JP2008025506A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine controller which can surely prevent the generation of the smell of the exhaust gas from a catalyst and also can suppress the deterioration of the catalyst as much as possible. <P>SOLUTION: In carrying out a decelerating fuel cut operation, the decelerating F/C period throttle opening control is executed if a fuel increment history exists (step 104). During the execution, whether or not a downstream catalyst is in a lean state, in other words, whether or not the generation of hydrogen sulfide is stopped, is judged. When the downstream catalyst becomes in the lean state, the inlet air volume after that time is integrated. The decelerating F/C period throttle opening control is continued until the integrated inlet air volume becomes a required judging value. As a result, air can be supplied into an exhaust passage until hydrogen sulfide remaining in the exhaust passage on the downstream side of the downstream catalyst is removed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

When an automobile is accelerated rapidly, the fuel injection amount is generally increased and combustion is performed at an air / fuel ratio richer than the stoichiometric air / fuel ratio. In that case, unburned fuel flows into the exhaust purification catalyst. When unburned fuel flows into the catalyst, sulfur oxide adsorbed on the catalyst may be reduced by the unburned fuel, and hydrogen sulfide (H ₂ S) may be generated. This hydrogen sulfide has a strange odor. For this reason, conventionally, when the vehicle stops immediately after rapid acceleration, an occupant may feel the odor of hydrogen sulfide in the exhaust gas (hereinafter referred to as “catalyst exhaust odor”).

  Japanese Patent Laid-Open No. 2006-29323 discloses that for the purpose of preventing the generation of catalyst exhaust odor, the throttle opening is made larger than the idle opening during deceleration accompanied by a fuel cut, and a large amount of air (oxygen) is supplied to the catalyst. ) Has been disclosed. If a large amount of air is circulated through the catalyst during deceleration, the catalyst can be in a lean state (oxidized state) until the vehicle stops. When the catalyst becomes lean, the production of hydrogen sulfide in the catalyst stops.

JP 2006-29323 A

  By the way, the catalyst has such a property that it deteriorates more easily as a large amount of air (oxygen) flows in a high temperature state. For this reason, conventionally, when control is performed to increase the throttle opening during deceleration with fuel cut, when the catalyst enters a lean state in order to prevent excessive air from flowing through the catalyst. Thus, the throttle opening is returned to the idle opening.

  However, the above conventional control cannot completely prevent the generation of catalyst exhaust odor. According to the knowledge of the present inventors, this is considered to be as follows. Generation of hydrogen sulfide in the catalyst stops when the catalyst enters a lean state, but at this point, hydrogen sulfide still remains in the exhaust pipe and the muffler downstream from the catalyst. For this reason, it is considered that after the vehicle stops, hydrogen sulfide remaining in the exhaust pipe, particularly in the muffler, is gradually released from the tail pipe end, and a catalyst exhaust odor is felt.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a control device for an internal combustion engine capable of suppressing deterioration of the catalyst as much as possible while reliably preventing generation of catalyst exhaust odor. And

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A catalyst disposed in the exhaust passage of the internal combustion engine;
Fuel cut means for performing fuel cut during deceleration of the internal combustion engine;
An air increase means for performing an air increase control for increasing the amount of air flowing through the catalyst more than that during idling when a fuel cut during deceleration is performed when the catalyst is in a rich state;
Determination means for determining whether or not the catalyst is in a lean state during the execution of the air increase control;
Integrated air amount acquisition means for acquiring the integrated air amount flowing downstream from the catalyst;
With
When it is determined that the catalyst is in a lean state and the accumulated air amount has reached a predetermined determination value, the air increase control is terminated.

The second invention is the first invention, wherein
The determination value is set to a value that can secure an air amount necessary to drive out hydrogen sulfide remaining in the exhaust passage downstream of the catalyst.

The third invention is the first or second invention, wherein
An intake air amount adjusting means for adjusting the amount of air sucked into the internal combustion engine;
The air increasing means controls the amount of air flowing through the catalyst by controlling the intake air amount adjusting means.

According to a fourth invention, in any one of the first to third inventions,
A return air amount acquisition means for acquiring a return air amount that is the amount of air actually taken into the internal combustion engine when returning from the fuel cut;
Ignition retarding means for retarding the ignition timing as the return air amount increases;
Is further provided.

According to a fifth invention, in any one of the first to fourth inventions,
Vehicle speed detection means for detecting the vehicle speed;
Flow rate correction means for correcting the flow rate of air flowing through the catalyst according to the vehicle speed when the air increase control is performed;
Is further provided.

The sixth invention is the fifth invention, wherein
The flow rate correction means increases the flow rate of the air flowing through the catalyst as the vehicle speed is lower when the air increase control is performed.

According to a seventh invention, in any one of the first to sixth inventions,
Vehicle speed detection means for detecting the vehicle speed;
A determination value correcting means for increasing the determination value when the vehicle speed is low when the air increase control is performed;
Is further provided.

  According to the first aspect of the present invention, when the catalyst disposed in the exhaust passage of the internal combustion engine is in the rich state, the air increase control is performed so that the amount of air flowing through the catalyst is larger than that in the idling state when the fuel is cut off. Can be implemented. When the air increase control is performed, the air increase control is terminated when the integrated air amount flowing downstream from the catalyst reaches a predetermined determination value after the determination that the catalyst is in a lean state. Can be made. For this reason, the air increase control can be continued until the hydrogen sulfide remaining in the exhaust passage on the downstream side of the catalyst is sufficiently removed. Therefore, even if the exhaust gas drifts into the vehicle when the vehicle is stopped or at a very low speed, it is possible to reliably prevent the occupant from feeling the catalyst exhaust odor. In addition, since air exceeding the amount necessary for preventing the generation of catalyst exhaust odor is not allowed to flow through the catalyst, deterioration of the catalyst can be suppressed as much as possible.

  According to the second aspect of the invention, the determination value is set to a value that can secure an integrated air amount necessary to drive off the hydrogen sulfide remaining in the exhaust passage downstream of the catalyst. It can be expressed more reliably.

  According to the third aspect, when the air increase control is executed, the amount of air flowing through the catalyst can be controlled by controlling the intake air amount adjusting means for adjusting the amount of air taken into the internal combustion engine. For this reason, the said effect can be acquired, without using a special apparatus, for example, the secondary air supply apparatus etc. which introduce | transduce secondary air into an exhaust system.

  According to the fourth aspect of the invention, the return air amount that is the amount of air actually sucked into the internal combustion engine upon return from the deceleration fuel cut is acquired, and the ignition timing is retarded as the return air amount increases. Can do. When the air increase control is executed during the deceleration fuel cut, the intake air amount may be larger than normal when returning from the deceleration fuel cut. According to the fourth invention, when such a situation occurs, the ignition timing is retarded, so that it is possible to suppress the generation of excessive torque. For this reason, when returning from the deceleration fuel cut, it is possible to reliably prevent the engine speed from becoming excessively high or causing a torque shock.

  According to the fifth aspect of the invention, the flow rate of the air flowing through the catalyst can be corrected according to the vehicle speed when the air increase control is performed. For this reason, it is possible to set the optimum air flow rate according to the vehicle speed in order to prevent the generation of catalyst exhaust odor and suppress the progress of catalyst deterioration as much as possible.

  According to the sixth aspect of the invention, when the air increase control is performed, the flow rate of the air flowing through the catalyst can be increased as the vehicle speed is lower. For this reason, when the vehicle speed is low and there is a high possibility that the vehicle will stop or become extremely slow in a short time, the flow rate of the air flowing in the exhaust passage is increased and the remaining hydrogen sulfide is quickly removed. can do. Therefore, even when the vehicle is actually stopped or in an extremely low speed state in a short time, it is possible to more reliably prevent the occupant from feeling the catalyst exhaust odor. In addition, when it can be determined that the vehicle speed is high and there is a large margin of time until the vehicle is stopped or extremely low, the amount of air flowing through the catalyst can be prevented from becoming larger than necessary. For this reason, the progress of the deterioration of the catalyst can be further suppressed while the generation of the catalyst exhaust odor is prevented.

  According to the seventh aspect of the invention, when the air increase control is performed, the determination value of the integrated air amount that is used for the end determination of the air increase control can be increased as the vehicle speed is lower. For this reason, when the vehicle speed is low, that is, when there is a high possibility that the exhaust gas drifts in the vehicle, the total amount of air flowing through the exhaust passage can be increased, so that the remaining hydrogen sulfide is more reliably removed. be able to. Therefore, even when the vehicle speed is low, the generation of catalyst exhaust odor can be more reliably prevented. Further, when the vehicle speed is high and the possibility of exhaust gas drifting in the vehicle is low, the total amount of air flowing through the catalyst can be prevented from becoming larger than necessary. For this reason, the progress of the deterioration of the catalyst can be further suppressed while the generation of the catalyst exhaust odor is prevented.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of this embodiment includes a spark ignition type internal combustion engine 10. The internal combustion engine 10 is mounted on an automobile. That is, the power generated by the internal combustion engine 10 is transmitted to the driving wheels of the automobile via a transmission (not shown).

  An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. An air flow meter 16 that detects the amount of air flowing through the intake passage 12, that is, the intake air amount Ga of the internal combustion engine 10, is disposed in the intake passage 12. A throttle valve 18 is disposed on the downstream side of the air flow meter 16. The throttle valve 18 is an electronically controlled valve that is driven by a throttle motor 20 based on an accelerator opening or the like. In the vicinity of the throttle valve 18, a throttle position sensor 22 for detecting the throttle opening is disposed. The accelerator opening is detected by an accelerator position sensor 24 provided in the vicinity of the accelerator pedal.

  The internal combustion engine 10 is a multi-cylinder engine having a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders. A surge tank 25 for distributing intake air to each cylinder is provided downstream of the throttle valve 18.

  A fuel injection valve 26 for injecting fuel is disposed in the intake port of each cylinder. Each cylinder is provided with an intake valve 28 and an exhaust valve 29 for connecting or disconnecting the intake port and the exhaust port and the cylinder (combustion chamber). Further, each cylinder is provided with a spark plug 30 that emits a spark for igniting the air-fuel mixture in the cylinder. The internal combustion engine 10 is not limited to the configuration shown in the figure, and may be, for example, a system in which fuel is directly injected into a cylinder.

  Each cylinder of the internal combustion engine 10 includes a cylinder 32 and a piston 34. A crank angle sensor 38 for detecting the rotation angle of the crankshaft 36 is attached in the vicinity of the crankshaft 36 that is rotationally driven by the reciprocating motion of the piston 34. The crank angle sensor 38 is a sensor that reverses the Hi output and the Lo output each time the crankshaft 36 rotates by a predetermined rotation angle. According to the output of the crank angle sensor 38, the rotational position and rotational speed (engine speed NE) of the crankshaft can be detected.

  The exhaust passage 14 of the internal combustion engine 10 is provided with an upstream catalyst 40 and a downstream catalyst 42 disposed downstream thereof as an exhaust purification catalyst. The upstream catalyst 40 is a relatively small capacity catalyst generally called a start converter (SC). The downstream catalyst 42 is a catalyst having a relatively large capacity, generally called an underfloor converter (UFC). The upstream catalyst 40 is disposed at a position closer to the exhaust port than the downstream catalyst 42, and exhaust gas having a high temperature flows in. Therefore, the upstream catalyst 40 is warmed up in a short time from the start and has good exhaust purification performance. Demonstrate. On the other hand, the downstream catalyst 42 takes a longer time to warm up than the upstream catalyst 40, but has a large capacity, and thus exhibits excellent exhaust purification performance once warmed up.

  An oxygen sensor 44 is disposed near the outlet of the downstream catalyst 42. The oxygen sensor 44 has a characteristic of suddenly changing the output depending on whether the air-fuel ratio of the exhaust gas at that position is rich or lean.

  The exhaust gas that has passed through the downstream catalyst 42 sequentially passes through the exhaust pipe 46, the muffler 47, and the tail pipe 48, and is released into the atmosphere.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. The ECU 50 can control the operating state of the internal combustion engine 10 based on those sensor outputs.

[Features of Embodiment 1]
Next, an outline of the operation of the system in the present embodiment will be described.

(Throttle valve control during deceleration fuel cut)
The system of the present embodiment is a process for stopping fuel injection from the fuel injection valve 26 when the internal combustion engine 10 is decelerating (accelerator OFF state) and the engine speed NE is equal to or higher than a set value, that is, fuel cut ( Implement F / C). The fuel cut performed during deceleration is hereinafter referred to as “deceleration fuel cut”.

  Further, the system of the present embodiment performs fuel increase control for increasing the fuel injection amount so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio when the load is high. When the fuel increase control is performed, rich exhaust gas containing unburned fuel flows through the exhaust passage 14. Therefore, the upstream catalyst 40 and the downstream catalyst 42 are in a state where unburned fuel is abundant (hereinafter referred to as “rich state”).

During normal operation, sulfur oxides contained in the exhaust gas are adsorbed and accumulated by the upstream catalyst 40 and the downstream catalyst 42. When the upstream catalyst 40 and the downstream catalyst 42 are in a rich state and are at a high temperature, the unburnt fuel acts as a reducing agent, so that the sulfur oxide adsorbed on the upstream catalyst 40 and the downstream catalyst 42 Is reduced and hydrogen sulfide (H ₂ S) is easily generated.

  As described above, when the fuel increase control is performed, the upstream catalyst 40 and the downstream catalyst 42 are in a rich state and become high temperature. For this reason, it becomes easy to produce | generate hydrogen sulfide which has a strange odor in exhaust gas.

  Conversely, in order to prevent hydrogen sulfide from being generated in the upstream catalyst 40 and the downstream catalyst 42, the upstream catalyst 40 and the downstream catalyst 42 are in a state where oxygen is abundant (the upstream catalyst 40 and the downstream catalyst 42 fill oxygen). Occluded state). This state is hereinafter referred to as “lean state”.

  Even if hydrogen sulfide is generated in the exhaust gas, if the vehicle is traveling at a speed above a certain level, the exhaust gas will not drift inside the vehicle, so the smell of exhaust gas caused by hydrogen sulfide ( (Hereinafter referred to as “catalyst exhaust odor”) is not felt by the passenger. However, when the vehicle stops or the vehicle speed is extremely low, there is a possibility that exhaust gas drifts into the vehicle. For this reason, if hydrogen sulfide is contained in the exhaust gas in a situation where the vehicle stops or the vehicle speed becomes extremely slow immediately after the fuel increase control is performed, there is a possibility that the occupant may feel the catalyst exhaust odor.

  When the internal combustion engine 10 is decelerated immediately after the fuel increase control is performed, hydrogen sulfide is generated in the upstream catalyst 40 and the downstream catalyst 42, and the vehicle may stop soon. For this reason, it will be in the situation where a passenger | crew may feel a catalyst exhaust odor. In this case, in order to prevent the generation of the catalyst exhaust odor, it is necessary to make the upstream catalyst 40 and the downstream catalyst 42 lean while the internal combustion engine 10 is decelerating to stop the production of hydrogen sulfide.

  Therefore, in the present embodiment, the internal combustion engine 10 is decelerated immediately after the fuel increase control is performed, and the throttle valve 18 is opened to be larger than the idle opening while the deceleration fuel cut is being executed (hereinafter referred to as “deceleration”). "Throttle opening control during F / C"). During the deceleration fuel cut, the air sucked into the internal combustion engine 10 flows into the exhaust passage 14 as it is. Therefore, according to the throttle opening control during deceleration F / C, a large amount of air can flow to the upstream catalyst 40 and the downstream catalyst 42 during deceleration. Therefore, since the upstream catalyst 40 and the downstream catalyst 42 can be sufficiently leaned during deceleration, the production of hydrogen sulfide can be stopped.

  When air flows into the rich upstream catalyst 40 and downstream catalyst 42, it is oxidized from the upstream side. That is, the upstream catalyst 40 is in a lean state first, and then the downstream catalyst 42 is in a lean state. Whether or not the downstream catalyst 42 is in a lean state can be determined by various methods, but in the present embodiment, it can be determined by the output of the oxygen sensor 44. That is, it can be determined that the downstream catalyst 42 is in a lean state when the output of the oxygen sensor 44 changes from a rich output to a lean output.

  By the way, the upstream catalyst 40 and the downstream catalyst 42 have a property that deterioration is more likely to proceed as a large amount of air flows when the temperature is high. For this reason, even when the throttle opening control at the time of deceleration F / C is performed to prevent the catalyst exhaust odor, from the viewpoint of suppressing the deterioration of the upstream catalyst 40 and the downstream catalyst 42, air does not flow more than necessary. It is desirable to make it. Therefore, conventionally, when the downstream catalyst 42 is in a lean state, the throttle opening control during deceleration F / C is terminated and the throttle opening is returned to the idle opening.

  However, when the downstream catalyst 42 is in a lean state, hydrogen sulfide still remains in the exhaust pipe 46 on the downstream side, particularly in the muffler 47. When the throttle opening is returned to the idle opening, the air flow rate is reduced, so that the hydrogen sulfide in the exhaust pipe 46 and the muffler 47 remains without being discharged. For this reason, even after the vehicle stops, the hydrogen sulfide remaining inside the exhaust pipe 46 and the muffler 47 is gradually released from the tail pipe 48, and the occupant may feel a catalyst exhaust odor. Thus, if the throttle opening control at the time of deceleration F / C is terminated when the downstream catalyst 42 is in a lean state, a situation in which the catalyst exhaust odor cannot be completely prevented may occur.

  In view of the circumstances as described above, in order to prevent the catalyst exhaust odor more reliably, the exhaust pipe 46, the muffler 47, and the tail pipe 48 are not used until the vehicle stops or becomes extremely low speed. It is necessary to destroy all hydrogen sulfide remaining until the end. Therefore, in the present embodiment, the deceleration F is continued until the hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 is expelled even after the downstream catalyst 42 becomes lean. It was decided to continue throttle opening control at / C.

  Specifically, first, the air necessary and sufficient to drive out the hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 after the downstream catalyst 42 becomes lean. The total flow rate (integrated air amount) is set in advance as a determination value. That is, this determination value is set to a larger value as the volumes of the exhaust pipe 46 and the muffler 47 are larger. Then, the air amount flowing downstream of the downstream catalyst 42 after the downstream catalyst 42 becomes lean is integrated, and the throttle opening control at the deceleration F / C is continued until the integrated air amount reaches the determination value. At that time, the throttle opening is returned to the idle opening.

  As a result, the hydrogen sulfide remaining inside the exhaust pipe 46, the muffler 47, and the tail pipe 48 can be surely expelled before the vehicle stops or becomes extremely low speed. For this reason, when a vehicle stops or becomes very low speed, it can prevent reliably that a passenger | crew senses a catalyst exhaust odor. Further, after the hydrogen sulfide is driven out, the throttle opening is returned to the idle opening to reduce the intake air amount. For this reason, progress of deterioration of the upstream catalyst 40 and the downstream catalyst 42 can be suppressed as much as possible while reliably preventing the catalyst exhaust odor.

(Ignition retarding control after deceleration fuel cut recovery)
FIG. 2 is a diagram for explaining the ignition retard control after returning from the deceleration fuel cut, which is performed in the present embodiment. In FIG. 2, a thin broken line indicates a case where the throttle opening during throttle opening control during deceleration F / C is relatively large, and a broken line indicates a moderate throttle opening during throttle opening control during deceleration F / C. Shows the case.

  As shown in FIG. 2B, when the throttle valve 18 is suddenly closed when returning from the deceleration fuel cut, it is positioned on the upstream side of the throttle valve 18 as shown by a thick line in FIG. The amount of intake air detected by the air flow meter 16 decreases rapidly. However, as indicated by a thin solid line or a broken line in FIG. 2C, the amount of air actually sucked into the internal combustion engine 10 does not decrease suddenly but gradually decreases. This is because the air in the surge tank 25 continues to flow into the internal combustion engine 10 even after the throttle valve 18 is closed.

  For this reason, when the throttle opening control at the time of deceleration F / C is performed, the amount of air actually taken into the internal combustion engine 10 after returning from the deceleration fuel cut tends to be larger than normal. As a result, the torque is excessively generated immediately after returning from the deceleration fuel cut, so that the engine speed NE is likely to be too high or a torque shock is likely to occur. Therefore, in the present embodiment, the ignition timing is retarded as the amount of air actually taken into the internal combustion engine 10 at the time of return from the deceleration fuel cut. If the ignition timing is retarded, the torque can be reduced, so that the above problem can be avoided.

[Specific Processing in Embodiment 1]
FIG. 3 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined time.

  According to the routine shown in FIG. 3, it is first determined whether or not the deceleration fuel cut is being executed (step 100). If it is determined that the deceleration fuel cut is being executed, it is next determined whether or not there is a fuel increase history (step 102). The fuel increase history is a history indicating that fuel increase control for dealing with high load operation has been performed recently. If there is a fuel increase history, it can be determined that the upstream catalyst 40 and the downstream catalyst 42 are in a rich state. In other words, it can be determined that hydrogen sulfide is easily generated in the upstream catalyst 40 and the downstream catalyst 42. Therefore, if it is determined in step 102 that there is a fuel increase history, throttle opening control during deceleration F / C is executed to stop the generation of hydrogen sulfide in the upstream catalyst 40 and the downstream catalyst 42 ( Step 104). That is, control for opening the throttle valve 18 to a predetermined opening larger than the idle opening is performed.

  On the other hand, if it is determined in step 100 that deceleration fuel cut is not being executed, or if it is determined in step 102 that there is no fuel increase history, throttle opening control during deceleration F / C is executed. do not have to. Therefore, in these cases, execution of throttle opening control during deceleration F / C is prohibited (step 106), and after the fuel increase history is deleted (step 108), the current processing cycle is ended. .

  On the other hand, when the throttle opening control during deceleration F / C is executed in step 104, a large amount of air flows through the exhaust passage 14 by opening the throttle valve 18. Thereby, the upstream catalyst 40 and the downstream catalyst 42 are sequentially oxidized from the upstream side, and change from the rich state to the lean state. During execution of such throttle opening control during deceleration F / C, according to the routine shown in FIG. 3, it is determined whether or not the entire downstream catalyst 42 has become lean (step 110). This determination is performed based on the output of the oxygen sensor 44 in this embodiment. That is, it can be determined that the downstream catalyst 42 is in the lean state when the output of the oxygen sensor 44 changes from the rich output to the lean output.

  In the present invention, the method for determining whether or not the downstream catalyst 42 is in a lean state is not limited to the above method, and various known methods such as a method for estimating based on the oxygen storage capacity may be used. Can be adopted.

  When the downstream catalyst 42 is in the lean state, it can be determined that the generation of hydrogen sulfide in the upstream catalyst 40 and the downstream catalyst 42 has stopped at that time. It is assumed that the ECU 50 integrates the detected value of the intake air amount Ga by the air flow meter 16 after the time when it is determined that the downstream catalyst 42 is in the lean state in another routine. This integrated value is hereinafter referred to as “integrated intake air amount after lean determination”. During the deceleration fuel cut, the air sucked into the internal combustion engine 10 is discharged into the exhaust passage 14 as it is. For this reason, the integrated intake air amount after the lean determination becomes a value corresponding to the integrated air amount that flows downstream from the downstream catalyst 42 after the downstream catalyst 42 enters the lean state.

  When the downstream catalyst 42 is in a lean state, the generation of hydrogen sulfide in the upstream catalyst 40 and the downstream catalyst 42 is stopped, but the hydrogen sulfide generated so far is downstream from the downstream catalyst 42, that is, the exhaust pipe. 46, muffler 47, and tail pipe 48. Therefore, if the integrated air amount flowing downstream from the downstream catalyst 42 after this time reaches a certain judgment value, the hydrogen sulfide remaining inside the exhaust pipe 46, the muffler 47, and the tail pipe 48 is expelled. Can be judged. Such an appropriate determination value is stored in the ECU 50 in advance.

  According to the routine shown in FIG. 3, it is possible to determine whether or not hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 has been driven out based on the above-described concept. That is, first, the value of the integrated intake air amount after the lean determination is taken in (step 112), and then it is determined whether or not the value is less than the determination value (step 114).

  If it is determined in step 114 that the integrated intake air amount after the lean determination is less than the determination value, the hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 is still not present. It can be judged that it was not completely destroyed. Therefore, in this case, it is next determined whether or not the deceleration fuel cut is continued (step 118). When it is determined that the deceleration fuel cut is continued, the current processing cycle is terminated. Then, by repeatedly executing this routine at predetermined time intervals, the throttle opening control during deceleration F / C is continued.

  On the other hand, if it is determined in step 114 that the accumulated intake air amount after the lean determination has reached the determination value, the hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 Can be determined to have been destroyed. Therefore, in this case, execution of throttle opening control during deceleration F / C is prohibited at this time (step 116). That is, the throttle valve 18 is closed to the idle opening.

  As described above, according to the routine processing shown in FIG. 3, when deceleration fuel cut is continued, hydrogen sulfide remaining inside the exhaust pipe 46, the muffler 47, and the tail pipe 48 is expelled. Until then, execution of throttle opening control during deceleration F / C can be continued. For this reason, even when the vehicle stops thereafter or becomes extremely low speed and the exhaust gas discharged from the tail pipe 48 drifts into the vehicle, the passenger is surely prevented from feeling the catalyst exhaust odor. be able to.

  Further, after the hydrogen sulfide remaining in the exhaust pipe 46, the muffler 47, and the tail pipe 48 is sufficiently removed, the throttle opening control at the time of deceleration F / C is finished and the throttle valve 18 is opened idle. After that, the air is not unnecessarily supplied to the upstream catalyst 40 and the downstream catalyst 42 thereafter. That is, the upstream catalyst 40 and the downstream catalyst 42 are not deteriorated more than necessary. Thus, according to the present embodiment, it is possible to achieve both the prevention of the catalyst exhaust odor and the suppression of deterioration of the upstream catalyst 40 and the downstream catalyst 42 in a well-balanced manner.

  By the way, in the present system, when the engine speed NE decreases to a predetermined return speed, or when the accelerator pedal is depressed, the fuel injection is resumed from the deceleration fuel cut. According to the routine shown in FIG. 3, it is determined in step 118 whether the deceleration fuel cut is continued. Then, when it is determined that the situation should be returned from the deceleration fuel cut, the ignition timing retarding control at the time of the deceleration fuel cut return is performed as follows.

  First, the fuel increase history is deleted (step 120). Next, the detection value Gafc (see FIG. 2C) by the air flow meter 16 at the time of return from the deceleration fuel cut is taken. Then, ignition timing retarding control is executed according to the Gafc value (step 124).

  In the present embodiment, the ECU 50 calculates the amount of air actually taken into the internal combustion engine 10 after returning from the deceleration fuel cut based on the Gafc value and the elapsed time since the fuel cut return. Is assumed to be stored. That is, the ECU 50 stores a relational expression corresponding to the curve shown in FIG. FIG. 4 is a map showing the relationship between the actual intake air amount calculated based on the relational expression and the ignition timing retardation amount. In step 124, the ignition timing is retarded according to this map. That is, the ignition timing retard amount is controlled to increase as the actual intake air amount at that time increases. As a result, the ignition timing is delayed as the actual intake air amount increases and the torque tends to become excessive, so that the torque can be suppressed. For this reason, it is possible to reliably prevent the engine speed NE from becoming excessively high or causing a torque shock after returning from the fuel cut.

  In the routine shown in FIG. 3, when the ignition timing retard control at the time of fuel cut recovery as described above is executed, it is subsequently determined whether or not the ignition timing retard control is completed (step 126). ). In the present embodiment, the ignition timing retarding control is performed over a predetermined period of time so that it can be determined that the actual intake air amount has converged to the value detected by the air flow meter 16. Therefore, if it is determined in step 126 that the elapsed time after returning from the fuel cut has not yet reached the predetermined time, the ignition timing retarding control is continued (step 128). On the other hand, if it is determined that the elapsed time after returning from the fuel cut has reached the predetermined time, the ignition timing retardation control is terminated.

In the first embodiment described above, as a method of increasing the amount of air flowing through the exhaust passage 14 during deceleration fuel cut in order to prevent the generation of catalyst exhaust odor, a method of opening the throttle valve 18 larger than the idle opening ( Although the case of taking the throttle opening control during deceleration F / C) has been described, in the present invention, in addition to this, for example, the following method can also be adopted.
(1) In an internal combustion engine system having an idle speed control valve that bypasses the throttle valve 18, a method for increasing the opening of the idle speed control valve.
(2) In an internal combustion engine system having an intake variable valve mechanism that can adjust the intake air amount by continuously changing the operating angle and lift amount of the intake valve 28, the operating angle and lift amount of the intake valve 28 are How to make it bigger than when idle.
(3) In an internal combustion engine system having a secondary air supply device capable of introducing secondary air into the exhaust passage 14 upstream of the upstream catalyst 40 and the downstream catalyst 42, the secondary air is supplied by the secondary air supply device. how to.

  In the first embodiment described above, the downstream catalyst 42 corresponds to the “catalyst” in the first invention, and the throttle opening control at the time of deceleration F / C corresponds to the “air increase control” in the first invention. is doing. Further, when the ECU 50 stops the fuel injection from the fuel injection valve 26 while the internal combustion engine 10 is decelerating, the “fuel cutting means” in the first aspect of the invention executes the processing of steps 100 to 104 described above. The “air increasing means” in the first invention executes the process of step 110, and the “determination means” in the first invention executes the process of step 112, so that the first invention is executed. The “accumulated air amount acquisition means” in FIG.

  In the first embodiment, the throttle valve 18 corresponds to the “intake air amount adjusting means” in the third aspect of the invention. Further, when the ECU 50 executes the process of step 122, the “return-time air amount acquisition means” in the fourth aspect of the invention executes the process of step 124, thereby causing the “ignition delay” in the fourth aspect of the invention. Each “corner means” is realized.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 5 and FIG. 6. The description will focus on the differences from the first embodiment described above, and the same matters will be described. Simplify or omit. The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later using the hardware configuration shown in FIG.

[Features of Embodiment 2]
In the present embodiment, similarly to the first embodiment, the throttle opening control during deceleration F / C is performed during deceleration fuel cut. As described above, in order to prevent the occupant from feeling the catalyst exhaust odor, the exhaust pipe 46, the muffler 47, and the tail pipe 48 (hereinafter referred to as the "muffler 47") until the vehicle stops or reaches the extremely low vehicle speed state. It is necessary to surely remove the hydrogen sulfide remaining in the inside.

  When the throttle opening control at the time of deceleration F / C is being executed, it can be determined that the shorter the vehicle speed is, the shorter the time is until the vehicle stops or reaches a very low vehicle speed. Therefore, in that case, it can be said that the hydrogen sulfide remaining in the muffler 47 and the like should be expelled quickly. For this purpose, it is preferable to increase the flow rate of air flowing through the exhaust passage 14 per hour.

  On the other hand, when the vehicle speed is high, it can be determined that the time is long until the vehicle stops or reaches an extremely low vehicle speed. In this case, it can be said that it is not necessary to expel the hydrogen sulfide remaining in the muffler 47 etc. so quickly.

  Therefore, in this embodiment, the flow rate per hour of the air flowing through the exhaust passage 14 in the throttle opening control during deceleration F / C is changed according to the vehicle speed.

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 5, the same steps as those shown in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The routine shown in FIG. 5 is the same as the routine shown in FIG. 3 except that step 130 is added between step 102 and step 104.

  According to the routine shown in FIG. 5, when the throttle opening control at the time of deceleration F / C is executed, a correction amount (hereinafter referred to as “Ga correction amount”) of the intake air amount corresponding to the vehicle speed is taken in (step 130). The Ga correction amount is a value indicating how much the intake air amount during execution of throttle opening control during deceleration F / C is increased as compared with the intake air amount during idling. In step 130, the Ga correction amount is calculated based on the map shown in FIG. According to this map, the Ga correction amount is calculated to increase as the vehicle speed decreases.

  In the present embodiment, deceleration F / C throttle opening control is executed based on the Ga correction amount calculated as described above (step 104). That is, the opening degree of the throttle valve 18 is controlled so that the intake air amount is larger than that during idling by the Ga correction amount. That is, the throttle opening is increased as the Ga correction amount increases.

  According to the present embodiment described above, as described above, the throttle opening during execution of the throttle opening control during deceleration F / C is increased as the vehicle speed is lower. For this reason, as the vehicle speed is lower, the flow rate of the air flowing through the muffler 47 and the like can be increased, so that the remaining hydrogen sulfide can be rapidly expelled. Therefore, even when the vehicle stops or becomes extremely low speed in a short time, hydrogen sulfide such as the muffler 47 can be surely removed by that time. For this reason, it can prevent more reliably that a passenger | crew senses a catalyst exhaust odor.

  Further, according to the present embodiment, the throttle opening during execution of throttle opening control during deceleration F / C is made smaller as the vehicle speed is higher. That is, when it can be determined that the vehicle speed is high and there is a large margin of time until the vehicle is stopped or extremely low, the amount of air flowing through the exhaust passage 14 can be prevented from becoming larger than necessary. For this reason, it is possible to further suppress the progress of deterioration of the upstream catalyst 40 and the downstream catalyst 42 while preventing the generation of the catalyst exhaust odor.

  In the second embodiment described above, the vehicle speed sensor 49 corresponds to the “vehicle speed detection means” in the fifth aspect of the present invention. Further, the “flow rate correcting means” in the fifth and sixth aspects of the present invention is realized by the ECU 50 executing the processing of steps 130 and 104 described above.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 7 and FIG. 8. The difference from the above-described first and second embodiments will be mainly described, and the same matters will be described. The description is simplified or omitted. The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 7 to be described later using the hardware configuration shown in FIG.

[Features of Embodiment 3]
As in the first embodiment, in the present embodiment, when the throttle opening control at the time of deceleration F / C is executed, the integrated intake air amount after the lean determination, that is, the downstream catalyst after the downstream catalyst 42 enters the lean state. When the integrated air amount flowing downstream of 42 reaches the determination value, the throttle opening control during deceleration F / C is prohibited (terminated).

  In this case, in the present embodiment, the determination value is changed according to the vehicle speed. Specifically, the determination value is increased as the vehicle speed is lower. That is, the lower the vehicle speed, the longer the throttle opening control during deceleration F / C.

  Even if the vehicle is not stopped, if the vehicle speed is low, the exhaust gas may drift into the vehicle. For this reason, in order to prevent the generation of the catalyst exhaust odor more reliably, the throttle valve 18 is closed in order to more surely remove the hydrogen sulfide remaining on the downstream side of the downstream catalyst 42 as the vehicle speed is lower. It is preferable to flow a larger amount of air before that.

  Based on this concept, in the present embodiment, as the vehicle speed is lower, the throttle opening control at the time of deceleration F / C is extended and executed so that more air flows to the downstream side of the downstream catalyst 42. Therefore, it was decided to remove hydrogen sulfide more reliably.

[Specific Processing in Embodiment 3]
FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 7, the same steps as those shown in FIG. 3 or FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The routine shown in FIG. 7 is the same as the routine shown in FIG. 5 except that step 132 is added between step 112 and step 114.

  According to the routine shown in FIG. 7, when the value of the integrated intake air amount after the lean determination is acquired (step 112), the process of acquiring the determination value of the integrated intake air amount according to the vehicle speed is subsequently performed ( Step 132). Here, the determination value is calculated based on the map shown in FIG. According to this map, the determination value is calculated to increase as the vehicle speed decreases.

  In this embodiment, the determination value calculated in step 132 is compared with the integrated intake air amount after lean determination (step 114) until the integrated intake air amount after lean determination reaches the determination value. , Throttle opening control continues during deceleration F / C.

  As a result, as the vehicle speed is lower, the throttle opening control during deceleration F / C is extended, and more air can flow downstream of the downstream catalyst 42. For this reason, hydrogen sulfide remaining on the downstream side of the downstream catalyst 42 can be more surely driven off at a lower vehicle speed at which the exhaust gas may drift in the vehicle. Therefore, even when the vehicle speed is low, generation of catalyst exhaust odor can be prevented more reliably.

  Further, according to the present embodiment, the execution of the deceleration F / C throttle opening control is terminated earlier as the vehicle speed is higher and the possibility of exhaust gas drifting in the vehicle is lower. For this reason, it is possible to prevent the amount of air flowing through the exhaust passage 14 from being increased more than necessary. Therefore, it is possible to further suppress the progress of deterioration of the upstream catalyst 40 and the downstream catalyst 42 while preventing the generation of the catalyst exhaust odor.

  In the third embodiment described above, the vehicle speed sensor 49 corresponds to the “vehicle speed detection means” in the seventh aspect of the present invention. Further, the “determination value correcting means” in the seventh aspect of the present invention is realized by the ECU 50 executing the processing of step 132 described above.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the ignition retard control after the return from a deceleration fuel cut. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure which shows the map which ECU refers in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a figure which shows the map which ECU refers in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure which shows the map which ECU refers in Embodiment 3 of this invention.

Explanation of symbols

10 internal combustion engine 12 intake passage 14 exhaust passage 18 throttle valve 20 throttle motor 22 throttle position sensor 24 accelerator position sensor 25 surge tank 26 fuel injection valve 40 upstream catalyst 42 downstream catalyst 44 oxygen sensor 46 exhaust pipe 47 muffler 48 tail pipe 50 ECU

Claims (7)

A catalyst disposed in the exhaust passage of the internal combustion engine;
Fuel cut means for performing fuel cut during deceleration of the internal combustion engine;
An air increase means for performing an air increase control for increasing the amount of air flowing through the catalyst more than that during idling when a fuel cut during deceleration is performed when the catalyst is in a rich state;
Determination means for determining whether or not the catalyst is in a lean state during the execution of the air increase control;
Integrated air amount acquisition means for acquiring the integrated air amount flowing downstream from the catalyst;
With
The control apparatus for an internal combustion engine, wherein when it is determined that the catalyst is in a lean state and the integrated air amount has reached a predetermined determination value, the air increase control is terminated.   2. The internal combustion engine according to claim 1, wherein the determination value is set to a value that can secure an air amount necessary to drive off hydrogen sulfide remaining in the exhaust passage downstream of the catalyst. Control device. An intake air amount adjusting means for adjusting the amount of air sucked into the internal combustion engine;
3. The control apparatus for an internal combustion engine according to claim 1, wherein the air increasing means controls the amount of air flowing through the catalyst by controlling the intake air amount adjusting means. A return air amount acquisition means for acquiring a return air amount that is the amount of air actually taken into the internal combustion engine when returning from the fuel cut;
Ignition retarding means for retarding the ignition timing as the return air amount increases;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising: Vehicle speed detection means for detecting the vehicle speed;
Flow rate correction means for correcting the flow rate of air flowing through the catalyst according to the vehicle speed when the air increase control is performed;
The control device for an internal combustion engine according to any one of claims 1 to 4, further comprising:   6. The control apparatus for an internal combustion engine according to claim 5, wherein the flow rate correction means increases the flow rate of the air flowing through the catalyst as the vehicle speed is lower when the air increase control is performed. Vehicle speed detection means for detecting the vehicle speed;
A determination value correcting means for increasing the determination value when the vehicle speed is low when the air increase control is performed;
The control apparatus for an internal combustion engine according to any one of claims 1 to 6, further comprising:

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