JP2009185684A - Failure diagnostic device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnostic device of an internal combustion engine having two superchargers which specifies positions of abnormalities. <P>SOLUTION: The failure diagnostic device of the internal combustion engine includes first and second superchargers which are arranged in parallel with each other and a control valve having an intake selector valve and an intake bypass valve. The intake selector valve is provided at the intake passage of the second supercharger, and the intake bypass valve is provided at the intake bypass passage which connects the outlet of the compressor of the second supercharger with the inlet of the compressor of the first supercharger. The control valve is used for switching a twin turbo mode and a single turbo mode. The failure diagnostic device of the internal combustion engine is also provided with a pressure sensor on the compressor outlet side which is provided downstream of the compressor of the second supercharger and upstream of the intake selector valve, and used for detecting the outlet pressure of the compressor of the second supercharger. In the single turbo mode, the failure diagnosis of at least one of the control valves is performed based on outlet pressure when at least either open movement or close movement is performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a failure diagnosis device for an internal combustion engine having two superchargers arranged in parallel, and more particularly to a device that performs failure diagnosis based on the outlet pressure of one of the superchargers.

  An internal combustion engine having first and second superchargers arranged in parallel has been proposed. In such an internal combustion engine, a single turbo mode in which the second supercharger is not used for supercharging and the first supercharger is used for supercharging according to the operating state, and the first and second superchargers are supercharged. It is used by switching to the twin turbo mode. In this internal combustion engine, a control valve such as an intake switching valve is provided to switch between the twin turbo mode and the single turbo mode. If these control valves are not properly opened and closed, the target boost pressure cannot be obtained, and the internal combustion engine may be damaged. For this reason, there is a need for an apparatus for determining abnormality of the internal combustion engine, such as failure diagnosis of a control valve.

Patent Document 1 uses a differential pressure sensor in an internal combustion engine having two superchargers to check whether there is a failure in a control valve such as an intake switching valve based on the differential pressure between the upstream and downstream of the intake switching valve. An apparatus for diagnosing is disclosed.
Japanese Patent No. 3157350

  However, in the failure diagnosis using the differential pressure sensor in the apparatus of Patent Document 1, it is not possible to specify which control valve has failed. For this reason, after the failure of the control valve is found, it is necessary to identify which control valve has failed using another means.

  Accordingly, an object of the present invention is to provide a failure diagnosis device for identifying an abnormal point in an internal combustion engine having two superchargers.

  An internal combustion engine failure diagnosis apparatus according to the present invention includes first and second superchargers arranged in parallel, an intake air switching valve provided in an intake passage connected to the second supercharger, and a second supercharger. An intake air bypass valve provided in an intake air bypass passage connecting an exhaust gas switching valve provided in an exhaust passage connected to the charger and an outlet of the compressor of the second supercharger and an inlet of the compressor of the first supercharger Single turbo mode in which the first and second superchargers are used for supercharging and the second supercharger is not used for supercharging and the first supercharger is used for supercharging A control valve used for switching between the turbo mode and a compressor for detecting an outlet pressure of the compressor of the second supercharger, which is provided downstream of the compressor of the second supercharger and upstream of the intake air switching valve With a pressure sensor on the outlet side. In the Bo mode, the exhaust switching valve and the intake switching valve are closed, the intake bypass valve is opened, and in the single turbo mode, at least one control valve of the control valves is opened or closed. Fault diagnosis for one of the control valves is performed based on the outlet pressure when at least one of them is performed, or based on the relationship between the outlet pressure and the atmospheric pressure in the single turbo mode and the downstream pressure of the intake air switching valve. Is called.

  When the open / close state of the control valve is changed in the single turbo mode, the outlet pressure of the compressor of the second supercharger varies corresponding to the changed control valve. Based on the behavior of the outlet pressure, it becomes possible to identify the control valve in which the failure has occurred. Further, the relationship between the outlet pressure of the compressor of the second supercharger and the atmospheric pressure in the single turbo mode, and the state of the downstream pressure of the intake switching valve such as the intake manifold pressure are different between when the control valve is operating normally and when it is abnormal. For this reason, it becomes possible to identify the control valve in which a failure has occurred based on such a relationship.

  Preferably, in the single turbo mode, the failure diagnosis of the intake bypass valve is performed based on the relationship between the outlet pressure and the atmospheric pressure before and after receiving an instruction to close the intake bypass valve.

  In the single turbo mode, the outlet pressure of the compressor of the second supercharger is equal to the atmospheric pressure. Thereafter, by closing the intake bypass valve, the outlet pressure rises and becomes greater than the atmospheric pressure. Therefore, failure diagnosis of the intake bypass valve can be performed based on the behavior of the outlet pressure in such a state.

  Preferably, in the single turbo mode, an instruction is received for the intake bypass valve to be closed, and the relationship between the outlet pressure and the atmospheric pressure before receiving the instruction for opening and closing the intake switching valve, and the instruction is received. Failure diagnosis of the intake air switching valve is performed based on the relationship between the outlet pressure later and the downstream pressure of the intake air switching valve.

  In the single turbo mode, the outlet pressure of the compressor of the second supercharger is equal to the atmospheric pressure. Thereafter, by closing the intake bypass valve and opening and closing the intake switching valve, the outlet pressure instantaneously becomes higher than atmospheric pressure and lower than the downstream pressure of the intake switching valve. Based on the behavior of the outlet pressure in such a state, it is possible to perform failure diagnosis of the intake air switching valve.

  Preferably, the control valve has an intake reed valve provided in an intake reed passage communicating between the upstream and downstream of the intake switching valve, and in the single turbo mode, instructs the intake bypass valve to be closed. A failure diagnosis of the intake reed valve is performed based on the behavior of the outlet pressure after receiving the instruction to make the exhaust switching valve open.

  In the single turbo mode, the outlet pressure rises when the intake bypass valve is closed and the exhaust gas switching valve is opened. When the outlet pressure becomes larger than the downstream pressure of the intake air switching valve by a predetermined amount, the intake reed valve opens and the outlet pressure once becomes constant. Then rise again. Based on the behavior of the outlet pressure in such a state, it is possible to perform failure diagnosis of the intake reed valve.

  Preferably, in the single turbo mode, the failure diagnosis of the exhaust gas switching valve is performed based on the relationship between the outlet pressure and the atmospheric pressure and the relationship between the target value and the execution value of the downstream pressure of the intake air switching valve.

  In the single turbo mode, the relationship between the atmospheric pressure and the compressor outlet pressure, and the relationship between the target value and the execution value of the pressure downstream of the intake air switching valve are different between when the exhaust gas switching valve is operating normally and when it is abnormal. For this reason, it becomes possible to perform failure diagnosis of the exhaust gas switching valve based on these.

  As described above, according to the present invention, it is possible to provide a failure diagnosis device that identifies an abnormal point in an internal combustion engine having two superchargers.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The internal combustion engine 1 includes a control unit 5, first and second superchargers 13a and 13b, an engine body 30, a compressor inlet side intake passage 51, a compressor outlet side intake passage 52, an intake manifold 55, a turbine inlet side exhaust passage 72, And a turbine outlet side exhaust passage 73.

  The control unit 5 includes a CPU, a ROM storing a control program, a RAM storing various data, and the like. Signals from various sensors such as the compressor outlet side pressure sensor 15 are input, and the intake air switching valve 19 and the like are input. A control signal is output to control each part of the vehicle including the internal combustion engine 1. In particular, the control unit 5 controls the control valve (intake air) used to switch between the twin turbo mode and the single turbo mode based on the outlet pressure P2 of the second compressor 13b2 detected by the compressor outlet side pressure sensor 15. The failure diagnosis of the bypass valve 17, the intake switching valve 19, the intake reed valve 21, and the exhaust switching valve 31) is performed.

  Moreover, the control part 5 incorporates the atmospheric pressure sensor 6 which detects atmospheric pressure P1. In the present embodiment, the atmospheric pressure P <b> 1 is used for failure diagnosis of the intake bypass valve 17, the intake air switching valve 19, and the intake reed valve 21. However, the atmospheric pressure P1 may be detected by using a pressure sensor (not shown) provided on the compressor inlet side intake passage 51 in place of the atmospheric pressure sensor 6.

  During the operation of the internal combustion engine 1, air is sucked into the combustion chamber of each cylinder of the engine body 30 via the compressor inlet side intake passage 51, the compressor outlet side intake passage 52, and the intake manifold 55 (see FIG. 1). (See solid arrow). The fuel injected from the injector mixes with the sucked air to form an air-fuel mixture. The air-fuel mixture is combusted by ignition of the spark plug based on the ignition signal from the control unit 5. A crankshaft (not shown) rotates by the reciprocating motion of the piston according to the explosive force caused by the combustion of the air-fuel mixture. The exhaust gas generated by the combustion is exhausted through the exhaust manifold 71, the turbine inlet side exhaust passage 72, and the turbine outlet side exhaust passage 73 (see the broken line arrow in FIG. 1).

  Next, the configuration of each part of the internal combustion engine 1 will be described focusing on the first and second superchargers 13a and 13b. The first and second superchargers 13a and 13b are arranged in parallel. The first supercharger 13a serves as a main turbocharger, and the second supercharger 13b serves as a sub turbocharger. The first supercharger 13a operates from the low intake air amount region to the high intake air amount region, and the second supercharger 13b stops in the low intake air amount region. Therefore, in the low intake air amount region, the operation is performed in the single turbo mode in which the second supercharger 13b is not used for supercharging and the first supercharger 13a is used for supercharging, and in the high intake air amount region. The first and second superchargers 13a and 13b are operated in a twin turbo mode in which supercharging is used.

  The first supercharger 13a has a first turbine 13a1 and a first compressor 13a2, and the second supercharger 13b has a second turbine 13b1 and a second compressor 13b2. The inlet sides of the first and second turbines 13 a 1 and 13 b 1 are connected to a turbine inlet side exhaust passage 72 communicated with the exhaust manifold 71. The outlet sides of the first and second turbines 13a1 and 13b1 are connected to a turbine outlet side exhaust passage 73 communicated with an exhaust gas purification catalyst (not shown).

  The inlet sides of the first and second compressors 13 a 2 and 13 b 2 are connected to the compressor inlet side intake passage 51. The compressor inlet side intake passage 51 is provided with an air cleaner 11 and an air flow meter 12 for detecting the amount of air flowing through the air cleaner, that is, the total amount of intake air. The outlet sides of the first and second compressors 13 a 2 and 13 b 2 are connected to a compressor outlet side intake passage 52 communicated with the intake manifold 55. An intercooler 23 and a throttle valve 25 are provided in the compressor outlet side intake passage 52.

  In order to switch between the twin turbo mode and the single turbo mode, that is, to switch between the operation and stop of the second supercharger 13b, the turbine inlet side exhaust passage 72 is connected to the second turbine 13b1 on the inlet side to the second turbine 13b1. An exhaust gas switching valve 31 is provided for switching between blocking and opening the flow of exhaust gas, and the air flow from the second compressor 13b2 to the intake manifold 55 is provided on the outlet side of the second compressor 13b2 in the compressor outlet side intake passage 52. An intake air switching valve 19 that switches between flow blocking and opening is provided.

  In order to smoothly switch from the single turbo mode to the twin turbo mode, on the compressor outlet side intake passage 52, between the outlet of the second compressor 13b2 and the intake air switching valve 19, and in the compressor inlet side intake passage 51. An intake bypass passage 53 that communicates with the inlet side of one compressor 13a2 is provided. The intake bypass passage 53 is provided with an intake bypass valve 17 that switches between blocking and opening the air flow.

  In the single turbo mode, both the intake air switching valve 19 and the exhaust gas switching valve 31 are closed, but the intake bypass valve 17 is opened, whereby the first supercharger 13a is operated, and the second The supercharger 13b stops. In the twin turbo mode, both the intake switching valve 19 and the exhaust switching valve 31 are opened, but the intake bypass valve 17 is closed, thereby operating the first and second superchargers 13a and 13b. To do.

  An intake reed valve 21 that opens and closes according to the pressure difference is provided in an intake reed passage (bypass passage of the intake air switching valve 19) 54 that communicates the upstream and downstream of the intake switching valve 19. That is, when the intake air switching valve 19 is closed, when the outlet pressure P2 of the second compressor 13b2 becomes larger than the outlet pressure of the first compressor 13a2 (≈ intake manifold pressure P3) by a predetermined amount, the valve is opened. Air flows from the upstream side to the downstream side through the intake reed valve 21.

  The intake bypass passage 53 and the intake lead passage 54 are set narrower than the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52.

  When the operating state is switched from the single turbo mode to the twin turbo mode, the exhaust gas switching valve 31 is first changed from the closed state to the opened state, and then the intake bypass valve 17 is opened and the intake switching valve 19 is closed. In this state, the outlet pressure P2 of the second compressor 13b2 gradually increases while avoiding the surge of the second compressor 13b2, and then the intake bypass valve 17 is closed and the intake reed valve 21 is opened. . Thereafter, the intake air switching valve 19 is changed from the closed state to the opened state. When the intake switching valve 19 is opened, the intake reed valve 21 is closed.

  On the compressor outlet side intake passage 52, downstream of the second compressor 13 b 2 of the second supercharger 13 b and upstream of the intake air switching valve 19, the compressor outlet side for detecting the outlet pressure P 2 of the second compressor 13 b 2. A pressure sensor 15 is provided. In this embodiment, the outlet pressure P2 of the second compressor 13b2 is a control valve used for switching between the twin turbo mode and the single turbo mode, that is, an intake bypass valve 17, an intake switching valve 19, an intake reed valve 21, And used for failure diagnosis of the exhaust gas switching valve 31.

  An intake manifold pressure sensor 27 that detects a pressure in the intake manifold 55, that is, an intake manifold pressure P3, is provided in the intake manifold 55. In the present embodiment, the intake manifold pressure P <b> 3 is used for failure diagnosis of the intake air switching valve 19 and the exhaust gas switching valve 31.

  In the present embodiment, a mode in which the intake manifold pressure sensor 27 normally provided in the intake manifold 55 of the internal combustion engine 1 is used for failure diagnosis of the intake air switching valve 19 or the like will be described. Another pressure sensor disposed on the passage 52 and downstream of the intake air switching valve 19 may be used for failure diagnosis of the intake air switching valve 19 or the like.

  Next, details of the failure diagnosis of the intake bypass valve 17 will be described with reference to the flowchart of FIG. The failure diagnosis of the intake bypass valve 17 is performed while the internal combustion engine 1 is operating in the single turbo mode. The failure diagnosis of the intake bypass valve 17 is not limited to once.

  The condition of the single turbo mode is that the second compressor 13b2 is used when the amount of exhaust gas leaked from the exhaust switching valve 31 in the closed state is increased and the intake bypass valve 17 is normally closed in step S33. This is because the outlet pressure P2 rises quickly, and the difference between the outlet pressure P2 and the atmospheric pressure P1 becomes large so that the presence or absence of a failure can be easily confirmed.

  Before the failure diagnosis of the intake bypass valve 17 is started, since it is operated in the single turbo mode, the exhaust switching valve 31 is closed, the intake switching valve 19 is closed, and the intake bypass valve 17 is The valve is open. When these control valves are normally opened and closed, air flows between the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52 via the intake bypass passage 53. Therefore, the atmospheric pressure P1 and the outlet pressure P2 are equal, that is, there is almost no difference between the atmospheric pressure P1 and the outlet pressure P2.

  When the failure diagnosis of the intake bypass valve 17 is started, in step S31, the control unit 5 determines whether or not the atmospheric pressure P1 and the outlet pressure P2 of the second compressor 13b2 are equal to each other. It is determined whether or not there is almost no difference between the atmospheric pressure P1 and the outlet pressure P2.

  If they are not equal, at least one of the closing operation of the exhaust gas switching valve 31, the closing operation of the intake air switching valve 19, and the opening operation of the intake air bypass valve 17 for operating in the single turbo mode is not functioning correctly. As shown in FIG. If equal, the process proceeds to step S33.

  In step S32, the control unit 5 performs at least one of the valve closing operation of the exhaust gas switching valve 31, the valve closing operation of the intake air switching valve 19, and the valve opening operation of the intake air bypass valve 17 for operating in the single turbo mode. After determining that there is an abnormality and setting the fail-safe mode, the failure diagnosis of the intake bypass valve 17 is terminated.

  In step S <b> 33, a control signal related to an instruction to close the intake bypass valve 17 is output to the intake bypass valve 17. When the intake bypass valve 17 operates normally based on the control signal, the air flow in the compressor outlet side intake passage 52 and the intake bypass passage 53 is blocked. However, although the exhaust gas switching valve 31 is closed, a part of the exhaust gas flows into the second turbine 13b1 due to the gas leakage of the exhaust gas switching valve 31, so that the second compressor 13b2 rotates and enters the second compressor 13b2. Air flows in. For this reason, the air that has flowed into the second compressor 13b2 is pushed into the passage between the second compressor 13b2, the intake bypass valve 17, and the intake air switching valve 19, and the outlet pressure P2 of the second compressor 13b2 rises. It becomes larger than the atmospheric pressure P1.

  In step S34, the control unit 5 determines whether or not the outlet pressure P2 of the second compressor 13b2 is larger than the atmospheric pressure P1.

  If not, the intake bypass valve 17 is not closed in accordance with the control signal output in step S33, and an intake bypass passage 53 is provided between the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52. Then, the process proceeds to step S36 assuming that the air is in a flowing state. If larger, the process proceeds to step S35.

  In step S35, the control unit 5 determines that the opening / closing operation of the intake bypass valve 17 is normal, returns each control valve to the opened / closed state in the single turbo mode, and then ends the failure diagnosis of the intake bypass valve 17. In step S36, the control unit 5 determines that there is an abnormality in the closing operation of the intake bypass valve 17, sets the fail-safe mode, and ends the failure diagnosis of the intake bypass valve 17.

  As a result, failure diagnosis of the intake bypass valve 17 can be performed without providing the intake bypass valve 17 with an opening sensor for monitoring the open / closed state. The control from step S31 to S36 is performed in a single turbo mode in which the second supercharger 13b is not used for supercharging and can be completed in about several seconds. Therefore, the opening / closing operation of the intake bypass valve 17 is performed in the internal combustion engine 1. The influence on the driving state is small.

  In addition, in the failure diagnosis of the intake bypass valve 17, the above-described form is desirable for the opening / closing instruction procedure of the intake bypass valve 17 and the open / closed state of other valves from the viewpoint of detection sensitivity, but is not limited thereto. Even in other procedures, it is possible to perform failure diagnosis of the intake bypass valve 17 based on the behavior of the outlet pressure P2 when receiving an instruction for the intake bypass valve 17 to close.

  Next, details of the failure diagnosis of the intake air switching valve 19 will be described using the flowchart of FIG. The failure diagnosis of the intake air switching valve 19 is performed while the internal combustion engine 1 is operating in the single turbo mode. The failure diagnosis of the intake air switching valve 19 is not limited to once.

  The condition for the single turbo mode is that the first supercharger 13a is moderately supercharged so that the downstream pressure of the intake air switching valve 19, that is, the intake manifold pressure P3 is increased, and the intake air switching valve in step S53 is set. This is because the difference between the outlet pressure P2 of the second compressor 13b2 and the intake manifold pressure P3 when the opening / closing operation 19 fails is made large so that the presence or absence of the failure can be easily confirmed.

  Before the failure diagnosis of the intake switching valve 19 is started, since the operation is performed in the single turbo mode, the exhaust switching valve 31 is closed, the intake switching valve 19 is closed, and the intake bypass valve 17 is The valve is open. When these control valves are normally opened and closed, air flows between the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52 via the intake bypass passage 53. Therefore, the atmospheric pressure P1 and the outlet pressure P2 are equal, that is, there is almost no difference between the atmospheric pressure P1 and the outlet pressure P2.

  When the failure diagnosis of the intake air switching valve 19 is started, in step S51, the control unit 5 determines whether or not the atmospheric pressure P1 and the outlet pressure P2 of the second compressor 13b2 are equal. It is determined whether or not there is almost no difference between the atmospheric pressure P1 and the outlet pressure P2.

  If they are not equal, it is assumed that at least one of the closing operation of the exhaust gas switching valve 31 for performing the single turbo mode, the closing operation of the intake air switching valve 19 and the opening operation of the intake air bypass valve 17 is not functioning correctly. The process proceeds to step S52. If equal, the process proceeds to step S53.

  In step S52, the control unit 5 has an abnormality in at least one of the closing operation of the exhaust switching valve 31, the closing operation of the intake switching valve 19, and the opening operation of the intake bypass valve 17 for performing the single turbo mode. After determining that it exists and setting the fail-safe mode, the failure diagnosis of the intake air switching valve 19 is terminated.

  In step S53, after the intake bypass valve 17 is closed and the intake switching valve 19 is instructed to open and close in a pulse manner, that is, after the valve is opened, the valve is immediately closed (after about 0.5 seconds). A control signal relating to the instruction to output is output to the intake bypass valve 17 and the like. When the intake air switching valve 19 or the like operates normally based on the control signal, the air flow in the intake air bypass passage 53 is blocked. Further, the air flow in the compressor outlet side intake passage 52 is blocked except at the moment when the intake air switching valve 19 is opened. At the moment when the intake switching valve 19 is opened, air flows between the outlet of the second compressor 13b2 and the intake manifold 55 in the compressor outlet side intake passage 52. Therefore, the intake air in a high pressure state Air flows backward from the manifold 55 to the outlet of the second compressor 13b2 in a low pressure state, and the outlet pressure P2 of the second compressor 13b2 is higher than the atmospheric pressure P1 and lower than the intake manifold pressure P3 (P1 < P2 <P3).

  In step S54, the control unit 5 determines whether or not the outlet pressure P2 of the second compressor 13b2 is instantaneously higher than the atmospheric pressure P1 and lower than the intake manifold pressure P3.

  When the outlet pressure P2 of the second compressor 13b2 is not instantaneously higher than the atmospheric pressure P1 and lower than the intake manifold pressure P3, the intake air switching valve 19 instantly changes according to the control signal output in step S53. Therefore, the flow proceeds to step S56 on the assumption that no air is instantaneously flowing between the outlet of the second compressor 13b2 and the intake manifold 55. When the outlet pressure P2 of the second compressor 13b2 is instantaneously higher than the atmospheric pressure P1 and lower than the intake manifold pressure P3, the process proceeds to step S55.

  In step S55, the control unit 5 determines that the opening / closing operation of the intake air switching valve 19 is normal, returns each control valve to the open / closed state in the single turbo mode, and then ends the failure diagnosis of the intake air switching valve 19. In step S56, the control unit 5 determines that there is an abnormality in the opening / closing operation of the intake air switching valve 19, and after setting the fail safe mode, ends the failure diagnosis of the intake air switching valve 19.

  This makes it possible to perform failure diagnosis of the intake air switching valve 19 without providing the intake air switching valve 19 with an opening degree sensor for monitoring the open state and the closed state. The control from step S51 to S56 is performed in a single turbo mode in which the second supercharger 13b is not used for supercharging and can be completed in about several seconds. Therefore, the opening / closing operation of the intake air switching valve 19 is performed in the internal combustion engine 1. The influence on the driving state is small. In particular, in step S53, the intake switching valve 19 is opened, but since the opened state is instantaneous, the influence on the operating state of the internal combustion engine 1 is small.

  In addition, in the failure diagnosis of the intake air switching valve 19, the above-mentioned form is desirable for the opening / closing instruction procedure of the intake air switching valve 19 and the open / closed state of other valves from the viewpoint of detection sensitivity, but is not limited thereto. Even in other procedures, failure diagnosis of the intake air switching valve 19 can be performed based on the behavior of the outlet pressure P2 when an instruction to open and close the intake air switching valve 19 is received.

  Next, details of the failure diagnosis of the intake reed valve 21 will be described using the flowchart of FIG. The failure diagnosis of the intake reed valve 21 is performed while the internal combustion engine 1 is operating in the single turbo mode. The failure diagnosis of the intake reed valve 21 is not limited to once.

  The condition of the single turbo mode is that an appropriate exhaust gas flow rate is ensured and the first turbine 13a1 is exhausted to the extent that it does not hinder the operation even if the exhaust gas switching valve 31 is opened in step S72. When the gas flows and the first supercharger 13a is appropriately supercharged, and when the exhaust gas switching valve 31 is opened in step S72, as much exhaust as possible in the second turbine 13b1. This is to make the gas flow and to shorten the time required for confirming the behavior of the outlet pressure P2 in step S73.

  Before the failure diagnosis of the intake reed valve 21 is started, since it is operated in the single turbo mode, the exhaust switching valve 31 is closed, the intake switching valve 19 is closed, and the intake bypass valve 17 is The valve is open. When these control valves are normally opened and closed, air flows between the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52 via the intake bypass passage 53. Therefore, the atmospheric pressure P1 and the outlet pressure P2 are equal, that is, there is almost no difference between the atmospheric pressure P1 and the outlet pressure P2.

  When the failure diagnosis of the intake bypass valve 17 is started, a control signal related to an instruction to close the intake bypass valve 17 is output to the intake bypass valve 17 in step S71. In step S 72, a control signal related to an instruction to open the exhaust gas switching valve 31 for a predetermined time (about 1 second) is output to the exhaust gas switching valve 31. If the exhaust switching valve 31 can be adjusted to a medium opening other than closing and opening, the opening may be set to a predetermined opening instead of being fully opened in step S72. When the exhaust gas switching valve 31 is fully opened, nearly half of the exhaust gas flows into the second turbine 13b1, so that the exhaust gas required by the first supercharger 13a for operation in the single turbo mode cannot be secured. This is because there is a fear.

  Based on these control signals, when the intake bypass valve 17 and the like operate normally and the intake reed valve 21 functions normally, the air flow in the compressor outlet side intake passage 52 and the intake bypass passage 53 is cut off. Is done. However, since a part of the exhaust gas flows through the second turbine 13b1, the second compressor 13b2 rotates and air flows into the second compressor 13b2. For this reason, the air flowing into the second compressor 13b2 is pushed into the passage between the second compressor 13b2, the intake bypass valve 17, and the intake air switching valve 19, and the outlet pressure P2 of the second compressor 13b2 increases. Thereafter, when the outlet pressure P2 becomes larger than the pressure downstream of the intake reed valve 21, that is, the outlet pressure of the first compressor 13a2 and the intake manifold pressure P3, the intake reed valve 21 is opened and air is taken in. The air flows into the intake manifold 55 through the reed valve 21 from the outlet of the second compressor 13b2. For this reason, after the intake reed valve 21 is opened, the outlet pressure P2 is once maintained in a constant state in which it does not rise or fall. However, since the intake lead passage 54 is narrower than the compressor outlet side intake passage 52, the air flowing into the second compressor 13b2 through the intake reed valve 21 cannot be released downstream of the intake reed valve 21. For this reason, the outlet pressure P2 then increases.

  In step 73, the control unit 5 determines whether or not a behavior is observed in which the outlet pressure P2 of the second compressor 13b2 rises, then maintains a constant state, and then rises again. If such behavior is not observed, it is determined that the opening / closing operation of the intake reed valve 21 is not functioning properly, and the process proceeds to step S75.

  In step S74, the control unit 5 determines that the opening / closing operation of the intake reed valve 21 is normal, returns each control valve to the opened / closed state in the single turbo mode, and then ends the failure diagnosis of the intake reed valve 21. In step S75, the control unit 5 determines that there is an abnormality in the opening / closing operation of the intake reed valve 21, sets the fail safe mode, and ends the failure diagnosis of the intake reed valve 21.

  As a result, it is possible to perform failure diagnosis of the intake reed valve 21 without providing the intake reed valve 21 with an opening degree sensor for monitoring the valve open state and the valve closed state. The control from step S71 to S75 is performed in a single turbo mode in which the second supercharger 13b is not used for supercharging and can be completed in about several seconds. Therefore, the opening / closing operation of the intake reed valve 21 is performed in the internal combustion engine 1. The influence on the driving state is small.

  It should be noted that, in the failure diagnosis of the intake reed valve 21, the opening / closing instruction procedure of the other control valve performed to open / close the intake reed valve 21 and the open / closed state of the other control valve are the above-described forms from the viewpoint of detection sensitivity. However, the present invention is not limited to this, and the outlet pressure P2 of the second compressor 13b2 when receiving the operation instruction of the control valve for opening and closing the intake reed valve 21 is also not limited to this and other procedures. Based on the behavior, failure diagnosis of the intake reed valve 21 can be performed.

  Next, details of the failure diagnosis of the exhaust gas switching valve 31 will be described using the flowchart of FIG. The failure diagnosis of the exhaust gas switching valve 31 is performed while the internal combustion engine 1 is operating in the single turbo mode. Or the form performed every predetermined time may be sufficient.

  Since the failure diagnosis of the exhaust gas switching valve 31 is performed when operating in the single turbo mode, the exhaust gas switching valve 31 is closed, the intake air switching valve 19 is closed, and the intake bypass valve 17 is open. Has been. When these control valves are normally opened and closed, air flows between the compressor inlet side intake passage 51 and the compressor outlet side intake passage 52 via the intake bypass passage 53. Therefore, the atmospheric pressure P1 and the outlet pressure P2 are equal, that is, there is almost no difference between the outlet pressure P2 and the atmospheric pressure P1.

  When the internal combustion engine 1 is set to the single turbo mode, in step S81, the control unit 5 determines that the difference between the outlet pressure P2 of the second compressor 13b2 and the atmospheric pressure P1 is equal to or greater than the first pressure difference threshold value P11 and the target intake manifold. It is determined whether or not the difference between the pressure P3 ′ and the intake manifold pressure P3 is equal to or greater than the second pressure difference threshold value P12. The target intake manifold pressure P3 ′ is a value set according to the operating state of the internal combustion engine 1, and when the internal combustion engine 1 is functioning normally, the target intake manifold pressure P3 ′ and the intake manifold pressure P3 are the same. There is almost no difference between the value, that is, the target intake manifold pressure P3 ′ and the intake manifold pressure P3.

  The first pressure difference threshold value P11 and the second pressure difference threshold value P12 are the difference between the outlet pressure P2 and the atmospheric pressure P1 that are assumed when there is an abnormality in the opening / closing operation of the exhaust gas switching valve 31 in the single turbo mode, A value corresponding to the difference between the target intake manifold pressure P3 ′ and the intake manifold pressure P3 is set.

  If at least one of the conditions in step S81 is not satisfied, step S81 is repeated. When both conditions in step S81 are satisfied, the process proceeds to step S82.

  In step S82, the control unit 5 determines that the difference between the outlet pressure P2 of the second compressor 13b2 and the atmospheric pressure P1 is greater than or equal to the first pressure difference threshold value P11 and that the difference between the target intake manifold pressure P3 ′ and the intake manifold pressure P3 is the first. It is determined whether or not a state in which the pressure difference threshold value P12 is equal to or greater than 2 has elapsed for a predetermined time. Due to the change in the operating state, the difference between the outlet pressure P2 and the atmospheric pressure P1 is not less than the first pressure difference threshold value P11 and the difference between the target intake manifold pressure P3 ′ and the intake manifold pressure P3 is the second pressure difference threshold value P12 in the short term. Since this may occur, in the present embodiment, it is determined that there is an abnormality in the opening / closing operation of the exhaust gas switching valve 31 depending on whether or not this state has passed for a certain period of time. If this state is resolved before the predetermined time elapses, the process returns to step S81, and the failure diagnosis of the exhaust gas switching valve 31 is repeatedly performed. If the predetermined time has elapsed, the process proceeds to step S83. In step S83, the control unit 5 determines that there is an abnormality in the opening / closing operation of the exhaust gas switching valve 31, that is, it is not in a normal valve closing state, and after setting the fail safe mode, performs a fault diagnosis of the exhaust gas switching valve 31. finish.

  This makes it possible to perform failure diagnosis of the exhaust gas switching valve 31 without providing an opening degree sensor or the like for monitoring the open / closed state of the exhaust gas switching valve 31. Further, the failure diagnosis of the exhaust gas switching valve 31 in the present embodiment can be performed while maintaining the open / closed state of the exhaust gas switching valve 31 or the like in the single turbo mode, so that the operation in the single turbo mode is not hindered. It can be done at all times in the state that is.

  Further, the failure diagnosis of the exhaust gas switching valve 31, the failure diagnosis of the intake air switching valve 19, the failure diagnosis of the intake air bypass valve 17, and the failure diagnosis of the intake reed valve 21 in this embodiment are sequentially repeated in the single turbo mode. Thus, when one of the exhaust switching valve 31, the intake switching valve 19, the intake bypass valve 17, and the intake reed valve 21 fails, such a failure can be found before the other control valve fails. .

  In this embodiment, based on the atmospheric pressure P1 obtained by the atmospheric pressure sensor 6, the outlet pressure P2 of the second compressor 13b2 obtained by the compressor outlet pressure sensor 15, and the intake manifold pressure P3 obtained by the intake manifold pressure sensor 27. Thus, abnormality determination of the internal combustion engine 1, that is, failure diagnosis of the intake bypass valve 17, the intake switching valve 19, the intake reed valve 21, and the exhaust switching valve 31 used for switching between the twin turbo mode and the single turbo mode is performed. It becomes possible.

  The intake manifold pressure sensor 27 is usually provided in an internal combustion engine equipped with a supercharger. The atmospheric pressure sensor 6 is normally built in the control unit 5. For this reason, in the present embodiment, it is possible to determine the abnormality of the internal combustion engine 1 only by newly adding the compressor outlet-side pressure sensor 15, so that the apparatus is not complicated for the abnormality determination. Absent. In particular, there is an advantage that a wire harness and a circuit can be simplified as compared with a mode in which an opening degree sensor is provided for each valve for performing failure diagnosis and failure diagnosis is performed.

  Further, by checking the behavior of the outlet pressure P2 under different conditions for each control valve, it becomes possible to identify the failed valve, so that there is an advantage that repair for the failure can be easily performed.

It is a block diagram of the internal combustion engine in this embodiment. It is a flowchart which shows the procedure of a failure diagnosis of an intake bypass valve. It is a flowchart which shows the procedure of a failure diagnosis of an intake switching valve. It is a flowchart which shows the procedure of a failure diagnosis of an intake reed valve. It is a flowchart which shows the procedure of failure diagnosis of an exhaust gas switching valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Control part 6 Atmospheric pressure sensor 11 Air cleaner 12 Air flow meter 13a, 13b 1st, 2nd supercharger 13a1, 13b1 1st, 2nd turbine 13a2, 13b2 1st, 2nd compressor 15 Compressor outlet side pressure sensor 17 Intake Bypass Valve 19 Intake Switch Valve 21 Intake Reed Valve 23 Intercooler 25 Throttle Valve 27 Intake Manifold Pressure Sensor 30 Engine Body 31 Exhaust Switch Valve 51 Compressor Inlet Side Intake Passage 52 Compressor Outlet Side Intake Passage 53 Intake Bypass Passage 54 Intake Bypass Passage 55 Intake manifold 71 Exhaust manifold 72 Turbine inlet side exhaust passage 73 Turbine outlet side exhaust passage

Claims (5)

First and second superchargers arranged in parallel;
An intake switching valve provided in an intake passage connected to the second supercharger, an exhaust switching valve provided in an exhaust passage connected to the second supercharger, and a compressor of the second supercharger And a turbocharger in which the first and second superchargers are used for supercharging. The twin turbocharger has an intake bypass valve provided in an intake bypass passage that connects an outlet of the compressor and an inlet of a compressor of the first supercharger. A control valve used to switch between a mode and a single turbo mode in which the second supercharger is not used for the supercharging and the first supercharger is used for the supercharging;
A compressor outlet-side pressure sensor for detecting an outlet pressure of the compressor of the second supercharger, which is provided downstream of the compressor of the second supercharger and upstream of the intake air switching valve;
In the single turbo mode, the exhaust switching valve and the intake switching valve are closed, and the intake bypass valve is opened.
In the single turbo mode, at least one of the control valves is based on the outlet pressure when at least one of the opening operation and the closing operation is performed, or the outlet pressure in the single turbo mode is large. A failure diagnosis apparatus for an internal combustion engine, wherein a failure diagnosis for one of the control valves is performed based on a relationship with an atmospheric pressure and a downstream pressure of the intake air switching valve.   In the single turbo mode, failure diagnosis of the intake bypass valve is performed based on a relationship between the outlet pressure and the atmospheric pressure before and after receiving an instruction to close the intake bypass valve. The failure diagnosis apparatus according to claim 1.   In the single turbo mode, received an instruction to close the intake bypass valve and an instruction to open and close the intake switching valve, and the relationship between the outlet pressure and the atmospheric pressure before receiving the instruction The failure diagnosis apparatus according to claim 1, wherein a failure diagnosis of the intake air switching valve is performed based on a relationship between the outlet pressure later and a downstream pressure of the intake air switching valve. The control valve has an intake reed valve provided in an intake reed passage communicating the upstream and downstream of the intake switching valve;
In the single turbo mode, based on the behavior of the outlet pressure after receiving an instruction to close the intake bypass valve and an instruction to open the exhaust switching valve, The failure diagnosis apparatus according to claim 1, wherein failure diagnosis is performed. In the single turbo mode, failure diagnosis of the exhaust gas switching valve is performed based on the relationship between the outlet pressure and the atmospheric pressure and the relationship between the target value and the execution value of the downstream pressure of the intake air switching valve. A failure diagnosis device for an internal combustion engine characterized by the above.

Images