JP2008223597A - Exhaust control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately detect deterioration of a catalyst, in an exhaust control device for an internal combustion engine performing an exhaust control with respect to the internal combustion engine having a plurality of cylinder groups. <P>SOLUTION: The exhaust control device is suitably used for the exhaust control with respect to the internal combustion engine having first and second cylinder groups. A first catalyst and a second catalyst are respectively disposed on an exhaust passage each connected to the first cylinder group and the second cylinder group. A first control valve is disposed on a communication passage for connecting an exhaust passage upstream of the first catalyst and an exhaust passage upstream of the second catalyst. A first valve control means sets the first control valve to be closed when detecting deterioration states of the first and second catalysts. Therefore, the deterioration states of both first and second catalyst is accurately detected, and degradation in fuel economy caused by the deterioration detection is effectively suppressed since their deterioration states can be detected at the same time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust control device for an internal combustion engine that performs exhaust control on an internal combustion engine having a plurality of cylinder groups.

  In an internal combustion engine having a plurality of cylinder groups (banks) such as a so-called V-type internal combustion engine, a configuration in which a catalyst is individually disposed on an exhaust passage of each cylinder group and a catalyst is disposed on the downstream side of the merging position of the exhaust passage. Exhaust gas purification devices are known. An example of such an exhaust purification device is described in Patent Document 1.

JP-A-8-121153

  However, in the technique described in Patent Document 1 described above, when controlling the exhaust system flow rate of each cylinder group, it is necessary to adjust two control valves, and the control tends to be complicated. Further, when the combustion state is different for each cylinder group (for example, air-fuel ratio or back pressure), exhaust gas may be mixed in the communication path. For this reason, it has been difficult to accurately detect the deterioration of the catalyst.

  The present invention has been made to solve the above-described problems, and in an exhaust control device for an internal combustion engine that performs exhaust control on an internal combustion engine having a plurality of cylinder groups, it is possible to appropriately detect deterioration of the catalyst. The purpose is to do.

  In one aspect of the present invention, an exhaust control device for an internal combustion engine that performs exhaust control on an internal combustion engine having a first cylinder group and a second cylinder group includes the first cylinder group and the second cylinder. A first catalyst and a second catalyst provided on an exhaust passage connected to each of the groups, an exhaust passage upstream of the first catalyst, and an exhaust passage upstream of the second catalyst. A first control valve that is provided on the communication passage to be connected and controls the flow rate of the exhaust gas flowing through the communication passage; and when detecting the deterioration state of the first catalyst and the second catalyst, First valve control means for performing control to close one control valve.

  The exhaust control device for an internal combustion engine described above is preferably used for performing exhaust control on an internal combustion engine having a first cylinder group and a second cylinder group. The first catalyst and the second catalyst are provided on exhaust passages connected to the first cylinder group and the second cylinder group, respectively, and the first control valve is located upstream of the first catalyst. Provided on the communication passage connecting the exhaust passage on the side and the exhaust passage on the upstream side of the second catalyst, and controls the flow rate of the exhaust gas flowing through the communication passage. And the 1st valve control means performs control which closes the 1st control valve in order to detect the deterioration state of both the 1st catalyst and the 2nd catalyst. Thereby, the flow rate of the exhaust gas flowing through the exhaust passage of each cylinder group can be made substantially the same, and the occurrence of exhaust interference (pulsation, inflow, etc.) can be suppressed. Therefore, exhaust gas set to a desired air-fuel ratio can be supplied to the first catalyst and the second catalyst, and the oxygen storage amounts of the first catalyst and the second catalyst can be appropriately measured. Can do. Therefore, according to the exhaust control device for an internal combustion engine, it is possible to accurately detect the deterioration states of both the first catalyst and the second catalyst, that is, it is possible to prevent erroneous detection. . Moreover, according to the exhaust control device for an internal combustion engine, the deterioration state of both the first catalyst and the second catalyst can be detected at the same time, so that the deterioration of fuel consumption caused by the deterioration detection is effectively suppressed. It becomes possible to do.

  In one aspect of the exhaust gas control apparatus for an internal combustion engine, the first valve control means is configured such that when the accumulated exhaust heat amount in the internal combustion engine to both the first catalyst and the second catalyst is a predetermined value or more. In addition, control for closing the first control valve is performed.

  In this aspect, for example, when both the first catalyst and the second catalyst are in the active state, the first valve control means sets the first control valve to be closed and detects the deterioration state. Thereby, it becomes possible to detect the deterioration states of both the first catalyst and the second catalyst with higher accuracy.

  Preferably, in the exhaust control device for an internal combustion engine, the integrated exhaust heat amount is calculated based on an estimated value of exhaust gas temperature and an inflow gas amount to the first catalyst and the second catalyst. be able to.

  In another aspect of the exhaust control device for an internal combustion engine, the second control valve is provided on an exhaust passage connected to the first cylinder group and controls a flow rate of exhaust gas flowing through the exhaust passage. And a third control valve that is provided on an exhaust passage connected to the second cylinder group and controls a flow rate of exhaust gas flowing through the exhaust passage, and a failure of the first control valve is determined. In order to detect a deterioration state of one of the first catalyst and the second catalyst when the failure determination means and the failure determination means determine that the first control valve has failed. And a second valve control means for controlling to open one of the second control valve and the third control valve and to close the other.

  In this aspect, when the first control valve is in failure, the first catalyst is opened by opening one of the second control valve and the third control valve and closing the other. And the deterioration state of either one of the second catalyst is detected. As a result, even when the first control valve has an open failure, it is possible to accurately detect the respective deterioration states of the first catalyst and the second catalyst.

  Preferably, in the exhaust control device for an internal combustion engine, a turbocharger turbine is disposed on an exhaust passage of the first cylinder group, and the second valve control means is a load in the internal combustion engine. Alternatively, the second control valve and the third control valve are controlled based on the supercharging pressure in the turbocharger. Thereby, the torque that can be generated by opening and closing the second control valve and the third control valve at the start of deterioration detection or the like can be appropriately controlled.

  Preferably, the second valve control means opens the second control valve when the load is equal to or higher than a predetermined value, or when the supercharging pressure is equal to or higher than a predetermined pressure, and the third valve control means. When the load is less than the predetermined value, or when the supercharging pressure is less than the predetermined pressure, the second control valve is closed and the third control valve is closed. Can be opened.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Device configuration]
FIG. 1 shows a schematic configuration of an exhaust control device for an internal combustion engine according to an embodiment of the present invention. In FIG. 1, solid arrows indicate an example of gas flow, and broken arrows indicate signal input / output. In the following description, the subscript “L” or “R” is added to the reference symbol when the left and right components are distinguished, and the subscript is omitted when the left and right components are not distinguished.

  The internal combustion engine 1 is configured as a V-type 6-cylinder engine in which three banks (cylinders) 8La and 8Ra are provided in the left and right banks (cylinder groups) 8L and 8R, respectively. The internal combustion engine 1 is a device that generates power by burning a mixture of air and fuel supplied via an intake passage 3 and an intake manifold 7. The left bank 8L corresponds to the first cylinder group in the present invention, and the right bank 8R corresponds to the second cylinder group in the present invention.

  An air passage (AC) 2a, an air flow meter (AFM) 2b, an intercooler (IC) 5, a throttle valve 6 and the like are provided in the intake passage 3 for guiding intake air to the cylinders 8La and 8Ra. The air cleaner 2a purifies the supplied intake air, the air flow meter 2b detects the intake air flow rate that passes through, and the intercooler 5 cools the intake air. Further, a compressor 4 a of a turbocharger 4 is disposed in the intake passage 3.

  The exhaust manifolds 9L and 9R of the banks 8L and 8R are connected to the exhaust passages 11L and 11R, respectively. The exhaust passage 11L and the exhaust passage 11R are connected via the communication passage 10. Specifically, the communication passage 10 connects the exhaust passage 11L on the upstream side of the start catalyst 12L and the exhaust passage 11R on the upstream side of the start catalyst 12R. An exhaust switching valve 13 a that can adjust the flow rate of the exhaust gas flowing through the communication path 10 is provided on the communication path 10. The exhaust gas switching valve 13a is controlled to be opened or closed by a control signal S13a supplied from the ECU 50. The exhaust gas switching valve 13a corresponds to the first control valve in the present invention. Further, a turbine 4b of the turbocharger 4 is disposed on the exhaust passage 11L in the left bank 8L. Note that the exhaust passage 11R in the right bank 8R is not connected to the turbine 4b.

  A start catalyst 12L is provided in the exhaust passage 11L, and a start catalyst 12R is provided in the exhaust passage 11R. The exhaust passage 11L and the exhaust passage 11R join at the joining portion 14 on the downstream side of the start catalysts 12L and 12R, and are connected to the common exhaust passage 15. A NOx catalyst 16 is provided in the common exhaust passage 15. The start catalysts 12L and 12R correspond to the first catalyst and the second catalyst in the present invention, respectively.

  Furthermore, exhaust switching valves 13b and 13c are provided on the exhaust passages 11L and 11R of the banks 8L and 8R at positions downstream of the start catalysts 12L and 12R. The exhaust gas switching valves 13b and 13c have a role of controlling the flow rate of the exhaust gas flowing through the exhaust passages 11L and 11R, respectively. The exhaust switching valves 13b and 13c are controlled to be opened and closed by control signals S13b and S13c supplied from the ECU 50. The exhaust gas switching valves 13b and 13c correspond to the second control valve and the third control valve in the present invention, respectively.

Various sensors are provided in an exhaust control device for an internal combustion engine. Specifically, A / F sensors 20L and 20R for detecting the air-fuel ratio (A / F) of the exhaust gas discharged from the banks 8L and 8R are provided near the outlets of the exhaust manifolds 9L and 9R. . The A / F sensors 20L and 20R supply detection signals S20L and S20R corresponding to the detected A / F to the ECU 50. Further, oxygen sensors (O ₂ sensors) 21L and 21R for detecting the oxygen concentration in the exhaust gas are provided on the exhaust passages 11L and 11R on the downstream side of the start catalysts 12L and 12R. The oxygen sensors 21L and 21R supply detection signals S21L and S21R corresponding to the detected oxygen concentration to the ECU 50.

  The ECU (Engine Control Unit) 50 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The ECU 50 mainly performs processing for detecting the deterioration state of the start catalysts 12L and 12R (hereinafter referred to as “deterioration detection processing”). In this case, the ECU 50 detects the deterioration state of the start catalysts 12L, 12R based on the detection signals S20L, S20R, S21L, S21R supplied from the A / F sensors 20L, 20R and the oxygen sensors 21L, 21R. In the present embodiment, the ECU 50 determines whether or not the deterioration detection process can be performed on both of the start catalysts 12L and 12R, and the start catalysts 12L and 12R are deteriorated based on the determination result. Perform detection processing. Further, the ECU 50 controls the exhaust gas switching valves 13a, 13b, and 13c before executing the deterioration detection process. In this case, the ECU 50 controls the flow of exhaust gas by supplying control signals S13a, S13b, and S13c to the exhaust gas switching valves 13a, 13b, and 13c. The ECU 50 also controls other components of the exhaust control device for the internal combustion engine, but a description of portions that are not particularly related to the present embodiment is omitted.

  As described above, the ECU 50 functions as the first valve control means, the second valve control means, and the failure determination means in the present invention.

  In the above description, an exhaust control device for an internal combustion engine having a configuration in which the turbine 4b of the turbocharger 4 is provided on the exhaust passage 11L of the left bank 8L is shown, but the application of the present invention is not limited to this. The present invention can also be applied to an exhaust control device for an internal combustion engine having a configuration in which a turbine 4b is provided on the exhaust passage 11R of the right bank 8R. In this case, the right bank 8R corresponds to the first cylinder group, the left bank 8L corresponds to the second cylinder group, the start catalyst 12R corresponds to the first catalyst, and the start catalyst 12L corresponds to the second cylinder group. It corresponds to a catalyst, the exhaust gas switching valve 13c corresponds to a second control valve, and the exhaust gas switching valve 13b corresponds to a third control valve.

  Below, the catalyst deterioration detection method which concerns on embodiment of this invention is demonstrated.

[First Embodiment]
First, the catalyst deterioration detection method according to the first embodiment will be described.

  In the first embodiment, the ECU 50 performs the deterioration detection process simultaneously on both of the start catalysts 12L and 12R provided in the exhaust passages 11L and 11R of the two banks 8L and 8R. In this case, the ECU 50 determines whether or not it is possible to simultaneously execute the deterioration detection process on both of the start catalysts 12L and 12R (hereinafter, “deterioration detection execution”). This is called “determination”. That is, in the first embodiment, when it is possible to simultaneously detect the deterioration states of both of the start catalysts 12L and 12R, the deterioration detection process is performed on the start catalysts 12L and 12R. Specifically, the ECU 50 determines whether or not the temperatures of both the start catalysts 12L and 12R are equal to or higher than the activation temperature in the deterioration detection execution determination (that is, both the start catalysts 12L and 12R can appropriately function). It is determined whether it is in such a state (active state). More specifically, the ECU 50 determines whether or not the temperatures of both the start catalysts 12L and 12R are equal to or higher than the activation temperature, and the accumulated exhaust heat amount in the internal combustion engine 1 to both the start catalysts 12L and 12R is equal to or greater than a predetermined value. This is done by determining whether or not there is. By performing the deterioration detection process after performing such deterioration detection execution determination, it is possible to accurately detect the deterioration states of both the start catalysts 12L and 12R.

  In the first embodiment, when it is determined in the above-described deterioration detection execution determination that the deterioration detection process can be executed, the ECU 50 detects both deterioration states of the start catalysts 12L and 12R at the same time. In addition, control for setting the exhaust gas switching valves 13a, 13b, and 13c to a predetermined state (hereinafter referred to as “exhaust gas switching valve control”) is performed. That is, the exhaust gas switching valve control is executed as a preparation for the deterioration detection process. Specifically, the ECU 50 sets the exhaust switching valve 13a provided in the communication passage 10 to be closed and sets the exhaust switching valves 13b and 13c provided in the exhaust passages 11L and 11R to be opened. Perform detection processing. By performing such an exhaust switching valve control, it is possible to shut off the flow of exhaust gas in the communication passage 10 and flow the exhaust gas independently to each of the exhaust passages 11L and 11R (that is, the exhaust passage 11L, The exhaust gas does not go back and forth between 11R). Therefore, during the deterioration detection process, the flow rate of the exhaust gas flowing through the exhaust passages 11L, 11R of the banks 8L, 8R can be made substantially the same, and the occurrence of exhaust interference (pulsation, inflow, etc.) can be suppressed. . As a result, it is possible to accurately detect the deterioration states of both of the start catalysts 12L and 12R.

  After executing the above-described deterioration detection execution determination and exhaust gas switching valve control, the ECU 50 starts the deterioration detection process for the start catalysts 12L and 12R. For example, the ECU 50 executes the deterioration detection process for the start catalysts 12L and 12R according to the following procedure. The ECU 50 executes air-fuel ratio control that changes the air-fuel ratio (A / F) between air and fuel supplied to the banks 8L and 8R between rich and lean. The ECU 50 determines the deterioration states of both the start catalysts 12L and 12R based on the output values of the A / F sensors 20L and 20R and the oxygen sensors 21L and 21R obtained when the air-fuel ratio control is executed. To detect. For example, the ECU 50 measures the oxygen storage amount of the start catalysts 12L and 12R based on the output value of the sensor, and detects the deterioration state of the start catalysts 12L and 12R based on the oxygen storage amount.

  As described above, in the catalyst deterioration detection method according to the first embodiment, the exhaust switching valve 13a provided in the communication passage 10 is set to be closed in a situation where both of the start catalysts 12L and 12R are at the activation temperature or higher. Then, the deterioration detection process is performed on the start catalysts 12L and 12R. As a result, the deterioration states of both the start catalysts 12L and 12R can be detected at the same time, and the oxygen storage amount of the start catalysts 12L and 12R can be appropriately measured, so that both the start catalysts 12L and 12R are deteriorated. Can be detected with high accuracy (that is, erroneous detection can be prevented). In addition, according to the catalyst deterioration detection method according to the first embodiment, both deterioration states of the start catalysts 12L and 12R can be detected at the same time, so that deterioration of fuel consumption caused by the deterioration detection process is effectively suppressed. It becomes possible.

  Next, with reference to FIG. 2, the process performed in the catalyst deterioration detection method according to the first embodiment will be described. FIG. 2 is a flowchart showing processing according to the first embodiment. This process is basically executed before the deterioration detection process. In this process, mainly, it is determined whether or not the deterioration states of both of the start catalysts 12L and 12R can be detected at the same time (determination detection execution determination), and the exhaust gas switching valves 13a, 13b, Control for setting 13c to a predetermined state (exhaust gas switching valve control) or the like is performed. This process is executed by the ECU 50.

  First, in step S101, the ECU 50 determines whether or not it is a situation in which deterioration states of both of the start catalysts 12L and 12R can be detected simultaneously (determination detection execution determination). Specifically, ECU 50 determines whether or not the temperatures of both start catalysts 12L and 12R are equal to or higher than the activation temperature. Specifically, the ECU 50 determines whether or not the temperatures of both the start catalysts 12L and 12R are equal to or higher than the activation temperature, and determines whether or not the accumulated exhaust heat amount to both the banks 8L and 8R is equal to or higher than a predetermined value. Do by judging. Here, the integrated exhaust heat amount corresponds to the energy (input heat amount) input to the start catalysts 12L and 12R. Therefore, the ECU 50 calculates the integrated exhaust heat amount based on the estimated value of the exhaust gas temperature and the amount of gas flowing into the start catalysts 12L and 12R.

  If the integrated exhaust heat quantity is equal to or greater than the predetermined value (step S101; Yes), the process proceeds to step S102. On the other hand, when the integrated exhaust heat quantity is less than the predetermined value (step S101; No), the process exits the flow. In this case, since the temperatures of the start catalysts 12L and 12R are not higher than the activation temperature (both of the start catalysts 12L and 12R or one of them is not higher than the activation temperature), the deterioration detection process is not executed.

  In step S102, the ECU 50 determines whether or not the operating condition of the internal combustion engine 1 satisfies a condition capable of executing the deterioration detection process (hereinafter referred to as “deterioration detection execution condition”). Specifically, the ECU 50 determines whether or not the temperature of the cooling water that cools the internal combustion engine 1, the rotational speed of the internal combustion engine 1, the load, and the like are within predetermined ranges. If the deterioration detection execution condition is satisfied (step S102; Yes), the process proceeds to step S103. If the deterioration detection execution condition is not satisfied (step S102; No), the process exits the flow.

  In step S103, the ECU 50 executes control (exhaust switching valve control) for setting the exhaust switching valves 13a, 13b, and 13c to a predetermined state in order to detect the deterioration states of both of the start catalysts 12L and 12R at the same time. Specifically, the ECU 50 sets the exhaust gas switching valve 13a provided in the communication passage 10 to be closed, and sets the exhaust gas switching valves 13b and 13c provided in the exhaust passages 11L and 11R to be open. In this case, ECU50 controls each by supplying control signal S13a, S13b, S13c to exhaust gas switching valve 13a, 13b, 13c. By performing such an exhaust switching valve control, it is possible to shut off the flow of exhaust gas in the communication passage 10 and flow the exhaust gas independently to each of the exhaust passages 11L and 11R. When the above process ends, the process exits the flow.

  According to the processing described above, it is possible to simultaneously detect the deterioration states of both of the start catalysts 12L and 12R, and to accurately detect the deterioration states of both of the start catalysts 12L and 12R. Moreover, since the deterioration states of both of the start catalysts 12L and 12R can be detected at the same time, it is possible to effectively suppress the deterioration of fuel consumption caused by the deterioration detection process.

[Second Embodiment]
Next, a catalyst deterioration detection method according to the second embodiment will be described.

  In the second embodiment, the failure of the exhaust gas switching valve 13a is determined, and when it is determined that the exhaust gas switching valve 13a is malfunctioning, one of the exhaust gas switching valve 13b and the exhaust gas switching valve 13c is set to open. In addition, it is different from the first embodiment in that the deterioration state of one of the start catalysts 12L and 12R is detected by setting the other closed. That is, in the first embodiment, the deterioration detection process is performed on both of the start catalysts 12L and 12R. However, in the second embodiment, when the exhaust gas switching valve 13a is out of order, the start catalysts 12L and 12R. A deterioration detection process is performed on one of the above. In this case, in the second embodiment, the deterioration detection process is performed for each of the start catalysts 12L and 12R.

  Specifically, in the second embodiment, the ECU 50 controls the exhaust switching valve 13b and the exhaust switching valve 13c as described above based on the load (traveling load) in the internal combustion engine 10 or the supercharging pressure in the turbocharger 4. I do. Specifically, the ECU 50 should execute the deterioration detection process in the supercharging state based on the running load or the supercharging pressure when the exhaust gas switching valve 13a has an open failure (a failure that does not close while being open). It is determined whether the deterioration detection process in the natural intake state should be executed. And based on such a determination result, either one of the exhaust gas switching valves 13b and 13c is set to open, and the other is set to closed. As described above, by controlling the exhaust gas switching valves 13b and 13c when the exhaust gas switching valve 13a is in an open failure state, it is possible to concentrate all exhaust gas in one of the exhaust passages 11L and 11R. Accordingly, it is possible to appropriately perform the deterioration detection process for each of the start catalysts 12L and 12R while suppressing the occurrence of exhaust interference (such as pulsation and inflow). Further, torque that can be generated by opening and closing the exhaust gas switching valves 13b and 13c at the start of the deterioration detection process in order to determine whether the deterioration detection process should be executed in a natural intake state or a supercharged state. Can be controlled appropriately.

  More specifically, when the traveling load is equal to or greater than a predetermined value (or when the supercharging pressure is equal to or higher than the predetermined pressure), the ECU 50 determines that the deterioration detection process in the supercharging state should be executed, and the turbine 4b The exhaust switching valve 13b provided in the exhaust passage 11L provided with is opened, and the exhaust switching valve 13c provided in the exhaust passage 11R not provided with the turbine 4b is closed. In this case, since all exhaust gas flows through the exhaust passage 11L in which the turbine 4b is disposed, it is possible to appropriately perform the deterioration detection process only on the start catalyst 12L provided in the exhaust passage 11L. . On the other hand, when the traveling load is less than the predetermined value (or when the supercharging pressure is less than the predetermined pressure), the ECU 50 determines that the deterioration detection process in the natural intake state should be executed, and the exhaust The switching valve 13b is closed and the exhaust switching valve 13c is opened. In this case, since all exhaust gas flows through the exhaust passage 11R in which the turbine 4b is not disposed, it is possible to appropriately perform the deterioration detection process only on the start catalyst 12R provided in the exhaust passage 11R. Become.

  Next, with reference to FIG. 3, the process performed in the catalyst deterioration detection method according to the second embodiment will be described. FIG. 3 is a flowchart showing processing according to the second embodiment. This process is basically executed before the deterioration detection process. Further, the processing is executed by the ECU 50. In addition, since the process of step S201-S203 is the same as the process of step S101-S103 shown in FIG. 2, the description is abbreviate | omitted. Here, the process after step S204 is demonstrated.

  In step S204, the ECU 50 determines whether or not the exhaust gas switching valve 13a has an open failure. As one example, the ECU 50 determines whether or not the exhaust gas switching valve 13a has an open failure by checking the opening / closing of the valve based on the stroke sensor output in the exhaust gas switching valve 13a. In another example, the ECU 50 determines whether or not the exhaust gas switching valve 13a has an open failure by detecting a closed state of the valve based on a back pressure change or a back pressure difference when the exhaust gas switching valve 13a is operated. To do.

  If the exhaust gas switching valve 13a has an open failure (step S204; Yes), the process proceeds to step S205. On the other hand, when the exhaust gas switching valve 13a has not failed to open (step S204; No), the process exits the flow. In this case, as shown in the first embodiment described above, the deterioration detection process is simultaneously performed on both the start catalysts 12L and 12R by flowing the exhaust gas through both the exhaust passages 11L and 11R.

  In step S205, it is determined whether or not the traveling load in the internal combustion engine 10 is in a natural intake state. That is, it is determined whether the traveling load is in a natural intake state or a supercharging state. Here, the ECU 50 determines whether the deterioration detection process in the supercharging state should be executed or the deterioration detection process in the natural intake state should be executed. For example, the ECU 50 determines whether or not the vehicle is in a natural intake state by determining whether or not the traveling load is less than a predetermined value. Note that the determination in step S205 may be performed based on the supercharging pressure instead of the traveling load. In this case, the ECU 50 determines whether or not it is in a natural intake state by determining whether or not the supercharging pressure is less than a predetermined pressure.

  If the travel load is in the natural intake state (step S205; Yes), the process proceeds to step S206. In step S206, the ECU 50 performs control for executing the deterioration detection process in the natural intake state. Specifically, the ECU 50 closes the exhaust switching valve 13b provided in the exhaust passage 11L in which the turbine 4b is disposed, and the exhaust switching valve provided in the exhaust passage 11R in which the turbine 4b is not disposed. Open 13c. As a result, the total exhaust gas flows through the exhaust passage 11R where the turbine 4b is not disposed, and the total exhaust gas is supplied to the start catalyst 12R. After controlling the exhaust gas switching valves 13b and 13c in this way, the ECU 50 permits execution of the deterioration detection process for the start catalyst 12R. When the above process ends, the process exits the flow.

  On the other hand, when the traveling load is not in the natural intake state (step S205; No), that is, when the traveling load is in the supercharged state, the process proceeds to step S207. In step S207, the ECU 50 performs control for executing the deterioration detection process in the supercharged state. Specifically, the ECU 50 opens the exhaust switching valve 13b provided in the exhaust passage 11L in which the turbine 4b is disposed, and the exhaust switching valve provided in the exhaust passage 11R in which the turbine 4b is not disposed. 13c is closed. As a result, the total exhaust gas flows into the exhaust passage 11L where the turbine 4b is disposed, and the total exhaust gas is supplied to the start catalyst 12L. After controlling the exhaust gas switching valves 13b and 13c in this manner, the ECU 50 permits execution of the deterioration detection process for the start catalyst 12L. When the above process ends, the process exits the flow.

  According to the catalyst deterioration detection method according to the second embodiment described above, it is possible to accurately detect the deterioration states of the start catalysts 12L and 12R even when the exhaust gas switching valve 13a has an open failure. .

1 shows a schematic configuration of an exhaust control device for an internal combustion engine according to an embodiment of the present invention. It is a flowchart which shows the process which concerns on 1st Embodiment. It is a flowchart which shows the process which concerns on 2nd Embodiment.

Explanation of symbols

1 Internal combustion engine
3 Intake passage 4 Turbocharger 8L, 8R Bank (cylinder group)
10 communication passage 11L, 11R exhaust passage 12L, 12R start catalyst 13a, 13b, 13c exhaust switching valve 20L, 20R A / F sensor 21L, 21R oxygen sensor 50 ECU

Claims (6)

In an exhaust control device for an internal combustion engine that performs exhaust control on an internal combustion engine having a first cylinder group and a second cylinder group,
A first catalyst and a second catalyst provided on an exhaust passage connected to each of the first cylinder group and the second cylinder group;
A first control for controlling the flow rate of the exhaust gas that is provided on the communication passage that connects the exhaust passage on the upstream side of the first catalyst and the exhaust passage on the upstream side of the second catalyst, and that flows through the communication passage. A valve,
An internal combustion engine comprising: first valve control means for performing control to close the first control valve when detecting the deterioration state of the first catalyst and the second catalyst. Exhaust control device.   The first valve control means is a control for closing the first control valve when an accumulated exhaust heat amount in the internal combustion engine to both the first catalyst and the second catalyst is equal to or greater than a predetermined value. The exhaust control device for an internal combustion engine according to claim 1, wherein:   The internal combustion engine according to claim 2, wherein the integrated exhaust heat quantity is calculated based on an estimated value of exhaust gas temperature and an inflow gas quantity to the first catalyst and the second catalyst. Engine exhaust control device. A second control valve provided on an exhaust passage connected to the first cylinder group and controlling a flow rate of exhaust gas flowing through the exhaust passage;
A third control valve provided on an exhaust passage connected to the second cylinder group and controlling a flow rate of exhaust gas flowing through the exhaust passage;
Failure determination means for determining failure of the first control valve;
In order to detect the deterioration state of one of the first catalyst and the second catalyst when the failure determination means determines that the first control valve has failed, the second control unit 4. The apparatus according to claim 1, further comprising: a second valve control unit that performs control to open one of the control valve and the third control valve and close the other. 5. An exhaust control device for an internal combustion engine according to claim 1. A turbocharger turbine is disposed on the exhaust passage of the first cylinder group,
The second valve control means controls the second control valve and the third control valve based on a load in the internal combustion engine or a supercharging pressure in the turbocharger. 5. An exhaust control device for an internal combustion engine according to 4. The second valve control means opens the second control valve when the load is equal to or greater than a predetermined value, or when the supercharging pressure is equal to or greater than a predetermined pressure, and the third control valve Close
When the load is less than the predetermined value, or when the supercharging pressure is less than the predetermined pressure, the second control valve is closed and the third control valve is opened. An exhaust control device for an internal combustion engine according to claim 5.

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