JP2013181517A - Internal combustion engine control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more properly remove a particulate matter (PM) accumulated at the end of an insulating member that is provided between a heating element for generating heat through power distribution and heating a catalyst by heat generation, and a case for storing the heating element in an electric heated catalyst (EHC).SOLUTION: An internal combustion engine control system includes: a fuel-cut control execution part; and an air-fuel ratio perturbation control execution part that executes air-fuel ratio perturbation control to oxidize PM accumulated at the end of an insulation member of an EHC. At least any of an execution start period for the next air-fuel ratio perturbation, amplitude in air-fuel ratio, and the length of execution time is adjusted based on the integration value of the execution time or the execution number of fuel-cut control executed while a temperature of the EHC is equal to or higher than an oxidation temperature of the PM after the execution previous air-fuel ratio perturbation control is completed.

Description

  The present invention relates to an internal combustion engine control system including an electrically heated catalyst provided in an exhaust passage.

  Conventionally, as an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, an electrically heated catalyst (hereinafter also referred to as EHC) in which the catalyst is heated by a heating element that generates heat when energized has been developed. Has been.

  Patent Document 1 discloses a catalytic converter for burning particulate matter (hereinafter referred to as PM) discharged from an internal combustion engine, and a particulate matter in which the amount of PM discharged from the internal combustion engine exceeds a predetermined level. Air-fuel ratio perturbation control for changing the air-fuel ratio of the internal combustion engine at a predetermined cycle between an air-fuel ratio richer than the stoichiometric air-fuel ratio and an air-fuel ratio leaner than the stoichiometric air-fuel ratio when it is determined that the engine is in an excessive state. An internal combustion engine comprising: an air-fuel ratio perturbation means to be executed; and an air-fuel ratio control means for maintaining the air-fuel ratio of the internal combustion engine in the vicinity of the theoretical air-fuel ratio when it is determined that the internal combustion engine is not in an excessive particulate matter state. An exhaust emission control device for an engine is disclosed. Patent Document 2 also discloses a technique related to air-fuel ratio perturbation control.

  In Patent Document 3, switching of the control mode between a normal mode in which the engine is controlled in a normal operation state and a forced regeneration mode in which the filter provided in the exhaust passage is heated to remove PM by combustion, A technique for permitting when an engine non-injection state occurs is disclosed.

  Patent Document 4 discloses an air-fuel ratio modulation means for forcibly changing the air-fuel ratio of exhaust flowing into a three-way catalytic converter provided in an exhaust passage of an internal combustion engine between a rich air-fuel ratio and a lean air-fuel ratio, and a three-way catalyst. Disclosed is an internal combustion engine exhaust gas purification device comprising modulation characteristic changing means for changing a modulation characteristic of an air-fuel ratio modulation means in accordance with a CO storage amount correlation value that correlates with a CO storage capability of a converter. Yes.

JP 2010-196552 A JP 2004-225618 A JP 2006-274843 A JP 2004-1000049 A JP 2006-022779 A

  In the EHC, an insulating member that insulates electricity is provided between a heating element that generates heat when energized and a case that the heating element accommodates. By providing this insulating member, it is possible to suppress a short circuit between the heating element and the case.

  However, in EHC, the end of the insulating member is exposed to the exhaust. Therefore, the conductive PM contained in the exhaust adheres to the end of the insulating member. As a result, when PM accumulates at the end of the insulating member, there is a risk that the PM is short-circuited between the heating element and the case. In order to suppress such a short circuit between the heating element and the case due to PM, it is necessary to remove PM deposited on the end portion of the insulating member.

  The present invention has been made in view of such a problem, and an object of the present invention is to more suitably remove PM deposited on an end portion of an EHC insulating member.

  The present invention is based on the integrated value of the execution time of fuel cut control executed in the state where the temperature of EHC is equal to or higher than the oxidation temperature of PM after the end of execution of the previous air-fuel ratio perturbation control or the number of executions thereof. The air-fuel ratio perturbation control execution start timing, the air-fuel ratio amplitude, or the length of the execution time is adjusted.

More specifically, the control system for an internal combustion engine according to the present invention is:
Electric heating comprising: a heating element that generates heat when energized and heats the catalyst by generating heat; a case that houses the heating element; and an insulating member that is provided between the heating element and the case to insulate electricity. Type catalyst is provided in the exhaust passage,
An internal combustion engine control system in which the air-fuel ratio is controlled in the vicinity of the theoretical air-fuel ratio during normal operation,
A fuel cut control execution unit for executing fuel cut control for stopping fuel injection in the internal combustion engine during deceleration operation;
The air-fuel ratio of the internal combustion engine is set between an air-fuel ratio richer than the stoichiometric air-fuel ratio and an air-fuel ratio leaner than the stoichiometric air-fuel ratio in order to oxidize particulate matter deposited on the end of the insulating member of the electrically heated catalyst. An air-fuel ratio perturbation control execution unit for executing air-fuel ratio perturbation control that fluctuates in a predetermined cycle at
Fuel cut control is performed by the fuel cut control execution unit when the temperature of the electrically heated catalyst is equal to or higher than the oxidation temperature of the particulate matter after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. The execution time of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit, the amplitude of the air-fuel ratio, or the execution based on the integrated value of the execution time of the control or the number of executions thereof Adjust at least one of the lengths of time.

  When the fuel cut control is executed, the amount of oxygen supplied to the EHC increases. Therefore, when fuel cut control is executed in a state where the temperature of EHC is equal to or higher than the oxidation temperature of PM, PM deposited on the end portion of the insulating member can be oxidized and removed. In particular, since the temperature at the downstream end of the insulating member does not easily decrease due to the heat capacity of EHC even if fuel cut control is executed, oxidation of PM deposited on the downstream end is likely to be promoted.

  When air-fuel ratio perturbation control is executed, the amount of oxygen supplied to the EHC can be increased and the temperature of the EHC can be increased. Therefore, PM deposited on the end portion of the insulating member can be oxidized and removed. However, since it is difficult to supply oxygen to the downstream side of the EHC, even if air-fuel ratio perturbation control is executed, oxidation of PM deposited on the downstream end of the insulating member is difficult to be promoted.

  Here, even when the PM accumulation amount at only one of the upstream end and the downstream end of the insulating member increases, there is a possibility that the heating element and the case are short-circuited by the PM. Therefore, if the PM deposited on the upstream end of the insulating member is removed by executing the air-fuel ratio perturbation control, if the PM deposited on the downstream end of the insulating member is not sufficiently removed, heat is generated. It is difficult to suppress a short circuit with the body case. Moreover, when the air-fuel ratio perturbation control is executed, the temperature of the EHC rises, which may promote the deterioration of the EHC.

Therefore, in the present invention, the fuel cut control is executed by the fuel cut control execution unit when the EHC temperature is equal to or higher than the oxidation temperature of PM after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. The execution time of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit, the amplitude of the air-fuel ratio, or the length of the execution time based on the integrated value of the execution time of the control or the number of times of execution Adjust at least one of the above.

  When fuel cut control is executed in a state where the EHC temperature is equal to or higher than the oxidation temperature of PM, the integrated value of the execution time of the control or the number of executions thereof is the removal amount of PM accumulated at the downstream end of the insulating member. There is a correlation. Therefore, the execution time of the next air-fuel ratio perturbation control is determined based on the integrated value of the execution time of the control when the fuel cut control is executed in a state where the temperature of the EHC is equal to or higher than the oxidation temperature of PM or the number of executions thereof. By adjusting, the next perturbation control can be executed at a suitable time.

  Further, the amplitude of the air-fuel ratio and the execution time in the air-fuel ratio perturbation control have a correlation with the amount of PM removed deposited on the upstream end of the insulating member. Therefore, the air-fuel ratio in the next air-fuel ratio perturbation control is based on the integrated value of the execution time of the fuel cut control when the fuel cut control is executed in a state where the EHC temperature is equal to or higher than the oxidation temperature of PM or the number of executions thereof. By adjusting the amplitude or the length of the execution time of the next air-fuel ratio perturbation control, the amount of PM removed at the downstream end of the insulating member removed by executing the fuel cut control and the next empty air-fuel ratio perturbation control are adjusted. The PM removal amount at the upstream end portion of the insulating member that is removed by executing the fuel ratio perturbation control can be made to correspond.

  Therefore, according to the present invention, it is possible to remove PM deposited at the end of the insulating member of the EHC while suppressing execution of unnecessary air-fuel ratio perturbation control. As a result, it is possible to suppress a short circuit between the heating element and the case due to PM while suppressing deterioration of EHC.

  In the control system for an internal combustion engine according to the present invention, the fuel cut control execution unit is in a state where the EHC temperature is equal to or higher than the oxidation temperature of PM after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the fuel cut control is executed is equal to or longer than the predetermined integration time, or when the execution count is equal to or more than the predetermined number of times, the air-fuel ratio perturbation control execution unit performs the next empty The fuel ratio perturbation control may be executed.

  Here, the predetermined integration time may be an integration value of the execution time of the fuel cut control in which it can be determined that PM is sufficiently removed at the downstream end portion of the insulating member by executing the fuel cut control. Further, the predetermined number of times may be the number of executions of the fuel cut control that can be determined that the PM is sufficiently removed at the downstream end portion of the insulating member by executing the fuel cut control.

  According to the above, the next air-fuel ratio perturbation control is executed in a state where PM is removed at the downstream end portion of the insulating member by executing the fuel cut control, thereby the upstream end of the insulating member. PM is removed in the part. In other words, the next air-fuel ratio perturbation control is suppressed from being executed in a state where PM is not sufficiently removed at the downstream end of the insulating member. Therefore, it is possible to remove PM deposited on the end portion of the insulating member of the EHC while suppressing execution of unnecessary air-fuel ratio perturbation control.

In the control system for an internal combustion engine according to the present invention, the fuel cut control execution unit is in a state where the EHC temperature is equal to or higher than the oxidation temperature of PM after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the fuel cut control is executed is greater than when the integrated value of the execution time of the control is small, or when the execution number of the control is large As compared with the case where the number of executions of the air-fuel ratio is small, the air-fuel ratio amplitude of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution section may be increased.

  In the control system for an internal combustion engine according to the present invention, the fuel cut control is performed in a state where the temperature of EHC is equal to or higher than the oxidation temperature of PM after the end of the previous execution of the air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the fuel cut control is executed by the execution unit is large compared to when the integrated value of the execution time of the control is small, or when the number of executions of the control is large The execution time of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit may be made longer than when the number of times of execution of the control is small.

  According to these, the PM removal amount at the downstream end portion of the insulating member removed by executing the fuel cut control and the insulating member removed by executing the next air-fuel ratio perturbation control. The amount of PM removed at the upstream end can be made to correspond.

  Further, during normal operation of the internal combustion engine, the amount of PM attached to the upstream end of the insulating member is larger than the amount of PM attached to the downstream end thereof. Therefore, the amount of PM deposited at the upstream end of the insulating member tends to be larger than the amount of PM deposited at the downstream end. Further, when the fuel cut control is executed, the temperature of the upstream end portion of the insulating member is likely to be lower than the temperature of the downstream end portion thereof. Therefore, even if fuel cut control is executed, PM deposited on the upstream end of the insulating member is less likely to be removed than PM deposited on the downstream end.

  Therefore, in the present invention, after the air-fuel ratio perturbation control execution unit starts executing the air-fuel ratio perturbation control, the PM accumulation amount at the upstream end portion of the EHC insulating member is equal to the PM accumulation amount at the downstream end portion of the insulating member. The air-fuel ratio perturbation control may be continued until the predetermined accumulation amount difference becomes smaller than the accumulation amount.

  According to this, after the execution of the air-fuel ratio perturbation control, the fuel cut control is executed even when the PM accumulation amount at the upstream end of the insulating member increases or when the EHC temperature is equal to or higher than the oxidation temperature of PM. As a result, even when the PM accumulated at the downstream end of the insulating member is removed, the difference between the PM amount remaining at the upstream end of the insulating member and the PM amount remaining at the downstream end is reduced. can do. That is, a state in which both the PM deposition amount at the upstream end portion of the insulating member and the PM deposition amount at the downstream end portion thereof are sufficiently reduced to suppress a short circuit with the case of the heating element. can do.

  In addition, as the speed of the vehicle equipped with the internal combustion engine increases, the operation state of the internal combustion engine becomes a decelerating operation, and the execution time of the control when the fuel cut control execution unit executes the fuel cut control tends to increase. Therefore, removal of PM deposited on the downstream end portion of the insulating member due to execution of the fuel cut control is facilitated. Further, the higher the temperature of the exhaust gas flowing into the EHC, the higher the EHC temperature. Therefore, when the operation state of the internal combustion engine is decelerated and fuel cut control is executed, removal of PM accumulated on the downstream end of the insulating member is easily promoted.

  Therefore, in the present invention, the air-fuel ratio perturbation control execution unit has a higher temperature of the exhaust gas flowing into the EHC when the speed of the vehicle equipped with the internal combustion engine is larger than when the speed of the vehicle is small. In some cases, the execution time of the air-fuel ratio perturbation control may be made longer than when the temperature of the exhaust gas is low.

When the execution time of the air-fuel ratio perturbation control is lengthened, it is possible to increase the removal amount of PM deposited on the upstream end portion of the insulating member that is removed by executing the air-fuel ratio perturbation control. Therefore, according to the above, when the fuel cut control is executed after the completion of the perturbation control, the removal of the PM accumulated on the downstream end of the insulating member is facilitated, and the air-fuel ratio perturbation control is performed. It is possible to promote removal of PM deposited on the upstream end portion of the insulating member. As a result, after the execution of the air-fuel ratio perturbation control is completed, PM accumulated on the downstream end of the insulating member is removed by performing fuel cut control in a state where the EHC temperature is equal to or higher than the oxidation temperature of PM. In addition, the difference in the amount of PM remaining at the upstream end and the downstream end of the insulating member can be further reduced.

  In the present invention, the air-fuel ratio perturbation control execution unit has a higher temperature of the exhaust gas flowing into the EHC when the speed of the vehicle equipped with the internal combustion engine is higher than when the speed of the vehicle is low. In some cases, the predetermined accumulation amount difference may be made larger than when the temperature of the exhaust gas is low. When the predetermined accumulation amount is increased, the execution time of the air-fuel ratio perturbation control becomes longer. Therefore, the same effect as described above can be obtained.

  According to the present invention, it is possible to remove PM deposited on the end of the insulating member of the EHC while suppressing execution of unnecessary air-fuel ratio perturbation control.

1 is a diagram illustrating a schematic configuration of an intake / exhaust system and an EHC of an internal combustion engine according to Embodiment 1. FIG. 3 is a flowchart illustrating a flow of fuel cut control according to the first embodiment. 3 is a flowchart showing a flow of air-fuel ratio perturbation control according to the first embodiment. 6 is a flowchart showing a calculation flow of a PM accumulation amount in an upstream protruding portion of an inner pipe according to a second embodiment. 6 is a flowchart showing a calculation flow of a PM accumulation amount in a downstream protrusion of an inner pipe according to a second embodiment. 6 is a flowchart showing a flow of air-fuel ratio perturbation control according to the second embodiment. FIG. 10 is a diagram illustrating a relationship between a vehicle speed (vehicle speed) and a correction coefficient for correcting an execution time of air-fuel ratio perturbation control according to the third embodiment. It is a figure which shows the relationship between the temperature of the exhaust_gas | exhaustion which flows into EHC based on Example 3 (inflow exhaust gas temperature), and the correction coefficient for correct | amending the execution time of air-fuel ratio perturbation control.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Example 1>
[Schematic configuration of intake and exhaust system and EHC of internal combustion engine]
FIG. 1 is a diagram showing a schematic configuration of an intake / exhaust system and an EHC of an internal combustion engine according to the present embodiment.

The EHC 1 according to the present embodiment is provided in the exhaust pipe 2 of the internal combustion engine 10. The internal combustion engine 10 is a gasoline engine for driving a vehicle. The internal combustion engine 10 is provided with a water temperature sensor 21 that detects the temperature of the cooling water. The intake pipe 11 of the internal combustion engine 10 is provided with an air flow meter 12 and a throttle valve 13. The air flow meter 12 is a sensor that detects the intake air amount of the internal combustion engine 10. The throttle valve 13 adjusts the intake air amount of the internal combustion engine 1.

  An air-fuel ratio sensor 22 and a first exhaust temperature sensor 23 are provided upstream of the EHC 1 in the exhaust pipe 2. A second exhaust temperature sensor 24 is provided downstream of the EHC 1 in the exhaust pipe 2. The air-fuel ratio sensor 22 is a sensor that detects the air-fuel ratio of the exhaust discharged from the internal combustion engine 1. The first and second exhaust temperature sensors 23 and 24 are sensors that detect the temperature of the exhaust. Note that the arrows in FIG. 1 indicate the flow direction of the exhaust gas in the exhaust pipe 2.

  The EHC 1 includes a catalyst carrier 3, a case 4, a mat 5, an inner tube 6, and an electrode 7. The catalyst carrier 3 is accommodated in the case 4. The catalyst carrier 3 is formed in a columnar shape, and is installed so that its central axis is coaxial with the central axis A of the exhaust pipe 2. The central axis A is a central axis common to the exhaust pipe 2, the catalyst carrier 3, the inner pipe 6, and the case 4. A three-way catalyst 31 is supported on the catalyst carrier 3. The catalyst supported on the catalyst carrier 3 is not limited to a three-way catalyst, and may be an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst.

  The catalyst carrier 3 is formed of a material that generates electric resistance and generates heat when energized. An example of the material of the catalyst carrier 3 is SiC. The catalyst carrier 3 has a plurality of passages extending in the direction in which the exhaust flows (that is, in the direction of the central axis A) and having a cross section perpendicular to the direction in which the exhaust flows in a honeycomb shape. Exhaust gas flows through this passage. The cross-sectional shape of the catalyst carrier 3 in the direction orthogonal to the central axis A may be an ellipse or the like.

  A pair of electrodes 7 are connected to the outer peripheral surface of the catalyst carrier 3. The electrode 7 is formed by a surface electrode 7a and a shaft electrode 7b. The surface electrode 7 a extends in the circumferential direction and the axial direction along the outer peripheral surface of the catalyst carrier 3. The surface electrodes 7 a are provided on the outer peripheral surface of the catalyst carrier 3 so as to face each other with the catalyst carrier 3 interposed therebetween. One end of the shaft electrode 7b is connected to the surface electrode 7a. The other end of the shaft electrode 7 b protrudes outside the case 4 through the electrode chamber 9 formed in the case 4.

  Electricity is supplied to the electrode 7 from the battery via the supply power control unit 27. When electricity is supplied to the electrode 7, the catalyst carrier 3 is energized. When the catalyst carrier 3 generates heat by energization, the three-way catalyst 31 supported on the catalyst carrier 3 is heated, and its activation is promoted. The supply power control unit 27 performs ON / OFF switching of supply of electricity to the electrode 7 (that is, energization to the catalyst carrier 3) and adjustment of supply power.

  The case 4 is made of metal. As a material for forming the case 4, a stainless steel material can be exemplified. A mat 5 is sandwiched between the inner wall surface of the case 4 and the outer peripheral surface of the catalyst carrier 3. That is, the catalyst carrier 3 is supported by the mat 5 in the case 4. An inner tube 6 is sandwiched between the mats 5. The inner tube 6 is a tubular member centered on the central axis A. The mat 5 is divided into the case 4 side and the catalyst carrier 3 side by the inner tube 6 by sandwiching the inner tube 6.

  The mat 5 is formed of an electrical insulating material. Examples of the material for forming the mat 5 include ceramic fibers mainly composed of alumina. The mat 5 is wound around the outer peripheral surface of the catalyst carrier 3 and the outer peripheral surface of the inner tube 6. The mat 5 is divided into an upstream portion 5a and a downstream portion 5b, and a space is formed between the upstream portion 5a and the downstream portion 5b. Since the mat 5 is sandwiched between the catalyst carrier 3 and the case 4, electricity is suppressed from flowing to the case 4 when the catalyst carrier 3 is energized.

The inner tube 6 is made of a stainless steel material. In addition, an electrical insulating layer is formed on the entire surface of the inner tube 6. Examples of the material for forming the electrical insulating layer include ceramic or glass. The main body of the inner tube 6 may be formed of an electrical insulating material such as alumina. Further, as shown in FIG. 1, the upstream end of the inner pipe 6 protrudes from the upstream end face of the mat 5 into the exhaust, and the downstream end of the inner pipe 6 is exhausted from the downstream end face of the mat 5. Protruding. Hereinafter, a portion of the inner pipe 6 that protrudes from the end face of the mat 5 into the exhaust is referred to as a “projection”. Further, the inner pipe 6 is not necessarily provided.

  The case 4 and the inner tube 6 have through holes for passing the shaft electrode 7b. An electrode chamber 9 is formed by a space in the case 4 between the upstream portion 5 a and the downstream portion 5 b of the mat 5. That is, in this embodiment, the electrode chamber 9 is formed over the entire outer peripheral surface of the catalyst carrier 3 between the upstream portion 5a and the downstream portion 5b of the mat 5. In addition, without dividing the mat 5 into the upstream portion 5a and the downstream portion 5b, a space serving as an electrode chamber may be formed by forming a through hole only in a portion through which the electrode 7 of the mat 5 passes.

  An electrode support member 8 that supports the shaft electrode 7 b is provided in the through hole opened in the case 4. The electrode support member 8 is made of an electrical insulating material, and is provided between the case 4 and the electrode 7 without a gap.

  The internal combustion engine 10 is provided with an electronic control unit (ECU) 20. An air flow meter 12, a water temperature sensor 21, an air-fuel ratio sensor 22, a first exhaust temperature sensor 23, and a second exhaust temperature sensor 24 are electrically connected to the ECU 20. In addition, an accelerator opening sensor 25 and a vehicle speed sensor 26 are also electrically connected to the ECU 20. The accelerator opening sensor 25 is a sensor that detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. The vehicle speed sensor 26 is a sensor that detects the speed of the vehicle on which the internal combustion engine 1 is mounted. And the output value of each sensor is input into ECU20.

  Further, the ECU 20 is electrically connected to a throttle valve 13, a fuel injection valve (not shown) of the internal combustion engine 10, and a supply power control unit 27. Then, these devices are controlled by the ECU 20.

  In this embodiment, the catalyst carrier 3 corresponds to a heating element according to the present invention. However, the heating element according to the present invention is not limited to the carrier supporting the catalyst. For example, the heating element may be a structure installed on the upstream side of the catalyst. In the present embodiment, the mat 5 and the inner tube 6 correspond to the insulating member according to the present invention. However, the insulating member according to the present invention is not necessarily constituted by the mat 5 and the inner tube 6 and may be any member that can electrically insulate the catalyst carrier 3. For example, the insulating member can be formed of only the mat 5.

[PM removal control]
As described above, the inner pipe 6 is sandwiched between the mats 5 in the EHC 1. With such a configuration, it is possible to suppress a short circuit between the catalyst carrier 3 and the case 4 due to condensed water generated by condensation of moisture in the exhaust gas and infiltrating into the mat 5. Further, the upstream and downstream protrusions of the inner pipe 6 can prevent the condensed water from reaching the catalyst carrier 3 along the end face of the mat 5. Therefore, a short circuit between the catalyst carrier 3 and the case 4 due to condensed water at the end face of the mat 5 can also be suppressed.

  However, the protruding portion of the inner pipe 6 is exposed to the exhaust gas. Therefore, PM in the exhaust adheres to the protruding portion of the inner pipe 6. PM has conductivity. Therefore, if PM accumulates on the end surface of the mat 5 and the protruding portion of the inner tube 6, there is a possibility that the catalyst carrier 3 and the case 4 are short-circuited by the PM. In order to suppress such a short circuit between the catalyst carrier 3 and the case 4 caused by PM, it is necessary to remove PM deposited on the protruding portion of the inner tube 6.

  Here, in this embodiment, the fuel cut control for stopping the fuel injection in the internal combustion engine 10 is executed by the ECU 20 during the deceleration operation. When the fuel cut control is executed, air is discharged from the internal combustion engine 10. Therefore, the amount of oxygen supplied to EHC1 increases. Therefore, when fuel cut control is executed in a state where the temperature of EHC1 is equal to or higher than the oxidation temperature of PM, PM deposited on the protruding portion of the inner pipe 6 can be oxidized and removed.

  However, when the fuel cut control is executed, the temperature of the gas supplied to the EHC 1 decreases. Therefore, the temperature of the upstream protruding portion of the inner pipe 6 is likely to decrease, and when the temperature falls below the oxidation temperature of PM, PM deposited on the upstream protruding portion is not oxidized. On the other hand, the temperature of the protruding portion on the downstream side of the inner pipe 6 is not easily lowered by the heat capacity of the EHC 1 even if the fuel cut control is executed. Therefore, if fuel cut control is executed when the temperature of EHC1 is equal to or higher than the oxidation temperature of PM, the oxidation of PM deposited on the protruding portion on the downstream side of the inner pipe 6 is easily promoted.

  Further, in this embodiment, air-fuel ratio perturbation control is executed by the ECU 20 in order to oxidize and remove PM accumulated on the protruding portion of the inner pipe 6. In the internal combustion engine 10, during normal operation, the air-fuel ratio is controlled with the target air-fuel ratio as the theoretical air-fuel ratio. In the air-fuel ratio perturbation control, the air-fuel ratio of the internal combustion engine 10 is fluctuated at a predetermined cycle between an air-fuel ratio richer than the stoichiometric air-fuel ratio and an air-fuel ratio leaner than the stoichiometric air-fuel ratio. The air-fuel ratio perturbation control is realized by periodically changing the fuel injection amount and fuel injection timing in the internal combustion engine 10.

  When the air-fuel ratio perturbation control is executed, when the air-fuel ratio of the internal combustion engine 10 becomes leaner than the stoichiometric air-fuel ratio, oxygen is supplied to the EHC 1, and thus the amount of oxygen supplied to the EHC 1 than during normal operation. Will increase. Furthermore, since the oxidation of the unburned fuel component (HC) by the three-way catalyst 31 of EHC1 is promoted, the temperature of EHC1 can be raised to the oxidation temperature of PM or higher. Therefore, the PM deposited on the inner pipe 6 can be oxidized and removed by executing the air-fuel ratio perturbation control.

  However, since the oxygen supplied to the EHC 1 by executing the air-fuel ratio perturbation control is consumed for the oxidation of the HC in the three-way catalyst 31, it is difficult to supply it downstream of the EHC 1. Therefore, according to the air-fuel ratio perturbation control, the oxidation of PM deposited on the upstream protruding portion of the inner pipe 6 is promoted, but the oxidation of PM deposited on the downstream protruding portion of the inner pipe 6 is hardly promoted.

  Then, by executing the air-fuel ratio perturbation control, even if the PM deposited on the upstream protruding portion of the inner pipe 6 is removed, the PM deposited on the downstream protruding portion of the inner pipe 6 is not sufficiently removed. There is a possibility that the catalyst carrier 3 and the case 4 are short-circuited by PM deposited on the downstream projecting portion of the inner pipe 6 and the downstream end face of the mat 5. Furthermore, when the air-fuel ratio perturbation control is executed, the temperature of the EHC 1 rises, and there is a risk of promoting the deterioration of the EHC 1. Therefore, in order to suppress the deterioration of EHC1, it is necessary to suppress the execution of unnecessary air-fuel ratio perturbation control.

Therefore, in the present embodiment, when the fuel cut control is executed, the upstream protrusion of the inner pipe 6 can be determined at a timing at which it can be determined that the PM accumulated on the downstream protrusion of the inner pipe 6 is sufficiently removed. Air-fuel ratio perturbation control is executed in order to remove PM accumulated in the part. Specifically, after the previous execution of the air-fuel ratio perturbation control, the integrated value of the execution time of the control when the fuel cut control is executed in a state where the temperature of the EHC 1 is equal to or higher than the oxidation temperature of PM (hereinafter, When the integrated value is simply referred to as the integrated value of the fuel cut control execution time) is equal to or longer than the predetermined integrated time, the next air-fuel ratio perturbation control is executed. In other words, the next air-fuel ratio perturbation control is not executed while the integrated value of the execution time of the fuel cut control has not reached the predetermined integrated time.

  Here, the predetermined integration time is an integration value of the execution time of the fuel cut control at which it can be determined that PM has been sufficiently removed from the downstream protruding portion of the inner pipe 6 by executing the fuel cut control.

  According to the above, it is possible to suppress the next air-fuel ratio perturbation control from being executed in a state where PM deposited on the downstream protrusion of the inner pipe 6 is not sufficiently removed. Therefore, it is possible to remove PM deposited on the end portion of the insulating member of the EHC while suppressing execution of unnecessary air-fuel ratio perturbation control.

  Further, based on the integrated value of the execution time of the fuel cut control, the amplitude of the air / fuel ratio in the next air / fuel ratio perturbation control and the length of the execution time of the next air / fuel ratio perturbation control are adjusted. Note that the air-fuel ratio amplitude in the air-fuel ratio perturbation control is the air-fuel ratio when the air-fuel ratio of the internal combustion engine 10 is richer than the stoichiometric air-fuel ratio, and the air-fuel ratio of the internal combustion engine 10 is leaner than the stoichiometric air-fuel ratio. This is the difference from the air / fuel ratio when the air / fuel ratio is set to a different value.

  Here, the larger the integrated value of the execution time of the fuel cut control, the larger the PM removal amount in the downstream protruding portion of the inner pipe 6 removed by executing the fuel cut control. The larger the air-fuel ratio amplitude in the air-fuel ratio perturbation control is, and the longer the execution time of the air-fuel ratio perturbation control is, the longer the upstream protruding portion of the inner pipe 6 is removed by the execution of the air-fuel ratio perturbation control. The amount of removal of PM in is increased.

  Therefore, specifically, when the integrated value of the fuel cut control execution time is large, the amplitude of the air-fuel ratio in the next air-fuel ratio perturbation control is made larger than when the integrated value of the control execution time is small. In addition, the execution time of the next air-fuel ratio perturbation control is lengthened.

  According to this, the removal amount of PM in the downstream protruding portion of the inner pipe 6 removed by executing the fuel cut control, and the inner pipe removed by executing the next air-fuel ratio perturbation control 6 can be made to correspond to the amount of removal of PM in the upstream projecting portion. Therefore, it is possible to suppress the execution of unnecessary air-fuel ratio perturbation control that removes only excessive PM accumulated on the upstream protruding portion of the inner pipe 6.

[Control flow of fuel cut control and air-fuel ratio perturbation control]
Hereinafter, the flow of fuel cut control and air-fuel ratio perturbation control according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart showing a flow of fuel cut control according to the present embodiment. FIG. 3 is a flowchart showing a flow of air-fuel ratio perturbation control according to the present embodiment. These flows are stored in advance in the ECU 20 and are repeatedly executed by the ECU 20.

  In the flow shown in FIG. 2, it is determined in step S101 whether or not fuel cut control (F / C control) is being executed. The fuel cut control is executed when a deceleration operation condition, which is a condition for setting the operation state of the internal combustion engine 10 to the deceleration operation state, is satisfied. Whether or not the deceleration operation condition is satisfied is determined by the ECU 20 based on the detection value of the accelerator opening sensor 25. For example, the ECU 20 may determine that the deceleration operation condition is satisfied when the detected value of the accelerator opening sensor 25 becomes zero. In this case, when the detected value of the accelerator opening sensor 25 becomes larger than zero, the ECU 20 determines that the deceleration operation condition is not satisfied, and stops the execution of the fuel cut control.

If an affirmative determination is made in step S101, the process of step S102 is executed next. If a negative determination is made, the execution of this flow is temporarily terminated. In step S102, it is determined whether or not the temperature Tehc of EHC1 is equal to or higher than the oxidation temperature Tpmo of PM. Note that the temperature Tehc of the EHC 1 is estimated by the ECU 20 based on the detection value of the second exhaust temperature sensor 24.

  If an affirmative determination is made in step S102, the process of step S103 is executed next, and if a negative determination is made, execution of this flow is temporarily terminated. When an affirmative determination is made in step S102, it can be determined that the fuel cut control is being executed in a state where the temperature Tehc of EHC1 is equal to or higher than the oxidation temperature Tpmo of PM. In step S103, an integrated value Σtfc of execution time of fuel cut control is calculated. The calculated integrated value Σtfc of the fuel cut control execution time is stored in the ECU 20.

  In the flow shown in FIG. 3, in step S201, it is determined whether or not there is a request for removing PM accumulated on the protruding portion of the inner pipe 6 of the EHC1. For example, it may be determined that there is a PM removal request when the integrated value of the PM emission amount from the internal combustion engine 10 is equal to or greater than a predetermined value after the end of the previous execution of the air-fuel ratio perturbation control. Note that the PM accumulation amount from the internal combustion engine 10 can be estimated based on the operating state of the internal combustion engine 10. Alternatively, it may be determined that there is a PM removal request every time the operation time of the internal combustion engine 10 reaches a predetermined time or every time the integrated value of the fuel injection amount in the internal combustion engine 10 reaches a predetermined amount.

  If an affirmative determination is made in step S201, the process of step S202 is executed next. If a negative determination is made, the execution of this flow is temporarily terminated. In step S202, it is determined whether or not the integrated value Σtfc of the fuel cut control execution time stored in the ECU 20 is equal to or greater than a predetermined integrated time Σt0. The predetermined integration time Σt0 is determined in advance by experiments or the like and is stored in the ECU 20.

  If an affirmative determination is made in step S202, the process of step S203 is executed next, and if a negative determination is made, the execution of this flow is temporarily terminated. In step S203, the air-fuel ratio amplitude ΔA / F and the air-fuel ratio perturbation control execution time tex in the air-fuel ratio perturbation control are calculated based on the integrated value Σtfc of the fuel cut control execution time.

  Here, the larger the integrated value Σtfc of the fuel cut control execution time is, the larger the air-fuel ratio amplitude ΔA / F in the air-fuel ratio perturbation control is calculated. Further, the larger the integrated value Σtfc of the fuel cut control execution time is, the larger the execution time text of the air-fuel ratio perturbation control is calculated. The relationship between the integrated value Σtfc of the execution time of the fuel cut control, the amplitude ΔA / F of the air / fuel ratio in the air / fuel ratio perturbation control, and the execution time tex of the air / fuel ratio perturbation control is previously determined based on experiments and the like. It is determined and stored in the ECU 20 as a map or a function. In step S203, this map or function is used to calculate the air-fuel ratio amplitude ΔA / F and the air-fuel ratio perturbation control execution time text in the air-fuel ratio perturbation control.

  Next, in step S204, air-fuel ratio perturbation control is executed. At this time, the amplitude of the air-fuel ratio is controlled to the amplitude ΔA / F calculated in step S203. In addition, when the execution time tex calculated in step S203 has elapsed after the start of execution of the air-fuel ratio perturbation control, the execution is stopped.

According to the above flow, even if there is a PM removal request, the air-fuel ratio perturbation control is not executed if the integrated value Σtfc of the fuel cut control execution time has not reached the predetermined integrated time Σt0. Further, when the integrated value Σtfc of the fuel cut control execution time is large, the amplitude ΔA / F of the air-fuel ratio in the air-fuel ratio perturbation control is made larger than when the integrated value Σtfc of the execution time of the control is small. Further, when the integrated value Σtfc of the fuel cut control execution time is large, the execution time of the air-fuel ratio perturbation control is made longer than when the integrated value Σtfc of the control execution time is small.

  Note that the values of the air-fuel ratio amplitude ΔA / F and the air-fuel ratio perturbation control execution time tex in the air-fuel ratio perturbation control need to be continuously changed with respect to the integrated value Σtfc of the fuel cut control execution time. It may be changed step by step. Further, either one of the air-fuel ratio amplitude ΔA / F in the air-fuel ratio perturbation control or the execution time text of the air-fuel ratio perturbation control may be adjusted according to the integrated value Σtfc of the fuel cut control execution time. .

  Further, in this embodiment, instead of the integrated value of the execution time of the fuel cut control, the fuel executed in the state where the temperature of EHC1 is equal to or higher than the oxidation temperature of PM after the end of the previous execution of the air-fuel ratio perturbation control. Based on the number of times of execution of cut control (hereinafter, this number of times of execution is simply referred to as the number of times of execution of fuel cut control), at least one of the execution time of the next air-fuel ratio perturbation control, the amplitude of the air-fuel ratio, or the execution time is determined. You may adjust.

  For example, when there is a PM removal request, if the number of executions of the fuel cut control is a predetermined number or more, the air-fuel ratio perturbation control may be executed. In this case, the next air-fuel ratio perturbation control is not executed while the number of executions of the fuel cut control has not reached the predetermined number. Here, the predetermined number of times is the number of executions of the fuel cut control that can be determined that PM has been sufficiently removed from the downstream projecting portion of the inner pipe 6 by executing the fuel cut control. The predetermined number is not necessarily plural.

  Further, when the number of executions of the fuel cut control is large, the air-fuel ratio amplitude in the air-fuel ratio perturbation control may be made larger than when the number of executions of the control is small. Further, the execution time of the air-fuel ratio perturbation control may be made longer when the number of executions of the fuel cut control is large than when the number of executions of the control is small.

  Even in the case where the inner pipe 6 is not provided in the EHC 1 according to the present embodiment and the insulating member according to the present invention is configured only by the mat 5, PM is provided on the upstream end face or the downstream end face of the mat 5. As a result, PM may cause a short circuit between the catalyst carrier 3 and the case 4 due to the PM. Therefore, in such a configuration, it is necessary to remove PM deposited on the end face of the mat 5 in order to suppress a short circuit between the catalyst carrier 3 and the case 4.

  The PM accumulated on the downstream end face of the mat 5 is removed when the fuel cut control is executed in a state where the temperature of the EHC 1 is equal to or higher than the oxidation temperature of the PM, similarly to the PM accumulated on the downstream protruding portion of the inner pipe 6. Is done. Further, the PM deposited on the upstream end face of the mat 5 can be removed by executing air-fuel ratio perturbation control, similarly to the PM deposited on the upstream protruding portion of the inner pipe 6. Therefore, also in such a configuration, the execution timing of the next air-fuel ratio perturbation control, the amplitude of the air-fuel ratio, or the execution based on the integrated value or the number of executions of the fuel cut control execution time, as in the above-described embodiment. You may adjust at least one of time.

<Example 2>
The intake / exhaust system and the EHC configuration of the internal combustion engine according to this embodiment are the same as those in the first embodiment. Also in the present embodiment, as in the first embodiment, by performing fuel cut control and air-fuel ratio perturbation control, PM deposited on the protruding portion of the inner pipe 6 of the EHC 1 is oxidized and removed. Hereinafter, the air-fuel ratio perturbation control according to the present embodiment will be described with respect to differences from the first embodiment.

[Air-fuel ratio perturbation control]
During normal operation of the internal combustion engine 10, the amount of PM attached to the upstream protruding portion of the inner pipe 6 is larger than the amount of PM attached to the downstream protruding portion of the inner pipe 6. Therefore, the amount of PM deposited on the upstream protruding portion of the inner pipe 6 tends to be larger than the amount of PM deposited on the downstream protruding portion of the inner pipe 6. For this reason, even when the execution of the air-fuel ratio perturbation control is completed, even if the PM accumulation amount in the upstream protruding portion of the inner pipe 6 has decreased to an amount equivalent to the PM accumulation amount in the downstream protruding portion of the inner pipe 6. In the subsequent normal operation, there is a high possibility that the PM accumulation amount in the upstream protrusion of the inner pipe 6 is larger than the PM accumulation amount in the downstream protrusion of the inner pipe 6.

  Further, as described above, even if the fuel cut control is performed in a state where the temperature of EHC 1 is equal to or higher than the oxidation temperature of PM, PM deposited on the upstream protrusion of the inner pipe 6 It is harder to remove than PM deposited on the surface. For this reason, even when the execution of the air-fuel ratio perturbation control is completed, even if the PM accumulation amount in the upstream protruding portion of the inner pipe 6 has decreased to an amount equivalent to the PM accumulation amount in the downstream protruding portion of the inner pipe 6. Thereafter, when the fuel cut control is executed in a state where the temperature of EHC 1 is equal to or higher than the oxidation temperature of PM, the PM accumulation amount in the upstream protrusion portion of the inner pipe 6 becomes the PM accumulation amount in the downstream protrusion portion of the inner pipe 6. More likely to be.

  On the other hand, according to the air-fuel ratio perturbation control, oxidation of PM deposited on the upstream protruding portion of the inner pipe 6 is easily promoted. Therefore, in the present embodiment, when air-fuel ratio perturbation control is executed, the PM deposition amount at the upstream protruding portion of the inner pipe 6 is more than a predetermined deposition amount difference than the PM deposition amount at the downstream protruding portion of the inner pipe 6. The execution of the control is continued until it becomes less.

  According to this, even if the PM accumulation amount in the upstream protruding portion of the inner pipe 6 increases after the execution of the air-fuel ratio perturbation control, or when the temperature of the EHC 1 is equal to or higher than the oxidation temperature of PM, the fuel cut control is performed. Even when the PM accumulated on the downstream projecting portion of the inner pipe 6 is removed by the execution, the PM amount remaining on the upstream projecting portion of the inner tube 6 and the PM remaining on the downstream projecting portion of the inner tube 6 The difference from the amount can be reduced. That is, both the PM accumulation amount at the upstream protrusion of the inner tube 6 and the PM accumulation amount at the downstream protrusion of the inner tube 6 can suppress a short circuit with the case 4 of the catalyst carrier 3. A sufficiently reduced state can be obtained.

[Calculation method of the amount of PM deposition on the protruding part of the inner pipe]
Here, a method of calculating the PM accumulation amount in the protruding portion of the inner pipe 6 according to the present embodiment will be described with reference to FIGS. FIG. 4 is a flowchart showing a calculation flow of the PM accumulation amount in the upstream protruding portion of the inner pipe 6 according to the present embodiment. FIG. 5 is a flowchart illustrating a calculation flow of the PM accumulation amount in the downstream protrusion of the inner pipe 6 according to the present embodiment. These flows are stored in advance in the ECU 20 and are repeatedly executed by the ECU 20.

  In the flow shown in FIG. 4, in step S301, based on the cooling water temperature Tw detected by the water temperature sensor 21, the air-fuel ratio A / F of the internal combustion engine 1, and the intake air amount Ga of the internal combustion engine 1 detected by the air flow meter 12. Thus, the PM emission amount kpm1 from the internal combustion engine 1 is calculated.

  As the cooling water temperature Tw is lower and the air-fuel ratio A / F is lower, the PM discharge amount kpm1 increases. Further, the larger the intake air amount Ga, the larger the exhaust gas flow rate, so the PM discharge amount kpm1 increases. Such a relationship among the coolant temperature Tw, the air-fuel ratio A / F of the air-fuel mixture, the intake air amount Ga, and the PM discharge amount kpm1 from the internal combustion engine 1 can be obtained in advance based on experiments or the like. Stored as a map or function. In step S301, the PM emission amount kpm1 from the internal combustion engine 1 is calculated using this map or function.

  Next, in step S302, it is determined whether or not fuel cut control is being executed. If an affirmative determination is made in step S302, then the process of step S303 is executed. In step S303, based on the temperature Tgin of the exhaust gas flowing into the EHC 1 detected by the first exhaust gas temperature sensor 23, the oxidation amount kpm2Fr of PM accumulated on the upstream protruding portion of the inner pipe 6 during the execution of the fuel cut control. Is calculated.

  As the temperature Tgin of the exhaust gas flowing into the EHC 1 is higher, the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6 during execution of the fuel cut control increases. However, when the temperature Tgin of the exhaust gas flowing into the EHC 1 is lower than the oxidation temperature of PM, the PM oxidation amount kpm2Fr becomes zero. Such a relationship between the temperature Tgin of the exhaust gas flowing into the EHC 1 and the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6 during execution of fuel cut control is obtained in advance based on experiments or the like. Stored in the ECU 20 as a map or a function. In step S303, the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6 during execution of the fuel cut control is calculated using this map or function.

  On the other hand, if a negative determination is made in step S302, the process of step S304 is performed next. In step S304, it is determined whether air-fuel ratio perturbation control is being executed. If an affirmative determination is made in step S304, then the process of step S305 is executed. In step S305, based on the temperature Tgin of the exhaust gas flowing into the EHC 1 detected by the first exhaust temperature sensor 23, the oxidation of PM deposited on the upstream protruding portion of the inner pipe 6 during the execution of the air-fuel ratio perturbation control. The quantity kpm2Fr is calculated.

  As the temperature Tgin of the exhaust gas flowing into the EHC 1 is higher, the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6 during the execution of the air-fuel ratio perturbation control increases. However, if the temperature Tgin of the exhaust gas flowing into the EHC 1 is equal to or lower than a predetermined exhaust temperature at which the temperature of the EHC 1 does not rise to the oxidation temperature of PM even when the air-fuel ratio perturbation control is executed, this PM oxidation amount kpm2Fr Becomes zero. The relationship between the temperature Tgin of the exhaust gas flowing into the EHC 1 and the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6 during execution of the air-fuel ratio perturbation control is based on experiments and the like in advance. It can be obtained and stored in the ECU 20 as a map or function. In step S305, the oxidation amount kpm2Fr of PM deposited on the upstream protrusion of the inner pipe 6 in the air-fuel ratio perturbation control is calculated using this map or function.

  If a negative determination is made in step S304, neither fuel cut control nor perturbation control is executed, and therefore PM deposited on the protruding portion of the inner pipe 6 is not oxidized. Therefore, in this case, in step S306, zero is calculated as the oxidation amount kpm2Fr of PM deposited on the upstream protruding portion of the inner pipe 6.

Following the process of step S303, S304, or S306, the process of step S307 is executed. In step S307, the PM accumulation amount cpmFr in the upstream protruding portion of the inner pipe 6 is calculated using the following equation (1).
cpmFr (i) = cpmFr (i−1) + kpm1 * b−kpm2Fr (1)
cpmFr (i): Current PM accumulation amount cpmFr (i-1): PM accumulation amount calculated by the previous execution of this flow kpm1: PM emission amount calculated in step S301 b: PM emission from the internal combustion engine 1 A coefficient indicating the ratio of the amount of PM adhering to the upstream protruding portion of the inner pipe 6 with respect to the amount (the value of the coefficient b may be variable according to the intake air amount Ga of the internal combustion engine 1).
kpm2Fr: PM oxidation amount calculated in step S303, S304, or S306

  Next, in step S308, it is determined whether or not the value cpmFr calculated in step S307 is greater than or equal to zero. If a negative determination is made in step S308, then in step S310, zero is calculated as the calculated value of the PM accumulation amount cpmFr in the upstream protruding portion of the inner pipe 6. On the other hand, if an affirmative determination is made in step S308, then in step S309, the PM accumulation amount cpmFr calculated in step S307 is calculated as the calculated value of the PM accumulation amount cpmFr in the upstream protruding portion of the inner pipe 6.

  In the flow shown in FIG. 5, the cooling water temperature Tw detected by the water temperature sensor 21, the air-fuel ratio A / F of the internal combustion engine 1, and the air flow meter 12 are detected in step S 401 as in step S 301 of the flow shown in FIG. 4. Based on the intake air amount Ga of the internal combustion engine 1, the PM discharge amount kpm1 from the internal combustion engine 1 is calculated.

  Next, in step S402, it is determined whether or not fuel cut control is being executed. If an affirmative determination is made in step S402, then the process of step S403 is executed. In step S403, based on the temperature Tgout of the exhaust gas flowing out from the EHC 1 detected by the second exhaust temperature sensor 24, the oxidation amount kpm2Rr of PM deposited on the downstream protrusion of the inner pipe 6 during the execution of the fuel cut control. Is calculated.

  As the temperature Tgout of the exhaust gas flowing out from the EHC 1 is higher, the oxidation amount kpm2Rr of PM deposited on the downstream protruding portion of the inner pipe 6 during execution of the fuel cut control increases. However, when the temperature Tgout of the exhaust gas flowing out from the EHC 1 is lower than the oxidation temperature of PM, the PM oxidation amount kpm2Rr becomes zero. Such a relationship between the temperature Tgout of the exhaust gas flowing out from the EHC 1 and the oxidation amount kpm2Rr of PM deposited on the downstream protruding portion of the inner pipe 6 during execution of fuel cut control is obtained in advance based on experiments or the like. Stored in the ECU 20 as a map or a function. In step S403, the oxidation amount kpm2Rr of PM deposited on the downstream protrusion of the inner pipe 6 during execution of the fuel cut control is calculated using this map or function.

    On the other hand, when a negative determination is made in step S302, the fuel cut control is not executed, and therefore, PM deposited on the downstream protruding portion of the inner pipe 6 is not oxidized. Therefore, in this case, in step S404, zero is calculated as the oxidation amount kpm2Rr of PM deposited on the downstream protruding portion of the inner pipe 6. As described above, even if air-fuel ratio perturbation control is executed, PM deposited on the downstream protruding portion of the inner pipe 6 is not easily oxidized. The accumulated PM is oxidized only when the fuel cut control is executed, and the oxidation amount kpm2Rr of PM accumulated on the downstream protruding portion of the inner pipe 6 is calculated.

Following the process of step S403 or S404, the process of step S405 is executed. In step S405, the PM deposition amount cpmRr in the downstream protrusion of the inner pipe 6 is calculated using the following equation (2).
cpmRr (i) = cpmRr (i−1) + kpm1 * c−kpm2Rr (2)
cpmRr (i): Current PM accumulation amount cpmRr (i-1): PM accumulation amount calculated by the previous execution of this flow kpm1: PM emission amount calculated in step S401 c: PM emission from the internal combustion engine 1 A coefficient indicating the ratio of the amount of PM adhering to the protruding portion on the downstream side of the inner pipe 6 with respect to the amount (the value of the coefficient c may be variable depending on the intake air amount Ga of the internal combustion engine 1).
kpm2Fr: oxidation amount of PM calculated in step S403 or S404

  Next, in step S406, it is determined whether or not the value cpmRr calculated in step S405 is greater than or equal to zero. If a negative determination is made in step S406, then in step S408, zero is calculated as the calculated value of the PM accumulation amount cpmRr in the downstream protruding portion of the inner pipe 6. On the other hand, if an affirmative determination is made in step S406, then in step S407, the PM accumulation amount cpmRr calculated in step S405 is calculated as the calculated value of the PM accumulation amount cpmRr in the downstream protruding portion of the inner pipe 6.

[Control flow of air-fuel ratio perturbation control]
Next, the flow of air-fuel ratio perturbation control according to this embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing a flow of air-fuel ratio perturbation control according to the present embodiment. This flow is stored in advance in the ECU 20 and is repeatedly executed by the ECU 20.

  In this flow, it is determined in step S501 whether air-fuel ratio perturbation control is being executed. If an affirmative determination is made in step S501, the process of step S502 is executed next. If a negative determination is made, the execution of this flow is temporarily terminated.

  In step S502, the PM accumulation amount cpmFr at the upstream protruding portion of the inner pipe 6 and the PM accumulation amount cpmRr at the downstream protruding portion of the inner pipe 6 are read, which are respectively calculated by the method described above and stored in the ECU 20.

  Next, in step S503, the temperature Tgin of the exhaust gas flowing into the EHC 1 detected by the first exhaust temperature sensor 23 is a temperature at which the temperature of the EHC 1 does not rise to the oxidation temperature of PM even when the air-fuel ratio perturbation control is executed. It is determined whether or not the exhaust gas temperature is higher than a predetermined exhaust gas temperature Tg0. If an affirmative determination is made in step S503, the process of step S504 is executed next, and if a negative determination is made, the process of step S505 is executed.

  In step S504, it is determined whether or not a value obtained by subtracting the PM accumulation amount cpmFr in the upstream protrusion of the inner tube 6 from the PM accumulation amount cpmRr in the downstream protrusion of the inner tube 6 is equal to or greater than a predetermined accumulation amount difference Δcpm. Is done. When an affirmative determination is made in step S504, it can be determined that the PM deposition amount cpmFr at the upstream protruding portion of the inner pipe 6 is smaller than the PM deposition amount cpmRr at the downstream protruding portion of the inner pipe 6 by a predetermined deposition amount difference Δcpm or more. In this case, next, in step S505, the execution of the air-fuel ratio perturbation control is stopped.

  On the other hand, if a negative determination is made in step S504, the PM accumulation amount cpmFr in the upstream protrusion of the inner pipe 6 is still smaller than the PM accumulation amount cpmRr in the downstream protrusion of the inner pipe 6 by a predetermined accumulation amount difference Δcpm or more. It can be judged that it is not. In this case, in step S506, the execution of the air-fuel ratio perturbation control is continued.

<Example 3>
The intake / exhaust system and the EHC configuration of the internal combustion engine according to this embodiment are the same as those in the first embodiment. Also in the present embodiment, as in the first embodiment, by performing fuel cut control and air-fuel ratio perturbation control, PM deposited on the protruding portion of the inner pipe 6 of the EHC 1 is oxidized and removed. Hereinafter, the air-fuel ratio perturbation control according to the present embodiment will be described with respect to differences from the first embodiment.

[Air-fuel ratio perturbation control]
The higher the speed of the vehicle on which the internal combustion engine 10 is mounted, the longer the execution time of the control when the operation state of the internal combustion engine 10 is reduced and the fuel cut control is executed. Therefore, removal of PM deposited on the downstream protrusion of the inner pipe 6 due to execution of the fuel cut control is facilitated. Further, the higher the temperature of the exhaust gas flowing into EHC1, the higher the temperature of EHC1. Therefore, when the operation state of the internal combustion engine 1 is decelerated and the fuel cut control is executed, the removal of PM accumulated on the downstream protruding portion of the inner pipe 6 is easily promoted.

  Therefore, in the present embodiment, when the air-fuel ratio perturbation control is executed, the vehicle speed is detected by the vehicle speed sensor 26 and the temperature of the exhaust gas flowing into the EHC 1 detected by the first exhaust gas temperature sensor 23. Thus, the length of execution time of the control is corrected. Specifically, when the vehicle speed is high, the execution time of the air-fuel ratio perturbation control is made longer than when the vehicle speed is low. Further, when the temperature of the exhaust gas flowing into the EHC 1 is high, the execution time of the air-fuel ratio perturbation control is made longer than when the temperature of the exhaust gas is low.

  FIG. 7 is a diagram illustrating the relationship between the vehicle speed (vehicle speed) and the correction coefficient for correcting the execution time of the air-fuel ratio perturbation control according to the present embodiment. FIG. 8 is a diagram showing the relationship between the temperature of the exhaust gas flowing into the EHC 1 (inflow exhaust gas temperature) and the correction coefficient for correcting the execution time of the air-fuel ratio perturbation control according to this embodiment. As shown in FIG. 7 or 8, the correction coefficient value increases as the speed of the vehicle increases and as the temperature of the exhaust gas flowing into the EHC 1 increases. In this embodiment, by multiplying these correction coefficients by the length of the execution time of the air-fuel ratio perturbation control calculated based on a predetermined or integrated value of the execution time of the fuel cut control, The length of execution time of the air-fuel ratio perturbation control is corrected. Thereby, the execution time of the air-fuel ratio perturbation control can be lengthened as the speed of the vehicle is higher and the temperature of the exhaust gas flowing into the EHC 1 is higher.

  If the execution time of the air-fuel ratio perturbation control is lengthened, it is possible to increase the removal amount of PM deposited on the upstream protruding portion of the inner pipe 6 that is removed by executing the air-fuel ratio perturbation control. Therefore, according to the present embodiment, when the fuel cut control is executed after the execution of the air-fuel ratio perturbation control is completed, the removal of the PM accumulated on the projecting portion on the downstream side of the inner pipe 6 is facilitated. By executing the fuel ratio perturbation control, it is possible to promote the removal of PM deposited on the upstream protruding portion of the inner pipe 6. As a result, after the execution of the air-fuel ratio perturbation control, the fuel cut control is executed in a state where the temperature of the EHC is equal to or higher than the oxidation temperature of the PM, so that the PM deposited on the downstream protruding portion of the inner pipe 6 is removed. In this case, the difference between the PM amount remaining in the upstream protruding portion of the inner pipe 6 and the PM amount remaining in the downstream protruding portion of the inner pipe 6 can be further reduced.

  In the present embodiment, it is not always necessary to correct the execution time of the air-fuel ratio perturbation control based on both the vehicle speed and the temperature of the exhaust gas flowing into the EHC 1. The execution time may be corrected.

[Modification]
Here, a modification of the present embodiment will be described. In the present modification, when air-fuel ratio perturbation control is performed, the PM accumulation amount at the upstream protrusion of the inner pipe 6 is more predetermined than the PM accumulation amount at the downstream protrusion of the inner pipe 6 as in the second embodiment. The execution of the control is continued until the accumulation amount difference becomes smaller.

In this modification, when the air-fuel ratio perturbation control is executed, the vehicle speed detected by the vehicle speed sensor 26 and the EH detected by the first exhaust temperature sensor 23 are detected.
Based on the temperature of the exhaust gas flowing into C1, the value of the predetermined accumulation amount difference is corrected. Specifically, when the vehicle speed is high, the predetermined accumulation amount difference is made larger than when the vehicle speed is low. Further, when the temperature of the exhaust gas flowing into the EHC 1 is high, the predetermined accumulation amount difference is made larger than when the temperature of the exhaust gas is low.

  Also in this case, the predetermined accumulation amount difference is multiplied by a correction coefficient determined based on the vehicle speed as shown in FIG. 7 and a correction coefficient determined based on the temperature of the exhaust gas flowing into the EHC 1 as shown in FIG. The value of the predetermined accumulation amount difference is corrected. As a result, the larger the vehicle speed and the higher the temperature of the exhaust gas flowing into the EHC 1, the larger the predetermined accumulation amount difference.

  When the predetermined accumulation amount difference increases, the execution time of the air-fuel ratio perturbation control becomes longer. Therefore, also in this modification, the execution time of the air-fuel ratio perturbation control can be lengthened as the speed of the vehicle increases and the temperature of the exhaust gas flowing into the EHC 1 increases. Therefore, the same effect as described above can be obtained.

  In this modification as well, it is not always necessary to correct the predetermined accumulation amount difference based on both the vehicle speed and the temperature of the exhaust gas flowing into the EHC 1, and the predetermined accumulation amount difference is corrected based on either one. You may do it.

  In addition, in a vehicle equipped with a hybrid system having an internal combustion engine and an electric motor as a drive source, the effect of engine braking is transmitted by transmitting the rotation of the drive shaft to the internal combustion engine on which fuel cut control is performed when the vehicle is decelerated. (Hereinafter, such a mode is referred to as a B range mode) may be selected. When such a B range mode is selected, the fuel cut control is easily performed. Therefore, the removal of PM deposited on the protruding portion on the downstream side of the EHC inner pipe is facilitated. Therefore, when the B range mode is selected, the air fuel ratio perturbation control is made longer, so that it accumulates in the upstream protruding portion of the inner pipe of the EHC by executing the air fuel ratio perturbation control. PM removal may be promoted. As a result, the difference between the PM amount remaining in the upstream protruding portion of the inner pipe after execution of the air-fuel ratio perturbation control and the PM amount remaining in the downstream protruding portion of the inner pipe after execution of the fuel cut control is made smaller. be able to.

1 ... Electric heating catalyst (EHC)
2 ... exhaust pipe 3 ... catalyst carrier 7 ... electrode 10 internal combustion engine 11 intake pipe 12 air flow meter 13 throttle valve 21 water temperature sensor 22 air-fuel ratio sensor 23 First exhaust temperature sensor 24 Second exhaust temperature sensor 25 Accelerator opening sensor 26 Vehicle speed sensor 27 Supply power control unit 31 Three-way catalyst

Claims (7)

Electric heating comprising: a heating element that generates heat when energized and heats the catalyst by generating heat; a case that houses the heating element; and an insulating member that is provided between the heating element and the case to insulate electricity. Type catalyst is provided in the exhaust passage,
An internal combustion engine control system in which the air-fuel ratio is controlled in the vicinity of the theoretical air-fuel ratio during normal operation,
A fuel cut control execution unit for executing fuel cut control for stopping fuel injection in the internal combustion engine during deceleration operation;
The air-fuel ratio of the internal combustion engine is set between an air-fuel ratio richer than the stoichiometric air-fuel ratio and an air-fuel ratio leaner than the stoichiometric air-fuel ratio in order to oxidize particulate matter deposited on the end of the insulating member of the electrically heated catalyst. An air-fuel ratio perturbation control execution unit for executing air-fuel ratio perturbation control that fluctuates in a predetermined cycle at
Fuel cut control is performed by the fuel cut control execution unit when the temperature of the electrically heated catalyst is equal to or higher than the oxidation temperature of the particulate matter after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. The execution time of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit, the amplitude of the air-fuel ratio, or the execution based on the integrated value of the execution time of the control or the number of executions thereof An internal combustion engine control system that adjusts at least one of the lengths of time.   Fuel cut control is performed by the fuel cut control execution unit when the temperature of the electrically heated catalyst is equal to or higher than the oxidation temperature of the particulate matter after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the control is executed is equal to or greater than a predetermined integral time, or when the number of executions is equal to or greater than the predetermined number of times, the next air-fuel ratio perturbation by the air-fuel ratio perturbation control execution unit The control system for an internal combustion engine according to claim 1, wherein the control is executed.   Fuel cut control is performed by the fuel cut control execution unit when the temperature of the electrically heated catalyst is equal to or higher than the oxidation temperature of the particulate matter after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the control is executed is larger than when the integrated value of the execution time of the control is small, or when the execution number of the control is large, 3. The control system for an internal combustion engine according to claim 1, wherein the air-fuel ratio amplitude of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit is made larger than when the air-fuel ratio perturbation control is small.   Fuel cut control is performed by the fuel cut control execution unit when the temperature of the electrically heated catalyst is equal to or higher than the oxidation temperature of the particulate matter after the previous execution of the air / fuel ratio perturbation control by the air / fuel ratio perturbation control execution unit. When the integrated value of the execution time of the control when the control is executed is larger than when the integrated value of the execution time of the control is small, or when the execution number of the control is large, The control system for an internal combustion engine according to any one of claims 1 to 3, wherein an execution time of the next air-fuel ratio perturbation control by the air-fuel ratio perturbation control execution unit is made longer than when the air-fuel ratio perturbation control execution time is small.   After the air-fuel ratio perturbation control execution unit starts executing the air-fuel ratio perturbation control, the amount of particulate matter accumulated at the upstream end of the insulating member of the electrically heated catalyst is the downstream end of the insulating member. The control system for an internal combustion engine according to any one of claims 1 to 4, wherein the air-fuel ratio perturbation control is continued until a difference of a predetermined accumulation amount or less than an accumulation amount of particulate matter in the section. When the speed of the vehicle on which the air-fuel ratio perturbation control execution unit is mounted is high, the speed of the exhaust gas flowing into the electrically heated catalyst is higher when the speed of the vehicle is low or when the speed of the vehicle is low. 6. The control system for an internal combustion engine according to claim 1, wherein an execution time of the air-fuel ratio perturbation control is made longer than when the temperature of the exhaust gas is low.   When the speed of the vehicle on which the air-fuel ratio perturbation control execution unit is mounted is high, the speed of the exhaust gas flowing into the electrically heated catalyst is higher when the speed of the vehicle is low or when the speed of the vehicle is low. 5. The control system for an internal combustion engine according to claim 4, wherein the predetermined accumulation amount difference is made larger than when the temperature of the exhaust gas is low.

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