh sheets 36 formed by braiding metal fine wires, and one end surface in the superimposing direction is an inflow of exhaust gas. The surface 37 is set, and the other end surface is set as an exhaust gas discharge surface 38. And this catalyst carrier 35 comprises the subcatalyst converter 27 by carrying | supporting catalyst bodies, such as Pt, for example.

  Here, as shown in FIG. 3, the projected area of the sub-catalytic converter 27 is set smaller than the projected area of the main catalytic converter 26 (that is, the projected area of the sub-catalytic converter 27 is in the middle of the housing 25. It is set smaller than the opening area). Further, the sub-catalytic converter 27 is formed so that the exhaust gas inflow surface 37 becomes a convex curved surface by, for example, each mesh sheet 36 being curved in an arch shape. The sub-catalyst converter 27 configured in this manner is a position in the housing 25 that faces the exhaust gas inlet 25a of the housing 25 and is separated from the main catalyst converter 26 on the immediately upstream side. For example, it is hold | maintained at the inner peripheral surface of the housing 25 via the welding part 39 set to four corners.

  In the exhaust gas purification device 21 configured as described above, when the engine 1 is cold-started or the like, first, the sub-catalytic converter 27 having a small heat capacity is heated up to the activation temperature at an early stage. Part of the exhaust gas that has passed through is purified. Thereby, a predetermined purification performance can be ensured even during cold start. Further, after the engine 1 is warmed up, a sufficient purification performance can be ensured by the main catalytic converter 26 heated to the activation temperature.

  By the way, when bad fuel is used for the engine 1, the bad fuel component contained in the exhaust gas may adhere to the sub-catalytic converter 27 and the main catalytic converter 26. Even in such a case, the main catalytic converter 26 is also used. By the sub-catalyst converter 27 that is spaced apart immediately upstream of the exhaust gas purification device 21, it is possible to suppress an increase in flow path resistance and a reduction in purification performance.

  That is, the inflow surface 31 of the main catalytic converter 26 is prevented from adhering bad fuel components in the projection region of the sub catalytic converter 27 due to the masking effect of the sub catalytic converter 27 disposed immediately upstream. The projected area of the sub-catalytic converter 27 is set smaller than the opening area of the housing 25, and an exhaust gas bypass space is secured in the housing 25 at the side of the sub-catalytic converter 27. Therefore, even if a bad fuel component is contained in the exhaust gas, clogging or the like does not occur over the entire inflow surface 31 of the main catalytic converter 26, and the sub catalytic converter 27 is disposed in the housing 25. Since the inner opening surface is not blocked over the entire surface, an increase in flow resistance and a decrease in purification performance due to clogging of the inflow surface 31 of the main catalytic converter 26 can be suppressed.

  Further, by forming the inflow surface 37 of the sub-catalytic converter 27 with a convex curved surface with respect to the inflow direction of the exhaust gas, even if a bad fuel component is deposited on the inflow surface 37 of the sub-catalytic converter 27, the deposit Can be easily separated by exhaust pulsation or the like in a predetermined operation mode. The separated deposit passes through the cell 33 of the main catalytic converter 26 which is not clogged and is discharged as a solid.

  In this case, by configuring the sub-catalytic converter 27 with a superposed body of a plurality of light and thin mesh sheets 36, the surface of the sub-catalytic converter 27 can be easily vibrated according to exhaust gas pulsation, etc. The peelability of the deposit can be improved.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Cylinder block 3 ... Cylinder head 5 ... Combustion chamber 6 ... Intake port 7 ... Exhaust port 10 ... Intake manifold 12 ... Air chamber 13 ... Throttle chamber 14 ... Throttle actuator 14a ... Throttle valve 15 ... Intake pipe 16 ... Air cleaner DESCRIPTION OF SYMBOLS 17 ... Chamber 20 ... Exhaust manifold 21 ... Exhaust gas purification device 22 ... Exhaust pipe 23 ... Muffler 25 ... Housing 25a ... Exhaust gas inlet 26 ... Main catalytic converter 27 ... Sub catalytic converter 30 ... Catalyst carrier 31 ... Inflow surface 32 ... Exhaust surface Surface 33 ... Cell 35 ... Catalyst carrier 36 ... Mesh sheet 37 ... Inflow surface 38 ... Discharge surface 39 ... Welded part

Claims (2)

A housing interposed in the exhaust passage;
A main catalytic converter having a plurality of cells communicating from the exhaust gas inflow surface to the exhaust surface, wherein the inflow surface is disposed over the entire opening surface in the middle of the housing;
A sub-catalytic converter having a smaller heat capacity than the main catalytic converter disposed in the housing and spaced apart immediately upstream from the main catalytic converter,
The sub-catalytic converter is configured to have a projected area smaller than an opening area of the housing, and an exhaust gas inflow surface is formed as a convex curved surface.   The exhaust gas purification device according to claim 1, wherein the sub-catalytic converter is configured by superimposing a plurality of mesh members.

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