JP2005220880A - Control device for multi-cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, suppressing that an exhaust emission control means is excessively heated at the time of regeneration, in the internal combustion engine in which cylinder cut-off control is performed at the time of regeneration of the exhaust emission control means. <P>SOLUTION: This control device for the multi-cylinder internal combustion engine executes cylinder cut-off control that when executing regeneration accompanying the rise of temperature of the exhaust emission control means in the multi-cylinder internal combustion engine having the exhaust emission control means in an exhaust passage, for raising exhaust temperature, at least one intake/exhaust valve of a part of cylinders of the internal combustion eigne is closed and stopped and also fuel supply is stopped, and executes fuel cutting for stopping fuel supply to each cylinder of the internal combustion engine when the speed of a vehicle with the internal combustion engine mounted is reduced. When executing fuel cutting (step 103) during execution of regeneration (step 101), one of intake valve and exhaust valve of the part of the cylinders is operated in opening/closing, and the other is operated in opening/closing or opened (step 105). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for a multi-cylinder internal combustion engine.

  Usually, an exhaust gas purification device is provided in an exhaust system of an internal combustion engine to purify exhaust gas. As such an exhaust purification device, various devices have been conventionally used, and one of them is a particulate filter (hereinafter referred to as “NOx storage filter”) carrying a NOx storage catalyst in the exhaust passage. What you do is known. According to such an exhaust purification device using a NOx storage filter, it is possible to remove exhaust particulate matter (PM) such as soot contained in exhaust gas and remove nitrogen oxides (NOx). Become.

  On the other hand, when the above NOx occlusion filter is used, various regeneration processes aiming at recovery of the exhaust gas purification performance of the filter are periodically performed. That is, for example, PM regeneration processing for oxidizing and removing exhaust particulates deposited on the NOx storage filter, NOx reduction purification processing for removing and reducing NOx stored in the NOx storage catalyst, and sulfur stored in the NOx storage catalyst A sulfur poisoning regeneration process or the like for releasing oxide (SOx) is performed.

  When such regeneration processing is performed, it may be necessary to increase the temperature of the NOx storage filter. In such a case, the number of cylinders is reduced to increase the load per cylinder and to reduce the exhaust gas. A method for increasing the filter temperature by increasing the temperature is known.

  However, when the regeneration process is performed by raising the filter temperature by this method, the temperature rises to such an extent that the NOx occlusion filter is damaged (for example, melting of the filter or thermal deterioration of the NOx occlusion catalyst carried on the filter). There is a case.

  Such excessive temperature rise may occur, for example, when a so-called “fuel cut” is performed during the regeneration process as described above. The fuel cut is to stop the fuel supply when it is determined that the vehicle is in a deceleration state (for example, an engine brake state) in which fuel supply is not necessary, thereby improving the fuel consumption. However, if such fuel cut is performed when the regeneration process is performed while increasing the filter temperature by the reduced cylinder control as described above, the amount of exhaust gas flowing through the NOx storage filter rapidly decreases. As a result, the amount of heat deprived from the NOx occlusion filter suddenly decreases, the temperature of the filter is excessively increased, and the NOx occlusion catalyst carried on the filter may be thermally deteriorated.

  On the other hand, as a technique for preventing the deterioration of the catalyst due to such fuel cut, for example, in Patent Document 1, if the temperature of the catalyst is equal to or higher than a predetermined value during the fuel cut, at least either the intake valve or the exhaust valve is used. A configuration is disclosed in which one side is closed to prohibit the introduction of exhaust gas into the catalyst. However, this is to prevent air from flowing into the high-temperature catalyst as it is and the catalyst from being exposed to an excessive oxygen atmosphere and deteriorating, and a fuel cut is performed during the regeneration process as described above. It cannot be applied in some cases.

  That is, for example, when the fuel cut is performed during the regeneration process, if the introduction of the exhaust gas into the NOx storage filter is prohibited, the amount of heat taken away from the NOx storage filter by the exhaust gas flowing in decreases. The filter temperature rises rapidly, and the possibility of melting of the filter or thermal deterioration of the NOx storage catalyst carried on the filter increases.

JP 2003-74385 A JP 2002-106325 A JP 2001-271663 A JP-A-11-294146 JP 10-2239 A

  The present invention has been made in view of the above, and an object of the present invention is to provide an exhaust purification means (for example, the NOx occlusion filter) in the exhaust system so that the exhaust purification means can be reduced during the regeneration process. Provided is a control apparatus for a multi-cylinder internal combustion engine capable of suppressing an excessive increase in temperature of the exhaust gas purification means during the regeneration process in a multi-cylinder internal combustion engine in which cylinder control is performed and the exhaust temperature is raised. It is to be.

  The present invention provides a control device for a multi-cylinder internal combustion engine described in each claim as a means for solving the above-mentioned problems.

  The first aspect of the present invention is to increase the exhaust temperature when a regeneration process with a temperature rise is performed on a multi-cylinder internal combustion engine having exhaust purification means in the exhaust passage in order to recover the exhaust purification performance of the exhaust purification means. In order to achieve this, at least one of the intake valve and the exhaust valve is in a closed valve stop state for some cylinders of the multi-cylinder internal combustion engine, and the reduced-cylinder control for stopping the fuel supply is performed, and the multi-cylinder internal combustion engine is mounted. In a control apparatus for a multi-cylinder internal combustion engine that performs a fuel cut to stop fuel supply to each cylinder of the multi-cylinder internal combustion engine when the vehicle is decelerated, when performing the fuel cut during the regeneration process A control apparatus for a multi-cylinder internal combustion engine, characterized in that one of the intake valves and exhaust valves of the some cylinders is opened / closed and the other is opened / closed or opened. Subjected to.

  If the fuel cut is performed when the cylinder reduction control is performed as described above and the exhaust gas temperature is raised to perform the regeneration process, the amount of air sucked into the cylinders that have been operating decreases, and the same As a result, the amount of exhaust gas discharged from the cylinder decreases, and as a result, the amount of exhaust gas flowing through the exhaust purification means decreases rapidly. When the amount of exhaust gas flowing in this way rapidly decreases, the temperature of the exhaust gas purification means may increase rapidly. This is because the amount of heat taken away from the exhaust purification means by the exhaust gas flowing in rapidly decreases, and as a result, the exhaust purification means may be overheated.

  On the other hand, in the first invention, when the fuel cut is performed during the regeneration process, one of the intake valves and the exhaust valves of the some cylinders is opened and closed, and the other is opened and closed. Alternatively, the valve is opened. By doing so, the cylinders that have been inoperative due to the reduced cylinder control and have stopped performing intake and exhaust are made to perform intake and exhaust, and the amount of exhaust gas is compensated. It is possible to prevent the amount of exhaust gas flowing through the exhaust purification unit from being rapidly reduced with the implementation, and as a result, it is possible to prevent the exhaust purification unit from being overheated.

  In addition, when fuel cut is performed, combustion is not performed in the cylinder, and air only passes through the cylinder. In this specification, however, gas exhausted from the cylinder is exhausted including this case as well. It will be referred to as gas.

  According to a second aspect of the present invention, in the first aspect of the present invention, the apparatus has a temperature detection means for detecting the temperature of the exhaust purification means, and is detected by the temperature detection means when the fuel cut is performed during the regeneration process. Only when the temperature of the exhaust purifying means is equal to or higher than a predetermined temperature, one of the intake valves and exhaust valves of the some cylinders is in an open / close operation state, and the other is in an open / close operation state or a valve open state. To be.

  When the amount of exhaust gas flowing through the exhaust purification means increases, the temperature rise of the exhaust purification means is suppressed, and the temperature is lowered. If the temperature of the exhaust purification unit becomes too low, the regeneration process being performed is temporarily stopped, and it is necessary to raise the temperature of the exhaust purification unit once again when restarting the regeneration process. In order to raise the temperature of the exhaust gas purification means, fuel or the like is required. From the viewpoint of efficient regeneration processing, it is preferable that the temperature of the exhaust gas purification means is not excessively lowered.

  On the other hand, if the fuel cut is performed when the reduction control is performed and the exhaust temperature is increased to perform the regeneration process as described above, the temperature of the exhaust purification unit rises. When the temperature is low, there is no problem if the temperature rises to some extent and does not reach an excessive temperature rise. In other words, according to the second aspect of the invention, by appropriately setting the predetermined temperature, only when there is a higher possibility of excessive temperature rise, the cylinder is disabled due to the reduced cylinder control, and intake and exhaust are not performed. Since the cylinder that has been used is configured to perform intake and exhaust, the amount of exhaust gas is supplemented, so that it is possible to efficiently perform the regeneration process while suppressing the occurrence of excessive temperature rise.

  According to a third aspect, in the first aspect, the apparatus has temperature detecting means for detecting the temperature of the exhaust purification means, and is detected by the temperature detecting means when the fuel cut is performed during the regeneration process. The number of cylinders in which one of the intake valve and the exhaust valve is in the open / close operation state and the other is in the open / close operation state or the open state among the some cylinders based on the temperature of the exhaust purification means Is determined.

  According to the third aspect of the invention, the amount of exhaust gas flowing through the exhaust purification unit can be adjusted according to the temperature of the exhaust purification unit. By doing so, it is possible to suppress the temperature of the exhaust gas purification unit from being lowered more than necessary, and thus it is possible to efficiently perform the regeneration process while suppressing the occurrence of excessive temperature rise.

  According to a fourth aspect of the invention, in any one of the first to third aspects of the invention, the exhaust purification means further includes an inflowing oxygen amount estimation means for estimating an amount of oxygen flowing in a unit time. When the cylinder reduction control is performed, based on the oxygen amount estimated by the inflowing oxygen amount estimating means, at least one of the intake valve and the exhaust valve is brought into a closed stop state, and the number of cylinders that stop the fuel supply is determined. It is determined.

  Since the temperature of the exhaust gas purification means can be raised by an oxidation reaction of hydrocarbons or the like in the exhaust gas purification means, the degree of this temperature increase depends on the amount of oxygen flowing into the exhaust gas purification means per unit time. In addition, when the above-described cylinder reduction control is performed, the intake / exhaust amount per operating cylinder increases as the number of operating cylinders decreases, and the intervals between the intake and the exhaust become longer, and as a result, flows into the exhaust purification means. The flow of exhaust gas pulsates greatly. Since the exhaust gas contains oxygen, if the flow of the exhaust gas flowing into the exhaust purification unit pulsates as described above, the amount of oxygen flowing into the exhaust purification unit per unit time also pulsates greatly. Become.

  When the amount of oxygen flowing into the exhaust purification unit in a unit time pulsates in this way, the average inflowing oxygen amount is the amount of the inflowing oxygen amount, even though the exhaust purification unit does not overheat. At the peak, there is a risk that the exhaust purification means will overheat. That is, when the cylinder reduction control is performed, there is a possibility that the temperature of the exhaust purification unit is excessively increased due to the pulsation of the amount of oxygen flowing into the exhaust purification unit per unit time.

  On the other hand, according to the fourth aspect of the present invention, when the cylinder reduction control is performed when the regeneration process is performed, the intake valve and the exhaust valve are controlled based on the oxygen amount estimated to flow into the exhaust purification unit per unit time. At least one of the cylinders is brought into a closed valve stop state, and the number of cylinders for stopping the fuel supply is determined. The inflowing oxygen amount at the peak of the pulsation of the inflowing oxygen amount generated as a result of the reduced cylinder control tends to increase if the number of cylinders to be deactivated is increased in the reduced cylinder control and decrease if the number of cylinders to be deactivated is decreased. is there. Therefore, according to the fourth aspect of the invention, the inflowing oxygen amount at the peak of the inflowing oxygen amount pulsation can be adjusted to be less than the inflowing oxygen amount at which the exhaust purification means is overheated, It is possible to suppress the exhaust purification means from being overheated.

The fifth aspect of the invention increases the exhaust temperature when performing a regeneration process with a temperature rise to recover the exhaust purification performance of the exhaust purification means for a multi-cylinder internal combustion engine having exhaust purification means in the exhaust passage. In order to achieve this, in a control apparatus for a multi-cylinder internal combustion engine, a cylinder reduction control is performed in which at least one of an intake valve and an exhaust valve is closed and the fuel supply is stopped for some cylinders of the multi-cylinder internal combustion engine. And an inflowing oxygen amount estimation means for estimating the amount of oxygen flowing into the exhaust purification means per unit time, and the inflowing oxygen amount estimation means estimates when the cylinder reduction control is performed during the regeneration process. A control device for a multi-cylinder internal combustion engine in which at least one of an intake valve and an exhaust valve is closed and the number of cylinders for stopping fuel supply is determined based on the oxygen amount Subjected to.
According to the fifth aspect of the invention, it is possible to suppress the exhaust purification means from being overheated when the regeneration process is performed in the same manner as described for the fourth aspect of the invention.

  The invention described in each claim relates to the above-described regeneration in a multi-cylinder internal combustion engine in which an exhaust gas purification unit is provided in an exhaust system and the exhaust temperature is increased by performing a reduction cylinder control during a regeneration process for the exhaust gas purification unit. There is a common effect that the exhaust purification means can be prevented from being overheated during the processing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are assigned to the same members.

  FIG. 1 is a diagram for explaining a case where the present invention is applied to a four-cylinder in-cylinder injection compression ignition type internal combustion engine mounted on a vehicle. The present invention can also be applied to other types of multi-cylinder internal combustion engines, for example, in-cylinder injection spark ignition internal combustion engines. 2 is a schematic plan view of the intake system and the like of the internal combustion engine shown in FIG. 1, and # 1 to # 4 in the figure indicate the first cylinder to the fourth cylinder, respectively.

  1 and 2, 1 is an internal combustion engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, and 4 is an intake manifold, Reference numeral 5 denotes an exhaust manifold. In FIG. 2, 2a indicates an intake valve of each cylinder, and 2b indicates an exhaust valve.

  As shown in FIG. 1, the intake manifold 4 is connected to the outlet of the compressor 7a of the variable displacement type exhaust turbocharger 7 via the downstream intake duct 6, and the inlet of the compressor 7a is connected to the upstream intake duct 8 and It is connected to an air cleaner 10 via an air flow meter 9. A throttle valve 12 driven by a step motor 11 is arranged in the downstream intake duct 6, and an intercooler 13 for cooling intake air flowing in the intake duct 6 is arranged around the downstream intake duct 6. Is done. In the configuration shown in FIG. 1, the engine cooling water is guided into the intercooler 13, and the intake air is cooled by the engine cooling water.

  On the other hand, the exhaust manifold 5 is connected to the inlet of the turbine 7b of the exhaust turbocharger 7, and the outlet of the turbine 7b is connected to a particulate filter (supporting a NOx occlusion catalyst constituting exhaust purification means) via an exhaust pipe 14. That is, the casing 16 containing the NOx storage filter) 15 is connected. A temperature sensor 21 for detecting or estimating the temperature of the NOx storage filter 15 is attached to the casing 16. Without providing such a temperature sensor 21, the relationship between the operating state of the engine and the temperature of the NOx storage filter 15 is obtained in advance, and the temperature of the NOx storage filter 15 is estimated based on the operating state of the engine. You can also.

  The exhaust pipe 14 and the downstream side intake duct 6 are connected to each other via an exhaust recirculation (hereinafter referred to as EGR) passage 17, and an EGR control valve 19 driven by a step motor 18 is disposed in the EGR passage 17. The An EGR cooler 20 for cooling the EGR gas flowing in the EGR passage 17 is disposed in the EGR passage 17. In the configuration shown in FIG. 1, the engine cooling water is guided into the EGR cooler 20, and the EGR gas is cooled by the engine cooling water.

  The fuel injection valve 3 is connected to a fuel reservoir, a so-called common rail 32 through a fuel supply pipe 31. Fuel is supplied into the common rail 32 from an electrically controlled fuel pump 33 with variable discharge amount, and the fuel supplied into the common rail 32 is supplied to the fuel injection valve 3 via each fuel supply pipe 31. A fuel pressure sensor 34 for detecting the fuel pressure in the common rail 32 is attached to the common rail 32, and a fuel pump 33 is set so that the fuel pressure in the common rail 32 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 34. The discharge amount is controlled.

  The electronic control unit 50 is composed of a digital computer, and is connected to each other by a bidirectional bus 51. A ROM (read only memory) 52, a RAM (random access memory) 53, a CPU (microprocessor) 54, an input port 55, and an output port 56. It comprises. Output signals of the air flow meter 9, the temperature sensor 21, and the fuel pressure sensor 34 are input to the input port 55 via the corresponding AD converters 57, respectively.

  The accelerator pedal 44 is connected to a load sensor 45 that generates an output voltage proportional to the amount of depression of the accelerator pedal 44 (accelerator opening), and the output voltage of the load sensor 45 is input via a corresponding AD converter 57. Input to port 55. Further, the input port 55 is connected to a crank angle sensor 46 that generates an output pulse every time the crankshaft rotates, for example, 15 °, and a vehicle speed sensor (not shown) that detects the vehicle speed of the vehicle on which the internal combustion engine is mounted. None) is also connected, and the electronic control unit 50 calculates the acceleration of the vehicle based on the signal from the vehicle speed sensor.

  On the other hand, the output port 56 is connected to the fuel injection valve 3, the step motor 11 for driving the throttle valve 12, the step motor 18 for driving the EGR control valve 19, the fuel pump 33, and the like through corresponding drive circuits 58. The components can be controlled by signals from the electronic control unit 50.

  In this embodiment, when it is determined that the vehicle on which the internal combustion engine is mounted is in a deceleration state (for example, an engine brake state), “fuel cut” is performed to stop the supply of fuel to each cylinder. It is like that. More specifically, in this embodiment, for example, the fuel cut is executed when the accelerator opening is zero over a predetermined time and the engine speed is equal to or higher than the predetermined speed. When the engine speed falls below the predetermined speed after entering the fuel cut state, or when the accelerator opening is increased after entering the fuel cut state, the fuel cut state is canceled and the fuel supply is stopped. Resumed.

  3A and 3B show the structure of the NOx storage filter 15. 3A shows a front view of the NOx storage filter 15, and FIG. 3B shows a side sectional view of the NOx storage filter 15. As shown in FIG. As shown in FIGS. 3 (A) and 3 (B), the NOx storage filter 15 has a honeycomb structure and includes a plurality of exhaust flow passages 60 and 61 extending in parallel with each other. These exhaust flow passages include an exhaust gas inflow passage 60 whose downstream end is closed by a plug 62 and an exhaust gas outflow passage 61 whose upstream end is closed by a plug 63. In addition, the hatched part in FIG. Therefore, the exhaust gas inflow passages 60 and the exhaust gas outflow passages 61 are alternately arranged via the thin partition walls 64. In other words, in the exhaust gas inflow passage 60 and the exhaust gas outflow passage 61, each exhaust gas inflow passage 60 is surrounded by four exhaust gas outflow passages 61, and each exhaust gas outflow passage 61 is surrounded by four exhaust gas inflow passages 60. Are arranged as follows.

  The NOx occlusion filter 15 is formed of a porous material such as cordierite, for example. Therefore, the exhaust gas flowing into the exhaust gas inflow passage 60 is contained in the surrounding partition wall 64 as indicated by an arrow in FIG. Through the exhaust gas outflow passage 61 adjacent thereto. At this time, the exhaust particulates contained in the exhaust gas are collected by the porous material and removed from the exhaust gas, thereby preventing the exhaust particulates from being released into the atmosphere.

  Further, a NOx storage catalyst is supported on the surface of the partition wall 64 and in the internal pores. The NOx storage catalyst used here is selected from, for example, alkali metals such as potassium K, sodium Na, lithium Li, and cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y. And at least one of the above and a noble metal such as platinum Pt.

  Such a NOx storage catalyst is lean when the air-fuel ratio of the exhaust gas flowing therethrough (that is, the ratio of air and fuel supplied to the exhaust passage upstream of the NOx storage filter 15, the combustion chamber 2 or the intake passage, etc.) is lean. The NOx is occluded, and the air-fuel ratio of the exhaust gas that circulates is reduced, and if a reducing agent is present, the NOx occluded is removed and reduced and purified (NOx occlusion and desorption and reduction and purification action).

  In the compression ignition type internal combustion engine as shown in FIG. 1, the combustion air-fuel ratio, that is, the average air-fuel ratio in the combustion chamber 2 is lean, so that the exhaust gas air-fuel ratio is also lean, and the NOx storage catalyst is an exhaust gas. Occlude NOx inside. Further, when the combustion air-fuel ratio is made rich by increasing the fuel injection amount or the like, the air-fuel ratio of the exhaust gas is reduced and the reducing agent is present, so the NOx storage catalyst disengages the stored NOx. NOx released and removed is reduced and purified.

  In the present embodiment, the NOx occlusion / release and reduction / purification action of the NOx occlusion catalyst is used to convert NOx in the exhaust gas into the NOx occlusion catalyst when the internal combustion engine is operated with the combustion air-fuel ratio lean. The NOx storage catalyst is changed by changing the combustion air-fuel ratio of the internal combustion engine to a rich state when it is determined that the stored NOx must be removed and reduced and purified, such as when the NOx purification rate decreases after being stored for a certain period of time. The NOx reduction and purification process for removing and purifying NOx stored in the NOx is performed to recover the NOx storage capacity of the NOx storage catalyst.

  In some cases, the fuel of the internal combustion engine contains a sulfur component. In this case, the exhaust gas contains sulfur oxide (SOx). When SOx is present in the exhaust gas, the NOx storage catalyst stores SOx in the exhaust gas by exactly the same mechanism as that for storing NOx.

  However, SOx stored in the NOx storage catalyst is relatively stable and generally tends to be accumulated in the NOx storage catalyst. If the amount of SOx stored in the NOx storage catalyst increases, the NOx storage capacity of the NOx storage catalyst decreases and it becomes impossible to sufficiently remove NOx in the exhaust gas. A poison problem arises.

  On the other hand, SOx stored in the NOx storage catalyst can be separated by the same mechanism as NOx. However, since SOx is occluded in the NOx occlusion catalyst in a relatively stable form, the SOx occluded in the NOx occlusion catalyst cannot be released at a temperature at which normal NOx reduction purification control is performed (for example, about 250 ° C. or more). Have difficulty. For this reason, in order to eliminate sulfur poisoning, the temperature of the NOx storage catalyst is raised to a temperature higher than that during the NOx reduction purification process, that is, the sulfur content release temperature (for example, 600 ° C. or higher), It is necessary to carry out sulfur poisoning regeneration processing to make the fuel ratio rich. In the present embodiment, the amount of SOx accumulated in the NOx storage catalyst is estimated from the vehicle travel distance or the fuel consumption amount, and when it is determined that the removal of SOx is necessary based on the value, the cylinder reduction control described later is performed. As a result, the NOx occlusion filter 15 is heated and the combustion air-fuel ratio, that is, the average air-fuel ratio in the combustion chamber 2 is changed to a rich state, so that the sulfur poisoning regeneration process as described above is performed, and is carried by the filter. The NOx storage capacity of the NOx storage catalyst is restored.

  Further, the exhaust particulates collected by the NOx occlusion filter 15 are normally oxidized and removed continuously. However, when the amount of exhaust particulates is extremely large, the exhaust particulates are not completely removed and accumulate in layers on the filter. May end up. In this case, the exhaust particulate removal ability of the NOx occlusion filter 15 is reduced, and the contact opportunity between the supported NOx occlusion catalyst and the exhaust gas is reduced. As a result, the NOx occlusion ability is also lowered. . Therefore, in the above case, it is necessary to perform a PM regeneration process for forcibly oxidizing and removing the exhaust particulate deposited by raising the temperature of the NOx storage filter 15. In the present embodiment, the NOx occlusion filter 15 is controlled by performing the reduced cylinder control described later periodically or when it is determined that it is necessary to remove the accumulated exhaust particulate matter based on pressure loss or the like in the NOx occlusion filter 15. The PM regeneration process as described above is performed by raising the temperature.

  As described above, in this embodiment, in order to recover the exhaust purification performance such as the NOx storage capability and the exhaust particulate removal capability of the NOx storage filter 15, various regeneration processes (NOx reduction purification process, sulfur poisoning) Regeneration process, PM regeneration process). When performing these regeneration processes, the temperature of the NOx occlusion filter 15 may need to be raised. In this embodiment, in such a case, the exhaust temperature is raised by performing the reduced cylinder control. The temperature of the NOx storage filter 15 is raised.

  In the present embodiment, the cylinder reduction control is performed by closing both the intake valve and the exhaust valve in a closed state and stopping the fuel supply for some cylinders of the internal combustion engine. In another embodiment, the operation may be performed by bringing either one of the intake valve and the exhaust valve to a closed stop state and stopping the fuel supply for some cylinders of the internal combustion engine.

  When this cylinder reduction control is performed, the above-mentioned part of the cylinders are deactivated, and only the remaining cylinders are operated to generate the required torque. Therefore, the load per cylinder in operation is reduced. The exhaust gas temperature increases and the temperature of the NOx storage filter 15 can be increased.

  In the cylinder reduction control in the present embodiment, the number of cylinders (that is, idle cylinders) in which the intake / exhaust valves are closed and stopped and the fuel supply is stopped is the engine speed, the required torque (accelerator opening), etc. Is determined on the basis of a map determined in advance according to the engine operating state. In other words, this map represents the relationship between the number of deactivated cylinders that raise the exhaust temperature to a temperature suitable for the regeneration process and the engine operating state, and is obtained in advance by experiments or the like and stored in the ROM 52 of the electronic control unit 50. Let me.

  However, when such regeneration control is performed by increasing the temperature of the NOx occlusion filter 15 by performing such cylinder reduction control, the NOx occlusion filter 15 is damaged (for example, the filter is damaged or the NOx occlusion carried by the filter is carried out). In some cases, the temperature rises as the catalyst undergoes thermal degradation.

  One of cases where such excessive temperature rise is likely to occur is when a fuel cut is performed during the regeneration process. In other words, if the fuel cut is performed when the cylinder reduction control is performed and the exhaust temperature is increased to perform the regeneration process as described above, the amount of air taken into the cylinders that have been operating decreases. As a result, the amount of exhaust gas discharged from the cylinder decreases, and as a result, the amount of exhaust gas flowing through the NOx storage filter 15 decreases rapidly. When the amount of exhaust gas flowing in this way decreases rapidly, the amount of heat taken away from the NOx storage filter 15 by the flowing exhaust gas decreases rapidly, so the temperature of the NOx storage filter 15 increases rapidly and the temperature rises excessively. May end up.

  In view of such problems, the present embodiment is for suppressing the NOx storage filter 15 from being overheated as described above. Next, in order to realize this, FIG. 1 and FIG. A specific method that can be implemented by the configuration shown in FIG. FIG. 4 is a flowchart showing a control routine for carrying out this method. This control routine is executed by interruption every predetermined time by the electronic control unit 50.

  When this control routine starts, first, at step 101, it is determined whether or not the regeneration process (sulfur poisoning regeneration process, PM regeneration process) involving the temperature rise of the NOx storage filter 15 as described above is being performed. The As is apparent from the above description, this determination is substantially a determination as to whether or not the above-described cylinder reduction control is being performed. If it is determined in step 101 that the reproduction process is not being performed, the present control routine ends. If it is determined that the reproduction process is being performed, the process proceeds to step 103.

  In step 103, it is determined whether or not the above-described fuel cut is being performed. In this embodiment, as described above, the fuel cut is performed when it is determined that the vehicle on which the internal combustion engine is mounted is in a deceleration state (for example, an engine brake state). If it is determined in step 103 that the fuel cut is not being performed, the present control routine ends. If it is determined that the fuel cut is being performed, the process proceeds to step 105.

  Then, in the following step 105, the intake / exhaust valves in the closed / closed state of the cylinders that have been suspended in the cylinder reduction control for the regeneration process are brought into the normal opening / closing operation state, and this control routine ends. . That is, in step 105, the intake / exhaust valve of the idle cylinder is set to the combustion chamber in the cylinder in the same manner as the intake / exhaust valve of the active cylinder (however, the fuel supply is stopped because the fuel cut is being performed). It is opened and closed in response to the operation of the piston so as to perform intake and exhaust.

In this way, the idle cylinder that has been inactive due to the reduced cylinder control and has stopped performing intake and exhaust is configured to perform intake and exhaust, so the amount of exhaust gas from the active cylinder is reduced by performing the fuel cut. Can be compensated for to some extent, and the amount of exhaust gas flowing through the NOx occlusion filter 15 can be prevented from rapidly decreasing due to the fuel cut. As a result, it is possible to prevent the NOx storage filter 15 from being overheated.
Note that the control performed in step 105 can be said to be the cancellation of the cylinder reduction control in consideration of the premise that the fuel cut is being performed.

  By the way, when the amount of exhaust gas flowing through the NOx occlusion filter 15 is increased, the temperature rise of the filter 15 is suppressed, and the temperature is lowered. If the temperature of the NOx storage filter 15 becomes too low, the regeneration process being performed is temporarily stopped, and it is necessary to raise the temperature of the NOx storage filter 15 once again when restarting the regeneration process. In order to raise the temperature of the NOx occlusion filter 15, fuel or the like is required. From the viewpoint of efficient regeneration processing, it is preferable that the temperature of the NOx occlusion filter 15 is not lowered excessively.

  On the other hand, if the fuel cut is performed when the regeneration reduction process is performed by increasing the exhaust gas temperature as described above, the temperature of the NOx occlusion filter 15 increases. When the filter temperature is low, there is no problem because the temperature rises to some extent and does not reach an excessive temperature rise.

  Therefore, in another embodiment of the present invention, the control in step 105 described above is performed only when the filter temperature is high and the possibility of overheating is higher, and the regeneration process is performed while suppressing the occurrence of overheating. An efficient implementation may be attempted.

  FIG. 5 is a flowchart showing a control routine in this case. Here, the control in step 201 and step 203 is the same as the control in step 101 and step 103 of FIG. If it is determined at step 203 that the fuel cut is being performed, the routine proceeds to step 205 where the temperature Tc of the NOx storage filter 15 is detected.

  In the subsequent step 207, it is determined whether or not the temperature Tc obtained in step 205 is equal to or higher than a predetermined temperature Tb. Here, the predetermined temperature Tb is a minimum temperature at which the NOx occlusion filter 15 may be overheated due to, for example, a decrease in the amount of circulating exhaust gas, and is obtained in advance through experiments or the like. That is, it can be said that the determination here is a determination as to whether or not the NOx storage filter 15 may be overheated.

  If it is determined in step 207 that the temperature Tc of the NOx storage filter 15 is lower than a predetermined temperature Tb, the NOx storage filter 15 is not likely to be overheated. In this case, This control routine ends. On the other hand, if it is determined in step 207 that the temperature Tc of the NOx storage filter 15 is equal to or higher than a predetermined temperature Tb, the NOx storage filter 15 may be overheated. Then, go to step 209.

  In step 209, control corresponding to step 105 of the control routine of FIG. 4 is performed. That is, the intake / exhaust valves in the closed / closed state of the cylinders that have been suspended in the reduced cylinder control for the regeneration process are brought into the normal opening / closing operation state. And by doing in this way, the quantity of the exhaust gas which distribute | circulates the NOx storage filter 15 is supplemented, and it is suppressed that the NOx storage filter 15 overheats.

  As described above, in this embodiment, only when the filter temperature is high and the possibility of overheating is higher, the intake / exhaust valve in the closed / closed state of the deactivated cylinder is controlled to be in a normal opening / closing operation state. Has been. As a result, as described above, it is possible to efficiently perform the regeneration process while suppressing the occurrence of excessive temperature rise.

  In another embodiment, the temperature rise is caused by changing the number of cylinders that bring the intake / exhaust valves in the closed / closed state into a normal open / close operation state according to the temperature Tc of the NOx storage filter 15. It is also possible to achieve both the suppression of occurrence of noise and the efficient implementation of the reproduction process.

  That is, the flow amount of exhaust gas necessary to prevent the NOx storage filter 15 from excessively rising in temperature is determined according to the temperature Tc of the NOx storage filter 15. Further, when fuel cut is performed, the amount of exhaust gas is determined by the engine speed and the number of cylinders in which the intake / exhaust valves are in the open / close operation state. Therefore, if the exhaust gas amount is adjusted by changing the number of cylinders that open / close the intake / exhaust valves while considering the engine speed in accordance with the temperature Tc of the NOx storage filter 15, the temperature of the NOx storage filter 15 is adjusted. Tc can be adjusted, and it is possible to achieve both suppression of the occurrence of excessive temperature rise and efficient implementation of the regeneration process.

  FIG. 6 is a flowchart showing a control routine in such an embodiment. Here, the control in step 301 and step 303 is the same as the control in step 101 and step 103 in FIG. 4 and the control in step 201 and step 203 in FIG. 5, and the control in step 305 is the same as the control in step 205 in FIG. It is. When the temperature Tc of the NOx occlusion filter 15 is detected at step 305, the routine proceeds to step 307.

  In step 307, based on the temperature Tc obtained in step 305, the number of cylinders that bring the intake / exhaust valves in the closed / closed state into the open / close operation state is determined. More specifically, in the present embodiment, first, based on the temperature Tc obtained in step 305, the minimum circulating exhaust gas amount necessary for preventing the NOx storage filter 15 from being overheated is obtained, and then the exhaust gas amount is calculated. The number of cylinders to be realized or the minimum number of cylinders that realize the exhaust gas amount exceeding the exhaust gas amount is determined according to the engine speed. Then, by subtracting the number of cylinders (that is, the cylinders in which the intake / exhaust valves are in an open / closed operation state) that were operated in the cylinder reduction control for the regeneration process from the number of cylinders thus obtained, The number of cylinders to be obtained is calculated.

  In this way, when the number of cylinders for opening and closing the intake / exhaust valves that have been closed in step 307 is determined, the process proceeds to step 309. In step 309, control corresponding to step 105 of the control routine of FIG. 4 or step 209 of the control routine of FIG. 5 is performed on the number of cylinders obtained in step 307. That is, the intake / exhaust valves that are in the closed valve stop state are brought into a normal open / close operation state.

  As a result, the number of cylinders in which the intake / exhaust valves are normally opened / closed is the minimum flow exhaust gas necessary for the NOx storage filter 15 not to be overheated at the engine speed at that time. The number of cylinders that realize the amount, or the minimum number of cylinders that realize the exhaust gas amount that exceeds the exhaust gas amount. As a result, the amount of exhaust gas flowing through the NOx storage filter 15 is appropriately adjusted, and both the excessive temperature rise of the NOx storage filter 15 and the temperature Tc thereof are excessively reduced are suppressed. be able to.

  As described above, according to this embodiment, according to the temperature Tc of the NOx storage filter 15, the number of cylinders that bring the intake / exhaust valves in the closed / closed state into the normal open / close operation state is changed. Thus, it is possible to achieve both suppression of the occurrence of excessive temperature rise and efficient implementation of the regeneration process.

  In the above-described embodiment, it is necessary to make up both the intake valve and the exhaust valve in the closed state for the cylinders that are deactivated in the reduced cylinder control, and to supplement the amount of exhaust gas so as to suppress the excessive temperature rise of the NOx storage filter 15. However, in other embodiments, the intake / exhaust valves that have been in the closed / closed state are set to the normal open / close operation state. When one of them is in a closed valve stop state (in this case, the other is in a normal opening / closing state), when it is necessary to supplement the amount of exhaust gas to suppress excessive temperature rise of the NOx storage filter 15, the closed valve stop state It is also possible to open the valve that has been opened. Alternatively, when it is necessary to make both the intake valve and the exhaust valve closed and to make up the amount of exhaust gas in order to suppress the excessive temperature rise of the NOx storage filter 15 for the cylinder that is stopped in the cylinder reduction control, the valve is closed. One of the intake valve and the exhaust valve that have been stopped may be in a normal opening / closing operation state, and the other may be in a valve opening state. In addition, the amount of exhaust gas flowing through the NOx storage filter 15 may be adjusted by adjusting the opening degree of the valve that is in the above-described opening / closing operation state or valve opening state. Further, in each of the above-described embodiments, the case where the normal opening / closing operation synchronized with the operation of the piston is taken as the opening / closing operation state has been described. However, in other embodiments, the opening / closing timing and timing different from the opening / closing operation state are described. The state where the opening / closing operation is performed may be taken.

  In yet another embodiment, by controlling the exhaust turbocharger 7 in combination with the above-described controls, the excessive temperature rise of the NOx occlusion filter 15 is more reliably suppressed, or the NOx occlusion filter 15 is more specifically controlled. The temperature Tc may be adjusted. In this case, if the capacity of the turbine 7b of the exhaust turbocharger 7 is reduced and the recovered energy is increased, the amount of intake air increases, resulting in an increase in the amount of exhaust gas and the exhaust temperature at the outlet of the turbine 7b (ie, the NOx storage filter). The fact that the exhaust temperature at the 15 inlet) is low is utilized. That is, the capacity of the turbine 7b is reduced as the temperature Tc of the NOx storage filter 15 is to be kept lower.

  Similarly, when the electric turbocharger is used, the control of the electric turbocharger is performed in combination with the above-described controls, so that the excessive temperature rise of the NOx occlusion filter 15 can be more reliably suppressed or more detailed. In addition, the temperature Tc of the NOx storage filter 15 can be adjusted. That is, in this case, the exhaust temperature at the turbine outlet (that is, the exhaust temperature at the inlet of the NOx storage filter 15) can be lowered by increasing the regeneration amount in the electric turbocharger, and the temperature Tc of the NOx storage filter 15 is set. The amount of regeneration is increased as it is desired to keep it lower.

  Further, in the case where an electric turbocharger is used, the compressor of the electric turbocharger is driven by power and the EGR control valve 19 is opened, so that fresh air flows backward through the EGR passage 17 and flows into the NOx storage filter 15. The excessive temperature rise of the storage filter 15 can be suppressed, or the temperature Tc of the NOx storage filter 15 can be adjusted.

  That is, if the compressor of the electric turbocharger is driven by powering when the cylinder reduction control is performed, the pressure in the downstream side intake duct 6 and the intake manifold 4 is easily higher than the pressure in the exhaust pipe 14. When the EGR control valve 19 is opened in such a state, fresh air flows backward through the EGR passage 17 and flows into the NOx storage filter 15. At this time, fresh air passes through the EGR passage 17 and the EGR cooler 20, but since the temperature is lower than the exhaust gas that has undergone compression and expansion in the cylinder, the effect of cooling the NOx storage filter 15 is great.

  By controlling the compressor of the electric turbocharger and the EGR control valve 19, the amount of fresh air flowing into the NOx storage filter 15 can be adjusted, and thereby the degree to which the NOx storage filter 15 is cooled can be adjusted. Also by this method, the excessive temperature rise of the NOx storage filter 15 can be suppressed, or the temperature Tc of the NOx storage filter 15 can be adjusted.

  By the way, when the regeneration control is performed by increasing the temperature of the NOx occlusion filter 15 by performing the cylinder reduction control, the NOx occlusion filter 15 is not used even when the fuel cut as described above is not performed. There is a case where the temperature is increased so as to be damaged (for example, the filter is melted or the NOx storage catalyst is thermally degraded by the filter).

  One of the reasons why such excessive temperature rise occurs is the pulsation of the exhaust gas flow accompanying the execution of the reduced cylinder control. That is, the temperature of the NOx occlusion filter 15 is also raised by an oxidation reaction of hydrocarbons or the like in the filter 15, and the degree of the temperature rise depends on the amount of oxygen flowing into the NOx occlusion filter 15 per unit time. In addition, when the above-described cylinder reduction control is performed, the intake / exhaust amount per operating cylinder increases as the number of operating cylinders decreases, and the intervals between the intake and the exhaust become longer, resulting in the flow into the NOx storage filter 15. The exhaust gas flow that pulsates greatly pulsates. Since the exhaust gas contains oxygen, if the flow of the exhaust gas flowing into the NOx storage filter 15 pulsates greatly as described above, the amount of oxygen flowing into the NOx storage filter 15 per unit time also pulsates greatly. It will be.

  If the amount of oxygen flowing into the NOx storage filter 15 pulsates greatly in this way, the amount of inflowing oxygen may be an average inflowing oxygen amount even if the NOx storage filter 15 does not overheat. At this peak, the NOx storage filter 15 may be overheated.

  This will be described more specifically with reference to FIG. FIG. 7 is an example illustrating temporal changes in the amount of exhaust gas and the amount of oxygen flowing into the NOx storage filter 15 per unit time. 7 (A) and 7 (B) show a case where the same load operation is performed without executing the reduced cylinder control (FIG. 7A) and a case where the reduced cylinder control is performed (FIG. 7). 7 (B)). In the figure, the solid line represents the exhaust gas amount, the dotted line represents the oxygen amount, and K represents the upper limit value of the inflowing oxygen amount at which the NOx storage filter 15 is not overheated.

  For example, assuming that the internal combustion engine is a four-cycle internal combustion engine, the exhaust gas amount (and oxygen amount) discharged during the two rotations of the crankshaft may be during the execution of reduced cylinder control if the load is the same. This is almost the same as when no cylinder reduction control is performed. That is, the average value of the inflow exhaust gas amount (and the inflowing oxygen amount) per unit time during this period is substantially the same as when the reduced cylinder control is not performed even during the reduced cylinder control.

  However, as described above and as is clear from FIG. 7B, when the cylinder reduction control is performed, the amount of exhaust gas (and the amount of oxygen) flowing into the NOx storage filter 15 per unit time is reduced. It pulsates greatly. As a result, when the inflowing oxygen amount is considered as an average value, the upper limit value K may be exceeded at the peak of the inflowing oxygen amount even when the upper limit value K is not exceeded. Temperature can occur. That is, even if the NOx occlusion filter 15 does not overheat when the inflowing exhaust gas amount (and the inflowing oxygen amount) does not pulsate so much and the value of the inflowing exhaust gas amount is not always close to the average value, the NOx occlusion filter 15 does not overheat. When the cylinder reduction control is performed with the load, the NOx storage filter 15 may be excessively heated.

  The embodiment described below is for preventing the NOx storage filter 15 from being excessively heated in this way, and the configuration thereof is the same as the configuration shown in FIGS. 1 and 2. FIG. 8 is a flowchart showing a control routine that can be executed in order to prevent the NOx storage filter 15 from being overheated in the present embodiment. This control routine is executed by interruption every predetermined time by the electronic control unit 50.

  When this control routine starts, first, in step 401, it is determined whether or not the conditions for performing the regeneration process (sulfur poisoning regeneration process, PM regeneration process) accompanied with the temperature rise of the NOx storage filter 15 as described above are satisfied. Determined. Also in this embodiment, the NOx occlusion filter 15 required for the regeneration process is raised by increasing the exhaust gas temperature by performing the cylinder reduction control. Therefore, the determination here is substantially NOx. This is a determination as to whether or not the conditions for reducing cylinder control for increasing the temperature of the storage filter 15 are satisfied. If it is determined in step 401 that the conditions for execution of the reproduction process are not satisfied, the present control routine ends. If it is determined that the conditions for execution of the reproduction process are satisfied, the process proceeds to step 403. .

  In step 403, the number S of cylinders to be deactivated during the cylinder reduction control is temporarily determined. That is, for example, a map is prepared in advance so that the number of cylinders to be deactivated is determined according to the engine operating state, and the number of deactivated cylinders S is provisionally determined according to the engine operating state at that time based on the map. To do. If the number of deactivated cylinders S is provisionally determined in step 403, the process proceeds to step 405.

  In step 405, the NOx storage filter inflowing oxygen amount is the upper limit value K (that is, the inflowing oxygen at which the NOx storage filter 15 is not overheated when the cylinder reduction control is performed with the number of deactivated cylinders S temporarily determined in step 403. It is an upper limit value of the amount, and is determined in advance by experiments or the like). That is, here, the amount of oxygen flowing into the NOx storage filter 15 per unit time (that is, its change over time or pulsation) is estimated based on the engine operating state and the number of deactivated cylinders S, and the value of the inflowing oxygen amount at the peak time. Is less than or equal to the upper limit K. Note that the estimation of the inflowing oxygen amount may be performed by calculation each time, or a map may be created in advance and may be performed based on the map.

  If it is determined in step 405 that the estimated inflowing oxygen amount is greater than the upper limit value K, the routine proceeds to step 407, where the number of deactivated cylinders S is reduced by one, and the routine returns to step 405 again. Then, the above-described determination in step 405 is performed when the cylinder reduction control is performed with the new number of deactivated cylinders. When the number of deactivated cylinders S decreases, the degree of pulsation of the exhaust gas flowing into the NOx storage filter 15 decreases, and the peak value of the amount of oxygen flowing into the NOx storage filter 15 per unit time also decreases. If the determination and the reduction of the number of deactivated cylinders S in step 407 are repeated, the number of deactivated cylinders at which the estimated inflowing oxygen amount does not exceed the upper limit K is obtained.

  When it is determined in step 405 that the estimated inflowing oxygen amount is equal to or less than the upper limit value K, the process proceeds to step 409, where the number of deactivated cylinders S is determined as the number of deactivated cylinders S used for the cylinder reduction control. Then, the routine proceeds to step 411, where the cylinder reduction control is performed with the number of deactivated cylinders S, and this control routine ends.

  As described above, according to the present embodiment, when the cylinder reduction control is performed to increase the temperature of the NOx storage filter 15 for the regeneration process, the amount of oxygen flowing into the NOx storage filter 15 per unit time is the NOx. The number of idle cylinders is adjusted so as to be less than the amount of oxygen that can cause overheating of the storage filter 15. As a result, it is possible to prevent the NOx storage filter 15 from being overheated due to the pulsation of the exhaust gas flow accompanying the execution of the reduced cylinder control.

  In another embodiment, if it is determined in step 405 that the estimated inflowing oxygen amount exceeds the upper limit K, the capacity of the turbine 7b of the exhaust turbocharger 7 is reduced to reduce the inlet of the turbine 7b. The side pressure may be increased. In this way, the exhaust gas flow is blocked and the degree of pulsation is mitigated, so that the peak value of the inflowing oxygen amount can be lowered and the effect of suppressing the excessive temperature rise of the NOx storage filter 15 can be achieved. is there. Furthermore, when an electric turbocharger is used, the exhaust gas flow is stopped by increasing the regeneration amount in the electric turbocharger, and the peak value of the inflowing oxygen amount is reduced by reducing the degree of pulsation of the exhaust gas flow. The excessive temperature rise of the NOx storage filter 15 may be suppressed.

  As is clear from the above description, the control for suppressing the excessive temperature rise of the NOx occlusion filter 15 that may occur during the execution of the reduced cylinder control described later with reference to FIG. It is also possible to carry out the control together with the control for suppressing the excessive temperature rise of the NOx storage filter 15 that may occur when the fuel cut is performed during the execution of the cylinder reduction control described above with reference to FIG.

  In each of the above-described embodiments, the NOx storage filter 15 is used, but in other embodiments, a particulate filter or a NOx storage catalyst may be used instead.

FIG. 1 is a diagram for explaining a case where the present invention is applied to a four-cylinder in-cylinder injection compression ignition type internal combustion engine mounted on a vehicle. FIG. 2 is a schematic plan view of the intake system and the like of the internal combustion engine shown in FIG. FIG. 3 is a view showing the structure of the NOx occlusion filter, in which FIG. 3 (A) is a front view and FIG. 3 (B) is a side sectional view. FIG. 4 is a flowchart illustrating a control routine that can be executed in an embodiment of the present invention. FIG. 5 is a flowchart showing a control routine that can be executed in another embodiment of the present invention. FIG. 6 is a flowchart showing a control routine that can be executed in still another embodiment of the present invention. FIG. 7 is an example illustrating changes over time in the amount of exhaust gas and the amount of oxygen flowing into the NOx storage filter per unit time, and FIG. 7A shows a case where the cylinder reduction control is not performed. B) is a case where the reduced cylinder control is performed. FIG. 8 is a flowchart showing a control routine that can be executed in still another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine main body 2a ... Intake valve 2b ... Exhaust valve 3 ... Fuel injection valve 12 ... Throttle valve 15 ... NOx storage filter 19 ... EGR control valve

Claims (5)

For a multi-cylinder internal combustion engine having exhaust purification means in the exhaust passage,
When performing the regeneration process with a rise in temperature in order to restore the exhaust purification performance of the exhaust purification means, at least one of the intake valve and the exhaust valve for some cylinders of the multi-cylinder internal combustion engine to increase the exhaust temperature The cylinder reduction control is performed to stop the fuel supply and stop the valve closed
In a control apparatus for a multi-cylinder internal combustion engine that performs a fuel cut to stop fuel supply to each cylinder of the multi-cylinder internal combustion engine during deceleration of a vehicle on which the multi-cylinder internal combustion engine is mounted.
When the fuel cut is performed during the regeneration process, one of the intake valves and the exhaust valves of the some cylinders is opened / closed and the other is opened / closed or opened. A control apparatus for a multi-cylinder internal combustion engine. Temperature detecting means for detecting the temperature of the exhaust purification means,
When performing the fuel cut during the regeneration process, only when the temperature of the exhaust purification unit detected by the temperature detection unit is equal to or higher than a predetermined temperature, the intake valves of the some cylinders and The control device for a multi-cylinder internal combustion engine according to claim 1, wherein one of the exhaust valves is in an open / close operation state and the other is in an open / close operation state or a valve open state. Temperature detecting means for detecting the temperature of the exhaust purification means,
When the fuel cut is performed during the regeneration process, one of the intake valve and the exhaust valve is opened / closed among the some cylinders based on the temperature of the exhaust purification unit detected by the temperature detection unit. 2. The control device for a multi-cylinder internal combustion engine according to claim 1, wherein the number of cylinders that are in an operating state and in which the other is in an opening / closing operation state or a valve opening state is determined. An inflowing oxygen amount estimating means for estimating the amount of oxygen flowing into the exhaust purification means per unit time;
When performing the cylinder reduction control when the regeneration process is performed, based on the oxygen amount estimated by the inflowing oxygen amount estimating means, at least one of the intake valve and the exhaust valve is closed and fuel is supplied. The control device for a multi-cylinder internal combustion engine according to any one of claims 1 to 3, wherein the number of cylinders for stopping the engine is determined. The multi-cylinder engine is used to raise the exhaust temperature when a regeneration process with a temperature rise is performed on a multi-cylinder internal combustion engine having exhaust purification means in the exhaust passage to recover the exhaust purification performance of the exhaust purification means. In a control apparatus for a multi-cylinder internal combustion engine that performs a reduced-cylinder control that stops at least one of an intake valve and an exhaust valve in a closed valve state and stops fuel supply for some cylinders of the internal combustion engine.
An inflowing oxygen amount estimating means for estimating the amount of oxygen flowing into the exhaust purification means per unit time;
When performing the cylinder reduction control when the regeneration process is performed, based on the oxygen amount estimated by the inflowing oxygen amount estimating means, at least one of the intake valve and the exhaust valve is closed and fuel is supplied. A control device for a multi-cylinder internal combustion engine, in which the number of cylinders to be stopped is determined.

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