JP2009167961A - Abnormality determination device for internal combustion engine - Google Patents

Abstract

An apparatus for determining an abnormality of an internal combustion engine having two superchargers without complicating the apparatus.
An abnormality determination device for an internal combustion engine (1) includes first and second superchargers (13a, 13b) arranged in parallel. Twin turbo mode in which the first and second superchargers 13a and 13b are used for supercharging, and a single in which the second supercharger 13b is not used for supercharging and the first supercharger 13a is used for supercharging. Control valves (19, 31) used for switching between the turbo mode are provided. The rotation sensor 15 which detects the rotation speed N of the 2nd supercharger 13b is provided. A control unit 5 is provided for diagnosing a failure of the control valve based on the rotational speed N when the control valve is caused to perform at least one of an opening operation and a closing operation.
[Selection] Figure 1

Description

  The present invention relates to an abnormality determination device for an internal combustion engine having two superchargers arranged in parallel, and more particularly to a device for determining an abnormality based on the rotational speed 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, an intake switching valve and an exhaust switching valve are 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.

On the other hand, an apparatus for diagnosing the presence or absence of a turbocharger failure based on the number of rotations of the turbocharger mounted on the vehicle has been proposed. For example, Patent Document 1 has one turbocharger. In an internal combustion engine, an apparatus for diagnosing the presence or absence of a turbocharger failure based on the number of revolutions of the turbocharger while performing control for releasing the supercharging pressure via the intake bypass passage to avoid surging is disclosed.
JP 2006-57526 A

  However, since Patent Document 1 does not have a control valve such as an intake switching valve or an exhaust switching valve used for switching between the twin turbo mode and the single turbo mode, it is applied to failure diagnosis of these control valves. I can't. In addition, surge diagnosis of the two turbochargers cannot be performed. On the other hand, it is possible to diagnose the failure of these control valves by providing opening sensors for each control valve, but there are extra wiring harnesses and circuits that transmit signals from the opening sensors to the control unit, etc. And the device becomes complicated.

  Accordingly, an object of the present invention is to provide an apparatus for determining an abnormality of an internal combustion engine having two superchargers without complicating the apparatus.

  An abnormality determination apparatus for an internal combustion engine according to the present invention includes first and second superchargers arranged in parallel, a twin turbo mode in which the first and second superchargers are used for supercharging, and a second supercharger. A control valve used for switching between a single turbo mode in which the first turbocharger is not used for supercharging and the first supercharger is used for supercharging, and a rotation sensor for detecting the rotation speed of the second supercharger; And a control unit that performs failure diagnosis of the control valve based on the number of revolutions when the control valve is caused to perform at least one of the opening operation and the closing operation.

  Due to the operation of the control valve for switching between the twin turbo mode and the single turbo mode, the flow of exhaust gas to the turbine of the second turbocharger and the flow of air to the compressor of the second turbocharger fluctuate. Accordingly, the rotational speed of the second supercharger also varies. For this reason, it is possible to diagnose a failure of the control valve based on the behavior of the rotational speed. Moreover, it is possible to diagnose a malfunction of the control valve only by adding a rotation sensor for detecting the rotation speed of the second supercharger to the internal combustion engine having two superchargers and control based on the rotation speed. Therefore, the apparatus is not complicated.

  Preferably, the control valve has an exhaust switching valve for switching between shutting off and opening an exhaust passage connected to the second supercharger, and the control unit performs exhaust switching for an instruction to open the valve in the single turbo mode. Failure diagnosis of the exhaust gas switching valve is performed based on at least one of the rotational speed when the valve is received and the rotational speed when the exhaust switch valve receives an instruction to close the valve.

  If the exhaust gas switching valve is normally opened, the exhaust gas flowing into the turbine of the second supercharger increases as compared to the closed state, and the rotational speed of the second supercharger increases. On the other hand, if the exhaust gas switching valve is normally closed, the exhaust gas flowing into the turbine of the second supercharger is reduced as compared with the valve open state, and the rotational speed of the second supercharger is reduced. For this reason, it is possible to perform failure diagnosis of the exhaust gas switching valve by confirming the rotation speed of the second supercharger in such a state. Further, in the single turbo mode, since the second supercharger is not used for supercharging, the influence of the opening / closing operation of the exhaust gas switching valve on the operating state of the internal combustion engine is small.

  Preferably, the control valve further includes a pressure sensor that detects a supercharging pressure of the internal combustion engine, and the control valve includes an intake air switching valve that switches between blocking and opening of an intake passage connected to the second supercharger, In the single turbo mode, at least one of a supercharging pressure when the intake switching valve receives an instruction to open the valve and a supercharging pressure when the intake switching valve receives an instruction to close the valve And failure diagnosis of the intake air switching valve based on the rotational speed.

  If the intake switching valve is normally opened and closed, the valve is opened, so that air flows between the compressor outlet of the second supercharger and the engine body through the intake passage. Supply pressure fluctuates. Further, when the valve is closed, the air flow between the compressor outlet of the second supercharger and the engine body is blocked by the intake air switching valve, so that the supercharging pressure varies. The degree of fluctuation of the supercharging pressure varies depending on the rotation speed of the second supercharger. Therefore, it is possible to perform failure diagnosis of the intake air switching valve by confirming the supercharging pressure in this state and the rotation speed of the second supercharger. Further, in the single turbo mode, since the second supercharger is not used for supercharging, the influence of the opening / closing operation of the intake air switching valve on the operating state of the internal combustion engine is small.

  More preferably, the control valve failure diagnosis is performed when the internal combustion engine is operated in an idle state immediately after starting.

  By performing failure diagnosis immediately after startup, it is possible to perform failure diagnosis at the earliest possible point and enter the fail-safe mode. Also, by performing failure diagnosis in the idle state, the exhaust gas discharged at the time of failure diagnosis is suppressed as much as possible, and the influence on the operation state of the internal combustion engine due to the opening / closing operation of the control valve different from the normal operation is reduced. Is possible.

  An abnormality determination device for an internal combustion engine according to the present invention includes first and second superchargers arranged in parallel, a rotation sensor for detecting the rotation speed of a second supercharger, and first and second superchargers. In an air flow meter for detecting the total intake air amount of the internal combustion engine, a pressure sensor for detecting the supercharging pressure of the internal combustion engine, and a twin turbo mode in which the first and second superchargers are used for supercharging. A control unit that performs a surge diagnosis of the second supercharger based on the number and the supercharging pressure, and performs a surge diagnosis of the first supercharger based on the rotational speed, the total intake air amount, and the supercharging pressure; Is provided.

  The second operating point on the compressor performance map of the second supercharger is specified from the rotation speed and the supercharging pressure of the second supercharger, and it is determined whether or not the second operating point is within the surging region. By doing so, surge diagnosis of the second supercharger becomes possible. At this time, the second intake air amount to the second supercharger can be calculated from the compressor performance map of the second supercharger, the rotation speed of the second supercharger, and the supercharging pressure. Further, the first intake air amount to the first supercharger can be calculated from the difference between the total intake air amount to the internal combustion engine and the second intake air amount. Therefore, the first operating point on the compressor performance map of the first supercharger is specified from the supercharging pressure and the first intake air amount, and it is determined whether or not the first operating point is within the surging region. Thus, the surge diagnosis of the first supercharger becomes possible.

  As described above, according to the present invention, it is possible to provide an apparatus for determining an abnormality of an internal combustion engine having two superchargers without complicating the apparatus.

  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 rotation sensor 15 are input, and control signals are input to the intake air switching valve 19 and the like. To control each part of the vehicle including the internal combustion engine 1. In particular, the control unit 5 determines whether the internal combustion engine 1 is abnormal, that is, switches between the twin turbo mode and the single turbo mode, based on the rotational speed N of the second supercharger 13b detected by the rotation sensor 15. Failure diagnosis of the control valves (intake switching valve 19 and exhaust switching valve 31) used and surge diagnosis of the first and second superchargers 13a and 13b are performed.

  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 that has flowed through the air cleaner, that is, the total intake air amount GA. In the present embodiment, the total intake air amount GA is used for surge diagnosis of the first supercharger 13a. 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 of the second compressor 13b2 becomes larger than the outlet pressure of the first compressor 13a2, the valve is opened, and the air opens the intake reed valve 21. Flows from the upstream side to the downstream side.

  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 operation 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 open state, and then the intake bypass valve 17 is changed from the open state to the closed state. As a result, the outlet pressure of the second compressor 13b2 gradually increases while avoiding the surge of the second compressor 13b2 while the intake bypass valve 17 is kept open and the intake switching valve 19 is kept closed. The 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.

  The second supercharger 13b is provided with a rotation sensor 15 that detects the rotational speed N of the second supercharger 13b. In the present embodiment, the rotational speed N of the second supercharger 13b is used for fault diagnosis of the control valve used for switching between the twin turbo mode and the single turbo mode, that is, the intake switching valve 19 and the exhaust switching valve 31. It is used for surge diagnosis of the first and second superchargers 13a and 13b.

  In addition, a pressure sensor 27 that detects the supercharging pressure P is provided in the intake manifold 55. In the present embodiment, the supercharging pressure P is used for failure diagnosis of a control valve used for switching between the twin turbo mode and the single turbo mode, that is, the intake air switching valve 19, and the first and second overpressures are used. Used for surge diagnosis of the feeders 13a and 13b.

  In the present embodiment, as a sensor for detecting the supercharging pressure P used for failure diagnosis of the intake air switching valve 19, a pressure sensor 27 (in manifold pressure) that is normally provided in the intake manifold 55 of the internal combustion engine 1 is used. In order to diagnose the failure of the intake air switching valve 19, another pressure sensor disposed on the compressor outlet side intake passage 52 and downstream of the intake air switching valve 19 is connected to the boost pressure. The form which detects P may be sufficient.

  Further, a mode in which a pressure sensor 27 (intake manifold pressure sensor) that is normally provided in the intake manifold 55 of the internal combustion engine 1 is used as a sensor for detecting the supercharging pressure P used for surge diagnosis will be described. However, another type of pressure sensor arranged on the compressor outlet side intake passage 52 may detect the supercharging pressure P for surge diagnosis.

  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 immediately after the internal combustion engine 1 is started and in an idle state. The reason why the engine is immediately after the start is that if there is an abnormality in the exhaust gas switching valve 31, the internal combustion engine 1 may be damaged, so that a failure diagnosis is performed at the earliest possible time and the fail-safe mode is set. The condition of the idle state is to suppress the exhaust gas discharged at the time of failure diagnosis as much as possible, and to reduce the influence on the internal combustion engine 1 due to the opening / closing operation of the exhaust gas switching valve 31 etc. different from the normal operation. . Therefore, the failure diagnosis is a problem in the operation of the internal combustion engine 1 even when the exhaust gas switching valve 31 or the like is set in an open / close state different from the open / close state in the normal single turbo mode. As long as the engine is in a low load state and a low engine speed so as not to occur, it may be performed at other times, and the number of times is not limited to one.

Note that the rotation speed increase threshold value N ₁ , the rotation speed decrease threshold value N ₂ , the boost pressure increase threshold value P ₁ , and the boost pressure decrease threshold value P ₂ used for failure diagnosis of the exhaust gas switching valve 31 are supplied from the controller 5. In accordance with the control signal, the engine speed N and the supercharging pressure P that are assumed when the exhaust gas switching valve 31 or the like normally opens or closes are shown.

  Before the failure diagnosis of the exhaust gas switching valve 31 is started, the exhaust gas switching valve 31 is closed and the intake air switching valve 19 is closed because the engine is operating in an idle state, that is, a low-load single turbo mode. The intake bypass valve 17 is open. The variable nozzle of the first turbine 13a1 is set to an opening degree corresponding to the operating state.

When failure diagnosis of the exhaust gas switching valve 31 is started, in step S31, control signals related to respective instructions for opening the exhaust gas switching valve 31 and fully closing the variable nozzle of the first turbine 13a1 are sent to the control unit. 5 to the exhaust gas switching valve 31 or the like. When the exhaust gas switching valve 31 and the like operate normally based on the control signal, most of the exhaust gas discharged from the engine body 30 is supplied to the second turbine 13b1 and the rotation speed of the second supercharger 13b. N is increased to increase the threshold N ₁ or more rpm.

  In addition, the variable nozzle of the first turbine 13a1 is fully closed to suppress the inflow of exhaust gas to the first turbine 13a1 as much as possible, to secure the exhaust energy to the second turbine 13b1, This is to increase the detection sensitivity of the rotational speed N in step S35. Therefore, the fully closed state of the variable nozzle of the first turbine 13a1 may not be a state in which the nozzle is completely closed.

In step S32, the control unit 5, the rotational speed N of the second turbocharger 13b determines whether increased to the rotation speed increase threshold N ₁ or more. If not, the exhaust gas switching valve 31 is not normally opened / closed according to the control signal output in step S31, and the process proceeds to step S33, assuming that the exhaust gas is not properly supplied to the second turbine 13b1. It is done. If so, the process proceeds to step S34.

  In step S33, the control unit 5 determines that there is an abnormality in the opening operation of the exhaust gas switching valve 31, and after setting the fail-safe mode, ends the failure diagnosis of the exhaust gas switching valve 19.

In step S <b> 34, a control signal related to an instruction to close the exhaust gas switching valve 31 is output from the control unit 5 to the exhaust gas switching valve 31. When the exhaust gas switching valve 31 operates normally based on the control signal, the exhaust gas that is discharged from the engine main body 30 is cut off from being supplied to the second turbine 13b1 by the exhaust gas switching valve 31. rotational speed N of the 13b1 falls below the rotational speed reduction threshold _{N 2.}

In step S35, the control unit 5, the rotational speed N of the second turbocharger 13b determines whether drops below the rotational speed reduction threshold _{N 2 (N 1> N} 2). If not, the exhaust gas switching valve 31 is not closed in accordance with the control signal output in step S34, and the supply of exhaust gas to the second turbine 13b1 is not properly shut off. It is advanced. If so, the process proceeds to step S36.

  In step S34, when the exhaust gas switching valve 31 is closed, the opening of the variable nozzle of the first turbine 13a1 may be returned from the fully closed state to the normal opening. Although it is easier to confirm a decrease in the rotational speed of the second supercharger 13b when the fully closed state is maintained, it is desirable to set the opening degree from the fully closed state to a normal opening degree for exhaust gas discharge.

  In step S36, the control unit 5 determines that the opening / closing operation of the exhaust gas switching valve 31 is normal, returns each control valve to the open / closed state before the failure diagnosis, and then ends the failure diagnosis of the exhaust gas switching valve 31. In step S <b> 37, the control unit 5 determines that there is an abnormality in the valve closing operation of the exhaust gas switching valve 31, sets the fail safe mode, and then ends the failure diagnosis of the exhaust gas switching valve 31.

  This makes it possible to perform a failure diagnosis of the exhaust gas switching valve 31 without providing the exhaust gas switching valve 31 with an opening degree sensor or the like that monitors the valve opening state and the valve closing state. Since the control from step S31 to S37 can be completed in about several seconds, the opening / closing operation of the exhaust gas switching valve 31 or the like has little influence on the operating state of the internal combustion engine 1.

  Further, in the failure diagnosis of the exhaust gas switching valve 31, the open / close instruction procedure of the exhaust gas switching valve 31 and the open / closed state of other valves are preferably in the above-described form from the viewpoint of detection sensitivity, but are not limited thereto. Even in other procedures, the behavior of the rotational speed N of the second supercharger 13b when an instruction to open the exhaust gas switching valve 31 is received, and the instruction to make the exhaust gas switching valve 31 close. The failure diagnosis of the exhaust gas switching valve 31 can be performed based on at least one of the behaviors of the rotational speed N of the second supercharger 13b when receiving.

  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 immediately after the internal combustion engine 1 is started and in an idle state. The reason immediately after the start and the reason for the idling condition are the same as in the case of the failure diagnosis of the exhaust gas switching valve 31.

  Before the failure diagnosis of the intake switching valve 19 is started, the exhaust switching valve 31 is closed and the intake switching valve 19 is closed because the engine is operating in the idle state, that is, the low-load single turbo mode. The intake bypass valve 17 is open. The variable nozzle of the first turbine 13a1 is set to an opening degree corresponding to the operating state.

  When failure diagnosis of the intake switching valve 19 is started, in step S51, control signals relating to respective instructions for opening the exhaust switching valve 31 and fully closing the variable nozzle of the first turbine 13a1 are sent to the control unit. 5 to the exhaust gas switching valve 31 or the like. When the exhaust gas switching valve 31 and the like operate normally based on the control signal, most of the exhaust gas discharged from the engine body 30 is supplied to the second turbine 13b1 and the rotation speed of the second supercharger 13b. N rises.

  As the second turbine 13b1 rotates, the second compressor 13b2 rotates and air is sucked into the second compressor 13b2. Since the intake bypass passage 53 is narrower than the compressor outlet side intake passage 52, a part of the air sucked into the second compressor 13b2 reaches the compressor inlet side intake passage 51 via the intake bypass passage 53. The rest is on the compressor outlet side intake passage 52 and is pushed between the outlet of the second compressor 13 b 2 and the intake air switching valve 19. For this reason, the outlet pressure of the second compressor 13b2 increases.

  The reason why the variable nozzle of the first turbine 13a1 is fully closed is the same as in the case of the failure diagnosis of the exhaust gas switching valve 31.

In step S52, the control unit 5, after the rotational speed N of the second turbocharger 13b was confirmed to be elevated to the rotation speed increase threshold N ₁ or more, it proceeds to step S53.

  In step S <b> 53, after the intake switching valve 19 is switched to the open state, a control signal related to an instruction to immediately close the intake valve is output from the control unit 5 to the intake switching valve 19.

  When the intake air switching valve 19 operates normally based on the control signal, the air that has flowed into the second compressor 13 b 2 flows into the intake air bypass passage 53 by opening the intake air switching valve 19. In addition, since it flows into the intake manifold 55 via the compressor outlet side intake passage 52, the supercharging pressure P rises. Further, when the intake air switching valve 19 is then closed, the flow of air from the second compressor 13b2 to the intake manifold 55 is interrupted, and the increased supercharging pressure P decreases.

In step S54, the control unit 5, the boost pressure P is increased to boost pressure rise threshold P ₁ or that varies according to the rotational speed N of the second turbocharger 13b, and then, the second turbocharger determines whether drops below supercharging pressure decrease threshold P ₂ which varies as a function of the rotational speed N of 13b. The supercharging pressure increase threshold value P ₁ and the supercharging pressure decrease threshold value P ₂ correspond to the rotational speed N of the second supercharger 13b according to the rotational speed N of the second supercharger 13b. This is because the amount of air compressed by the second compressor 13b2 varies and the outlet pressure of the second compressor 13b2 varies.

Rotational speed N, which is used to set the boost pressure rise threshold P ₁ are those boost pressure P is detected at the vicinity of determining whether increased to boost pressure rise threshold P ₁ or more it is used The Similarly the rotational speed N is used to set the boost pressure decrease threshold P ₂ are those supercharging pressure P is detected at the vicinity of determining whether dropped below the boost pressure decrease threshold P ₂ used. When the rotational speed N is high, the supercharging pressure increase threshold value P ₁ and the supercharging pressure decrease threshold value P ₂ are both set to high values, and when the rotational speed N is low, the supercharging pressure increase threshold value P ₁ , and supercharging pressure decrease threshold P ₂ are both set to a low value.

Note that the rotation speed increase threshold value N ₁ , the rotation speed decrease threshold value N ₂ , the boost pressure increase threshold value P ₁ , and the boost pressure decrease threshold value P ₂ used for failure diagnosis of the exhaust gas switching valve 31 are supplied from the controller 5. In accordance with the control signal, the engine speed N and the supercharging pressure P that are assumed when the exhaust gas switching valve 31 or the like normally opens or closes are shown.

If the boost pressure P does not rise to the boost pressure rise threshold P ₁ or more is not opened in accordance with the control signal which the intake switching valve 19 is output in step S53, the compressed air from the second compressor 13b2 is compressor It is determined that the air does not properly flow into the intake manifold 55 via the outlet side intake passage 52. Further, even if the boost pressure P rises to the boost pressure rise threshold P ₁ or more, then, if not drop below the supercharging pressure decrease threshold P _2, the control signal which the intake switching valve 19 is output in step S53 Therefore, it is determined that the inflow of the compressed air from the second compressor 13b2 into the intake manifold 55 is not properly blocked. For this reason, when at least one of the conditions of step S54 is not satisfied, the process proceeds to step S56. When all the conditions of step S54 are satisfied, 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 before failure diagnosis, and 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. Since the control from step S51 to S56 can be completed in about several seconds, the opening / closing operation of the intake air switching valve 19 or the like has little influence on the operating state of the internal combustion engine 1.

  In addition, in the failure diagnosis of the intake air switching valve 19, the opening / closing instruction procedure of the intake air switching valve 19 and the open / closed state of other valves are preferably in the above-described form from the viewpoint of detection sensitivity, but are not limited thereto. Even in other procedures, the behavior of the supercharging pressure P when an instruction for opening the intake switching valve 19 is received and the excess when the instruction for setting the intake switching valve 19 is closed is received. Based on at least one of the behaviors of the supply pressure P and the rotation speed N, it is possible to perform a failure diagnosis of the intake air switching valve 19.

  In addition, when one of the exhaust gas switching valve 31 and the intake air switching valve 19 breaks down by sequentially repeating the failure diagnosis of the exhaust gas switching valve 31 and the failure diagnosis of the intake air switching valve 19 in this embodiment, Such a failure can be discovered before the control valve fails.

  Next, details of surge diagnosis of the first and second superchargers 13a and 13b will be described with reference to the flowchart of FIG. The surge diagnosis of the first and second superchargers 13a and 13b is performed in the twin turbo mode, that is, the internal combustion engine with both the intake switching valve 19 and the exhaust switching valve 31 opened and the intake bypass valve 17 closed. This is always done while 1 is in operation.

  When the surge diagnosis of the first and second superchargers 13a and 13b is started, in step S71, the rotational speed N and the pressure ratio π between the inlet and the outlet of the second compressor 13b2 calculated from the supercharging pressure P are calculated. Based on the above, the second operating point on the compressor performance map of the second supercharger 13b is calculated.

The compressor performance map is such that the vertical axis represents the pressure ratio π between the inlet and outlet of the compressor, and the horizontal axis represents the amount of air flowing into the compressor, that is, the intake air amount, and the compressor rotation speed N, the pressure ratio π, and the intake air amount Represents relationships and surge limits. FIG. 5 shows an example of the compressor performance map of the second compressor 13b2. Solid lines N _{11 to} N ₁₄ on the compressor performance map are equal rotation speed curves of the turbocharger including the compressor, and the rotation speed increases toward the upper right (N ₁₁ <N ₁₂ <N ₁₃ <N ₁₄ ). A broken line SL on the compressor performance map is a surging line (surge limit), and a region on the left side of the surging line SL is a surging region. Such a compressor performance map is unique to the compressor to be used, and its performance characteristics are obtained in advance by experiments and recorded in the ROM of the control unit 5 or the like. A similar compressor performance map is prepared for the first compressor 13a2.

  In step S72, it is determined whether or not the second operating point is within the surging area. If it is within the surging area, it is determined that surging may occur for the second supercharger 13b, and the process proceeds to step S73. If not in the surging area, the process proceeds to step S74.

  In step S73, feedback for avoiding surging of the second supercharger 13b is performed for the nozzle position control of the variable nozzle of the second supercharger 13b, and the process proceeds to step S74.

  In step S74, based on the compressor performance map of the second compressor 13b2, the rotational speed N of the second supercharger 13b, and the pressure ratio π of the second compressor 13b2 calculated from the supercharging pressure P, the second compressor 13b2 An inflow second intake air amount GA2 is calculated.

  In step S75, the first intake air amount GA1 flowing into the first compressor 13b1 is calculated from the difference between the total intake air amount GA and the second intake air amount GA2.

  In step S76, based on the pressure ratio π calculated from the supercharging pressure P and the first intake air amount GA1, the first operating point on the compressor performance map of the first supercharger 13a is calculated. In step S77, it is determined whether or not the first operating point is within the surging area. If it is within the surging area, it is determined that surging may occur for the first supercharger 13a, and the process proceeds to step S78. If it is not within the surging area, the process returns to step S71 and the surge diagnosis is repeated.

  In step S78, feedback for avoiding surging of the first supercharger 13a is performed with respect to the nozzle position control of the variable nozzle of the first supercharger 13a. Thereafter, the process returns to step S71, and the surge diagnosis is repeated. Is called.

  As a result, surge diagnosis of the first and second superchargers 13a and 13b can be performed. In addition, since the procedure of steps S74 to S77 is performed in a time of about several tens of ms, the feedback of the nozzle position control of the second supercharger 13b in step S73 and the nozzle position of the first supercharger 13a in step S78. Control feedback occurs almost simultaneously.

  In the present embodiment, based on the total intake air amount GA obtained by the air flow meter 12, the rotational speed N of the second supercharger 13 b obtained by the rotation sensor 15, and the supercharging pressure P obtained by the pressure sensor 27. Thus, it is possible to perform abnormality diagnosis of the internal combustion engine 1, that is, failure diagnosis of the intake switching valve 19 and the exhaust switching valve 31 used for switching between the twin turbo mode and the single turbo mode, and the first The surge diagnosis of the second superchargers 13a and 13b can be performed.

  The air flow meter 12 and the pressure sensor 27 are normally provided in an internal combustion engine equipped with a supercharger even when such abnormality determination is not performed. 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 rotation sensor 15, so that the apparatus is not complicated for the abnormality determination. 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.

It is a block diagram of the internal combustion engine in this embodiment. It is a flowchart which shows the procedure of failure diagnosis of an exhaust gas switching 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 the surge diagnosis of a 1st, 2nd supercharger. It is a figure which shows the compressor performance map of a 2nd compressor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Control part 11 Air cleaner 12 Air flow meter 13a, 13b 1st, 2nd supercharger 13a1, 13b1 1st, 2nd turbine 13a2, 13b2 1st, 2nd compressor 15 Rotation sensor 17 Intake bypass valve 19 Intake switching Valve 21 Intake lead valve 23 Intercooler 25 Throttle valve 27 Pressure sensor 30 Engine body 31 Exhaust gas switching valve 51 Compressor inlet side intake passage 52 Compressor outlet side intake passage 53 Intake bypass passage 54 Intake lead 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;
Twin turbo mode in which the first and second superchargers are used for supercharging, and a single in which the second supercharger is not used for supercharging and the first supercharger is used for supercharging A control valve used to switch between turbo mode,
A rotation sensor for detecting a rotation speed of the second supercharger;
An abnormality determination of the internal combustion engine, comprising: a control unit that performs a failure diagnosis of the control valve based on the rotation speed when the control valve performs at least one of an opening operation and a closing operation apparatus. The control valve has an exhaust gas switching valve that switches between blocking and opening an exhaust passage connected to the second supercharger,
In the single turbo mode, the control unit is configured to change the rotational speed when the exhaust switching valve receives an instruction to open the valve and the exhaust time when the exhaust switching valve receives an instruction to close the valve. The abnormality determination device according to claim 1, wherein a failure diagnosis of the exhaust gas switching valve is performed based on at least one of a rotational speed. A pressure sensor for detecting a boost pressure of the internal combustion engine;
The control valve has an intake air switching valve that switches between blocking and opening an intake passage connected to the second supercharger in the single turbo mode,
The control unit is configured such that the supercharging pressure when the intake switching valve receives an instruction to open the valve and the supercharging pressure when the intake switching valve receives an instruction to close the valve. The abnormality determination device according to claim 1, wherein a failure diagnosis of the intake air switching valve is performed based on at least one of the rotation speeds.   4. The abnormality determination device according to claim 2, wherein the failure diagnosis of the control valve is performed when the internal combustion engine is operated in an idle state immediately after starting. First and second superchargers arranged in parallel;
A rotation sensor for detecting a rotation speed of the second supercharger;
An air flow meter for detecting the total intake air amount of the internal combustion engine including the first and second superchargers;
A pressure sensor for detecting a supercharging pressure of the internal combustion engine;
In the twin turbo mode in which the first and second superchargers are used for supercharging, a surge diagnosis of the second supercharger is performed based on the rotational speed and the supercharging pressure, and the rotational speed, An abnormality determination device for an internal combustion engine, comprising: a control unit that performs a surge diagnosis of the first supercharger based on the total intake air amount and the supercharging pressure.

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