JP2015031166A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a spark ignition type internal combustion engine, for avoiding the PM jamming of a filter by suitably oxidizing and removing PMs trapped by the filter.SOLUTION: Even during filter regeneration as predetermined, when the temperature of the filter is lower than a predetermined temperature allowing the removal of particulate matters and the temperature of a catalyst is not lower than a first predetermined temperature allowing the oxidation of fuel delivered from the internal combustion engine, the exhaust emission control device for the spark ignition type internal combustion engine stops spark ignition in at least part of cylinders while continuing fuel supply. Even during the filter regeneration as predetermined, when the temperature of the filter is lower than the predetermined temperature allowing the removal of the particulate matters and the temperature of the catalyst belongs to a temperature range from a second predetermined temperature lower than the first predetermined temperature to the first predetermined temperature, the exhaust emission control device shifts a spark ignition timing for part of the cylinders to a timing close to a bottom dead center in an exhaust stroke while continuing fuel supply to at least part of the cylinders.

Description

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

  A filter for collecting particulate matter (hereinafter also referred to as PM) in the exhaust gas may be provided in the exhaust passage of the internal combustion engine. When the amount of PM collected in the filter (hereinafter also referred to as PM accumulation amount) reaches a certain amount, a process of oxidizing and removing PM is performed. This process is called filter regeneration. In order for the PM collected in the filter to be oxidized, it is necessary that the temperature of the filter is equal to or higher than a predetermined temperature, and the oxygen concentration in the filter is equal to or higher than the predetermined concentration.

  By the way, since a spark ignition type gasoline engine is usually operated at a stoichiometric air-fuel ratio or a rich air-fuel ratio, the oxygen concentration in the filter is low. The oxygen is supplied to the filter only when operating at a lean air-fuel ratio or when a fuel cut is performed by deceleration or the like. However, when the fuel cut is performed when the amount of accumulated PM is relatively large and the temperature of the filter is relatively high, the PM collected in the filter is oxidized all at once, and the reaction heat at this time causes The filter may overheat.

  On the other hand, when the PM accumulation amount is relatively large and the filter temperature is relatively high, it is known to suppress the overheating of the filter by prohibiting the fuel cut (for example, patent document). 1).

JP 2009-074426 A

  Conventionally, the filter regeneration condition is limited to the case where the temperature of the filter is relatively low, so that breakage due to overheating of the filter is suppressed. However, if the temperature of the filter is low enough to prevent sufficient filter regeneration, the PM collected in the filter will not be removed by oxidation even if the fuel cut is performed. In addition, the filter may be clogged. In general, a catalyst having oxidizing ability may be disposed upstream of the filter. By oxidizing the unburned fuel in the exhaust gas by this oxidizing ability and raising the exhaust gas temperature, the temperature of the filter is increased. Filter regeneration can be made possible even in a relatively low case.

  However, since the oxidation ability of the catalyst greatly depends on the catalyst temperature, it is difficult to sufficiently oxidize unburned fuel in the exhaust when the catalyst temperature is relatively low. In this case, there is a concern that unburned fuel is not only consumed wastefully but also unburned fuel is released to the outside.

  Therefore, the present invention has been made in view of the above-described problems, and its purpose is to suitably oxidize and remove PM trapped in a filter in a spark ignition type internal combustion engine. It is to avoid PM clogging.

In order to achieve the above object, the present invention captures a catalyst having an oxidation function provided in an exhaust passage of a spark ignition type internal combustion engine, and particulate matter in exhaust provided in an exhaust passage downstream of the catalyst. A filter to be collected, and the amount of particulate matter collected in the filter is equal to or greater than a predetermined amount, and a condition for performing fuel cut of the internal combustion engine during deceleration is satisfied. And a control device for oxidizing and removing the particulate matter collected by the filter. Further, the control device is configured such that the temperature of the filter is lower than a predetermined temperature at which particulate matter can be removed and the temperature of the catalyst is fed from the internal combustion engine even during the regeneration of the predetermined filter. A first control unit that stops spark ignition in at least some of the cylinders while continuing to supply fuel to the cylinders of the internal combustion engine when the temperature is equal to or higher than a first predetermined temperature at which the gas can be oxidized, and the predetermined filter regeneration Even when the temperature of the filter is lower than a predetermined temperature at which particulate matter can be removed, and the temperature of the catalyst is lower than the first predetermined temperature, the second predetermined temperature is lower than the first predetermined temperature. When the temperature belongs to the temperature range, at least some cylinders continue to supply fuel to the cylinders of the internal combustion engine, and the spark ignition timing in the some cylinders is shifted to the timing near the bottom dead center of the exhaust stroke. Having a second control unit.

  In the exhaust gas purification apparatus for an internal combustion engine, the filter regeneration process is performed by the control device when a predetermined amount or more of the particulate matter is collected in the filter and when the predetermined filter regeneration condition for satisfying the fuel cut is satisfied. . That is, at the time of regeneration of a predetermined filter, the fuel is cut and a large amount of oxygen is sent to the filter, so that the particulate matter collected in a predetermined amount or more is removed by oxidation. Therefore, the predetermined amount can be defined as a PM amount that requires filter regeneration or a PM amount that requires filter regeneration. Alternatively, the predetermined amount may be a PM amount that may cause clogging of the filter or a PM amount that adversely affects the internal combustion engine unless the filter is regenerated.

  Here, in general, the filter regeneration process requires that the temperature of the filter be higher than a predetermined temperature so as not to cause an excessive temperature rise in order to oxidize and remove the collected particulate matter. Therefore, the predetermined temperature is a temperature at which PM can be removed, but this predetermined temperature may be defined as a temperature at which PM is oxidized or a temperature at which the oxidation rate of PM falls within an allowable range. The predetermined temperature may be a value having a certain margin with respect to a temperature at which PM can be removed, a temperature at which PM is oxidized, or a temperature at which the oxidation rate of PM is within an allowable range.

  Here, when the temperature of the filter is lower than a predetermined temperature at which PM can be removed, it is difficult to realize the regeneration of the filter even if the fuel cut is performed. Therefore, when the PM accumulation amount is equal to or greater than the predetermined amount and the filter temperature is lower than the predetermined temperature at which PM can be removed, the filter temperature is reduced even though the filter needs to be regenerated. It can be said that the conditions required for reproduction are not satisfied. In such a case, the control device can send the unburned fuel to the catalyst having oxidation ability and raise the exhaust gas temperature flowing into the filter by the oxidation reaction at the catalyst. Therefore, it is desirable to raise the exhaust temperature in consideration of the catalyst temperature.

  More specifically, even when the predetermined filter is regenerated, the filter temperature is lower than the predetermined temperature and the catalyst temperature is equal to or higher than the first predetermined temperature, that is, the degree to which the unburned fuel supplied from the internal combustion engine can be oxidized. When the temperature is higher than the temperature at which the catalyst is activated, the first controller stops spark ignition in at least some of the cylinders while continuing to supply fuel to the cylinders of the internal combustion engine. As a result, unburned fuel and oxygen are supplied to the catalyst from the cylinder where the spark ignition is stopped, so heat is generated by the unburned fuel and oxygen reacting with the oxidizing ability of the catalyst, and the catalyst generates In addition, the temperature of the downstream filter can be raised to a predetermined temperature, so that the oxidative removal of the collected particulate matter can be promoted.

Further, even when the predetermined filter is being regenerated, when the filter temperature is lower than the predetermined temperature and the catalyst temperature is lower than the temperature at which the control by the first control unit is performed, that is, from the second predetermined temperature to the first When it belongs to a temperature range up to a predetermined temperature, the catalyst is not sufficiently active and cannot fully exhibit its oxidizing ability. In such a case, the second control unit continues the fuel supply to the cylinders of the internal combustion engine in at least some of the cylinders, while the spark ignition timing is at the bottom dead center of the exhaust stroke in some of the cylinders. It will be transferred to near time. As a result, it is possible to send exhaust gas containing a relatively large amount of unburned fuel that is relatively hot as a result of combustion and that is easily oxidized as the temperature rises, to the catalyst. Therefore, the catalyst temperature can be quickly raised, and the filter temperature can be raised. Further, by making the spark ignition timing near the bottom dead center of the exhaust stroke when the exhaust valve opens, the influence on the output of the internal combustion engine accompanying combustion can be suppressed. Therefore, an opportunity to perform the filter regeneration process by the process of the second control unit can be secured.

  According to the present invention, in a spark ignition internal combustion engine, PM trapped in a filter can be suitably oxidized and removed, and PM clogging in the filter can be avoided.

It is a figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, its intake system, and an exhaust system. FIG. 2 is a diagram illustrating a relationship between a filter temperature, a PM accumulation amount, and a region where fuel cut is performed with respect to a fuel cut executed in the internal combustion engine shown in FIG. 1. FIG. 2 is a diagram showing a correlation between a catalyst temperature mounted on the internal combustion engine shown in FIG. 1 and fuel injection and ignition modes, and a transition of an inflowing oxygen concentration to a filter and a transition of a total fuel injection amount with respect to the catalyst temperature. 2 is a flowchart showing a flow of filter regeneration control performed in the internal combustion engine shown in FIG. 1. FIG. 5 is a diagram showing a fuel injection pattern in an internal combustion engine when the catalyst temperature belongs to a range from a second activation temperature to an overheat protection temperature in the filter regeneration control shown in FIG. 4.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine according to the present embodiment and its intake system and exhaust system. An internal combustion engine 1 shown in FIG. 1 is a spark ignition type gasoline engine. The internal combustion engine 1 is mounted on a vehicle, for example. Further, the internal combustion engine 1 has a plurality of cylinders, for example, four cylinders, and when the cylinders are distinguished from each other, # 1 to # 4 are used as reference numbers.

  Here, an exhaust passage 2 is connected to the internal combustion engine 1. In the middle of the exhaust passage 2, a catalyst 3 and a filter 4 are provided in order from the upstream side. The catalyst 3 is a catalyst having an oxidation function and purifying exhaust gas. The catalyst 3 may be, for example, a three-way catalyst, an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst. The filter 4 collects PM in the exhaust gas. In this embodiment, the catalyst 3 corresponds to the catalyst having an oxidation function in the present invention.

A first temperature sensor 11 that detects the temperature of the exhaust gas is provided in the exhaust passage 2 upstream of the catalyst 3. A second temperature sensor 12 that detects the temperature of the exhaust gas is provided in the exhaust passage 2 downstream from the catalyst 3 and upstream from the filter 4. Based on the detection value of the first temperature sensor 11 or the second temperature sensor 12, the temperature of the catalyst 3 can be detected. Further, the temperature of the filter 4 can be detected based on the detection value of the second temperature sensor 12. Note that the temperatures of the catalyst 3 and the filter 4 may be estimated based on the operating state of the internal combustion engine 1. The exhaust passage 2 upstream of the catalyst 3 is provided with a first air-fuel ratio sensor 13 for detecting the air-fuel ratio of the exhaust. A second air-fuel ratio sensor 14 that detects the air-fuel ratio of the exhaust gas is provided in the exhaust passage 2 downstream of the catalyst 3 and upstream of the filter 4. Note that the first air-fuel ratio sensor 13 and the second air-fuel ratio sensor 14 may be oxygen concentration sensors that detect the oxygen concentration in the exhaust gas.

  Further, an intake passage 5 is connected to the internal combustion engine 1. A throttle 6 for adjusting the intake air amount of the internal combustion engine 1 is provided in the middle of the intake passage 5. An air flow meter 15 that detects the intake air amount of the internal combustion engine 1 is attached to the intake passage 5 upstream of the throttle 6. A fuel injection valve 7 that supplies fuel to the internal combustion engine 1 is attached to the internal combustion engine 1. The fuel injection valve 7 may inject fuel into the cylinder of the internal combustion engine 1 or may inject fuel into the intake passage 5. In addition, the internal combustion engine 1 is provided with a spark plug 8 that generates an electric spark in the cylinder.

  The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 controls the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the driver's request. In addition to the above sensors, the ECU 10 includes an accelerator opening sensor 17 for detecting an engine load by outputting an electric signal corresponding to the amount of depression of the accelerator pedal 16 by the driver, and a crank position sensor 18 for detecting the engine speed. Connected via electrical wiring, the output signals of these various sensors are input to the ECU 10.

  On the other hand, a throttle 6, a fuel injection valve 7, and a spark plug 8 are connected to the ECU 10 through electrical wiring, and these devices are controlled by the ECU 10. For example, when normal output control according to the load is performed in the internal combustion engine 1, the ECU 10 controls the fuel injection valve 7 so that the air-fuel ratio in the cylinder of the internal combustion engine 1 is normally at or near the stoichiometric air-fuel ratio. Control the fuel injection amount. Further, when the internal combustion engine 1 is decelerated (the vehicle 10 in which the internal combustion engine 1 is mounted may be decelerated), the ECU 10 stops the fuel supply from the fuel injection valve 7, that is, performs a fuel cut. The fuel cut is performed, for example, when the accelerator opening is not more than a predetermined opening and the engine speed is not less than a predetermined speed.

  In the internal combustion engine 1 configured as described above, particulate matter (PM) contained in the exhaust gas is collected by the filter 4 along with its operation and is accumulated there. If the amount of PM accumulated in this way increases, the exhaust pressure in the exhaust passage 2 increases, which may adversely affect the operation of the internal combustion engine 1. Therefore, the ECU 10 estimates the amount of PM deposited on the filter 4 (hereinafter referred to as PM deposition amount), and when the amount of PM deposition exceeds a predetermined amount, the accumulated PM is removed by oxidation. Is planned. Specifically, when the temperature of the filter 4 is equal to or higher than the temperature at which PM is oxidized, fuel is cut and a large amount of oxygen is supplied to the filter 4 to oxidize and remove the deposited PM. The PM accumulation amount may be estimated based on the past engine speed and engine load, or may be estimated based on the pressure difference between the exhaust upstream and downstream of the filter 4.

  As described above, it is preferable to quickly oxidize and remove the PM when the amount of accumulated PM in the filter 4 exceeds a predetermined amount. However, when the temperature of the filter 4 is lower than the temperature at which PM can be oxidized, Even if a fuel cut is performed to send oxygen to the filter 4, the deposited PM is not oxidized and sufficient PM removal may not be performed. Therefore, in such a case, the ECU 10 can regenerate the filter 4 by increasing the temperature of the filter 4 by increasing the temperature of the exhaust gas flowing into the filter 4 using the oxidizing ability of the catalyst 3. .

  Here, the oxidation ability of the catalyst 3 changes according to the catalyst temperature. When the temperature of the catalyst 3 does not reach the activation temperature sufficiently, the effective oxidizing ability cannot be exhibited, and therefore, the unburned fuel in the exhaust gas cannot be sufficiently oxidized, resulting in wasteful consumption of fuel and deterioration of emission. It becomes an inviting factor. Further, if the temperature of the catalyst 3 becomes excessively high, the catalyst 3 may be melted. Therefore, in this embodiment, when the PM accumulation amount in the filter 4 becomes a predetermined amount or more, if the temperature of the filter 4 is lower than the temperature at which PM can be oxidized, the filter according to the temperature of the catalyst 3 is used. Control is performed to raise the temperature of 4 and to remove the deposited PM by oxidation.

  Based on the above, the PM oxidation removal when the temperature of the filter 4 is lower than the temperature at which PM can be oxidized will be described in detail with reference to FIGS. FIG. 2 is a diagram illustrating the relationship among the temperature of the filter 4 according to the present embodiment, the amount of PM deposited on the filter 4, and the control regions A, B, and C for removing the deposited PM by oxidation. is there. Region A is a region in which control for oxidizing and removing deposited PM is performed when the PM deposition amount is equal to or greater than a predetermined amount and the temperature of the filter 4 is lower than a predetermined temperature that is a temperature at which PM can be oxidized. . Details of the control in the area A will be described later with reference to FIG.

  Next, region B is a region where fuel cut is prohibited even during deceleration. Region B is a region where the amount of accumulated PM is relatively large and the temperature of the filter 4 is relatively high, and when the fuel cut is performed, the PM collected in the filter 4 is oxidized all at once, so that the filter 4 This is a region that may overheat. The region B is a region where the temperature of the filter 4 is equal to or higher than, for example, about 750 ° C., but the higher the temperature of the filter 4, the easier it is to overheat even with a smaller amount of PM deposition. The higher the temperature of the filter 4 is, the larger the PM deposition amount is. On the other hand, even if the temperature of the filter 4 is high, if the amount of accumulated PM is small, the possibility that the filter 4 will overheat becomes low. Thus, in the region B, overheating of the filter 4 can be suppressed by prohibiting fuel cut during deceleration.

  Next, a region C is a region other than the region A and the region B, and is a region where fuel cut is performed in all cylinders during deceleration. In the region C, when the PM accumulation amount is less than the predetermined amount, it is not necessary to regenerate the filter 4, but fuel cut is performed in all cylinders in order to reduce fuel consumption. Further, in the region C, when the temperature of the filter 4 is equal to or higher than the predetermined temperature and the PM accumulation amount is equal to or higher than the predetermined amount, the fuel cut is performed in all the cylinders, thereby suppressing the fuel consumption during deceleration and the accumulated PM. Can be removed by oxidation.

  Here, the control performed in the area A will be described in detail with reference to FIG. FIG. 3 shows the transition of the oxygen concentration in the exhaust gas flowing into the filter 4 with respect to the temperature of the catalyst 3 when the control in the region A is performed in the middle stage, and the control in the region A is performed in the lower stage. The transition of the total fuel injection amount with respect to the temperature of the catalyst 3 is shown. This total injection amount is the total fuel injection amount in the four cylinders of the internal combustion engine 1 in one cycle. And the control content according to the area | region demarcated according to the catalyst temperature in the area | region A is described in the upper stage from the viewpoint of fuel injection and spark ignition.

The region A is defined according to the temperature of the catalyst 3 as a catalyst reaction impossible region, a temperature-oriented region, an oxygen concentration-oriented region, and a catalyst overheat protection region. In the catalyst overheat protection region, the temperature of the catalyst 3 is equal to or higher than the overheat protection temperature T0, and when the catalyst 3 is supplied with a large amount of oxygen, the catalyst 3 melts due to the heat of oxidation in the catalyst 3. This is a threshold value of the catalyst temperature that may possibly occur. Therefore, in the catalyst overheat protection region, overheating protection of the catalyst 3 is prioritized over PM oxidation removal by the filter 4, fuel cut is prohibited, and the air-fuel ratio in the cylinder exceeds the excess air ratio λ and flows into the filter 4. Fuel injection and spark ignition are performed so that the oxygen concentration is extremely low. Thereby, it is possible to suppress the supply of oxygen to the catalyst 3 and to lower the temperature of the catalyst 3 due to the latent heat of vaporization of unburned fuel in the exhaust.

  Next, the oxygen concentration important region is a state where the temperature of the catalyst is equal to or higher than the first activation temperature T1 and lower than the overheat protection temperature T0, and the first activation temperature T1 is the catalyst 3 if the catalyst temperature is higher than that. It is a threshold value of the catalyst temperature at which it can be determined that the catalyst temperature has sufficiently increased to the extent that the oxidation ability of the catalyst can be sufficiently exhibited. Therefore, when the temperature of the catalyst 3 is in the oxygen concentration important region, the catalyst 3 does not fall into an overheated state and is in a state where it can sufficiently exhibit its oxidizing ability. Therefore, in order to promptly raise the temperature of the filter 4 lower than the predetermined temperature and promote the oxidation removal of the accumulated PM, the first control is performed in which fuel injection is performed in at least some cylinders during deceleration and spark ignition is stopped. Done. Here, the optimum value of the fuel injection amount at the time of the first control and the number of cylinders that perform the fuel injection can be obtained in advance by experiments or simulations. Further, the spark ignition may be stopped only in the cylinder that performs fuel injection. Further, fuel injection may be performed in all the cylinders, and spark ignition may be stopped by the above-described method.

  When the first control is performed, oxygen and unburned fuel can be supplied to the catalyst 3. Since the oxidizing ability of the catalyst 3 can be fully utilized in the oxygen concentration-oriented region, heat is generated in the catalyst 3 by the oxygen and unburned fuel supplied by the first control, and the temperature of the filter 4 is thereby increased. Can be raised above a predetermined temperature. Further, since a large amount of oxygen can be discharged from at least the cylinder in which the spark ignition has been stopped, oxygen can be sufficiently supplied to the filter 4 as well. As described above, in the oxygen concentration priority region, the oxygen concentration supplied to the catalyst 3 and the filter 4 is emphasized. As a result, the oxygen concentration in the exhaust gas flowing into the filter 4 can be set to a predetermined concentration. The oxidation removal of the deposited PM can be promoted.

  Next, the temperature-oriented region is a state where the temperature of the catalyst is equal to or higher than the second activation temperature T2 and lower than the first activation temperature T1, and the second activation temperature T2 is the catalyst 3 if the catalyst temperature is lower than that temperature. It is a threshold value of the catalyst temperature at which it can be determined that the oxidation ability of the catalyst cannot be exhibited at all, or it can be regarded as not at all. Therefore, when the temperature of the catalyst 3 is in the temperature-oriented region, the catalyst 3 is in a state where it can exhibit a certain degree of oxidizing ability, but its oxidizing ability is not sufficient, and in order to exert an effective oxidizing ability. Is in a state where the catalyst temperature needs to be raised. Therefore, when the catalyst 3 is in such a state, the temperature of the catalyst 3 is raised by sending the oxygen necessary for oxidizing and removing the deposited PM to the catalyst 3 and the filter 4 with emphasis on the catalyst temperature. Priority is given to the second control, in which fuel injection is performed in at least some cylinders during deceleration, and the spark ignition timing in the injection cylinder is set to a timing near the bottom dead center of the exhaust stroke. Here, the optimum value of the fuel injection amount at the time of the second control and the number of cylinders that perform the fuel injection can be obtained in advance by experiments or simulations. Note that the cylinder that performs spark ignition may be a cylinder that performs fuel injection.

  In the second control, the spark ignition timing in the cylinder where the fuel is injected is set to a timing near the bottom dead center of the exhaust stroke. In other words, this time is the time when the exhaust valve of the cylinder starts to open or has already started. Therefore, the fuel supplied to the cylinders in the second control does not affect the engine output to the internal combustion engine 1 or has a very slight effect, so that fluctuations in the operating state of the internal combustion engine can be suppressed. it can. In the second control, since at least a part of the injected fuel is used for combustion, the exhaust temperature flowing from the cylinder to the catalyst 3 can be raised, and the fuel that has not been used for combustion is also heated to a certain extent in the cylinder. Therefore, the molecular weight of the unburned fuel can be reduced. This means that the unburned fuel is easily oxidized when it reaches the catalyst 3, and therefore promotes the oxidation of the unburned fuel by the catalyst 3 which is not sufficiently active. Thus, the temperature rise of the catalyst 3 is promoted, and as a result, the temperature rise of the filter 4 is also promoted.

Thus, in the temperature-oriented region, priority is given to the temperature increase of the catalyst 3 and fuel combustion is performed in the cylinder. Therefore, the oxygen concentration delivered to the filter 4 is lower than that in the oxygen concentration-oriented region. However, since the oxidizing ability of the catalyst 3 increases as the temperature of the catalyst 3 increases in the temperature-oriented region, the total injection amount in the second control is increased as the temperature of the catalyst 3 increases as shown in FIG. You can lose weight. Thereby, even during the second control, the oxygen concentration delivered to the filter 4 can be gradually increased, and the oxidation removal of the deposited PM by the filter 4 can be promoted as much as possible.

  Next, the catalyst reaction impossible region is a temperature at which the temperature of the catalyst 3 is lower than the second activation temperature T2. Therefore, in the catalytic reaction region, as in the region C, fuel cut is performed in all cylinders. Thus, fuel consumption is suppressed during deceleration.

  As described above, in the internal combustion engine 1, PM collected by the filter 4 is oxidized and removed. A specific flow of filter regeneration control when the temperature of the filter 4 and the PM accumulation amount belong to the region A is shown in FIG. 4 will be described. FIG. 4 shows that when the ECU 10 determines that the temperature of the filter 4 and the PM deposition amount belong to the region A, that is, the filter 4 reaches a predetermined temperature although PM of a predetermined amount or more is deposited on the filter 4. 6 is a flowchart showing a flow of filter regeneration control that is executed when the ECU 10 determines that it is not in a state. This routine is executed every predetermined time by the ECU 10.

  First, in S101, the temperature Tc of the catalyst 3 is detected. Thereafter, in S102, it is determined whether or not the catalyst temperature Tc is lower than the second activation temperature T2. Therefore, if a positive determination is made, the process proceeds to S107, and if a negative determination is made, the process proceeds to S103. In S103, it is determined whether or not the catalyst temperature Tc is equal to or higher than the overheat protection temperature T0. Therefore, if a positive determination is made, the process proceeds to S108, and if a negative determination is made, the process proceeds to S104. In S104, it is determined whether or not the catalyst temperature Tc is equal to or higher than the first activation temperature T1. Therefore, if a positive determination is made, the process proceeds to S105, and if a negative determination is made, the process proceeds to S106.

  Then, when the process proceeds to S105, that is, when it is determined that the temperature Tc of the catalyst 3 belongs to the oxygen concentration important region, the fuel in at least some of the cylinders is decelerated during the deceleration by the first control described above. Injection is performed and spark ignition is stopped. Further, when the process proceeds to S106, that is, when it is determined that the temperature Tc of the catalyst 3 belongs to the temperature-oriented region, fuel injection is performed in at least some cylinders during deceleration by the second control described above. And the spark ignition timing in the injection cylinder is set to a timing near the bottom dead center of the exhaust stroke. In addition, when the process proceeds to S107, that is, when it is determined that the temperature Tc of the catalyst 3 belongs to the non-catalytic reaction region, as shown in FIG. Is planned. When the process proceeds to S108, that is, when it is determined that the temperature Tc of the catalyst 3 belongs to the catalyst overheat protection region, as shown in FIG. Oxygen supply is suppressed.

  As described above, when the filter regeneration control shown in FIG. 4 is executed, even when a predetermined amount or more of PM accumulates on the filter 4 and its removal is necessary, the temperature of the filter 4 reaches the predetermined temperature. In the case where it is difficult to efficiently remove the oxidization, it is possible to oxidize and remove the deposited PM that is suitable for the degree of oxidation ability of the catalyst 3.

Here, details of fuel injection when the first control and the second control are performed in the filter regeneration control will be described with reference to FIG. FIG. 5 shows the fuel injection pattern in the first control and the second control in the upper part, and shows the outline of setting of the fuel injection pattern in the transition of the total injection amount shown in the lower part in FIG. As described above, when the catalyst temperature belongs to the temperature-oriented region (T2 ≦ Tc <T1), the catalyst temperature increases in order of decreasing so that the total fuel injection amount in the second control gradually decreases as the catalyst temperature increases. , Injection patterns 1, 2, 3, and 4 are set.
In the case of normal injection in which the accumulated PM is not oxidized and removed, in the internal combustion engine 1 having four cylinders, fuel injection is sequentially repeated in each cylinder in the order of # 1, # 3, # 4, and # 2. Therefore, in the injection pattern 1 in the second control, the fuel injection in the cylinder # 2 is cut (in FIG. 5, the fuel-cut cylinder is represented by the symbol “**”), and the remaining 3 A cycle in which fuel injection is performed in one cylinder is repeated. In the injection pattern 2, the cycle in which the fuel injection in the cylinders # 2 and # 3 is cut and the fuel injection is performed in the remaining two cylinders is repeated. Further, in the injection pattern 3, the cycle in which the fuel injection in the cylinders # 2, # 3, and # 4 is cut and the fuel injection is performed in the remaining cylinder # 1 is repeated. Further, in the injection pattern 4, fuel injection in the cylinders # 2, # 3, and # 4 is cut, and after the cycle in which fuel injection is performed in the remaining cylinder # 1, fuel injection in all cylinders is cut. The two cycles are repeated in sequence. By setting the injection pattern in this manner, the total fuel injection amount in the second control can be gradually reduced as the catalyst temperature rises as shown in FIG. The fuel injection amount in each cylinder in each injection pattern may be adjusted as appropriate so that the total injection amount changes as shown in FIG.

  When the catalyst temperature belongs to the oxygen concentration important region (T1 ≦ Tc <T0), unburned components for raising the temperature are sent to the catalyst 3 by the first control, and more oxygen is added to the catalyst 3 and the filter 4. In order to supply the fuel, the injection pattern 5 is set. The injection pattern 5 is a cycle in which fuel injection in all cylinders is cut after a cycle in which fuel injection in the cylinders # 2, # 3, and # 4 is cut and fuel injection is performed in the remaining cylinder # 1. Are performed twice, and these three cycles are sequentially repeated.

  Note that the injection pattern shown in FIG. 5 is merely an example, and as long as the purpose of the first control and the second control is achieved, the content of the injection pattern may be adjusted as appropriate, and set by each control. The number of spray patterns to be changed may be changed as appropriate.

1 Internal combustion engine 2 Exhaust passage 3 Catalyst 4 Filter 5 Intake passage 6 Throttle 7 Fuel injection valve 8 Spark plug 10 ECU
11 First temperature sensor 12 Second temperature sensor 13 First air fuel ratio sensor 14 Second air fuel ratio sensor 15 Air flow meter 16 Accelerator pedal 17 Accelerator opening sensor 18 Crank position sensor

Claims (1)

A catalyst having an oxidation function provided in an exhaust passage of a spark ignition type internal combustion engine;
A filter that is provided in an exhaust passage downstream of the catalyst and collects particulate matter in the exhaust;
The amount of the particulate matter collected by the filter is equal to or greater than a predetermined amount, and the condition for executing the fuel cut of the internal combustion engine at the time of deceleration is satisfied. A control device for oxidizing and removing the collected particulate matter;
An exhaust purification device for an internal combustion engine comprising:
The controller is
Even at the time of regeneration of the predetermined filter, the temperature of the filter is lower than a predetermined temperature at which particulate matter can be removed, and the temperature of the catalyst is a first predetermined value that can oxidize fuel fed from the internal combustion engine. A first controller that stops spark ignition in at least some of the cylinders while continuing to supply fuel to the cylinders of the internal combustion engine when the temperature is equal to or higher than the temperature;
Even during regeneration of the predetermined filter, the temperature of the filter is lower than a predetermined temperature at which particulate matter can be removed, and the temperature of the catalyst is lower than the second predetermined temperature lower than the first predetermined temperature. In the case where it belongs to a temperature range up to a predetermined temperature, at least some cylinders continue to supply fuel to the cylinders of the internal combustion engine while the spark ignition timing in the some cylinders is near the bottom dead center of the exhaust stroke A second control unit for shifting to the time of
An exhaust emission control device for an internal combustion engine.

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