JP2005201130A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of effectively inducing oxidation (combustion) reaction of unburnt gas in exhaust gas. <P>SOLUTION: The exhaust emission control device of the internal combustion engine comprises a catalytic converter 15 for performing purification of exhaust gas and an ignition plug 25 (exhaust gas combustion promotion means) for exhaust gas re-combustion for igniting exhaust gas on the exhaust gas upstream side rather than the catalytic converter 15. The ignition plug 25 for exhaust gas re-combustion is positioned near an exhaust valve 24. Thus, the exhaust gas containing unburnt gas such as high-temperature and high-concentration HC(hydrocarbon), CO or the like just after the exhaust valve 24, thereby effectively inducing the oxidation (combustion) reaction of the unburnt gas in the exhaust gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  Conventionally, in the exhaust system, when the temperature of the catalyst is low, unburned gas in the exhaust passage is combusted on the upstream side of the catalyst, the exhaust temperature is increased by combustion of the unburned gas, and this catalyst is activated quickly. Known from.

For example, Patent Document 1 discloses a technique in which high-pressure discharge is performed at a front position of a catalyst attached to an exhaust pipe and unburned gas is burned.
Japanese Patent Laid-Open No. 5-98950

  However, when the high-pressure discharge is performed immediately before the catalyst and the unburned gas is ignited as in Patent Document 1, the unburned gas is not sufficiently oxidized (combusted), and the unburned gas is oxidized before the catalyst and before the catalyst. There is a risk that the temperature of the exhaust gas will be insufficient and the catalyst will not be activated early.

  Therefore, the present invention provides an exhaust combustion promotion apparatus for an internal combustion engine having a catalyst for purifying exhaust and an exhaust combustion promotion means for igniting exhaust on the exhaust upstream side of the catalyst. It is characterized by being located in the vicinity.

  According to the present invention, the ignition (combustion) reaction of the unburned gas in the exhaust gas is performed by spark ignition of the exhaust gas containing unburned gas such as high temperature and high concentration HC (hydrocarbon) and CO immediately after the exhaust valve. Can be effectively induced.

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

  FIG. 1 is a system configuration diagram of an exhaust emission control device according to a first embodiment. A combustion chamber 2 in an engine 1 includes a throttle valve 5 whose valve opening is controlled by an air cleaner 3, an intake duct 4, and an ECU 12 described later. Air is supplied through an intake collector, an intake manifold 7 and an intake port 9 formed in a cylinder head 8 of the engine 1. The suction port 9 is formed according to the number of cylinders so as to correspond to each cylinder of the engine 1.

  The intake manifold 7 connected to the intake port 9 is provided with a fuel injection valve 10, and an air-fuel mixture is formed by the fuel injected from the fuel injection valve 10. The air-fuel mixture is ignited and burned in the combustion chamber 2 by spark ignition by the spark plug 11. The fuel injection valve 10 and the spark plug 11 are controlled by an engine control unit 12 (hereinafter referred to as ECU).

  On the other hand, exhaust gas discharged from the combustion chamber 2 of the engine 1 is released to the atmosphere through an exhaust port 13 formed in the cylinder head 8, an exhaust manifold 14, a catalytic converter 15, an exhaust duct 16, and a muffler 17. . The exhaust port 13 is formed in the cylinder head 8 according to the number of cylinders so as to correspond to each cylinder of the engine 1.

  The catalytic converter 15 is composed of, for example, a three-way catalyst, and an oxygen sensor 18 for detecting the oxygen concentration of the exhaust gas flowing into the catalytic converter 15 is provided on the exhaust upstream side. The oxygen concentration detected by the oxygen sensor 18 is input to the ECU 12.

  In FIG. 1, 19 is a cylinder block, 20 is an oil pan, 21 is a rocker cover, 22 is a piston, 23 is an intake valve, and 24 is an exhaust valve.

  An exhaust recombustion ignition plug 25 is disposed on the exhaust upstream side of the catalytic converter 15 as exhaust combustion promoting means for promoting combustion of unburned gas in the exhaust by spark ignition. The exhaust reburning ignition plug 25 is attached to the cylinder head 8 so as to be positioned in the vicinity of the exhaust valve 24 and to be directed upstream of the exhaust.

  Here, the HC concentration (HC amount) in the exhaust gas during the period in which the exhaust valve 24 is open is a maximum value immediately after the exhaust valve 24 is opened and immediately before the exhaust valve 24 is closed, as shown in FIG. It is known to take (first peak and second peak). Thus, in the first embodiment, the exhaust is spark-ignited by the exhaust recombustion ignition plug 25 immediately after the timing of the first peak when the HC (hydrocarbon) concentration in the exhaust gas reaches a maximum value, that is, immediately after the exhaust valve 24 is opened. Thus, the ignition timing of the exhaust recombustion ignition plug 25 is controlled by the ECU 12 so as to re-combust.

  Further, in the first embodiment, as shown in FIGS. 1, 3, and 4, an exhaust reburning ignition plug 25 is provided in the lower part (lower side in FIG. 3) in the exhaust port 13, and the exhaust port 13 is configured to ignite the exhaust on the lower side in the interior. This is because the main flow of exhaust in the first embodiment flows on the lower side in a cross section perpendicular to the exhaust flow direction of the exhaust port 13. 4 is an explanatory view schematically showing the exhaust port 13 viewed from the direction of arrow A in FIG.

  In such an exhaust purification device of the first embodiment, an exhaust recombustion ignition plug 25 is used for exhaust gas containing unburned gas such as high-temperature and high-concentration HC (hydrocarbon) and CO immediately after the exhaust valve 24. By spark ignition, an oxidation (combustion) reaction of unburned gas in the exhaust can be effectively induced and promoted. In particular, at the time of cold start, the amount of HC in the exhaust gas increases due to the increase in the starting amount of fuel, but the amount of HC in the exhaust gas is relatively reduced by the exhaust reburn until the exhaust gas reaches the catalytic converter 15. That is, by providing the exhaust combustion promoting means in the vicinity of the exhaust valve 24 that can be said to be the most upstream of the exhaust, the exhaust gas having the highest temperature is surely ignited and burned as much as possible before reaching the catalytic converter 15, thereby It is possible to greatly reduce the amount of HC flowing into the converter 15 and prevent the exhaust performance from deteriorating even if the catalytic converter 15 is in a state where the exhaust purification power is small before being activated. Further, since the exhaust gas temperature rises due to exhaust recombustion, it is not necessary to significantly retard the ignition timing in the cold state with respect to the air-fuel mixture in the combustion chamber 2, and the catalytic converter 15 does not deteriorate in drivability. Early activation can be performed, and further reduction of HC and CO released into the atmosphere can be achieved.

  Since the exhaust re-ignition ignition plug 25 is disposed in the vicinity of the exhaust valve 24 in the exhaust port 13, the exhaust system can be efficiently warmed up when the engine is cold.

  In addition, since the exhaust gas is reburned by the exhaust reburning ignition plug 25 at the first peak timing when the HC concentration in the exhaust gas reaches the maximum value, the HC in the exhaust gas can be reduced more effectively.

  Further, since the exhaust re-ignition ignition plug 25 ignites the exhaust at a position where the main flow of the exhaust flows in a cross section perpendicular to the exhaust flow direction, the exhaust can be efficiently re-combusted.

  Hereinafter, other embodiments of the present invention will be sequentially described. However, the same components as those in the first embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

  FIG. 5 shows an exhaust purification device according to a second embodiment of the present invention. The second embodiment is an embodiment in which the main flow of exhaust gas in the exhaust port flows upward in a cross section perpendicular to the exhaust flow direction of the exhaust port 13, and has substantially the same configuration as the above-described first embodiment. However, unlike the first embodiment, the exhaust recombustion ignition plug 25 is provided at the upper portion of the exhaust port 13. The exhaust reburning ignition plug 25 is directed to the exhaust upstream side as in the first embodiment described above.

  Also in the second embodiment, the same operational effects as those of the first embodiment described above can be obtained.

  FIG. 6 shows an exhaust emission control device according to the third embodiment of the present invention. The third embodiment is an embodiment in which the exhaust gas flowing in the exhaust port 13 flows substantially uniformly throughout the cross section of the exhaust port 13, and has substantially the same configuration as the first embodiment described above. The exhaust recombustion ignition plug 25 is provided on the axis L at the center of the exhaust hole. The exhaust reburning ignition plug 25 is directed to the exhaust upstream side as in the first embodiment described above.

  Also in the third embodiment, the same operational effects as those of the first embodiment described above can be obtained.

  FIG. 7 shows an exhaust purification device according to a fourth embodiment of the present invention. The fourth embodiment has basically the same configuration as the first embodiment described above, but the exhaust port 13 formed in the cylinder head 8 includes branch portions 31 corresponding to the cylinders, The catalytic converter 15 is connected to an exhaust downstream side end of the exhaust merging portion 32 which is formed to have an exhaust merging portion 32 where the branch portion 31 merges and opens to the cylinder head 8. In other words, the exhaust discharged from each cylinder joins at the exhaust joining portion 32 formed in the cylinder head 8, then flows out from the cylinder head 8, flows into the catalytic converter 15 connected to the exhaust downstream side, and then enters the catalytic converter. 15 to be purified. One exhaust recombustion ignition plug 33 is disposed in the exhaust merging portion 32 so that the exhaust merging portion 32 ignites the exhaust gas. Although not shown in FIG. 7, an oxygen sensor is disposed on the exhaust upstream side of the catalytic converter 15 as in the first embodiment. Further, the exhaust recombustion ignition plug 33 is directed to the exhaust upstream side, as in the first embodiment described above.

  In such a fourth embodiment, the same operational effects as those of the first embodiment described above can be obtained, and all the cylinders can be formed by one exhaust recombustion ignition plug 33 regardless of the number of cylinders of the internal combustion engine. There is an advantage that the exhaust from can be ignited.

  FIG. 8 shows an exhaust emission control device according to a fifth embodiment of the present invention. The fifth embodiment basically has the same configuration as the first embodiment described above, but secondary air is introduced upstream of the exhaust ignition position by the exhaust recombustion ignition plug 25. It has a configuration.

  More specifically, the secondary air supply pump 41 controlled by the ECU 12 causes a part of the air in the intake system from the upstream side of the air flow meter 3 to be disposed upstream of the exhaust recombustion ignition plug 25. Secondary air is introduced from the secondary air nozzle 42 into the exhaust. The exhaust reburning ignition plug 25 is directed to the exhaust upstream side as in the first embodiment described above.

  In the fifth embodiment, the same operational effects as those of the first embodiment described above can be obtained, and the oxidation reaction of the exhaust is more effectively induced by introducing secondary air into the exhaust. be able to.

  In the first to fifth embodiments described above, the ignition plug for exhaust recombustion is used as the exhaust combustion promoting means, but a glow plug can also be used as the exhaust combustion promoting means. When a glow plug is used as the exhaust combustion promoting means, the exhaust is heated by the glow plug and spontaneously ignites. When a glow plug is used, the exhaust is always heated by the glow plug during engine operation. Even when a glow plug is used as the exhaust combustion promoting means, the glow plug is disposed so as to face the exhaust upstream side as in the first embodiment.

  In the first to fifth embodiments described above, the exhaust reburning ignition plug ignites the exhaust immediately after the exhaust valve opens, but as shown in FIG. 9, the second peak timing, that is, the exhaust Even if the exhaust is ignited with the exhaust reburning ignition plug immediately before the valve 24 is closed, the HC in the exhaust can be reduced more effectively.

1 is a system configuration diagram of an exhaust emission control device according to a first embodiment of the present invention. Explanatory drawing which shows the change of HC density | concentration in exhaust_gas | exhaustion during the period when an exhaust valve is open. The principal part enlarged view in 1st Embodiment of this invention. Explanatory drawing which shows typically the exhaust port seen from the arrow A direction of FIG. The principal part enlarged view in 2nd Embodiment of this invention. The principal part enlarged view in 3rd Embodiment of this invention. The principal part enlarged view in 4th Embodiment of this invention. The system block diagram in 5th Embodiment of this invention. Explanatory drawing which shows the change of HC density | concentration in exhaust_gas | exhaustion during the period when an exhaust valve is open.

Explanation of symbols

DESCRIPTION OF SYMBOLS 8 ... Cylinder head 13 ... Exhaust port 15 ... Catalytic converter 24 ... Exhaust valve 25 ... Exhaust recombustion ignition plug (exhaust combustion promotion means)
33. Spark plug for exhaust recombustion (exhaust combustion promotion means)

Claims (8)

In an exhaust gas purification apparatus for an internal combustion engine, comprising: a catalyst that purifies exhaust gas; and an exhaust combustion promoting means that promotes combustion of exhaust gas upstream of the catalyst,
An exhaust emission control device for an internal combustion engine, wherein the exhaust combustion promoting means is located in the vicinity of the exhaust valve.   The internal combustion engine is multi-cylinder, and the exhaust discharged from the plurality of cylinders is purified by a catalyst after joining at an exhaust merging portion formed in the cylinder head. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the exhaust gas purification device is disposed in a merging portion.   The exhaust emission control device for an internal combustion engine according to claim 1 or 2, wherein the exhaust combustion promoting means is disposed at a position where a main flow of exhaust flows.   The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein secondary air is introduced into the exhaust gas upstream of the exhaust combustion promoting means.   The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust combustion promoting means promotes the combustion of exhaust immediately after the exhaust valve is opened.   The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust gas combustion promoting means promotes the combustion of exhaust gas immediately before the exhaust valve is closed.   The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust combustion promotion means is an ignition plug for exhaust recombustion, and is disposed so as to face the exhaust upstream side. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust combustion promoting means is an exhaust recombustion glow plug, and is disposed so as to face the exhaust upstream side.

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