JP2007285150A - Control unit for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control unit for an internal combustion engine capable of restraining worsening in exhaust emission when an exhaust gas purifier of a multi-cylinder internal combustion engine executes a cylinder cutoff operation before reaching the temperature practically showing a designated purification function and accelerating temperature rise of the exhaust gas purifier. <P>SOLUTION: The control unit for an internal combustion engine is provided with an independent throttle valve 10 arranged on every cylinder 2 of the internal combustion engine 1, and a variable operating valve mechanism 8 capable of changing a valve operating characteristic of an intake valve 6 arranged on every cylinder 2. The exhaust gas purifier 12 executes a cylinder cutoff operation before reaching to catalyst activation temperature, and fuel supply is controlled so that an air-fuel ratio of the operating cylinders becomes richer than a theoretical air-fuel ratio. An amount of air passing through the cutoff cylinders is controlled by respectively operating the independent throttle valve 10 and variable operating valve mechanism 8 so that the temperature rise of the exhaust gas purifier 12 is accelerated by air passing through the cutoff cylinder and exhaust gas discharged from the operating cylinders at the time of the cylinder cutoff operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that performs a reduced-cylinder operation before the exhaust purification device of a multi-cylinder internal combustion engine reaches a temperature at which a predetermined purification function can be achieved.

  It is well known to perform a reduced-cylinder operation in which fuel supply to some cylinders of a multi-cylinder internal combustion engine is stopped. As a control device for controlling the air amount for the idle cylinder during the reduced cylinder operation, an independent throttle valve provided for each cylinder so that the air amount for the idle cylinder is larger than the air amount for the active cylinder during the reduced cylinder operation. (Patent Document 1). This device improves exhaust emission by burning unburned fuel discharged from the operating cylinder by the air passed through the idle cylinder in the exhaust system.

JP-A 64-35031

  In general, when the lift amount of an intake valve of a cylinder is constant, the lower the rotational speed of the internal combustion engine is, the lower the rotation speed of the internal combustion engine is. The change in the amount of air is increased. For this reason, when the air amount passing through the idle cylinder is controlled only by the independent throttle valve as in Patent Document 1, the control accuracy of the air amount largely depends on the operation accuracy of the independent throttle valve. There is a limit to improving the operation accuracy of the independent throttle valve. Therefore, in the control using only the independent throttle valve, the controllability is deteriorated particularly in the low speed rotation region, the air amount becomes excessive and insufficient, and it becomes insufficient to burn the unburned fuel discharged from the operating cylinder in the exhaust system. easy. However, if the exhaust gas purification device provided in the exhaust system has reached a temperature at which the purification function can be exhibited, deterioration of exhaust emission is suppressed by the exhaust gas purification device even if the combustion of unburned fuel is insufficient. .

  However, when the reduced-cylinder operation is performed before the exhaust purification device reaches a temperature at which a predetermined purification function can be exhibited, typically immediately after a cold start, the purification function of the exhaust purification device cannot be expected. For this reason, if the combustion of the unburned fuel discharged from the operating cylinder is insufficient, the exhaust emission deteriorates. Further, if the combustion of the unburned fuel is insufficient, the amount of heat generated in the exhaust system is insufficient, so that the effect of promoting the temperature rise of the exhaust purification device due to the combustion of the unburned fuel is slowed down.

  Therefore, the present invention suppresses the deterioration of exhaust emissions and increases the exhaust purification device when the reduced-cylinder operation is performed before reaching a temperature at which the exhaust purification device of the multi-cylinder internal combustion engine can perform a predetermined purification function. An object of the present invention is to provide a control device for an internal combustion engine capable of promoting temperature.

  In the control device for an internal combustion engine of the present invention, before the exhaust purification device of the multi-cylinder internal combustion engine reaches a temperature at which a predetermined purification function can be achieved, a reduced-cylinder operation for stopping fuel supply to some cylinders is performed, And a control device for an internal combustion engine that controls fuel supply so that the air-fuel ratio of the air-fuel mixture supplied to the remaining cylinders during the reduced-cylinder operation is richer than the stoichiometric air-fuel ratio. An independent throttle valve that can be adjusted in opening degree, a variable valve mechanism that can change the valve operating characteristics of an intake valve provided for each cylinder, and a part of the cylinders during the reduced-cylinder operation. The independent throttle valve and the variable valve mechanism are operated to pass through the some cylinders so that the temperature of the exhaust purification device is accelerated by the passing air and the exhaust gas discharged from the remaining cylinders. Control the amount of air And air amount control means, by providing, for solving the above problems (claim 1).

  According to this control device, the amount of air passing through the cylinder (stop cylinder) for which fuel supply was stopped during the reduced cylinder operation changes not only the operation of the independent throttle valve but also the valve operating characteristics of the intake valve of the idle cylinder It is controlled by the operation of a possible variable valve mechanism. As a result, the proportion of the control accuracy of the amount of air passing through the idle cylinder that depends on the operation accuracy of the independent throttle valve decreases. In other words, in order to ensure the control accuracy of the amount of air passing through the idle cylinder, the operation accuracy of the independent throttle valve need not be increased more than necessary. Insufficient operation accuracy of the independent throttle valve can be compensated by changing the valve operating characteristics of the intake valve. Thereby, the control accuracy of the amount of air passing through the deactivated cylinder is improved as compared with the control using only the independent throttle valve. As a result, unburned fuel discharged from the remaining cylinders (operating cylinders) whose fuel supply is controlled to be richer than the stoichiometric air-fuel ratio during the reduced-cylinder operation can be sufficiently burned in the exhaust system. Therefore, deterioration of exhaust emission is suppressed, and the heat generation amount of the exhaust system is not insufficient, so that the temperature rise of the exhaust purification device can be promoted.

  In the control device of the present invention, taking into account the amount of unburned fuel contained in the exhaust gas discharged from the remaining cylinders, required air amount calculation means for calculating a required air amount to be passed through the some cylinders; A valve characteristic setting unit that sets a valve characteristic of the intake valve so that the opening time area of the intake valve of the partial cylinders increases as the calculation result of the required air amount calculation unit increases. The air amount control means may operate the variable valve mechanism so that the intake valves of the some cylinders operate with the valve characteristics set by the valve characteristic setting means. Item 2). In this case, the amount of unburned fuel discharged from the operating cylinder is taken into account, the required amount of air to be passed through the idle cylinder is calculated, and variable operation is performed so that the opening time area of the intake valve according to the required amount of air is obtained. The valve mechanism is operated. For this reason, air that is not excessive or deficient with respect to the amount of unburned fuel can be supplied to the exhaust system via the idle cylinder, so that unburned fuel can be reliably burned. The rate of change of the opening time area with respect to the required air amount may be constant or may change with respect to the required air amount. For example, the rate of change may decrease as the required air amount increases.

  As is well known, the opening time area of the intake valve is obtained by integrating the lift amount of the intake valve by the valve opening time. Therefore, for example, the valve operating characteristic setting unit is configured so that the opening time area of the intake valves of the some cylinders increases as the calculation result of the required air amount calculating unit increases as the valve operating characteristic. The maximum lift amount may be set (claim 3). The method for increasing the opening time area depends on the degree of freedom in changing the valve characteristics of the variable valve mechanism, but in addition to this mode, the maximum lift amount of the intake valve is required to increase the opening time area. The operating angle of the intake valve may be increased without changing the above, or both the operating angle of the intake valve and the maximum lift amount may be increased.

  Further, in the control device of the present invention, the opening degree control of the independent throttle valve may be appropriately performed. For example, the required air amount calculated by the required air amount calculating means and the engine speed of the multi-cylinder internal combustion engine are adjusted. And an opening setting means for setting the opening of the independent throttle valve corresponding to the part of the cylinders, and the air amount control means is configured to obtain the opening set by the opening setting means. The independent throttle valve corresponding to the part of the cylinders may be operated.

  In this aspect, the air-fuel ratio acquisition means for acquiring the air-fuel ratio of the atmosphere of the exhaust purification device, and the some cylinders corresponding to the deviation between the acquisition result of the air-fuel ratio acquisition means and a predetermined target air-fuel ratio Correction value calculation means for calculating a correction value for the opening of the independent throttle valve, wherein the opening setting means takes into account the correction value calculated by the correction value calculation means, The opening degree of the independent throttle valve corresponding to may be set (Claim 5). In this case, the air-fuel ratio of the atmosphere of the exhaust purification device is acquired, and the opening degree of the independent throttle valve is corrected according to the deviation between the acquisition result and the target air-fuel ratio. Therefore, the actual combustion state of the operating cylinder is reflected in the control of the amount of air that passes through the idle cylinder. Therefore, for example, even if the operating cylinder misfires for some reason and the amount of unburned fuel increases, an appropriate amount of air corresponding to the increase is supplied to the exhaust system via the idle cylinder. The deterioration of emissions can be reliably suppressed, and the temperature increase promoting effect of the exhaust emission control device can be reliably maintained.

  As described above, according to the present invention, the amount of air passing through the cylinder (stop cylinder) for which fuel supply was stopped during the reduced cylinder operation is not limited to the operation of the independent throttle valve, but the intake valve of the idle cylinder. Since control is performed by operating a variable valve mechanism that can change the valve characteristics, the control accuracy of the amount of air passing through the idle cylinder is improved as compared with control using only the independent throttle valve. As a result, deterioration of the exhaust emission is suppressed, and since the heat generation amount of the exhaust system is not insufficient, the temperature rise of the exhaust purification device can be promoted.

  FIG. 1 shows a main part of an internal combustion engine to which a control device of the present invention is applied. The internal combustion engine 1 is configured as an in-line four-cylinder spark ignition internal combustion engine (multi-cylinder internal combustion engine) in which four cylinders 2 are arranged in one direction. Note that cylinder numbers # 1 to # 4 are assigned from one end to the other end side in the direction in which the cylinders 2 are arranged. These cylinder numbers are used as necessary to distinguish the cylinders 2 from each other. A piston (not shown) connected to the crankshaft 3 via a connecting rod is inserted into each cylinder 2 in a state where it can reciprocate. The crankshaft 3 is provided with a crank angle sensor 21 for detecting the rotational speed (engine rotational speed) of the crankshaft 3. Each cylinder 2 is provided with an intake passage 4 and an exhaust passage 5, and two intake valves 6 for opening and closing the intake passage 4 and two exhaust valves 7 for opening and closing the exhaust passage 5 are provided for each cylinder 2. It has been. The valves 6 and 7 are not shown for the cylinders # 2 to # 4.

  The opening / closing operation of the intake valve 6 is performed by the variable valve mechanism 8. Although the detailed structure of the variable valve mechanism 8 is not shown, it is a known one that can freely change the valve characteristics of the intake valve 6. This mechanism 8 does not affect the valve operating characteristics of the intake valves 6 provided in the # 1 and # 4 cylinders 2 without affecting the valve operating characteristics of the intake valves 6 provided in the other # 2 and # 3 cylinders 2. It can be changed at the same time. The mechanism 8 does not affect the valve operating characteristics of the intake valves 6 provided in the # 2 and # 3 cylinders 2 without affecting the valve operating characteristics of the intake valves 6 provided in the other # 1 and # 4 cylinders 2. It is also possible to change at the same time. On the other hand, the opening / closing operation of the exhaust valve 7 is performed by a known valve operating mechanism (not shown) whose valve operating characteristics cannot be changed.

  The intake passage 4 has a branch portion 4a branched for each cylinder 2, and a surge tank portion 4b to which each branch portion 4a is connected. An air filter 9 for air filtration is provided on the upstream side of the surge tank portion 4b, and a pressure sensor 22 for detecting the internal pressure is provided in the surge tank portion 4b. Each branch portion 4a is provided with one independent throttle valve 10 whose opening degree can be adjusted so that the opening area thereof can be changed, and one injector 11 that supplies fuel downstream of the independent throttle valve 10 one by one. Is provided.

  On the other hand, the exhaust passage 5 has a branch portion 5a branched for each cylinder 2 and a collecting portion 5b where the branch portions 5a are gathered, and an exhaust purification device incorporating a three-way catalyst downstream of the gathering portion 5b. 12 is provided. An air-fuel ratio sensor 23 as an air-fuel ratio acquisition means for detecting the air-fuel ratio of the atmosphere is provided on the upstream side of the exhaust purification device 12, and the exhaust purification device 12 detects the bed temperature. A bed temperature sensor 24 is provided. Note that cooling water circulates in the internal combustion engine 1, and a water temperature sensor 25 for detecting the temperature of the cooling water is provided.

  The operation of the internal combustion engine 1 is controlled by an engine control unit (ECU) 20 as a control device. The ECU 20 is a computer including a microprocessor and peripheral devices such as a ROM and a RAM as storage means necessary for its operation, and determines the operating state of the internal combustion engine 1 based on signals from the various sensors 21 to 25 described above. Control appropriately. Although description of all the control which ECU20 implements is abbreviate | omitted, ECU20 controls the opening degree of each independent throttle valve 10 while controlling the fuel supply by each injector 11 provided for every cylinder 2. FIG. Further, the variable valve mechanism 8 is controlled so that the valve characteristic of the intake valve 6 is appropriately changed. Further, the ECU 20 controls the ignition timing of each cylinder 2. As will be described in detail later, when a predetermined condition is satisfied, the ECU 20 stops supplying fuel to the two cylinders # 1 and # 4 and supplies the remaining two cylinders # 2 and # 3 to the two cylinders 2. By continuing the fuel supply, the internal combustion engine 1 is caused to perform the reduced cylinder operation in which only the two cylinders # 2 and # 3 are operated. In the following description, the two cylinders # 1 and # 4 may be referred to as idle cylinders, and the two cylinders # 2 and # 3 may be referred to as active cylinders.

  2 and 3 are flowcharts showing an example of a control routine executed by the ECU 20 in connection with the gist of the present invention. The program of this routine is stored in a storage means such as a ROM of the ECU 20, read out in a timely manner, and repeatedly executed at predetermined intervals. As shown in FIG. 2, in step S1, it is determined whether or not the internal combustion engine 1 has been started. For example, the determination is made based on position information of an ignition switch (not shown) or a signal from the crank angle sensor 21. If it is not after the start, the subsequent processing is skipped and the current routine is terminated. When it is after the start, the process proceeds to step S2, and the operating state of the internal combustion engine 1 is acquired.

  The operating state acquired here depends on the processing contents thereafter. In this embodiment, the engine rotational speed Ne, the cooling water temperature Tw, and the catalyst bed temperature Tcat are acquired, and the downstream pressure Pm of the independent throttle valve 10 corresponding to the operating cylinder. The valve overlap OL between the intake valve 6 and the exhaust valve 7 related to the cylinder and the ignition timing SA related to the cylinder are acquired. The engine rotation speed Ne is directly acquired from the signal of the crank angle sensor 21, the cooling water temperature Tw is directly acquired from the signal of the water temperature sensor 25, and the catalyst bed temperature Tcat is directly acquired from the signal of the bed temperature sensor 24. The downstream pressure Pm is acquired by estimation based on the pressure of the surge tank 4b and the opening degree of the independent throttle valve 10. The pressure of the surge tank unit 4b is acquired from the signal of the pressure sensor 22 installed here. The valve overlap OL and the ignition timing SA are acquired by the ECU 20 referring to a map that gives these in association with the operating state such as the engine speed Ne.

  Next, in step S3, it is determined whether or not the internal combustion engine 1 has been warmed up. For this determination, the coolant temperature Tw acquired in step S2 is used. When the cooling water temperature Tw is less than the predetermined threshold value, it is determined that the warm-up is not completed, and the process proceeds to step S4. When the cooling water temperature Tw is equal to or higher than the threshold value, it is determined that the warm-up has been completed, the subsequent processing is skipped, and the current routine ends. In step S4, it is determined whether the catalyst bed temperature Tcat is lower than a predetermined temperature. This predetermined temperature is a temperature at which the exhaust purification device 12 can perform a predetermined purification function. This can be obtained experimentally in advance. The predetermined purification function is inherently possessed by the exhaust purification device 12. Since the exhaust purification device 12 has a built-in three-way catalyst, this purification function corresponds to a function of purifying harmful components (HC, NOx, CO, etc.) in the exhaust gas exceeding an allowable level.

  When the catalyst bed temperature Tcat is equal to or higher than the predetermined temperature, it can be said that the exhaust purification device 12 can perform the purification function, so the subsequent processing is skipped and the current routine is terminated. On the other hand, when the catalyst bed temperature Tcat is lower than the predetermined temperature, the processing of step S5 to step S17 is executed to promote the bed temperature of the exhaust gas purification device 12.

  In step S5, a reduced-cylinder operation for stopping fuel supply to some cylinders, that is, the two cylinders # 1 and # 4, is executed, and these cylinders are deactivated. In subsequent steps S5 to S9, a process of calculating the fuel injection amount Gfinj for each of the remaining cylinders during the reduced cylinder operation, that is, the two operating cylinders # 2 and # 3, is executed. This fuel injection amount Gfinj is calculated from the viewpoint of accelerating the temperature rise of the exhaust gas purification device 12, and this fuel injection amount Gfinj is a richer side of the air-fuel ratio of the air-fuel mixture supplied to the operating cylinder than the stoichiometric air-fuel ratio. Is calculated as such a value. A specific procedure for calculating the fuel injection amount Gfinj is as follows.

  First, in step S6, a basic injection amount Gfbase is calculated. The basic injection amount Gfbase is a fuel injection amount such that the air-fuel ratio of the air-fuel mixture supplied to the operating cylinder becomes the stoichiometric air-fuel ratio, and is calculated based on the engine speed Ne and the downstream pressure Pm acquired in step S2. . Specifically, a map for giving the basic injection amount Gfbase with the engine speed Ne and the downstream pressure Pm as variables is stored in the ECU 20 in advance, and the ECU 20 refers to the map to calculate the basic injection amount Gfbase. be able to.

  Next, in step S7, the required air-fuel ratio AFd is calculated. The required air-fuel ratio AFd is determined from the viewpoint of promoting the temperature rise of the exhaust purification device 12. Specifically, the ECU 20 calculates the required air-fuel ratio AFd so that unburned fuel is discharged from the operating cylinder to the exhaust system and combustion occurs in the exhaust system. Therefore, the required air-fuel ratio AFd becomes a richer value than the theoretical air-fuel ratio. The calculation of the required air-fuel ratio AFd can be realized by preparing a map in which the operating state of the internal combustion engine 1 and the catalyst bed temperature Tcat are variables and referring to the map.

  4 to 8 are explanatory diagrams respectively showing characteristics of maps used by the ECU 20 for calculating the required air-fuel ratio AFd. The map of FIG. 4 relates the required air-fuel ratio AFd to the catalyst bed temperature Tcat. If the catalyst bed temperature Tcat is low, a larger amount of heat is required to raise the temperature of the exhaust purification device 12. Therefore, as shown in FIG. 4, the required air-fuel ratio AFd on the rich side is calculated as the catalyst bed temperature Tcat is lower. However, if the fuel concentration is increased without limit in accordance with the low catalyst bed temperature Tcat, misfires are caused in the operating cylinders, and more unburned fuel than necessary is discharged to the exhaust system. Therefore, in the map of FIG. 4, the required air-fuel ratio AFd is given for each ignition limit air-fuel ratio AFcr defined as the rich limit, and the required air-fuel ratio AFd does not become richer than the ignition limit air-fuel ratio AFcr. ing. The ignition limit air-fuel ratio AFcr changes according to the operating state of the internal combustion engine 1. Various parameters that can be considered for determining the ignition limit air-fuel ratio AFcr are assumed. In this embodiment, the ignition limit air-fuel ratio AFcr is uniquely specified from the maps of FIGS.

  That is, in this embodiment, in order to identify the ignition limit air-fuel ratio AFcr, the ignition limit air-fuel ratio AFcr is uniquely determined based on the engine speed Ne, the downstream pressure Pm, the valve overlap OL, and the ignition timing SA acquired in step S2. It has come to be identified. Thereby, the ECU 20 calculates the required AFd with reference to the map of FIG. 4 based on the ignition limit air-fuel ratio AFcr specified in the maps of FIGS. 5 to 8 and the catalyst bed temperature Tcat acquired in step S2. Can do.

  Next, in step S8, a ratio AFR0 between the theoretical air-fuel ratio AFt and the required air-fuel ratio AFd is calculated. The ratio AFR0 is defined as AFR0 = AFt / AFd. Next, in step S9, the fuel injection amount Gfinj of the operating cylinder is calculated by multiplying the basic injection amount Gfbase calculated in step S6 by the ratio AFR0 calculated in step S8.

  In step S10, the passage air amount requirement value md of the idle cylinder is calculated. This required air amount value md corresponds to the required air amount of the present invention, and the amount of unburned fuel discharged from the operating cylinder is taken into account for the calculation. This unburned fuel amount corresponds to a value obtained by subtracting the basic injection amount Gfbase expected to burn in the operating cylinder from the fuel injection amount Gfinj for the operating cylinder. Then, the required passing air amount md is calculated based on the following equation so that the air-fuel ratio of the mixed gas of the exhaust gas of the working cylinder and the air supplied through the idle cylinder becomes the target air-fuel ratio AFtrg. In this embodiment, the target air-fuel ratio is set to the stoichiometric air-fuel ratio, and 14.5 is used as the stoichiometric air-fuel ratio.

      md = (Gfinj−Gfbase) × AFtrg

  Next, in step S11, the valve lift VL of the intake valve 6 of the idle cylinder is calculated based on the required passing air amount value md. This valve lift VL means the maximum lift amount of the intake valve 6. FIG. 9 schematically shows an example of a map used by the ECU 20 to calculate the valve lift VL. As is apparent from this figure, the valve lift VL calculated in step S11 increases as the passing air amount requirement value md increases. The passage air amount request value md and the valve lift VL may be associated with each other as appropriate. However, as indicated by the solid line in FIG. 9, the rate of change of the valve lift VL with respect to the passage air amount request value md is constant. Alternatively, as indicated by a broken line, the rate of change may be reduced as the required passing air amount value md increases. Moreover, since the amount of passing air varies depending on the air temperature (outside air temperature), a plurality of maps may be prepared according to the outside air temperature.

  Next, in step S12, the throttle opening degree TA of the independent throttle valve 10 corresponding to the deactivated cylinder is calculated. The throttle opening degree TA is calculated based on the required passing air amount value md and the engine speed Ne. For example, as shown in FIG. 10, the throttle opening degree TA is calculated by causing the ECU 20 to store a map that gives the throttle opening degree TA with the passing air amount request value md and the engine speed Ne as variables, and the ECU 20 refers to this map. This can also be realized. In step S12, the throttle opening degree TA is calculated in consideration of the throttle opening correction amount ΔTA calculated in step S17 described later. That is, the throttle opening degree TA finally obtained in step S12 is TA = TA + ΔTA.

  Next, in step S13, the variable valve mechanism 8 is operated so that the maximum lift of the intake valve 6 of the deactivated cylinder becomes the valve lift VL calculated in step S11. Next, in step S13, the independent throttle valve 10 is operated so that the opening degree of the independent throttle valve 10 corresponding to the deactivated cylinder becomes the opening degree TA obtained in step S12. In step S15, the injector 11 is operated so that the fuel injection amount for the operating cylinder becomes the fuel injection amount Gfinj calculated in step S9. Note that the opening of the independent throttle valve 10 corresponding to the operating cylinder and the valve lift are appropriately set according to the operating state of the internal combustion engine 1.

  Next, in step S16, it is determined whether or not the air-fuel ratio of the atmosphere of the exhaust purification device 12, that is, the exhaust air-fuel ratio AFe, is equal to the target air-fuel ratio AFtrg. The exhaust air-fuel ratio AFe is acquired directly based on the signal from the air-fuel ratio sensor 23. If the exhaust air-fuel ratio AFe and the target air-fuel ratio AFtrg (= 14.5) are equal, the process proceeds to step S18, and if not, the process proceeds to step S17. In step S17, these deviations δAF (δAF = AFtrg−AFe) are calculated, a throttle opening correction amount ΔTA corresponding to the deviation δAF is calculated, and the correction amount ΔTA is used to calculate the throttle opening TA in step S12. To reflect.

  In step S18, it is determined whether or not a suspension cancellation condition, that is, a condition for terminating the reduced-cylinder operation and returning to the normal operation is satisfied. In this determination process, various requirements are set from the viewpoint of whether or not the reduced-cylinder operation should be continued as the suspension cancellation condition, and the satisfaction of the suspension cancellation condition is affirmed when all or part of these requirements are satisfied. It may be. If the suspension cancellation condition is satisfied, the routine is returned to the normal operation in step S19 and the current routine is terminated. On the other hand, if the establishment of the suspension cancellation condition is denied, step S19 is skipped and the current routine is terminated in order to continue the reduced cylinder operation.

  By executing the above processing, the fuel injection amount Gfinj for the operating cylinder is calculated on the assumption that the unburned fuel is discharged from the operating cylinder, and the amount of air passing through the idle cylinder is the unburned fuel amount. Therefore, the temperature of the exhaust gas purification device 12 can be surely promoted by the air passing through the idle cylinder and the exhaust gas exhausted by the working cylinder during the reduced cylinder operation, and the exhaust emission is reduced. Deterioration can be reliably suppressed. Further, since the variable valve mechanism 8 is operated in addition to the independent throttle valve 10 to control the amount of air passing through the idle cylinder, the control accuracy is improved as compared with the control using the independent throttle valve 10 alone. Furthermore, since the air-fuel ratio of the atmosphere of the exhaust purification device 12 is measured and the opening degree TA of the independent throttle valve 10 is corrected, for example, when the combustion state deteriorates due to misfiring of the operating cylinder, etc., and the unburned fuel increases. However, it is possible to reliably suppress the deterioration of the exhaust emission and to reliably maintain the temperature increase promoting effect of the exhaust purification device 12.

  In the above embodiment, the ECU 20 functions as an air amount control unit according to the present invention by executing Steps S6 to S15 of FIGS. Further, by executing step S10, the required air amount calculating means according to the present invention is executed, and by executing step S11, the valve characteristic setting means according to the present invention is executed, thereby executing step S12. By executing step S17 as the degree setting means, the ECU 20 functions as the correction value calculating means of the present invention.

  However, the present invention is not limited to the above form and can be implemented in various forms. The number of cylinders of the internal combustion engine to which the present invention is applied is not particularly limited, and can be applied to multi-cylinder internal combustion engines such as three cylinders, six cylinders, and eight cylinders in addition to the four cylinders shown in FIG. In addition, the present invention is not limited to the types of internal combustion engines such as series, V-type, and horizontally opposed. Also, the variable valve mechanism is sufficient if it can increase or decrease the opening time area of the intake valve, and various mechanisms other than those described above can be adopted.

  Further, by providing an in-cylinder pressure sensor for detecting the pressure in the cylinder, the intake air amount of the operating cylinder can be calculated with high accuracy, and the ignition limit air-fuel ratio can be detected. Control accuracy can be further improved by executing the above-described control in consideration of these values.

  In the above embodiment, the maximum lift amount is set as the valve operating characteristic of the intake valve 6 of the idle cylinder, and the maximum lift amount is increased and the opening time area is increased as the passing air amount requirement value md is increased. In order to increase the time area, the operating angle of the intake valve 6 may be increased without changing the maximum lift amount of the intake valve 6 of the idle cylinder, or both the operating angle and the maximum lift amount of the intake valve 6 may be increased. It may be increased. Further, the amount of air passing through the idle cylinder correlates with the downstream pressure Pm of the independent throttle valve 10 corresponding to the idle cylinder. Accordingly, instead of calculating the required air passage amount value md of the idle cylinder, the required value of the downstream pressure Pm of the independent throttle valve 10 corresponding to the idle cylinder is calculated to control the amount of air passing through the idle cylinder. Good.

The figure which showed the principal part of the internal combustion engine to which the control apparatus of this invention was applied. The flowchart which showed an example of the control routine which concerns on embodiment of this invention. The flowchart which shows the continuation of FIG. Explanatory drawing which showed an example of the map which linked | related the required air fuel ratio AFd with the catalyst bed temperature Tcat. Explanatory drawing which showed an example of the map which linked | related the ignition limit air fuel ratio AFcr with the engine speed Ne. Explanatory drawing which showed an example of the map which linked | related ignition limit air-fuel ratio AFcr with the downstream pressure Pm of an independent throttle valve. Explanatory drawing which showed an example of the map which linked | related the ignition limit air fuel ratio AFcr with the valve overlap OL. Explanatory drawing which showed an example of the map which linked | related ignition limit air-fuel ratio AFcr with ignition timing SA. Explanatory drawing which showed typically an example of the map used for calculation of valve lift VL. Explanatory drawing which showed typically an example of the map used for calculation of the throttle opening degree TA.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 6 Intake valve 8 Variable valve mechanism 10 Independent throttle valve 12 Exhaust purification device 20 ECU (Air amount control means, Required air amount calculation means, Valve characteristic setting means, Opening setting means, Correction value calculation means )
23 Air-fuel ratio sensor (air-fuel ratio acquisition means)

Claims (5)

Before the exhaust purification device of the multi-cylinder internal combustion engine reaches a temperature at which a predetermined purification function can be achieved, a reduced cylinder operation for stopping fuel supply to some cylinders is performed, and the remaining cylinders are discharged during the reduced cylinder operation. In a control device for an internal combustion engine that controls fuel supply so that the air-fuel ratio of a supplied air-fuel mixture is richer than the stoichiometric air-fuel ratio,
An independent throttle valve that is arranged for each cylinder of the multi-cylinder internal combustion engine and can be adjusted in opening degree, a variable valve mechanism that can change the valve operating characteristics of the intake valve provided for each cylinder, and the reduced-cylinder operation The independent throttle valve and the variable valve mechanism are operated so that the temperature of the exhaust purification device is accelerated by the air passing through the some cylinders and the exhaust gas exhausted by the remaining cylinders. And an air amount control means for controlling the amount of air passing through the part of the cylinders. Taking into account the amount of unburned fuel contained in the exhaust gas discharged from the remaining cylinders, the required air amount calculating means for calculating the required air amount to pass through the some cylinders, and the required air amount calculating means Valve characteristic setting means for setting the valve characteristic of the intake valve so that the opening time area of the intake valve of the some cylinders increases as the calculation result increases,
The air amount control means operates the variable valve mechanism so that the intake valves of the some cylinders operate with the valve characteristics set by the valve characteristic setting means. The control apparatus for an internal combustion engine according to claim 1.   The valve operating characteristic setting means, as the valve operating characteristic, increases the maximum lift of the intake valve so that the opening time area of the intake valve of the some cylinders increases as the calculation result of the required air amount calculating means increases. The intake device for an internal combustion engine according to claim 2, wherein the amount is set. Opening degree setting means for setting the opening degree of the independent throttle valve corresponding to the some cylinders based on the required air amount calculated by the required air amount calculating means and the engine speed of the multi-cylinder internal combustion engine; In addition,
The said air quantity control means operates the said independent throttle valve corresponding to the said one part cylinder so that the opening degree which the said opening degree setting means set is obtained. Control device for internal combustion engine. Air-fuel ratio acquisition means for acquiring the air-fuel ratio of the atmosphere of the exhaust purification device, and the independent throttle valve corresponding to the some cylinders according to the deviation between the acquisition result of the air-fuel ratio acquisition means and a predetermined target air-fuel ratio Correction value calculating means for calculating a correction value of the opening degree of
5. The opening degree setting means sets the opening degree of the independent throttle valve corresponding to the some cylinders in consideration of the correction value calculated by the correction value calculation means. Control device for internal combustion engine.

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