JP2007127045A - 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 provided with the structure for coping with a failure even when the failure occurs in a plurality of second air supply systems. <P>SOLUTION: The exhaust emission control device of the internal combustion engine provided with a plurality of exhaust passages 3R-4R and 3L-4L comprises exhaust gas purification catalysts 5R and 5L arranged halfway in the exhaust passages respectively, a plurality of secondary air supply passages 6R and 6L formed for the secondary air suction upstream of the exhaust gas purification catalysts respectively, a plurality of air pumps 7R and 7L arranged for each the secondary air supply passage to supply the secondary air, a communication passage 10 for communicating with a plurality of the second air supply passages, and a communication switching means 11 for opening and closing the communication passage. The overall flow rate of the secondary air can be averaged and introduced by opening the communication passage 10 when the failure occurs in either of the secondary air supply systems, so that the emission can be prevented from deteriorating even when a part of the secondary air supply systems fails. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine having a plurality of exhaust passages. More specifically, the present invention relates to an exhaust gas purification device that purifies exhaust gas by arranging an exhaust gas purification catalyst for each of a plurality of exhaust passages.

  For example, in a V-type engine or the like, a plurality of cylinders are disposed in each of the left and right banks, and two cylinder groups are formed. Conventionally, there is known a structure in which an individual exhaust passage (exhaust system) is provided for each cylinder group, and an exhaust purification catalyst is disposed in each exhaust passage. Further, a technique is known in which secondary air is introduced upstream of the exhaust purification catalyst to promote warming of the catalyst and improve the purification function.

  For example, Patent Document 1 discloses an exhaust purification device for an internal combustion engine that combines the above-described techniques. That is, Patent Document 1 discloses an exhaust purification device that supplies secondary air to an exhaust system provided for each cylinder group of a V-type engine. This exhaust purification device includes a secondary air supply pipe branched from the intake system, and supplies secondary air to the upstream side of each exhaust purification catalyst. The exhaust system of each bank is provided with a supply pipe for supplying secondary air and a control valve for opening and closing the supply pipe. By alternately opening and closing the control valves at predetermined intervals, secondary air is alternately supplied to both banks. As a result, each bank periodically fluctuates between the exhaust secondary air-fuel ratio lean side and the rich side, so the secondary air supply amount is reduced, but the catalyst atmosphere is close to the theoretical air-fuel ratio due to the oxygen storage effect of the exhaust purification catalyst. Saved in. Therefore, it is possible to efficiently oxidize HC, CO, etc. and perform exhaust purification efficiently.

JP-A-5-86848

  However, the exhaust purification device of Patent Document 1 is configured to branch a secondary air supply pipe connected to an intake system so as to supply a part of the secondary air to the exhaust system. Secondary air is supplied. For this reason, when the air pump fails, the secondary air cannot be supplied to the exhaust system. Therefore, in this case, the exhaust purification catalyst is delayed in warming up, leading to deterioration of emissions. Further, the two exhaust passages provided in the V-type engine are independent. Therefore, even if a secondary air supply pipe is connected to each exhaust passage and an air pump is installed for each secondary air supply pipe, if a failure occurs in one of the secondary air supply pipes or the air pump, the above As well as worsening emissions.

  Furthermore, in the exhaust purification device of Patent Document 1, a control valve (open / close valve) is disposed in each secondary air supply pipe provided in each bank, and controls the flow of secondary air to the exhaust purification catalyst. Therefore, even when one of the control valves fails, there is a possibility that the emission will be deteriorated as described above.

  As described above, since the secondary air supply pipe arranged in the exhaust purification device of Patent Document 1 is independent, if a failure such as a pipe clogging or a defective control valve occurs on one side, the exhaust purification on the failure side is performed. Since sufficient secondary air cannot be supplied to the catalyst, the emission is deteriorated due to a delay in warm-up.

  Therefore, an object of the present invention is an exhaust purification device having a structure in which an exhaust purification catalyst is arranged in each of a plurality of exhaust systems and a secondary air is supplied, and even if any secondary air supply system has a problem. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine having a structure for dealing with this.

  An object of the present invention is to provide an exhaust purification device for an internal combustion engine having a plurality of exhaust passages, the exhaust purification catalyst disposed in the middle of each of the exhaust passages, and provided for introducing secondary air upstream of each exhaust purification catalyst. A plurality of secondary air supply passages, and a plurality of air pumps arranged for each of the secondary air supply passages for supplying secondary air, and a communication passage communicating the plurality of secondary air supply passages, This can be achieved by an exhaust emission control device for an internal combustion engine comprising communication switching means for opening and closing the communication passage.

  According to the present invention, since a communication passage that communicates a plurality of secondary air supply passages provided for introducing secondary air and a communication switching means that opens and closes the communication passage are provided, any secondary air supply system has a failure. When generated, the secondary air can be averaged and introduced by opening the communication passage. Therefore, even if a failure occurs in the secondary air supply system, deterioration of emissions can be suppressed. Further, the communication path can be closed when the secondary air is not introduced.

  A secondary air flow rate detecting means for detecting a secondary air flow rate in the plurality of secondary air supply passages; and a control means for controlling the communication switching means based on a detection signal of the secondary air flow rate detecting means. In addition, the control valve may control the opening degree of the communication path based on a secondary air flow rate difference between the secondary air supply paths. In this way, the secondary air flow rate can be averaged to suppress the deterioration of the emission.

  And when the secondary air flow rate difference between the secondary air supply passages is larger than a predetermined value, the control means may control the communication switching means to connect the communication paths. In this way, the occurrence of a failure in the secondary air supply system can be monitored, and when the failure occurs, the secondary air flow rate can be averaged to suppress the deterioration of emissions. The control means may control the communication switching means to shut off the communication path when secondary air is not introduced into the secondary air supply path. In this case, abnormal noise can be prevented.

  The internal combustion engine may include two cylinder groups, and the exhaust passage may be provided for each cylinder group to provide two exhaust systems. In this way, the present invention can be applied to an internal combustion engine having a plurality of cylinders in the left and right banks, such as a V-type engine.

  According to the present invention, an exhaust purification device having a structure in which an exhaust purification catalyst is arranged in each of a plurality of exhaust systems and a secondary air is supplied, even if a problem occurs in any of the secondary air supply systems. An exhaust emission control device for an internal combustion engine having a structure to cope with can be provided.

  Hereinafter, an exhaust emission control device for an internal combustion engine according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an internal combustion engine to which an exhaust emission control device according to an embodiment is applied. This internal combustion engine is a so-called V-type engine 1, and independent banks LB and RB are formed on the left and right. Four cylinders 2 are arranged in each of the left bank LB and the right bank RB to form independent cylinder groups. As will be described later, each cylinder group is provided with an individual exhaust passage (exhaust system). In FIG. 1, the intake system of the engine 1 is omitted for convenience of illustration. Also, components similar to the left and right are distinguished by attaching “L” to those belonging to the left bank LB and “R” to those belonging to the right bank RB.

  The left and right banks are formed symmetrically. The right bank RB of the V-type engine 1 is provided with an exhaust manifold 3R that collects exhaust gas discharged from the four cylinders 2R and an exhaust pipe 4R connected downstream thereof. An exhaust passage is formed by the exhaust manifold 3R and the exhaust pipe 4R. The same applies to the left bank LB on the opposite side, and an exhaust passage is formed by the exhaust manifold 3L and the exhaust pipe 4L. These exhaust passages are two independent exhaust systems. Exhaust purification catalysts 5R, 5L are attached in the middle of the respective exhausters 4R, 4L. As the exhaust purification catalysts 5R and 5L, an oxidation catalyst that burns HC or the like by an oxidation reaction, a three-way catalyst, or the like can be employed.

  Secondary air supply passages (hereinafter referred to as AI pipes) 6R and 6L for introducing secondary air are connected to the exhaust manifolds 3R and 3L. Air pumps 7R and 7L, air switching valves 8R and 8L, and reed valves 9R and 9L are arranged on the AI pipes 6R and 6L from the upstream side for sucking the secondary air. The AI pipes 6R and 6L are connected to the exhaust manifolds 3R and 3L on the downstream side of the reed valves 9R and 9L. The air pumps 7R and 7L take in the air Air as secondary air from the outside of the machine, and supply the air to the exhaust manifolds 3R and 3L. The air switching valves 8R and 8L open and close the AI pipes 6R and 6L. The reed valves 9R and 9L function as a backflow prevention valve.

  Further, air pressure sensors 12R and 12L for detecting air pressure in the pipes are attached to the AI pipes 6R and 6L. The air pressure sensors 12R and 12L function as secondary air flow rate detection means for confirming the flow rate of secondary air in the AI pipes 6R and 6L. Thus, when a pressure sensor is employ | adopted, the flow volume of secondary air can be converted from an air pressure. As the secondary air flow rate detection means, an air flow meter may be used instead of the air pressure sensor 12R. In the case of an air flow meter, the secondary air flow rate can be detected directly.

  Further, a communication passage 10 is provided on the downstream side of the reed valves 9R and 9L to connect the right AI pipe 6R and the left AI pipe 6L. An air switching valve 11 is provided in the middle of the communication path 10 as communication switching means. When the air switching valve 11 is in the closed state, the right AI pipe 6R and the left AI pipe 6L are maintained independently, and the structure is the same as that of the conventional exhaust purification device. That is, secondary air is individually introduced into the left and right sides, and is supplied to each independent exhaust system in the left and right banks.

  On the other hand, when the air switching valve 11 is opened, the right AI pipe 6R and the left AI pipe 6L communicate with each other, so that the secondary air flow rates in the left and right banks can be made uniform. Therefore, if the AI piping 6 of one bank is clogged, the air pump 7 fails, the air switching valve 8 fails, etc., the secondary air cannot be supplied as intended. Even in this case, the secondary air can be supplied from the normal bank side to the failed back side. Thereby, since secondary air can be supplied also to the exhaust purification catalyst 5 on the bank side where the failure has occurred, it is possible to suppress the deterioration of the emission.

  By the way, if the communication path 10 is provided, the right AI pipe 6R and the left AI pipe 6L can always be in communication with each other, so that it is possible to cope with a failure in one bank. When only the communication path 10 is provided as described above, the communication state is maintained even when the control for introducing the secondary air is not executed (when the AI control is not executed). However, when the secondary air does not flow through the AI pipe 6, there is a possibility that the exhaust gas circulates from the exhaust manifold 3 and moves back and forth between the left and right banks to generate noise. Therefore, when the secondary air is not introduced, it is desirable to shut off the right AI pipe 6R and the left AI pipe 6L. Therefore, the exhaust emission control device of this embodiment has a structure in which an air switching valve 11 is provided so that the communication passage 10 can be opened and closed.

  When the air switching valve 11 is provided in this way, when a problem occurs in the secondary air supply system of either the left or right bank RB or LB, that is, as described above, some sort of failure occurs in the shifted secondary air supply system. When this happens, it is desirable to be able to detect and handle this failure. Therefore, the exhaust emission control device of the present embodiment has a configuration for coping with a failure of the secondary air supply system. Hereinafter, this point will be described.

  The exhaust emission control device of the present embodiment checks the secondary air flow rate difference between the left and right AI pipes 6R and 6L based on the outputs of the left and right air pressure sensors 12R and 12L. If this flow rate difference is greater than or equal to a predetermined value, it is assumed that some failure has occurred in the secondary air supply system of the bank on one side, and the air switching valve 11 is opened to deal with this. FIG. 2 is a block diagram showing a configuration relating to drive control of the air switching valve 11 of the exhaust purification device applied to the V-type engine 1.

  As shown in FIG. 2, the exhaust emission control device includes an electronic control unit (hereinafter referred to as ECU) 13 serving as a control means. The ECU 13 is supplied with detection signals from the air pressure sensors 12R and 12L. The ECU 13 is connected via a bus 16 to a ROM 14 that stores a series of programs and data related to exhaust gas purification of the V-type engine 1 and a RAM 15 that provides a processing area. Note that the ECU 13 may be designed to use the ECU on the V-type engine 1 side. In this case, the configuration on the exhaust purification device side can be simplified.

  In FIG. 2, the left and right air pressure sensors 12R and 12L detect the pressure of the secondary air flowing in the left and right AI pipes 6R and 6L. The ECU 13 checks the secondary air flow rate difference between the AI pipes 6R and 6L based on the pressure difference. If this flow rate difference exceeds a predetermined value, the air switching valve 11 is opened because it is determined that some failure has occurred in the secondary air supply system of the AI pipe 6 on one side. As a result, secondary air is introduced from the normal AI pipe 6 side to the AI pipe 6 side where an abnormality has occurred. As a result, the secondary air can be supplied to the side of the AI pipe 6 where the abnormality has occurred, so that the exhaust purification catalyst can be warmed up and the deterioration of the emission can be suppressed.

  If secondary air cannot be introduced into the AI pipe 6 on the side where the failure has occurred, it is difficult to warm up the downstream exhaust purification catalyst 5, and the deterioration of emissions becomes serious. On the other hand, according to the exhaust purification device of the embodiment, secondary air can be supplementarily supplied from the normal AI pipe 6, so that the exhaust purification catalyst 5 on the downstream side of the abnormal side can be warmed up. . At this time, the amount of secondary air in the normal-side AI pipe 6 is reduced, but as a whole, deterioration of emissions can be suppressed as compared with a case where the exhaust purification catalyst on one side cannot be warmed up. Further, the flow rate can be reduced by increasing the amount of secondary air supplied by the normal-side air pump 7.

  FIG. 3 is a flowchart showing an example of a routine that the ECU 13 monitors and executes for failure of the secondary air supply system. For example, the ECU 13 activates this routine when it is confirmed that the ignition of the engine 1 is turned on.

  First, the ECU 13 checks whether or not a condition (AI execution condition) for introducing secondary air into the exhaust system of the engine 1 is established (step S11). Regarding whether the AI execution condition is satisfied, the ECU 13 determines whether the engine water temperature, intake air temperature, elapsed time after engine start, battery voltage, engine speed, engine load state, AI execution time, integrated secondary air amount, secondary Judgment based on air supply system status. Information related to any one or more of these determination elements is supplied to the ECU 13 so that the ECU 13 can confirm whether or not the AI execution condition is satisfied.

  If the ECU 13 determines that the AI execution condition is not satisfied in step S11, the ECU 13 closes the air switching valve 11. Thereby, the right AI pipe 6R and the left AI pipe 6L are maintained independently. On the other hand, if the ECU 13 determines in step S11 that the AI execution condition is satisfied, the flag indicating that the secondary air amount difference between the left and right banks RB and LB is larger than a predetermined value has not been set. (OFF) is confirmed (step S12), and whether or not AI is being executed is confirmed (step S13).

  The ECU 13 keeps the air switching valve 11 open (step S18) when the flag that the secondary air amount difference is larger than the predetermined value is set in step S12 (in the case of No). Repeat routine processing. If it is determined in step S13 that AI is not being executed (No), the air switching valve 11 is kept closed (step S19), and the processing of this routine is repeated.

  When both the ECU 13 determines Yes in step S12 and step S13, the ECU 13 sequentially checks the detection signals from the left and right air pressure sensors 12R and 12L, and calculates the secondary air flow rate (AI flow rate), respectively (step S14, Step S15). And ECU13 has the flow volume difference more than predetermined value between right-and-left banks RB and LB. That is, if the flow rate difference between the secondary air flowing through the left and right AI pipes 6R and 6L is greater than or equal to a predetermined value, it is determined that there is a failure in any of the secondary air supply systems (step S16). . Then, the large flow rate difference flag is set to ON (step S17), the air switching valve 11 is switched to open (step S18), and the processing according to this routine is repeated.

  According to the exhaust gas purification apparatus of the embodiment described above, the air switching valve 11 is provided in the communication passage 10 communicating with the secondary air supply AI pipes 6R, 6L provided separately on the left and right, so that the AI pipe is provided as necessary. 6R and 6L can be communicated. The ECU 13 of the present embodiment closes the air switching valve 11 when the secondary air is not introduced, so that it is possible to prevent the generation of noise due to the exhaust gas flowing around. Furthermore, by providing the air pressure sensors 12R and 12L, it is possible to determine the presence or absence of a failure in any of the secondary air supply systems by checking the difference in the secondary air flow rate between the left and right. It is possible to reliably suppress the deterioration of emissions. The ECU 13 may check the difference in the secondary air flow rate between the left and right from the air pressure sensors 12R and 12L, and control the opening of the communication passage 10 so as to eliminate the difference between the left and right. That is, the ECU 13 may drive and control the air switching valve 11 so that the flow rates of the left and right banks are equal. By configuring in this way, it is possible to suppress the deterioration of emission.

  In the above embodiment, the exhaust purification device applied to the V-type engine 1 is illustrated as an example of the internal combustion engine. However, it goes without saying that the present invention can be applied to an internal combustion engine of another form having a plurality of exhaust passages. Moreover, although the structure which connects AI piping 6 to the exhaust manifold 3 is shown in the said Example, it does not restrict to such a piping structure. If it is upstream of the exhaust purification catalyst, the AI pipe 6 may be connected to the exhaust pipe 4 connected downstream of the exhaust manifold 3.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

It is the figure shown about the internal combustion engine to which the exhaust gas purification device of an Example is applied. It is the block diagram which showed the structure which concerns on drive control of the air switching valve of the exhaust gas purification apparatus applied to the engine. It is the flowchart which showed an example of the routine which ECU of an exhaust gas purification apparatus monitors and performs the failure of a secondary air supply system.

Explanation of symbols

1 V-type engine (internal combustion engine)
2 cylinder 3 exhaust manifold 4 exhaust pipe 5 exhaust purification catalyst 6 AI piping (secondary air supply passage)
7 Air pump 8 Air switching valve 10 Communication path 11 Air switching valve (communication switching means)
12 Air pressure sensor (secondary air flow rate detection means)
13 ECU (control means)
LB Left bank RB Right bank Air Secondary air

Claims (5)

An exhaust emission control device for an internal combustion engine comprising a plurality of exhaust passages,
An exhaust purification catalyst disposed in the middle of each of the exhaust passages, a plurality of secondary air supply passages provided for introducing secondary air upstream of each of the exhaust purification catalysts, and each secondary air supply passage. A plurality of air pumps for supplying secondary air;
An exhaust emission control device for an internal combustion engine, comprising: a communication passage that communicates with the plurality of secondary air supply passages; and a communication switching means that opens and closes the communication passage. Secondary air flow rate detection means for detecting secondary air flow rates in the plurality of secondary air supply passages, and control means for controlling the communication switching means based on detection signals of the secondary air flow rate detection means. ,
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the control valve controls an opening degree of the communication passage based on a difference in secondary air flow rate between the secondary air supply passages. The control means controls the communication switching means to connect the communication path when a difference in secondary air flow rate between the secondary air supply paths is larger than a predetermined value. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. The internal combustion engine according to claim 2, wherein the control means controls the communication switching means to shut off the communication path when secondary air is not introduced into the secondary air supply path. Exhaust purification equipment. The exhaust of the internal combustion engine according to any one of claims 1 to 4, wherein the internal combustion engine includes two cylinder groups, and the exhaust passage is provided for each cylinder group to form two exhaust systems. Purification equipment.

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