JP2020023907A - Control device of internal combustion engine - Google Patents

Abstract

To secure a period for performing poisoning regeneration during a combustion stop period.SOLUTION: An internal combustion engine control unit 110 performs fuel cut processing or fuel introduction processing when stopping combustion in a cylinder 11 of an internal combustion engine 10. The internal combustion engine control unit 110 comprises a stop determination part 113 for determining whether or not a stop condition of the combustion in the cylinder 11 is established. The internal combustion engine control unit 110 comprises an estimation part 114 for estimating a sulfur accumulation amount in a three-dimensional catalyst 22. The estimation part 114 changes an estimation method of the sulfur accumulation amount depending on the case that the fuel cut processor is performed, and the case that the fuel introduction processing is performed. Then, when the fuel cut processing or the fuel introduction processing is started when the sulfur accumulation amount is equal to or larger than an accumulation threshold, the internal combustion engine control unit 110 restarts the combustion in the cylinder 11 when the sulfur accumulation amount reaches a desorption determination value or smaller even if the stop determination part 113 determines that the stop condition is established.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device for an internal combustion engine applied to a spark ignition type internal combustion engine.

  Patent Literature 1 describes an example of an internal combustion engine using gasoline as a fuel. This exhaust gas purifying apparatus for an internal combustion engine includes a three-way catalyst provided in an exhaust passage, and a particulate filter provided downstream of the three-way catalyst in the exhaust passage.

  In the internal combustion engine described in Patent Literature 1, when the load applied to the internal combustion engine is low when the required torque for the internal combustion engine is reduced due to cancellation of the accelerator operation or the like, combustion in the cylinder may be stopped. is there. In such a combustion stop period, a fuel cut process for stopping the fuel injection of the fuel injection valve, and a fuel introduction process for injecting the fuel from the fuel injection valve and allowing the fuel to flow out of the cylinder into the exhaust passage without burning. Is selected. According to Patent Literature 1, when the particulate filter is regenerated, a fuel introduction process is executed. On the other hand, when the regeneration is not performed, a fuel cut process is executed.

  In the fuel introduction process, the fuel injected from the fuel injection valve flows through the exhaust passage together with the air. When the fuel is introduced into the three-way catalyst, the temperature of the three-way catalyst rises due to the combustion of the fuel. Then, the high-temperature gas flows into the particulate filter, and the temperature of the particulate filter rises. As a result, the particulate matter trapped in the particulate filter is burned.

US Patent Application Publication No. 2014/0041362

  When the fuel of the internal combustion engine contains a sulfur component, the sulfur component may be deposited on the three-way catalyst. When the sulfur component accumulates on the three-way catalyst, the purification efficiency of the three-way catalyst decreases because the maximum oxygen storage amount of the three-way catalyst decreases. Therefore, as poisoning regeneration that desorbs sulfur components deposited on the catalyst, oxygen is introduced into the three-way catalyst by performing a fuel cut process that stops combustion in the cylinder and stops fuel injection. Sulfur deposited on the three-way catalyst is released as a sulfur oxide.

  When the fuel cut-off process or the fuel introduction process is selected during the combustion stop period as in Patent Literature 1, when the fuel introduction process is performed during the combustion stop period, the fuel that has reached the three-way catalyst by the fuel introduction process is discharged together with oxygen. Burned. Therefore, the manner in which the poisoning regeneration proceeds is different from when the fuel cut process is being executed. That is, when the fuel introduction process is performed, the air-fuel ratio of the gas introduced into the three-way catalyst is different from the case where the fuel cut process is performed, so that the period for performing the poisoning regeneration is appropriately set. There was something I couldn't do.

  A control device for an internal combustion engine for solving the above-mentioned problem is applied to an internal combustion engine that burns an air-fuel mixture containing fuel injected from a fuel injection valve in a cylinder by spark discharge of an ignition device. When stopping combustion in the cylinder while the shaft is rotating, a fuel cut process for stopping the fuel injection of the fuel injection valve, and injecting fuel from the fuel injection valve, and the fuel is not A control device for an internal combustion engine that selects and executes any one of a fuel introduction process for causing fuel to flow out of the cylinder into an exhaust passage while maintaining combustion, and a condition for stopping combustion in the cylinder is satisfied. A stop determination unit for determining whether or not the sulfur deposition amount is estimated, and an estimation unit for estimating the sulfur accumulation amount on the catalyst disposed in the exhaust passage, wherein the sulfur accumulation amount estimated by the estimation unit is equal to or greater than a accumulation threshold. When the stop condition is determined to be satisfied by the stop determination unit and the fuel cut process or the fuel introduction process is started, the stop determination unit determines that the stop condition is satisfied. Even if it is, the combustion in the cylinder is restarted when the sulfur accumulation amount estimated by the estimation unit becomes equal to or less than the desorption determination value, and the fuel cut processing is executed by the estimation unit. The point is to change the method of estimating the sulfur accumulation amount between when the fuel introduction process is being performed and when the fuel introduction process is being performed.

  According to the above configuration, when the sulfur accumulation amount becomes equal to or less than the desorption determination value, the fuel cut process or the fuel introduction process is terminated, and the combustion in the cylinder is restarted. In the above configuration, the method of estimating the sulfur accumulation amount is changed between when the fuel cut process is being performed and when the fuel introduction process is being performed. Therefore, when performing the fuel introduction process in which the fuel is introduced into the catalyst together with the air, the sulfur accumulation amount can be estimated in consideration of the introduction of the fuel. Thus, even if the poisoning regeneration progresses in a different manner between when the fuel introduction process is performed and when the fuel cut process is performed, the sulfur accumulation amount is appropriately estimated in accordance with the difference. can do. Therefore, the completion of the poisoning regeneration can be appropriately determined based on the sulfur accumulation amount.

FIG. 1 is a configuration diagram schematically showing a control device including an internal combustion engine control unit as an embodiment of a control device for an internal combustion engine, and a hybrid vehicle equipped with the control device. FIG. 2 is a diagram showing a functional configuration of the internal combustion engine control unit and a schematic configuration of an internal combustion engine mounted on the hybrid vehicle. 5 is a flowchart showing a flow of processing executed by a stop determination unit in the internal combustion engine control unit. 5 is a flowchart illustrating a flow of a process for controlling a fuel injection valve and an ignition device. 9 is a flowchart illustrating a flow of a process performed during a combustion stop period. The flowchart which shows the flow of the process at the time of performing poisoning reproduction | regeneration. 4 is a timing chart in the case of performing poisoning regeneration during a combustion stop period.

Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to FIGS.
FIG. 1 shows a schematic configuration of a hybrid vehicle. As shown in FIG. 1, the hybrid vehicle includes an internal combustion engine 10, a power distribution integration mechanism 40 connected to the crankshaft 14 of the internal combustion engine 10, and a first motor generator connected to the power distribution integration mechanism 40. 71. A second motor generator 72 is connected to the power distribution integration mechanism 40 via a reduction gear 50, and a drive wheel 62 is connected via a reduction mechanism 60 and a differential 61.

  The power distribution integration mechanism 40 is a planetary gear mechanism, and has a sun gear 41 of an external gear and a ring gear 42 of an internal gear coaxially arranged with the sun gear 41. A plurality of pinion gears 43 that mesh with both the sun gear 41 and the ring gear 42 are arranged between the sun gear 41 and the ring gear 42. Each of the pinion gears 43 is supported by the carrier 44 so that the pinion gears 43 can freely rotate and revolve. The first motor generator 71 is connected to the sun gear 41. The crankshaft 14 is connected to the carrier 44. A ring gear shaft 45 is connected to the ring gear 42, and both the reduction gear 50 and the reduction mechanism 60 are connected to the ring gear shaft 45.

  When the output torque of the internal combustion engine 10 is input to the carrier 44, the output torque is distributed to the sun gear 41 and the ring gear 42. That is, by inputting the output torque of the internal combustion engine 10 to the first motor generator 71, the first motor generator 71 can generate electric power.

  On the other hand, when the first motor generator 71 functions as an electric motor, the output torque of the first motor generator 71 is input to the sun gear 41. Then, the output torque of the first motor generator 71 input to the sun gear 41 is distributed to the carrier 44 side and the ring gear 42 side. When the output torque of the first motor generator 71 is input to the crankshaft 14 via the carrier 44, the crankshaft 14 can be rotated. In the present embodiment, rotating the crankshaft 14 by driving the first motor generator 71 in this manner is referred to as “motoring”.

  The reduction gear 50 is a planetary gear mechanism, and includes a sun gear 51 of an external gear to which a second motor generator 72 is connected, and a ring gear 52 of an internal gear coaxially arranged with the sun gear 51. I have. The ring gear shaft 45 is connected to the ring gear 52. A plurality of pinion gears 53 that mesh with both the sun gear 51 and the ring gear 52 are arranged between the sun gear 51 and the ring gear 52. Each pinion gear 53 is rotatable but non-revolvable.

  When the vehicle is decelerated, the regenerative braking force corresponding to the amount of power generated by the second motor generator 72 can be generated in the vehicle by causing the second motor generator 72 to function as a generator. When the second motor generator 72 functions as an electric motor, the output torque of the second motor generator 72 is input to the drive wheels 62 via the reduction gear 50, the ring gear shaft 45, the reduction mechanism 60, and the differential 61. Is done. As a result, the drive wheels 62 can be rotated, that is, the vehicle can run.

  First motor generator 71 exchanges power with battery 77 via first inverter 75. The second motor generator 72 exchanges power with the battery 77 via the second inverter 76.

  As shown in FIG. 2, the internal combustion engine 10 is an in-line four-cylinder internal combustion engine having four cylinders 11 arranged in series. A piston connected to the crankshaft 14 via a connecting rod is accommodated in each cylinder 11 in a reciprocable manner.

  Air is introduced into each cylinder 11 through an intake passage 15. Further, the internal combustion engine 10 has the same number of fuel injection valves 17 as the cylinders 11. Each fuel injection valve 17 is an injection valve that injects fuel into the intake passage 15. Fuel and air injected from the fuel injection valve 17 are introduced into each cylinder 11 through the intake passage 15. Then, in each cylinder 11, an air-fuel mixture containing fuel and air is burned by spark discharge of the ignition device 19.

  Further, the internal combustion engine 10 includes an air flow meter 81 for detecting the intake air amount GA in the intake passage 15. The internal combustion engine 10 includes a crank angle sensor 82 that detects the rotation angle of the crank shaft 14.

  The exhaust gas generated in each cylinder 11 by the combustion of the air-fuel mixture is discharged to an exhaust passage 21. The exhaust passage 21 is provided with a three-way catalyst 22 and a particulate filter 23 disposed downstream of the three-way catalyst 22. The particulate filter 23 has a function of collecting particulate matter contained in exhaust gas flowing through the exhaust passage 21.

  An air-fuel ratio sensor 83 that detects the oxygen concentration in the gas flowing through the exhaust passage 21, that is, the air-fuel ratio of the air-fuel mixture, is disposed upstream of the three-way catalyst 22 in the exhaust passage 21. An exhaust temperature sensor 84 for detecting the temperature of gas flowing through the exhaust passage 21 is disposed between the three-way catalyst 22 and the particulate filter 23 in the exhaust passage 21.

  In the internal combustion engine 10, the combustion of the air-fuel mixture in the cylinder 11 may be stopped when the vehicle is running and the crankshaft 14 is rotating. The period during which the combustion in the cylinder 11 is stopped while the crankshaft 14 is rotating is referred to as a "combustion stop period CSP". In the combustion stop period CSP, each piston reciprocates in synchronization with the rotation of the crankshaft 14. Therefore, the air introduced into each cylinder 11 via the intake passage 15 flows out to the exhaust passage 21 without being used for combustion.

  In the combustion stop period CSP, a fuel cut process for stopping the fuel injection of each fuel injection valve 17, fuel is injected from each fuel injection valve 17, and the fuel is unburned from each cylinder 11 to the exhaust passage 21. Any one of the fuel introduction processes to be discharged is selected and executed. When the fuel introduction process is executed, the fuel injected from each fuel injection valve 17 flows through the exhaust passage 21 together with the air. Then, the fuel is introduced into the three-way catalyst 22. At this time, when the temperature of the three-way catalyst 22 is equal to or higher than the activation temperature and the amount of oxygen sufficient to burn the fuel is present in the three-way catalyst 22, the fuel is burned by the three-way catalyst 22. As a result, the temperature of the three-way catalyst 22 increases. Then, the high-temperature gas flows into the particulate filter 23, and the temperature of the particulate filter 23 rises. When oxygen is supplied to the particulate filter 23 and the temperature of the particulate filter 23 becomes equal to or higher than the combustible temperature, the particulate matter collected by the particulate filter 23 is burned.

Next, a control configuration of the hybrid vehicle will be described with reference to FIGS.
As shown in FIG. 1, the control device 100 of the hybrid vehicle calculates a required torque TQR, which is a torque to be output to the ring gear shaft 45, based on the accelerator opening ACC and the vehicle speed VS. The accelerator opening ACC is the amount of operation of the accelerator pedal AP by the driver of the vehicle, and is a value detected by the accelerator opening sensor 86. The vehicle speed VS is a value corresponding to the moving speed of the vehicle, and is detected by the vehicle speed sensor 87. The control device 100 controls the internal combustion engine 10 and each of the motor generators 71 and 72 based on the calculated required torque TQR.

  The control device 100 includes an internal combustion engine control unit 110 that controls the internal combustion engine 10 and a motor control unit 120 that controls the motor generators 71 and 72. The internal combustion engine control unit 110 corresponds to an example of a “control device for an internal combustion engine” in the present embodiment. When the fuel introduction process is executed during the combustion stop period CSP, the drive of the first motor generator 71 is controlled by the motor control unit 120 to perform the motoring. That is, the rotation speed of the crankshaft 14 during the combustion stop period CSP can be controlled through the execution of the motoring.

  FIG. 2 illustrates a functional configuration of the internal combustion engine control unit 110. The internal combustion engine control unit 110 includes, as functional units, an ignition control unit 111, an injection valve control unit 112, a stop determination unit 113, and an estimation unit 114.

  Detection signals from various sensors are input to the internal combustion engine control unit 110. The internal combustion engine control unit 110 calculates parameters for controlling the vehicle and the internal combustion engine 10 based on detection signals from various sensors. For example, the crank angle CA is calculated based on a detection signal from the crank angle sensor 82. Further, the engine speed NE of the internal combustion engine 10 is calculated based on the crank angle CA.

  The ignition control unit 111 controls the ignition device 19. When combusting the air-fuel mixture in the cylinder 11, the ignition control unit 111 causes the ignition device 19 to perform spark discharge at a timing when the piston reaches the vicinity of the compression top dead center. On the other hand, the ignition control unit 111 does not cause the ignition device 19 to perform spark discharge during the combustion stop period CSP.

The injection valve control unit 112 controls driving of the fuel injection valve 17. The processing procedure of the fuel injection valve 17 will be described later.
The stop determination unit 113 determines whether a condition for stopping combustion of the air-fuel mixture in the cylinder 11 is satisfied.

In addition, the stop determination unit 113 executes a series of processes related to poisoning regeneration when the condition for stopping combustion is satisfied. The flow of the processing will be described later.
The estimating unit 114 estimates the temperature of the three-way catalyst 22 based on the amount of fuel injected from the fuel injection valve 17 during execution of the fuel introduction process, and calculates the temperature as the catalyst temperature TC.

  Further, the estimation unit 114 estimates the sulfur accumulation amount SDP as the accumulation amount of the sulfur component accumulated on the three-way catalyst 22. The estimating unit 114 calculates the sulfur accumulation amount SDP by subtracting the desorption value from the accumulation value. The accumulation value used for calculating the sulfur accumulation amount SDP is calculated based on the integrated value of the fuel injection amount. The desorption value used for calculating the sulfur accumulation amount SDP is calculated as the amount of the sulfur component released from the three-way catalyst 22.

  When the fuel introduction process is being performed, the estimating unit 114 calculates a desorption value based on the catalyst temperature TC and the exhaust air-fuel ratio AF. Note that the exhaust air-fuel ratio AF is a value that is referred to when calculating the required value QPR of the fuel injection amount when the fuel introduction process is performed. The exhaust air-fuel ratio AF is set based on a target value of the catalyst temperature TC. Here, the higher the catalyst temperature TC, the easier the sulfur component is released from the three-way catalyst 22. Therefore, the higher the catalyst temperature TC, the larger the desorption value is calculated. Further, as the amount of oxygen supplied to the three-way catalyst 22 increases, the sulfur component is more likely to be released from the three-way catalyst 22. Therefore, as the exhaust air-fuel ratio AF is leaner, the desorption value is calculated as a larger value. On the other hand, when the fuel introduction process is not being performed, that is, when the fuel cut process is being performed, the estimating unit 114 calculates the desorption value based on the exhaust air-fuel ratio AF. As described above, the calculation method of the desorption value is switched between when the fuel cut process is being performed and when the fuel introduction process is being performed.

As described above, the estimating unit 114 changes the method of estimating the sulfur accumulation amount between when the fuel cut process is being performed and when the fuel introduction process is being performed.
FIG. 3 shows a flow of a process executed by the stop determination unit 113. This process is repeatedly executed at predetermined intervals.

  When the execution of this process is started, first, in step S101, it is determined whether a condition for stopping combustion in the cylinder 11 is satisfied. For example, when the required value of the output torque for the internal combustion engine 10 is equal to or less than “0”, the stop determination unit 113 determines that the stop condition is satisfied. On the other hand, when the required value of the output torque for the internal combustion engine 10 is larger than “0”, the stop determination unit 113 does not determine that the stop condition is satisfied, that is, determines that the stop condition is not satisfied. I do. If the stop condition is not satisfied (S101: NO), the process proceeds to step S102. In step S102, the combustion stop flag FLG1 is set to off. Thereafter, this processing routine is temporarily ended.

  On the other hand, when the stop condition is satisfied (S101: YES), the process proceeds to step S103. In step S103, the combustion stop flag FLG1 is set to ON. Thereafter, this processing routine is temporarily ended.

  The stop determination unit 113 requests that the combustion of the air-fuel mixture in the cylinder 11 be stopped when the combustion stop flag FLG1 is turned on from the off state. The stop determination unit 113 requests the restart of combustion of the air-fuel mixture in the cylinder 11 when the combustion stop flag FLG1 is turned off from the on state.

  With reference to FIG. 4, a processing procedure when the driving of the fuel injection valve 17 is controlled by the injection valve control unit 112 will be described. Note that a series of processing shown in FIG. 4 is executed for each fuel injection valve 17.

When this series of processing is executed, first, in step S104, it is determined whether the combustion stop flag FLG1 is on.
If the combustion stop flag FLG1 is off (S104: NO), the process proceeds to step S105. In step S105, a first calculation process for calculating the required value QPR of the fuel injection amount of the fuel injection valve 17 is performed. In the first calculation process, for example, the required value QPR is calculated so that the air-fuel ratio detection value AFS becomes the air-fuel ratio target value AFTr. The air-fuel ratio detection value AFS is an air-fuel ratio detected by the air-fuel ratio sensor 83. When the air-fuel mixture is burned in the cylinder 11, the air-fuel ratio target value AFTr is set to, for example, a stoichiometric air-fuel ratio or a value near the stoichiometric air-fuel ratio. Then, when the required value QPR is calculated, the process proceeds to the next step S106. In step S106, the drive of the fuel injection valve 17 is controlled based on the required value QPR calculated in step S105. Subsequently, in the next step S107, the ignition device 19 is controlled by the ignition control unit 111 so as to perform spark discharge. That is, the air-fuel mixture is burned in the cylinder 11. Then, a series of processing is temporarily ended.

  On the other hand, if the combustion stop flag FLG1 is on (S104: YES), the process proceeds to step S108. In step S108, a second calculation process for calculating the required value QPR of the fuel injection amount of the fuel injection valve 17 is performed. In the second calculation process, when the fuel cut process is being performed, the required value QPR is set to “0”. On the other hand, in the second calculation process, when the fuel introduction process is being performed, the required value QPR is calculated so as to be a value larger than “0”. However, the required value QPR of the fuel injection amount when the fuel introduction process is being executed is smaller than the required value QPR when burning the air-fuel mixture in the cylinder 11. Therefore, when the fuel injected from the fuel injection valve 17 is introduced into the cylinder 11 based on the required value QPR calculated in step S108, the air-fuel ratio in the cylinder 11 causes the combustion of the air-fuel mixture in the cylinder 11. The air-fuel ratio (ie, the stoichiometric air-fuel ratio) at the time of the fuel injection is a value on the lean side.

Here, a method of selecting the fuel cut process and the fuel introduction process during the combustion stop period CSP will be described. That is, after at least one of the following conditions (1) and (2) is not satisfied after the start of the combustion stop period CSP, the fuel cut process is executed. On the other hand, if both the conditions (1) and (2) are satisfied during the combustion stop period CSP, the fuel introduction processing is executed.
(1) It can be determined that the catalyst temperature TC is equal to or higher than the activation temperature.
(2) The estimated value of the trapped amount of particulate matter in the particulate filter 23 is equal to or larger than the determined trapped amount.

  Even if unburned fuel is introduced into the three-way catalyst 22, if the temperature of the three-way catalyst 22 is low, the fuel may not be burned in some cases. Therefore, the activation temperature is set as a criterion for determining whether the unburned fuel introduced into the three-way catalyst 22 can be burned.

  As the amount of collected particulate matter in the particulate filter 23 increases, clogging of the particulate filter 23 progresses. Therefore, a determined trapping amount is set as a criterion for determining whether or not clogging has progressed to such a degree that the particulate filter 23 needs to be regenerated. When the trapping amount increases, the pressure difference between the portion of the exhaust passage 21 between the three-way catalyst 22 and the particulate filter 23 and the portion of the exhaust passage 21 downstream of the particulate filter 23 tends to increase. Therefore, for example, an estimated value of the trapping amount can be calculated based on the differential pressure.

  When the required value QPR is calculated in step S108, the process proceeds to the next step S109. In step S109, the driving of the fuel injection valve 17 is controlled based on the required value QPR calculated in step S108. That is, when the fuel cut process is being performed, the fuel is not injected from the fuel injection valve 17 because the required value QPR is “0”. On the other hand, when the fuel introduction process is being executed, the fuel is injected from the fuel injection valve 17 because the required value QPR is larger than “0”. Subsequently, in the next step S110, the ignition control unit 111 controls the ignition device 19 so as not to perform spark discharge. Then, a series of processing is temporarily ended.

With reference to FIGS. 5 and 6, a flow of a series of processes relating to poisoning regeneration will be described.
A series of processes shown in FIG. 5 is repeatedly executed at predetermined intervals when the combustion stop flag FLG1 is on.

  When this process is started, in step S201, it is determined whether or not the sulfur accumulation amount SDP is equal to or more than the accumulation threshold value SDPTh. When the sulfur accumulation amount SDP increases, the maximum oxygen storage amount of the three-way catalyst 22 decreases, and the purification efficiency decreases. The accumulation threshold value SDPTh is set in order to determine whether or not the three-way catalyst 22 needs to be regenerated by poisoning. When the sulfur accumulation amount SDP is smaller than the accumulation threshold value SDPTh (S201: NO), a series of processes is temporarily ended.

  On the other hand, when the sulfur accumulation amount SDP is equal to or greater than the accumulation threshold value SDPTh (S201: YES), the process proceeds to step S202. In step S202, ON is set to the poisoning regeneration flag FLG2. Thereafter, the process proceeds to step S203.

In step S203, the deterioration suppression processing is prohibited. As a result, the later-described deterioration suppression processing is not performed. After that, a series of processing is once ended.
A series of processing shown in FIG. 6 is repeatedly executed at predetermined intervals when the poisoning regeneration flag FLG2 is on.

  When this process is started, first, in step S204, it is determined whether the sulfur accumulation amount SDP is equal to or less than the desorption determination value SDCTh. The desorption determination value SDCTh is a value set to determine whether or not the desorption of sulfur deposited on the three-way catalyst 22 has been completed. As the desorption determination value SDCTh, for example, “0” can be set. Further, a value larger than "0" can be set as the desorption determination value SDCTh. When the sulfur accumulation amount SDP is larger than the desorption determination value SDCTh (S204: NO), a series of processes is temporarily ended.

  On the other hand, when the sulfur accumulation amount SDP is equal to or smaller than the desorption determination value SDCTh (S204: YES), the process proceeds to step S205. In step S205, the deterioration suppression processing is permitted. For this reason, when the execution condition is satisfied, the deterioration suppressing process is executed. Then, the process proceeds to step S206.

In step S206, the poisoning regeneration flag FLG2 is set to off. Thereafter, the process proceeds to step S207.
In step S207, a combustion restart process is executed. When the combustion restart process is executed, the combustion of the air-fuel mixture is required even if the condition for stopping the combustion of the air-fuel mixture in the cylinder 11 is satisfied. Specifically, when the combustion restart processing is executed, the combustion stop flag FLG1 is set to off. Further, when the combustion restart processing is executed, the execution of the processing shown in FIG. 3 is prohibited for a prescribed period. When the processing in step S207 is performed, a series of processing ends.

  Here, the deterioration suppressing process will be described. The deterioration suppressing process is a process executed to suppress the deterioration of the three-way catalyst 22. If oxygen is supplied when the catalyst temperature TC is high, oxidation of oxygen in the three-way catalyst 22 may proceed rapidly. In the deterioration suppressing process, the supply of oxygen to the three-way catalyst 22 is suppressed to suppress this. Specifically, the deterioration suppression process prohibits the stop of the combustion of the air-fuel mixture in the cylinder 11 regardless of whether the stop condition is satisfied. The deterioration suppression process is executed, for example, when the catalyst temperature TC is equal to or higher than the limit temperature TCTh. The limit temperature TCTh is set as a value for determining whether or not the temperature of the three-way catalyst 22 is high. The limit temperature TCTh is a value higher than the activation temperature of the three-way catalyst 22.

The operation and effect of the present embodiment will be described.
FIG. 7 shows an example in which poisoning regeneration is performed during the combustion stop period CSP. In the example shown in FIG. 7, at the timing t1, the condition for stopping the combustion of the air-fuel mixture in the cylinder 11 is satisfied. In the example shown by the solid line in FIG. 7, it is determined that the execution condition of the fuel introduction process is satisfied at the timing t2. That is, in the example shown by the solid line, the fuel cut process and the fuel introduction process are executed during the combustion stop period CSP. On the other hand, in the example shown by the broken line in FIG. 7, it is determined that the execution condition of the fuel introduction process is not satisfied. That is, in the example shown by the broken line, the fuel cut process is executed during the combustion stop period CSP.

  First, an example shown by a broken line in FIG. 7 will be described. When the stop condition is satisfied at the timing t1, the combustion of the air-fuel mixture in the cylinder 11 is stopped as shown in FIG. Since the execution condition of the fuel introduction process is not satisfied, the fuel cut process is executed after the timing t1. As a result of the fuel cut process, the air drawn into the cylinder 11 from the intake passage 15 is discharged to the exhaust passage 21 without being burned. When the air reaches the three-way catalyst 22, the catalyst temperature TC decreases after the timing t1 as shown in FIG. 7C. In addition, since oxygen is supplied to the three-way catalyst 22 by the fuel cut process, the sulfur component is released from the three-way catalyst 22. As a result, as shown in FIG. 7D, the sulfur accumulation amount SDP starts to decrease after the timing t1. Then, the sulfur accumulation amount SDP reaches “0” at timing t5. When the sulfur accumulation amount SDP is “0”, that is, when the sulfur accumulation amount SDP becomes equal to or less than the desorption determination value SDCTh, the combustion return process is executed (S207). Therefore, at the timing t5, the combustion is restarted as shown in FIG.

Subsequently, an example shown by a solid line in FIG. 7 will be described. When the stop condition is satisfied at the timing t1, the combustion of the air-fuel mixture in the cylinder 11 is stopped as shown in FIG.
During the period from the timing t1 to the timing t2, the execution condition of the fuel introduction process is not satisfied, so the fuel cut process is executed. As a result of the fuel cut process, the air drawn into the cylinder 11 from the intake passage 15 is discharged to the exhaust passage 21 without being burned. When the air reaches the three-way catalyst 22, the catalyst temperature TC decreases as shown in FIG. Further, by supplying oxygen to the three-way catalyst 22, a sulfur component is released from the three-way catalyst 22. Therefore, as shown in FIG. 7D, the sulfur accumulation amount SDP starts to decrease.

  At a timing t2, execution of the fuel introduction process is started. Since the unburned fuel is introduced into the three-way catalyst 22, the combustion of the fuel in the three-way catalyst 22 causes the catalyst temperature TC to start increasing after the timing t2 as shown in FIG. 7C. The catalyst temperature TC reaches the limit temperature TCTh at the timing t3. That is, the execution condition of the deterioration suppression process is satisfied. Here, before the timing t1 at which it is determined that the stop condition is satisfied, the sulfur accumulation amount SDP is equal to or more than the accumulation threshold value SDPTh as shown in FIG. Execution of the deterioration suppression processing is prohibited (S203). Therefore, the stop of the combustion is continued without performing the deterioration suppressing process.

  After the timing t2, the sulfur component is likely to be deposited on the three-way catalyst 22 due to the effect of the fuel introduced by the fuel introduction process. Furthermore, since oxygen is combusted in the three-way catalyst 22 together with the fuel introduced by the fuel introduction process, the amount of oxygen for generating sulfur oxides released from the three-way catalyst 22 is likely to be insufficient. For this reason, as shown in FIG. 7D, the reduction rate of the sulfur accumulation amount SDP temporarily becomes slow. However, the rate of decrease of the sulfur accumulation amount SDP gradually increases as the catalyst temperature TC increases. Then, the sulfur accumulation amount SDP reaches “0” at timing t4, which is a point in time before timing t5.

  When the sulfur accumulation amount SDP is “0”, that is, when the sulfur accumulation amount SDP becomes equal to or less than the desorption determination value SDCTh, execution of the deterioration suppression process is permitted (S205). Further, a combustion return process is executed (S207). Therefore, at timing t4, the fuel introduction process is stopped as shown in FIG. 7B, and the combustion is restarted as shown in FIG. 7A. By stopping the fuel introduction process, the catalyst temperature TC starts to decrease after the timing t4 as shown in FIG. 7C. During the period from the timing t4 to the timing t6, the catalyst temperature TC is equal to or higher than the limit temperature TCTh, and therefore, the stop of the combustion is prohibited by executing the deterioration suppressing process.

  As described above, according to the present embodiment, when the sulfur accumulation amount SDP becomes equal to or less than the desorption determination value SDCTh, the fuel cut process or the fuel introduction process is terminated, and the combustion in the cylinder 11 is restarted.

Further, the estimating unit 114 changes the method of estimating the sulfur accumulation amount SDP between when the fuel cut process is being performed and when the fuel introduction process is being performed.
When the fuel introduction process is being performed, the higher the catalyst temperature TC, the more easily the sulfur component is released from the three-way catalyst 22. Therefore, the time until the poisoning regeneration is completed varies depending on the catalyst temperature TC when the fuel introduction process is being performed. FIG. 7 shows a case where the poisoning regeneration is completed earlier in the example shown by the solid line accompanying the execution of the fuel introduction process than in the example shown by the broken line. It may be completed after t5. In this regard, the estimating unit 114 of the present embodiment changes the method of estimating the sulfur accumulation amount SDP between when the fuel cut process is being performed and when the fuel introduction process is being performed. Specifically, when the fuel introduction process is being performed, the sulfur accumulation amount SDP is estimated in consideration of the catalyst temperature TC that increases due to the introduction of the fuel. Accordingly, even if the poisoning regeneration progresses in a different manner between the case where the fuel introduction process is being performed and the case where the fuel cut process is being performed, the sulfur accumulation amount SDP is appropriately adjusted in accordance with the difference. Can be estimated. Therefore, the completion of the poisoning regeneration can be appropriately determined based on the sulfur accumulation amount SDP.

This embodiment can be implemented with the following modifications. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.
In the above embodiment, the in-line four-cylinder internal combustion engine 10 is illustrated, but the number of cylinders and the cylinder arrangement of the internal combustion engine are not limited to this.

  In the above embodiment, the ignition device 19 is prevented from performing the spark discharge during the execution of the fuel introduction process. However, during the execution of the fuel introduction process, the ignition device 19 may be caused to perform spark discharge at a time when the air-fuel mixture does not burn in the cylinder 11. For example, when spark discharge is performed when the piston is located near the bottom dead center, the air-fuel mixture is not burned in the cylinder 11 where spark discharge has been performed. Therefore, during the fuel introduction process, even if spark discharge is performed, the fuel injected from the fuel injection valve 17 can flow out of the cylinder 11 to the exhaust passage 21 without burning.

  The internal combustion engine to which the control device for the internal combustion engine is applied may include an in-cylinder injection valve that is a fuel injection valve that injects fuel directly into the cylinder 11. In this case, during execution of the fuel introduction process, fuel may be injected into the cylinder 11 from the in-cylinder injection valve, and the fuel may flow out to the exhaust passage 21 without burning. Thus, unburned fuel can be introduced into the three-way catalyst 22.

  The hybrid vehicle system may be another system different from the system shown in FIG. 1 as long as the rotation speed of the crankshaft 14 can be controlled by driving the motor.

  The control device of the internal combustion engine may be embodied as a device applied to an internal combustion engine mounted on a vehicle having no power source other than the internal combustion engine. If the internal combustion engine mounted on such a vehicle is configured to restart combustion in the cylinder 11 when the sulfur accumulation amount SDP estimated by the estimation unit 114 becomes equal to or less than the desorption determination value SDCTh, The same effect as the above embodiment can be obtained.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 14 ... Crankshaft, 15 ... Intake passage, 17 ... Fuel injection valve, 19 ... Ignition device, 21 ... Exhaust passage, 22 ... Three-way catalyst, 23 ... Particulate filter, 40 ... Power Distribution integration mechanism, 41: sun gear, 42: ring gear, 43: pinion gear, 44: carrier, 45: ring gear shaft, 50: reduction gear, 51: sun gear, 52: ring gear, 53: pinion gear, 60: reduction Mechanism, 61: differential, 62: drive wheels, 71: first motor generator, 72: second motor generator, 75: first inverter, 76: second inverter, 77: battery, 81: air flow meter, 82: crank angle sensor, 83: air-fuel ratio sensor, 84: exhaust temperature sensor, 86: accelerator opening degree sensor, 87: vehicle speed sensor 100 ... control device, 110 ... engine control unit, 111 ... ignition control unit, 112 ... injection valve control unit, 113 ... stop determination unit, 114 ... estimation unit, 120 ... motor control unit.

Claims (1)

Applied to an internal combustion engine that burns a mixture containing fuel injected from a fuel injection valve in a cylinder by spark discharge of an ignition device,
When stopping combustion in the cylinder under the condition that the crankshaft of the internal combustion engine is rotating, a fuel cut process for stopping fuel injection of the fuel injection valve, and injecting fuel from the fuel injection valve A control device for an internal combustion engine that selects and executes any one of fuel introduction processes for causing the fuel to flow out of the cylinder to an exhaust passage while remaining unburned,
A stop determination unit that determines whether a condition for stopping combustion in the cylinder is satisfied,
An estimating unit for estimating the amount of sulfur accumulated on the catalyst disposed in the exhaust passage,
When the stop determination unit determines that the stop condition is satisfied when the sulfur deposition amount estimated by the estimation unit is equal to or greater than a deposition threshold and starts the fuel cut process or the fuel introduction process, Even if the stop determination unit determines that the stop condition is satisfied, the combustion in the cylinder is restarted when the sulfur accumulation amount estimated by the estimation unit becomes equal to or less than the desorption determination value. Things,
The control device for an internal combustion engine, wherein the estimating unit changes the method of estimating the sulfur accumulation amount when the fuel cut process is being executed and when the fuel introduction process is being executed.