JP2008088963A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of suppressing aggravation of exhaust emission even when abnormality occurs on either side of exhaust passages provided for every cylinder group. <P>SOLUTION: The control device is applied to the internal combustion engine wherein the exhaust passages 9L, 9R are provided for right and left banks 2L, 2R respectively, the exhaust passages 9L, 9R are provided with catalytic converters 10L, 10R respectively, and a communicating passage 11 serving for communication between the exhaust passages 9L, 9R is provided in the upstream of the catalytic converters 10L, 10R. When abnormality occurs in one of the exhaust passages 9L, 9R, selector valves 16L, 16R are operated to reduce distribution of exhaust gas flowing to the exhaust passage side with the occurrence of abnormality compared with distribution of exhaust gas flowing to the exhaust passage side without the occurrence of abnormality. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device applied to an internal combustion engine in which an exhaust passage is provided for each of a plurality of cylinder groups, and exhaust purification means capable of purifying exhaust gas is provided in each of the exhaust passages of each cylinder group. .

  A 6-cylinder V-type internal combustion engine is known in which an exhaust passage is provided for each of the left and right banks, a catalytic converter is provided in each exhaust passage, and a communication passage is provided on the upstream side of the catalytic converter. (Patent Document 1). In this internal combustion engine, the length of the communication passage and the exhaust passage and the position of the catalytic converter are set so that the exhaust pressure waves guided from both banks resonate in the communication passage, thereby increasing the output of the internal combustion engine.

Japanese Patent Laid-Open No. 3-286135

  In the internal combustion engine of Patent Document 1, the distribution of exhaust gas led to each exhaust passage is equally distributed. Therefore, if an abnormality such as a catalytic converter failure occurs, the distribution of exhaust gas cannot be changed. Therefore, exhaust gas purification on the exhaust passage side where abnormality has occurred becomes insufficient, and harmful components in the exhaust gas discharged to the atmosphere may increase, that is, exhaust emission may deteriorate.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can suppress deterioration of exhaust emission even when an abnormality occurs on either side of an exhaust passage provided for each cylinder group.

  In the control device for an internal combustion engine of the present invention, an exhaust passage is provided for each of a plurality of cylinder groups, an exhaust purification means capable of purifying exhaust is provided in each of the exhaust passages for each cylinder group, and the exhaust purification means In an internal combustion engine control device applied to an internal combustion engine provided with a communication passage communicating with the exhaust passage for each cylinder group on the upstream side, distribution of exhaust flowing through each of the exhaust passages for each cylinder group can be changed. Exhaust distribution changing means, abnormality detecting means for detecting which side of the exhaust passage for each cylinder group an abnormality accompanied by an increase in harmful components in the exhaust discharged to the atmosphere, and detection of the abnormality detecting means Based on the result, the exhaust distribution changing means for controlling the exhaust distribution changing means so that the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred becomes smaller than the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has not occurred. By providing a control means, and to solve the problems described above (claim 1).

  According to this control device, the distribution of the exhaust gas flowing to the exhaust passage side where an abnormality accompanied by an increase in harmful components in the exhaust gas discharged to the atmosphere is compared with the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has not occurred. Since the exhaust distribution changing means is controlled so as to be smaller, the inflow of exhaust gas to the exhaust passage side where an abnormality has occurred is restricted. Therefore, it is possible to suppress an increase in harmful components in the exhaust discharged to the atmosphere accompanying the occurrence of an abnormality, that is, deterioration of exhaust emission. In the present invention, to reduce the distribution, the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred is made zero, that is, an abnormality has occurred by blocking the inflow of exhaust gas to the exhaust passage side where the abnormality has occurred. This is a concept including directing all exhaust from a plurality of cylinder groups to a non-exhaust passage side.

  In one aspect of the control apparatus of the present invention, the internal combustion engine is used to control the fuel injection amount of the internal combustion engine in each of the exhaust passages provided for each cylinder group, and the air-fuel ratio of the exhaust gas Air-fuel ratio detecting means for outputting a signal corresponding to the air-fuel ratio detecting means, and the abnormality detecting means determines whether the air-fuel ratio detecting means determined to have failed by determining whether or not the air-fuel ratio detecting means has failed. It may be determined that the abnormality has occurred on the provided exhaust passage side (Claim 2). If the air-fuel ratio detection means fails, the fuel injection amount is not properly controlled and exhaust emission deteriorates. In this aspect, since it is determined that an abnormality has occurred when the air-fuel ratio detection means has failed, it is possible to suppress the deterioration of exhaust emissions accompanying the failure of the air-fuel ratio detection means.

  In one aspect of the control apparatus of the present invention, the internal combustion engine includes an air-fuel ratio detection unit that outputs a signal corresponding to an air-fuel ratio of exhaust gas to each of upstream and downstream of the exhaust gas purification unit provided for each cylinder group. The abnormality detecting means determines whether or not the exhaust purification performance of the exhaust purification means has deteriorated based on the air-fuel ratio upstream and downstream of the exhaust purification means. It may be determined that the abnormality has occurred on the side of the exhaust passage provided with the exhaust gas purifying means that has been determined to have decreased (Claim 3). When the exhaust gas purification performance of the exhaust gas purification means is deteriorated, the exhaust gas is exhausted to the atmosphere without being sufficiently purified, and the exhaust emission deteriorates. According to this aspect, since it is determined that an abnormality has occurred when the purification performance of the exhaust purification means is reduced, it is possible to suppress the deterioration of exhaust emission accompanying the reduction in the purification performance.

  In one aspect of the present invention, the exhaust distribution control means is configured so that the distribution of exhaust flowing to the exhaust passage side where the abnormality has occurred is smaller than the distribution of exhaust flowing to the exhaust passage side where the abnormality has not occurred. Throttle valve opening degree control means for limiting the opening degree of the throttle valve of the internal combustion engine when controlling the exhaust distribution changing means is further provided, and the throttle valve opening degree control means is an exhaust gas in which the abnormality has not occurred. The limit amount of the throttle valve opening may be changed in consideration of the purification performance of the exhaust gas purification means provided in the passage (claim 4). When the distribution of the exhaust to the exhaust passage side where the abnormality has occurred becomes small, the distribution of the exhaust to the exhaust passage side where the abnormality has not occurred becomes large. For this reason, there is a possibility that the burden on the exhaust passage side where no abnormality has occurred, specifically, the burden on the exhaust purification means increases, and the exhaust cannot be sufficiently purified. In this aspect, since the opening of the throttle valve is limited when the distribution of exhaust to the exhaust passage side where no abnormality has occurred increases, the absolute amount of exhaust flowing to the exhaust passage side where no abnormality has occurred is reduced. Can be reduced. Therefore, the burden on the exhaust gas purification means is not excessive and deterioration of exhaust emission can be suppressed. In addition, in this aspect, since the limit amount of the throttle valve opening is changed in consideration of the purification performance of the exhaust gas purification means provided in the exhaust passage where no abnormality has occurred, the throttle valve opening is more than necessary. It can prevent being restricted. For this reason, it is possible to prevent the exhaust emission from deteriorating while suppressing the output reduction of the internal combustion engine as much as possible.

  In one aspect of the control device of the present invention, the fuel injection of the internal combustion engine is performed based on a control input obtained by multiplying the deviation by a control gain so that the deviation between the detection result of the air-fuel ratio detection means and the target air-fuel ratio decreases. Air-fuel ratio control means for feedback-controlling the amount, wherein the air-fuel ratio control means is arranged such that the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred is distributed to the exhaust passage side where the abnormality has not occurred. When the exhaust distribution changing means is controlled to be smaller than the distribution of the flowing exhaust, the control gain is reduced compared to the normal time when the abnormality does not occur on any exhaust passage side. The combustion injection amount of the internal combustion engine is fed back so that the deviation between the detection result of the air-fuel ratio detection means provided on the exhaust passage side where the abnormality does not occur and the target air-fuel ratio decreases. Even if your good (claim 5). When an abnormality occurs in any of the exhaust passages, the air-fuel ratio is detected by the air-fuel ratio detecting means provided on the exhaust passage side where no abnormality has occurred in the exhaust that should flow to the exhaust passage where the abnormality has occurred. Will be. For this reason, the feedback system has a large dead time compared with the normal time when no abnormality occurs on any exhaust passage side. As a result, if the same control gain as that in the normal state is used, the control of the fuel injection amount of the internal combustion engine may diverge when there is an abnormality. According to this aspect, the deviation between the detection result of the air-fuel ratio detection means provided on the exhaust passage side where no abnormality has occurred and the target air-fuel ratio is reduced in a state where the control gain is smaller than normal when the abnormality occurs. Thus, since the combustion injection amount of the internal combustion engine is feedback controlled, control divergence can be prevented. As a result, the air-fuel ratio is accurately controlled at the time of abnormality, and deterioration of exhaust emission can be suppressed.

  In one aspect of the control apparatus of the present invention, the exhaust distribution control means distributes the exhaust gas flowing to the exhaust passage side where the abnormality has occurred compared to when the increase amount of the harmful component that may be generated by the abnormality is small. (Claim 6). Depending on the state of the abnormality that has occurred, there are cases where the exhaust gas can be purified while being insufficient even on the exhaust passage side where the abnormality has occurred. In such a case, even if a certain amount of exhaust is introduced to the side where the abnormality has occurred, the exhaust emission is not deteriorated. According to this aspect, the larger the increase amount of harmful components that can be caused by an abnormality, the smaller the distribution of exhaust flowing to the exhaust passage side where the abnormality has occurred. In other words, the greater the increase in harmful components that can occur due to an abnormality, the more restricted the introduction of exhaust into the exhaust passage where the abnormality has occurred. Conversely, the smaller the increase in harmful components that can occur due to an abnormality, the more permitted the introduction of exhaust into the exhaust passage where the abnormality has occurred. Therefore, according to this aspect, it is possible to prevent the exhaust emission from deteriorating while suppressing the burden on the exhaust passage side where no abnormality has occurred.

  As described above, according to the present invention, the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred accompanied by an increase in harmful components in the exhaust gas discharged to the atmosphere flows to the exhaust passage side where the abnormality has not occurred. Since the exhaust distribution changing means is controlled to be smaller than the exhaust distribution, the inflow of exhaust gas to the exhaust passage side where an abnormality has occurred is limited. Therefore, it is possible to suppress an increase in harmful components in the exhaust discharged to the atmosphere accompanying the occurrence of an abnormality, that is, deterioration of exhaust emission.

  FIG. 1 shows a main part of an internal combustion engine to which a control device of the present invention is applied. The internal combustion engine 1 is configured as a V-type 6-cylinder engine in which three cylinders 3 are provided in each of the left and right banks 2L and 2R. One cylinder group is constituted by the cylinders 3 in the left bank 2L, and another cylinder group is constituted by the cylinders 3 in the right bank 2R. One cylinder group only needs to include at least one cylinder 3. An intake passage 4 for guiding intake air to each cylinder 3 has an intake manifold 5 provided in common to each bank 2L, 2R. An air cleaner 6 for air filtration is provided in the intake passage 4, and a throttle valve 7 for adjusting the intake amount of air is provided downstream of the air cleaner 6. The throttle valve 7 is a well-known one that can be adjusted in opening between a fully closed position and a fully open position. The intake manifold 5 is provided with a fuel injection valve 8 for injecting fuel into the intake manifold 5 so that a fuel mixture is introduced into each cylinder 3.

  The air-fuel mixture introduced into each cylinder 3 is ignited by a spark plug (not shown) and burned. After the combustion, the exhaust from the cylinder 3 of each bank is guided to the exhaust passages 9L and 9R provided for each bank. The exhaust passages 9L and 9R for each bank are provided with catalytic converters 10L and 10R as exhaust purification means for purifying the exhaust, and the exhaust passages 9L and 9R on the upstream side of the catalytic converters 10L and 10R are communication passages. 11 communicate with each other. Each catalytic converter 10L, 10R is configured as a known three-way catalyst. Upstream of the catalytic converters 10L and 10R, upstream exhaust sensors 12L and 12R are provided downstream, and downstream exhaust sensors 13L and 13R are provided, respectively. These sensors are used in air-fuel ratio control, which will be described later. It functions as a detection means. These sensors are configured as well-known O2 sensors that output a signal corresponding to the air-fuel ratio.

  The internal combustion engine 1 is provided with an exhaust distribution change mechanism 15 as an exhaust distribution change means in order to change the distribution of the exhaust gas flowing through the exhaust passages 9L and 9R. The exhaust distribution changing mechanism 15 includes two switching valves 16L and 16R provided one at a connection portion between each exhaust passage 9L and 9R and the communication passage 11. Each switching valve 16L, 16R is configured as an electromagnetically driven valve that can hold the opening at an arbitrary position. The exhaust distribution changing mechanism 15 changes the position of the switching valves 16L and 16R from the state shown in FIG. 1 to the state shown in FIG. 2 or FIG. When any abnormality occurs, the distribution of exhaust gas to one side can be made smaller than the distribution to the other side. FIG. 2 shows the state of each switching valve 16L, 16R when an abnormality occurs on the exhaust passage 9L side provided in the left bank 2L, and FIG. 3 shows an abnormality on the exhaust passage 9R side provided in the right bank 2R. The state of the switching valves 16L and 16R in the case of As is apparent from these drawings, the exhaust distribution changing mechanism 15 of the present embodiment is configured such that when an abnormality occurs on the exhaust passage 9L side provided in the left bank 2L, the total amount of exhaust from each bank is transferred to the right bank 2R. When an abnormality occurs in the exhaust passage 9R provided in the right bank 2R on the contrary to the exhaust passage 9R provided, the entire amount of exhaust from each bank is provided in the left bank 2L. Further, it is configured to be guided to the exhaust passage 9L side. That is, the exhaust distribution changing mechanism 15 is configured so that the distribution of the exhaust to the exhaust passage side where the abnormality has occurred becomes 0%, and the distribution of the exhaust to the exhaust passage side where the abnormality has not occurred becomes 100%. , 16R can be changed.

  The operation of the exhaust distribution changing mechanism 15 is controlled by an engine control unit (ECU) 20. The ECU 20 is a well-known computer provided for properly controlling the operating state of the internal combustion engine 1. In addition to the control of the exhaust distribution changing mechanism 15, the ECU 20 sets main parameters of the internal combustion engine 1 such as the fuel injection amount and the ignition timing. Manipulate. For example, the ECU 20 performs air-fuel ratio feedback control using the outputs of the exhaust sensors 12L, 12R, 13L, and 13R described above in order to suppress deterioration of exhaust emissions of the internal combustion engine 1. That is, the ECU 20 uses the fuel injection valve 8 based on the control input obtained by multiplying the deviation by the control gain so that the deviation between the detection values (detection results) of the upstream exhaust sensors 12L and 12R and the predetermined target air-fuel ratio decreases. Feedback control of the fuel injection amount. Further, in the present embodiment, the ECU 20 corrects the target air-fuel ratio using the detection values of the downstream exhaust sensors 13L and 13R in order to increase the accuracy of this control. By executing this air-fuel ratio feedback control, the ECU 20 functions as an air-fuel ratio control means.

  FIG. 4 is a flowchart showing an example of a control routine of the exhaust distribution change control for the ECU 20 to control the exhaust distribution change mechanism 15. The routine program of FIG. 4 is stored in a storage means such as a ROM built in the ECU 20, and is repeatedly executed at predetermined intervals. As shown in FIG. 4, the ECU 20 determines in step S1 whether or not an abnormality has occurred on the exhaust passage 9L side of the left bank 2L. The presence / absence of an abnormality is determined based on whether or not there is an increase in harmful substances in the exhaust discharged into the atmosphere due to the abnormality, that is, whether or not the exhaust emission deteriorates due to the abnormality. Specifically, the exhaust sensor 12L, 13L on the left bank 2L side used for the condition that the purification performance of the catalytic converter 10L provided on the left bank 2L side falls below a predetermined limit and the air-fuel ratio feedback control described above. The ECU 20 determines that an abnormality has occurred on the exhaust passage 9L side of the left bank 2L when at least one of the conditions that a failure occurs in any of the above is established.

  The purification performance of the catalytic converter 10L can be grasped by a known method. For example, the reduction in purification performance can be determined based on the air-fuel ratio upstream and downstream of the catalytic converter 10L. When the purification performance of the catalytic converter 10L decreases, when the air-fuel ratio upstream of the catalytic converter 10L changes from rich to lean or from lean to rich with reference to the stoichiometric air-fuel ratio, from the time when the upstream exhaust sensor 12L detects the change. The time until it appears in the output of the downstream exhaust sensor 12R is shorter than normal. Thus, when the shortening time exceeds the threshold value, it can be determined that the purification performance of the catalytic converter 10L has deteriorated. As for the presence or absence of failure of the exhaust sensors 12L and 13L, it may be determined that the exhaust sensors 12L and 13L have failed because the output from the sensor cannot be obtained due to disconnection or the like, or the exhaust sensors 12L and 13L The failure may be determined based on the deterioration of the output reliability.

  If it is determined in step S1 that an abnormality has occurred on the exhaust bank 9L side of the left bank 2L, the process proceeds to step S2, and if not, the process proceeds to step S6. In step S2, the ECU 20 positions the switching valves 16L, 16R of the exhaust distribution changing mechanism 15 so that the distribution of exhaust to the exhaust passage 2L side becomes 0% and the distribution of exhaust to the exhaust passage 2R side becomes 100%. Is switched to the state shown in FIG. In subsequent step S3, the ECU 20 stops the above-described air-fuel ratio control using the exhaust sensors 12L and 13L on the left bank 2L side where the abnormality has occurred. Next, in step S4, in the air-fuel ratio control using the exhaust sensors 12R, 13R on the right bank 2R side, the control gain is changed to the control gain at the time of abnormality, and the fuel injection amount is controlled based on the control gain. . The control gain at the time of abnormality is set to a value smaller than the control gain at the time of normality from the viewpoint of preventing control divergence.

  Next, in step S5, the opening of the throttle valve 7 is limited so that the amount of intake air is limited, and this routine is finished. The limit amount of the opening degree of the throttle valve 7 is calculated based on the operating state of the internal combustion engine 1, the temperature of the catalytic converter 10R, and the degree of reduction in its purification performance. For example, the calculation of the limit amount is a map that gives the limit amount of the opening degree of the throttle valve 7 with the three physical quantities of the rotational speed (rotational speed) of the internal combustion engine 1, the temperature of the catalytic converter 10R and the maximum oxygen storage amount as variables. This can be realized by storing in the storage means of the ECU 20 and referring to this map after the ECU 20 acquires these physical quantities. This map shows that the higher the rotational speed of the internal combustion engine 1, the lower the temperature of the catalytic converter 10R, and the smaller the maximum oxygen storage amount, the larger the limit amount of the throttle valve 7 opening, in other words, the throttle valve 7. The opening degree is configured to be small.

  In step S6, it is determined whether or not an abnormality has occurred on the exhaust passage 9R side of the right bank 2R. The determination of whether or not an abnormality has occurred is performed in the same manner as in step S1. That is, whether or not an abnormality has occurred is determined on the basis of whether or not the abnormality causes an increase in harmful substances in the exhaust discharged to the atmosphere, that is, whether or not the exhaust emission deteriorates due to the abnormality. Specifically, the conditions under which the purification performance of the catalytic converter 10R provided on the right bank 2R side falls below a predetermined limit and any of the exhaust sensors 12R and 13R on the right bank 2R side used for the above-described air-fuel ratio feedback control are described. When at least one of the conditions in which the crab has occurred is satisfied, the ECU 20 determines that an abnormality has occurred on the exhaust passage 9R side of the right bank 2R. The grasping of the purification performance of the catalytic converter 10R and the failure of the exhaust sensors 12R and 13R are the same as in step S1.

  If it is determined in step S6 that an abnormality has occurred on the exhaust passage 9R side of the right bank 2R, the process proceeds to step S7. Otherwise, it is normal when no abnormality has occurred in any of the exhaust passages, so the process proceeds to step S11 to execute normal control, and the current routine is finished. That is, the ECU 20 switches the positions of the switching valves 16L and 16R of the exhaust distribution changing mechanism 15 to the state shown in FIG. 1 so that the exhaust gas is evenly distributed to the exhaust passages 9L and 9R. Execute. In step S7, the ECU 20 positions the switching valves 16L and 16R of the exhaust distribution changing mechanism 15 so that the distribution of exhaust to the exhaust passage 2R side becomes 0% and the distribution of exhaust to the exhaust passage 2L side becomes 100%. Is switched to the state of FIG. In subsequent step S8, the ECU 20 stops the above-described air-fuel ratio control using the exhaust sensors 12R and 13R on the right bank side where the abnormality has occurred. Next, in step S9, in the air-fuel ratio control using the exhaust sensors 12L and 13L on the left bank 2L side, the control gain is changed to a control gain at the time of abnormality, and the fuel injection amount is controlled based on the control gain. The control gain at the time of abnormality is set to a value smaller than the control gain at the time of normality from the viewpoint of preventing control divergence, as in the case of step S4. Next, in step S10, the opening of the throttle valve 7 is limited so that the intake air amount is limited, and the current routine is finished. The limit amount of the opening degree of the throttle valve 7 is calculated by the same method as in step S5.

  By executing the control of FIG. 4, the exhaust distribution change mechanism 15 prevents the inflow of exhaust gas to the exhaust passage side where an abnormality has occurred, so that deterioration of exhaust emission can be prevented. In addition, since the air-fuel ratio control using the exhaust sensor on the side where the abnormality has occurred is stopped, and the control gain is set small in the air-fuel ratio control using the exhaust sensor on the side where no abnormality has occurred, the control divergence is reduced. This can prevent the deterioration of exhaust emissions. Further, when an abnormality occurs, the opening degree of the throttle valve 7 is limited and a large amount of exhaust gas is prevented from flowing into one of the exhaust passages, so that deterioration of exhaust emission can be prevented. Moreover, since the limit amount is determined in consideration of the purification performance of the catalytic converter in addition to the operating state of the internal combustion engine 1, the opening degree of the throttle valve 7 is not excessively limited and the output of the internal combustion engine 1 is reduced. Can be suppressed.

  In the control of FIG. 4, the ECU 20 executes step S1 and step S6 as an abnormality detection unit according to the present invention, and executes step S2 and step S7 as an exhaust distribution control unit according to the present invention. By executing Step S9, the air-fuel ratio control means according to the present invention functions as the throttle valve opening degree control means according to the present invention by executing Step S5 and Step S10.

  However, the present invention is not limited to the above embodiment, and can be implemented in various forms within the scope of the gist of the present invention. In the embodiment described above, when an abnormality occurs on one exhaust passage side, the inflow of exhaust gas to the exhaust passage side where the abnormality has occurred is blocked, and the entire amount of exhaust gas is guided to the exhaust passage side where no abnormality has occurred. However, the present invention is not limited to this form. That is, the distribution of exhaust gas to the exhaust passage side where abnormality has occurred may be smaller than the distribution of exhaust gas to the exhaust passage side where abnormality has not occurred. Therefore, in consideration of the degree of abnormality, inflow of exhaust gas to the exhaust passage side where abnormality has occurred may be allowed.

  FIG. 5 is a flowchart showing an example of a control routine of the exhaust distribution change control according to another embodiment in which the distribution of exhaust gas to each exhaust passage side is changed in consideration of the degree of abnormality. In FIG. 5, the same processes as those in FIG. As shown in FIG. 5, when it is determined in step S1 that an abnormality has occurred on the exhaust passage 9L side of the left bank 2L, the process proceeds to step S21, and an increase amount of harmful components that can be discharged into the atmosphere accompanying the abnormality is calculated. . This increase is compared to normal. When the purification performance of the catalytic converter 10L decreases, unpurified harmful components increase in accordance with the degree of decrease. Also, harmful components increase according to the absolute amount of exhaust. Therefore, the increase amount is calculated, for example, by storing in the storage means of the ECU 20 a map that gives the increase amount of harmful components using the rotational speed of the internal combustion engine 1 and the degree of reduction in the purification performance of the catalytic converter 10L as variables. Can be realized by referring to this map after obtaining these parameters. The degree of reduction in the purification performance of the catalytic converter 10L is a physical quantity that correlates with the degree of reduction in the purification performance such as the time from when the upstream exhaust sensor 12L detects the air-fuel ratio change until it appears in the output of the downstream exhaust sensor 13L as described above. Can be obtained based on

  Next, in step S22, the distribution of the exhaust gas to the exhaust passage 9L side is calculated according to the increase amount of the harmful component calculated in step S21. This distribution can be calculated by using a map or the like set so that the distribution to the exhaust passage 9L becomes smaller when the increase amount of harmful components is large than when it is small. Subsequently, in step S23, the opening degree of each switching valve 16L, 16R of the exhaust distribution changing mechanism 15 is set so that the exhaust is guided to each exhaust passage with the distribution calculated in step S22. Even when an abnormality occurs on the exhaust passage 9R side, the same processing as described above is performed in steps S71 to S73. The other processes are the same as those in FIG. According to the control of FIG. 5, since the introduction of exhaust is allowed to the exhaust passage side where the abnormality has occurred in consideration of the degree of abnormality, the burden on the exhaust passage side where the abnormality has not occurred is suppressed while reducing the exhaust emission. Deterioration can be prevented.

  The control device according to the present invention is also applied to an internal combustion engine having three or more cylinder groups, an exhaust passage provided for each cylinder group, and an exhaust purification means provided in each exhaust passage for each cylinder group. Can do. For example, as shown in FIG. 6, exhaust passages 30A, 30B, 30C are provided for each of the three cylinder groups, and catalytic converters 31A, 31B, 31C as exhaust purification means are provided in these exhaust passages 30A, 30B, 30C, respectively. And the control apparatus according to the present invention can be applied to the internal combustion engine 100 provided with the communication passage 32 that communicates the exhaust passages 30A, 30B, and 30C with each other upstream of the catalytic converters 31A, 31B, and 31C. In the internal combustion engine 100 of FIG. 6, three switching valves 33A, 33B, and 33C are provided between the connection portions of the communication passage 32 and the exhaust passages 30A, 30B, and 30C and the catalytic converters 31A, 31B, and 31C. The exhaust distribution changing mechanism 34 is provided as exhaust distribution changing means. By arbitrarily operating the opening degree of each switching valve 33A, 33B, 33C of the exhaust distribution changing mechanism 34 by the ECU 40 that controls the internal combustion engine 100, the distribution of the exhaust gas to each exhaust passage side is appropriately changed. be able to. The control routine executed by the ECU 40 in the configuration of FIG. 6 may be the same as the control routines of FIGS. 4 and 5. When the ECU 40 executes the control routine, the ECU 40 can function as an abnormality detection unit and an exhaust distribution change unit according to the present invention. The ECU 40 uses the outputs of the upstream exhaust sensors 35A, 35B, 35C and the downstream exhaust sensors 36A, 36B, 36C provided upstream and downstream of the catalytic converters 31A, 31B, 31C, respectively, to control the air-fuel ratio described above. And also functions as air-fuel ratio control means according to the present invention. Further, the ECU 40 limits the opening degree of a throttle valve (not shown) of the internal combustion engine 100 when the distribution of exhaust gas to each exhaust passage side is changed, and also functions as a throttle valve opening control means according to the present invention.

The figure which showed the principal part of the internal combustion engine to which the control apparatus of this invention was applied. The figure which showed the state of each switching valve when abnormality arises in the exhaust passage side provided in the left bank. The figure which showed the state of each switching valve when abnormality arises in the exhaust passage side provided in the right bank. The flowchart which showed an example of the control routine of exhaust distribution change control. The flowchart which showed an example of the control routine of the exhaust distribution change control which concerns on another form. The figure which showed the other form of the internal combustion engine to which the control apparatus of this invention was applied.

Explanation of symbols

1,100 Internal combustion engine 2L Left bank (cylinder group)
2R right bank (cylinder group)
7 Throttle valves 9L, 9R Exhaust passages 10L, 10R Catalytic converter (exhaust purification means)
11 Communication path 15 Exhaust distribution change mechanism (Exhaust distribution change means)
12L, 12R, 35A, 35B, 35C Upstream exhaust sensor (air-fuel ratio detection means)
13L, 13R, 36A, 36B, 36C Downstream exhaust sensor (air-fuel ratio detection means)
20, 40 ECU (abnormality detection means, exhaust distribution control means, throttle valve opening control means, air-fuel ratio control means)

Claims (6)

An exhaust passage is provided for each of the plurality of cylinder groups, an exhaust purification means capable of purifying exhaust is provided in each of the exhaust passages for each cylinder group, and the exhaust passage for each cylinder group is provided upstream of the exhaust purification means. In a control device for an internal combustion engine applied to an internal combustion engine provided with a communication passage communicating with
Any of the exhaust distribution changing means capable of changing the distribution of the exhaust gas flowing in each of the exhaust passages for each cylinder group, and any abnormality in the exhaust passage for each cylinder group that causes an increase in harmful components in the exhaust discharged to the atmosphere. An abnormality detection means for detecting whether the abnormality has occurred, and based on the detection result of the abnormality detection means, the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred is distributed to the exhaust passage side where the abnormality has not occurred. An internal combustion engine control apparatus comprising: an exhaust distribution control unit that controls the exhaust distribution change unit so as to be smaller than the distribution. In the internal combustion engine, air-fuel ratio detection is used for controlling the fuel injection amount of the internal combustion engine and outputs a signal corresponding to the air-fuel ratio of the exhaust gas in each of the exhaust passages provided for each cylinder group. Means are provided,
The abnormality detection means determines whether the abnormality has occurred on the exhaust passage side provided with the air-fuel ratio detection means determined to have failed by determining whether or not the air-fuel ratio detection means has failed. The control apparatus for an internal combustion engine according to claim 1, wherein the control apparatus is an internal combustion engine. In the internal combustion engine, a signal that is used to control the fuel injection amount of the internal combustion engine and that corresponds to the air-fuel ratio of the exhaust is provided upstream and downstream of the exhaust purification unit provided for each cylinder group. Air-fuel ratio detection means for output is provided,
The abnormality detecting means determines whether or not the exhaust purification performance of the exhaust purification means has deteriorated based on the air-fuel ratio upstream and downstream of the exhaust purification means, thereby determining that the purification performance has deteriorated. 2. The control apparatus for an internal combustion engine according to claim 1, wherein it is determined that the abnormality has occurred on the side of the exhaust passage provided with a purifying means. The exhaust distribution control means controls the exhaust distribution change means so that the distribution of exhaust flowing to the exhaust passage side where the abnormality has occurred becomes smaller than the distribution of exhaust flowing to the exhaust passage side where the abnormality has not occurred. A throttle valve opening control means for limiting the opening of the throttle valve of the internal combustion engine,
The throttle valve opening control means changes a limit amount of the throttle valve opening in consideration of a purification performance of the exhaust purification means provided in an exhaust passage where the abnormality does not occur. Item 4. The control device for the internal combustion engine according to any one of Items 1 to 3. Air-fuel ratio control means for feedback-controlling the fuel injection amount of the internal combustion engine based on a control input obtained by multiplying the deviation by a control gain so that the deviation between the detection result of the air-fuel ratio detection means and the target air-fuel ratio decreases. In addition,
The air-fuel ratio control means is configured so that the distribution of exhaust flowing to the exhaust passage side where the abnormality has occurred is smaller than the distribution of exhaust flowing to the exhaust passage side where the abnormality has not occurred. Provided on the exhaust passage side where the abnormality does not occur in a state where the control gain is reduced compared to the normal time when the abnormality does not occur on any exhaust passage side when controlling the distribution changing means. 4. The control apparatus for an internal combustion engine according to claim 2, wherein the combustion injection amount of the internal combustion engine is feedback-controlled so that a deviation between a detection result of the air-fuel ratio detection means and a target air-fuel ratio decreases. .   The exhaust distribution control means reduces the distribution of the exhaust gas flowing to the exhaust passage side where the abnormality has occurred, when the increase amount of the harmful component that may be caused by the abnormality is large, compared to when it is small. The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein

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