JP2019070352A - Control device for internal combustion engine - Google Patents

Abstract

To provide a control device for an internal combustion engine capable of appropriately determining clogging of a catalyst device.SOLUTION: An electronic control unit 26 that is a control device for an internal combustion engine 10 includes a clogging determination section 29 for determining that clogging occurs in a catalyst device 19 on the condition that exhaust gas recirculation amount by an exhaust gas recirculation device 22 for recirculating exhaust gas from a portion upstream of the catalyst device 19 in an exhaust passage 13 to an intake passage 12 is a prescribed determination value or more and that feedback correction amount of air-fuel ratio feedback control based on a detection result obtained by an air-fuel ratio sensor 20 provided in a portion upstream of the catalyst device 19 in the exhaust passage 13 is a prescribed determination value or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine provided with a catalyst device for exhaust gas purification installed in an exhaust passage, and an exhaust gas recirculation device for recirculating the exhaust gas from an upstream side of the exhaust passage to the intake passage. It relates to a control device.

  As a control device for an internal combustion engine as described above, a device described in Patent Document 1 is known. The control device of this document measures the response time from the change of the air-fuel ratio of the air-fuel mixture burned in the combustion chamber to the appearance of the change of the air-fuel ratio in the detection value of the air-fuel ratio sensor installed in the exhaust passage. There is. If the catalyst device is clogged, the flow of the exhaust gas in the exhaust passage stagnates, and the arrival time of the exhaust gas from the combustion chamber to the installation position of the air-fuel ratio sensor becomes long, so the response time increases. Therefore, in the control device of the above document, when the measured value of the response time is equal to or more than the predetermined determination value, it is determined that the catalyst device is clogged.

JP, 2008-261287, A

The increase in the response time may also occur due to factors other than the clogging of the catalyst device, and there is a risk of an erroneous determination based only on the measurement result of the response time.
The present invention has been made in view of these circumstances, and an object of the present invention is to provide a control device of an internal combustion engine capable of accurately determining clogging of a catalyst device.

  A control device for an internal combustion engine that solves the above problems includes a catalyst device for exhaust gas purification installed in an exhaust passage, and an exhaust gas recirculation device that recirculates the exhaust gas from an upstream portion of the exhaust passage to the intake passage. And performing air-fuel ratio feedback control based on the detection result of an air-fuel ratio sensor provided in a portion on the upstream side of the catalyst device in the exhaust passage. Then, in the control device of the internal combustion engine, the exhaust gas recirculation amount by the exhaust gas recirculation device is equal to or greater than the predetermined determination value, and the feedback correction amount of the air-fuel ratio feedback control is equal to or more than the predetermined determination value. A clogging determination unit is provided that determines that the catalyst device is clogged under the conditions.

  The exhaust gas recirculation device recirculates the exhaust gas by the pressure difference between the exhaust passage side and the intake passage side. If clogging occurs and the flow of exhaust gas passing through the catalytic converter is stagnant, the pressure in the portion on the upstream side of the catalytic converter in the exhaust passage increases, so the amount of exhaust gas recirculation increases. On the other hand, the clogging of the catalytic converter also affects the detection result of the air-fuel ratio sensor provided on the upstream side of the catalytic converter in the exhaust passage, and the controllability of the air-fuel ratio feedback control is deteriorated. Cause an increase. The increase in the amount of exhaust gas recirculation and the increase in the amount of feedback correction may also be caused by factors other than clogging of the catalytic converter. However, due to factors other than clogging of the catalytic converter, both the increase of the exhaust gas recirculation amount and the increase of the feedback correction amount of the air-fuel ratio feedback control hardly occur simultaneously. Therefore, clogging of the catalyst device can be determined with high accuracy if the simultaneous occurrence of both is set as the determination condition. Therefore, according to the control device for an internal combustion engine, the clogging of the catalyst device can be accurately determined.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram which shows the structure of one Embodiment of the control apparatus of an internal combustion engine. The block diagram of the control structure of the clogging determination part provided in the control apparatus. The flowchart of the clogging determination processing routine which the said clogging determination part performs. The time chart which shows transition of the air-fuel ratio feedback amendment quantity in the period before and behind generation | occurrence | production of the clogging of a catalyst device.

Hereinafter, one embodiment of a control device for an internal combustion engine will be described in detail with reference to FIGS. 1 to 4. The control device of the present embodiment is applied to a vehicle-mounted internal combustion engine.
As shown in FIG. 1, an internal combustion engine 10 to which the control device of the present embodiment is applied includes a combustion chamber 11 that burns an air-fuel mixture. Further, the internal combustion engine 10 is provided with an intake passage 12 through which intake air flowing into the combustion chamber 11 flows, and an exhaust passage 13 through which exhaust gas discharged from the combustion chamber 11 flows.

  An air flow meter 14 is provided in the intake passage 12 for detecting the flow rate of fresh air (intake air amount GA) flowing through the intake passage 12. A throttle valve 15 is provided at a portion of the intake passage 12 downstream of the air flow meter 14. The intake passage 12 is connected to the combustion chamber 11 via an intake port 16 downstream of the throttle valve 15. The intake port 16 is provided with a fuel injection valve 17 for injecting fuel into the intake air flowing into the combustion chamber 11. In the combustion chamber 11, an ignition plug 18 for igniting the mixture of the intake air flowing in through the intake port 16 and the fuel by spark discharge is installed.

  The exhaust passage 13 is provided with a catalyst device 19 for exhaust gas purification. A catalyst that promotes the oxidation reaction and reduction reaction of harmful components in the exhaust gas is supported inside the catalytic converter 19. The exhaust gas is purified by the action of the catalyst. Further, an air-fuel ratio sensor 20 for detecting an air-fuel ratio AF of the air-fuel mixture burned in the combustion chamber 11 is provided at a portion on the upstream side of the catalyst device 19 in the exhaust passage 13. Further, an oxygen sensor 21 for detecting whether the air-fuel ratio AF is an air-fuel ratio richer than the stoichiometric air-fuel ratio or a lean air-fuel ratio is provided in a portion upstream of the catalyst device 19 in the exhaust passage 13 It is done.

  Further, the internal combustion engine 10 is provided with an exhaust gas recirculation device 22 that recirculates the exhaust gas from the portion of the exhaust passage 13 upstream of the catalyst device 19 to the intake passage 12. The exhaust gas recirculation device 22 includes an EGR (Exhaust Gas Recirculation) passage 23 and an EGR passage 23 that connect a portion of the exhaust passage 13 upstream of the catalyst device 19 and a portion of the intake passage 12 downstream of the throttle valve 15. And an EGR valve 25 for opening and closing the EGR passage 23.

  The internal combustion engine 10 is controlled by an electronic control unit 26 as a control device for the internal combustion engine 10. Detection results of the air flow meter 14, the air-fuel ratio sensor 20, and the oxygen sensor 21 described above are input to the electronic control unit 26. In addition, the electronic control unit 26 includes an NE sensor 27 for detecting the number of revolutions (engine speed NE) of the internal combustion engine 10 and an accelerator opening sensor 28 for detecting the depression amount of the accelerator pedal (accelerator opening ACC). The result is also entered. The electronic control unit 26 controls the opening of the throttle valve 15, controls fuel injection of the fuel injection valve 17, controls ignition timing of the spark plug 18, controls opening and closing of the EGR valve 25, etc. based on the detection results of these sensors. Various controls of the engine 10 are performed.

  Further, the electronic control unit 26 performs air-fuel ratio feedback control as part of control of the internal combustion engine 10. In the air-fuel ratio feedback control, the deviation between the air-fuel ratio of the mixture burned in the combustion chamber 11 and the target air-fuel ratio which is the target value of the air-fuel ratio is determined from the detection results of the air-fuel ratio sensor 20 and the oxygen sensor 21 In order to reduce the deviation, feedback correction of the fuel injection amount of the fuel injection valve 17 is performed.

  When a fuel containing a manganese-based additive is used as a fuel for the internal combustion engine 10, precipitates derived from manganese may be deposited in the catalyst device 19 to clog the catalyst device 19. Therefore, the electronic control unit 26 performs a clogging determination process of determining whether or not the catalyst device 19 is clogged while the internal combustion engine 10 is in operation. Then, when it is determined that the catalyst device 19 is clogged in the clog determining process, the electronic control unit 26 displays a warning on the display device 30 such as an information display provided in the vehicle compartment. There is. The electronic control unit 26 is provided with a clogging determination unit 29 that performs processing related to such clogging determination of the catalyst device 19.

  The configuration of the clogging determination unit 29 is shown in FIG. As shown in the figure, the clogging determination unit 29 is based on an EGR rate measurement process P100 for measuring the EGR rate RE, a measurement result of the EGR rate RE by the EGR rate measurement process P100, and a feedback correction amount FB of air fuel ratio feedback control. And a clogging determination process P200 for determining whether or not the catalyst device 19 is clogged.

  In the EGR rate measurement process P100, the EGR valve 25 is closed (EGR OFF) to open (EGR ON) when the operation state of the internal combustion engine 10 is stable, such as during idling operation while the vehicle is stopping. Switch. Then, the EGR rate RE is calculated from the measurement result of the intake air amount GA before and after the switching. Note that whether or not the internal combustion engine 10 is in a stable operating state is determined based on the engine speed NE, the accelerator opening degree ACC, and the like.

  All gases flowing into the combustion chamber 11 at the time of EGR off when the EGR valve 25 is closed are fresh air. On the other hand, the gas flowing into the combustion chamber 11 when the EGR valve 25 is opened with the EGR valve 25 opened becomes a mixed gas of fresh air and the exhaust gas recirculated by the exhaust gas recirculation device 22 (EGR gas). The amount of gas flowing into the combustion chamber 11 is independent of the flow rate of the EGR gas introduced into the intake passage 12 by the exhaust gas recirculation device 22, and the pressure on the downstream side of the throttle valve 15 in the intake passage 12 (intake Determined by the tube pressure). Therefore, when the EGR valve 25 is switched from the closed state to the open state in a state where the intake pipe pressure is constant, the flow rate of the exhaust gas (EGR gas) recirculated to the intake passage 12 according to the opening of the EGR valve 25 As a result, the intake air amount GA detected by the air flow meter 14 is reduced. Therefore, when the internal combustion engine 10 is in a stable operating state and the intake pipe pressure hardly changes, the amount of reduction of the intake air amount GA when the EGR valve 25 is switched from the closed state to the open state The amount Δ is equal to the flow rate of the EGR gas flowing into the intake passage 12 according to the opening of the EGR valve 25.

  On the other hand, the EGR rate RE represents the ratio of the amount of EGR gas to the total amount of gas flowing into the combustion chamber 11. As described above, when the EGR valve 25 is closed, all the gases flowing into the combustion chamber 11 are fresh air, and when the intake pipe pressure is constant, the gas flows into the combustion chamber 11 before and after switching from EGR off to EGR on. There is no change in the total amount of gas Here, the intake air amount GA before switching from EGR off to EGR on is referred to as a pre-switching air amount G1, and the intake air amount GA after switching is referred to as an after-switching air amount G2. In the EGR ratio measurement process P100, the quotient (= (G1-G2) / G1) obtained by dividing the difference obtained by subtracting the after-switching air amount G2 from the before-switching air amount G1 by the before-switching air amount G1 is calculated as the value of the EGR rate RE. By doing this, the EGR rate RE is measured.

  The value of the EGR rate RE measured in the EGR rate measurement process P100 is stored in the memory of the electronic control unit 26. The value of the EGR rate RE stored in the memory is held until measurement of the EGR rate RE is performed again by the EGR rate measurement process P100.

  FIG. 3 shows a flowchart of a clogging determination processing routine executed by the clogging determination processing P200. The processing of this routine is repeatedly performed at predetermined intervals while the internal combustion engine 10 is in operation.

  When the process of this routine is started, first, in step S100, it is determined whether a determination execution condition is satisfied. The determination execution condition is set to be satisfied when the internal combustion engine 10 is in a stable operating state, and is determined based on the engine rotational speed NE and the accelerator opening degree ACC. If the determination execution condition is satisfied (YES), the process proceeds to step S110. If the determination execution condition is not satisfied (NO), the process of the present routine is ended.

  When the process proceeds to step S110, in step S110, the value of the EGR rate RE measured by the EGR rate measurement process P100 and the feedback correction amount FB of the air-fuel ratio feedback control are read.

  Subsequently, in step S120, it is determined whether the value of the EGR rate RE read in step S110 is equal to or larger than a predetermined determination value α. Then, if the value of the EGR rate RE is greater than or equal to the determination value α (YES), the process proceeds to step S130, and if less than the determination value α (NO), the process of the present main routine is ended.

  When the process proceeds to step S130, in step S130, it is determined whether the absolute value of the feedback correction amount FB of the air-fuel ratio feedback control read in step S110 is equal to or larger than a predetermined determination value β. Then, if the absolute value of the feedback correction amount is greater than or equal to determination value β (YES), the process proceeds to step S140, and if less than determination value β (NO), the process of the present routine is ended. .

  In the present embodiment, when the process proceeds to step S140, it is determined that the catalyst device 19 is clogged. In this case, after the process of displaying a warning on the display device 30 is performed in step S140, the process of the present routine is ended.

Subsequently, the operation and effects of the control device for the internal combustion engine 10 according to the present embodiment configured as described above will be described.
In the exhaust gas recirculation device 22, the exhaust gas is recirculated by the pressure difference between the exhaust passage 13 side of the EGR passage 23 and the intake passage 12 side. On the other hand, in the EGR rate measurement process P100, the EGR rate RE is measured when the internal combustion engine 10 is in a stable operating state such as during idle operation while the vehicle is stopping, and the internal combustion engine 10 is operating normally. Then, the differential pressure during measurement has a substantially constant value. Therefore, when the internal combustion engine 10 is operating normally, the measured value of the EGR rate RE becomes a value within a certain range. The determination value α used in the determination process in step S120 in the clogging determination process routine is set to a value slightly larger than the upper limit value of the range of values that can be obtained by the measured value of the EGR rate RE during normal operation of the internal combustion engine 10. ing.

  When clogging occurs in the catalyst device 19, the flow of exhaust gas passing through the catalyst device 19 stagnates, and the pressure in the portion on the upstream side of the catalyst device 19 in the exhaust passage 13 increases. In the internal combustion engine 10 to which the control device of the present embodiment is applied, an EGR passage 23 is connected to a portion of the exhaust passage 13 upstream of the catalyst device 19. Therefore, when the catalyst device 19 is clogged, the differential pressure between the exhaust passage 13 side and the intake passage 12 side of the EGR passage 23 is increased, and the recirculation amount of the exhaust gas to the intake passage 12 by the exhaust recirculation device 22 is increased. Will increase. Therefore, when the catalyst device 19 is clogged, the measured value of the EGR rate RE in the EGR rate measurement process P100 can be a value equal to or larger than the determination value α.

  On the other hand, the clogging of the catalyst device 19 affects the detection result of the air-fuel ratio sensor 20 provided on the upstream side of the catalyst device 19 in the exhaust passage 13, and the influence is a feedback correction amount FB of air-fuel ratio feedback control. Appear in the value of. FIG. 4 shows the transition of the feedback correction amount FB before and after the clogging of the catalyst device 19. In fact, although clogging of the catalyst device 19 gradually progresses, in the same figure, for the convenience of explanation, at the time t1, the state where there is no clogging of the catalyst device 19 is switched instantly to the state where it is clogged. It is assumed.

  In the present embodiment, it is determined that the internal combustion engine 10 is in a stable operating state as a condition for determining whether the catalyst device 19 is clogged. When the internal combustion engine 10 is operating normally, the air-fuel ratio is not greatly disturbed when the determination execution conditions are satisfied, and the value of the feedback correction amount FB of the air-fuel ratio feedback control remains within a limited range near zero. . The upper limit value of the fluctuation range of the value of the feedback correction amount FB during such normal operation (= absolute value of the lower limit value of the fluctuation range) is used as the value of the judgment value β used in the judgment processing in step S130 in the clogging judgment processing routine. The value is set slightly larger than).

  If the catalyst device 19 is clogged, the flow of the exhaust gas passing through the catalyst device 19 is stagnated, and the arrival time of the exhaust gas from the combustion chamber 11 to the installation position of the air-fuel ratio sensor 20 becomes long. That is, the delay until the change of the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 11 appears in the detection result of the air-fuel ratio sensor 20 becomes large. As a result, since overcorrection occurs due to deterioration of the responsiveness of the air-fuel ratio feedback control, the fluctuation range of the value of the feedback correction amount FB becomes large. Therefore, when the catalyst device 19 is clogged, the absolute value of the feedback correction amount FB may become equal to or larger than the determination value β.

  Note that each of the increase in the exhaust gas recirculation amount and the increase in the feedback correction amount FB of the air-fuel ratio feedback control as described above may occur due to various factors other than the clogging of the catalyst device 19. However, factors other than the clogging of the catalyst device 19 at which the increase of the exhaust gas recirculation amount and the increase of the feedback correction amount FB of the air-fuel ratio feedback control occur simultaneously are limited. On the other hand, in the present embodiment, since it is determined that the catalyst device 19 is clogged only when both occur simultaneously, the clog of the catalyst device 19 can be determined with high accuracy. Therefore, according to the control device for the internal combustion engine 10 of the present embodiment, the clogging of the catalyst device 19 can be accurately determined.

The above embodiment can be modified as follows.
The control device of the above embodiment is applied to a spark ignition type internal combustion engine 10 that ignites the air-fuel mixture in the combustion chamber 11 by spark discharge of the spark plug 18, but the control device is a compression ignition type internal combustion engine The same applies to institutions.

  The catalyst device 19 may have a filter function of collecting particulate matter in the exhaust gas in addition to the exhaust gas purification function of the catalyst.

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Combustion chamber 12 Intake passage 13 Exhaust passage 14 Air flow meter 15 Throttle valve 16 Intake port 17 Fuel injection valve 18 Ignition plug 19 Catalyst device 20: air-fuel ratio sensor, 21: oxygen sensor, 22: exhaust recirculation device, 23: EGR passage, 24: EGR cooler, 25: EGR valve, 26: electronic control unit, 27: NE sensor, 28: accelerator opening degree Sensor, 29 ... clogging determination unit, 30 ... display device.

Claims (1)

A catalyst device for exhaust gas purification installed in an exhaust passage, an exhaust gas recirculation device for recirculating exhaust gas from a portion of the exhaust passage upstream of the catalyst device to an intake passage, and a catalyst device in the exhaust passage A control device for an internal combustion engine, which is applied to an internal combustion engine including an air-fuel ratio sensor provided in an upstream portion, and performs air-fuel ratio feedback control based on a detection result of the air-fuel ratio sensor,
The catalyst device is clogged on the condition that the exhaust gas recirculation amount by the exhaust gas recirculation device is equal to or greater than a predetermined judgment value, and the feedback correction amount of the air-fuel ratio feedback control is equal to or more than the predetermined judgment value. A control device for an internal combustion engine, comprising a clogging determination unit that determines that a load is occurring.