JP2011012610A - Control device for variable-cylinder internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To update a target value on control in switching between all-cylinder operation and reduced-cylinder operation to be suitable for an internal combustion engine to appropriately suppress a switching shock, in a control device for a variable cylinder internal combustion engine in which the all-cylinder operation and the reduced-cylinder operation can be switched.SOLUTION: The control device for a variable-cylinder internal combustion engine includes an air volume control means controlling an air volume flowing into a cylinder 16 so that an air volume ratio as a ratio between a volume of air flowing into one operating cylinder 16 before the switching and a volume of air flowing into one operating cylinder 16 after the switching becomes a target air volume ratio when switching between the all-cylinder operation and the reduced-cylinder operation from one operation to another. The air volume control means includes an updating means updating the target air volume ratio to suppress torque fluctuation, based on difference between torque before the switching and torque after the switching.

Description

  The present invention relates to a control device for a variable cylinder internal combustion engine capable of switching between full cylinder operation and reduced cylinder operation.

  2. Description of the Related Art A variable cylinder internal combustion engine that can stop combustion in some cylinders in a predetermined operating state in an internal combustion engine having a plurality of cylinders is known. When performing cylinder number control for switching between cylinder deactivation operation (reducing cylinder operation) in which combustion in some cylinders is deactivated and all cylinder operation in which combustion is performed in all cylinders, a switching shock may occur.

  For example, Patent Document 1 discloses an apparatus for preventing such a switching shock. This device is configured to correct the fuel injection amount calculated based on the engine rotation speed and the engine load based on the in-cylinder pressure when switching between cylinder deactivation operation and all cylinder operation.

JP 2000-186484 A

  By the way, due to various performance differences and deterioration with time of the internal combustion engine, there are some target values for control of the internal combustion engine that are difficult to continue to be used as fixed values. Among them, the target value related to air amount control when switching between all-cylinder operation and reduced-cylinder operation is also included, and in order to appropriately suppress the switching shock when switching between all-cylinder operation and reduced-cylinder operation, It is desirable to update such a target value as appropriate.

  Therefore, an object of the present invention is to update a control target value when switching between all-cylinder operation and reduced-cylinder operation so as to be suitable for an internal combustion engine, and appropriately suppress a switching shock.

  A control device for a variable cylinder internal combustion engine according to the present invention is an air amount control means for controlling the amount of air flowing into a cylinder in the control device for a variable cylinder internal combustion engine capable of switching between full cylinder operation and reduced cylinder operation. When switching from one of the all-cylinder operation and the reduced-cylinder operation to the other, the ratio of the amount of air flowing into one working cylinder before switching and the amount of air flowing into one working cylinder after switching Air amount control means for controlling the air amount so that a certain air amount ratio becomes the target air amount ratio, and the air amount control means changes the target air amount ratio between the pre-switching torque and the post-switching torque. Based on the above, an update means for updating to suppress torque fluctuation is provided.

  Preferably, an in-cylinder pressure sensor and torque calculation means for calculating torque based on an output signal from the in-cylinder pressure sensor are provided. The torque calculation means can calculate the pre-switching torque and the post-switching torque, respectively.

  Such a control device for a variable cylinder internal combustion engine suppresses torque fluctuations corresponding to the control of the air amount by the air amount control means when switching from one to the other of all cylinder operation and reduced cylinder operation. It is preferable to further include an ignition timing control means for controlling the ignition timing.

  Furthermore, the control device for the various variable cylinder internal combustion engines described above is configured so that the air amount ratio becomes the target air amount ratio when switching from one to the other of all cylinder operation and reduced cylinder operation. Before the amount control means controls the air amount, it is preferable to further include an EGR control means for reducing the EGR rate to a predetermined EGR rate or less.

1 is a schematic configuration diagram showing an internal combustion engine to which an embodiment according to the present invention is applied. It is a flowchart regarding switching from all-cylinder operation to reduced-cylinder operation. 3 is a time chart conceptually showing changes in various values on the same time axis when switching control is performed according to the flow of FIG. 2. It is a flowchart regarding switching from reduced-cylinder operation to all-cylinder operation. 5 is a time chart conceptually showing changes in various values on the same time axis when switching control is performed according to the flow of FIG. 4.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an internal combustion engine 10 to which an embodiment according to the present invention is applied. The internal combustion engine 10 shown in FIG. 1 generates power by burning a mixture of fuel and air in a combustion chamber 14 formed in a cylinder block 12 and reciprocating a piston 18 in the cylinder 16. The internal combustion engine 10 is a 4-cycle engine (4-stroke engine).

  Although only one cylinder is shown in FIG. 1, the internal combustion engine 10 is configured as an engine having four cylinders. The internal combustion engine 10 performs all cylinder operation that causes combustion of the air-fuel mixture in all the four cylinders 16 and cylinder deactivation operation that causes combustion of the air-fuel mixture only in the remaining cylinders 16 with some cylinders deactivated. This is an internal combustion engine that can be switched between (cylinder reduction operation), that is, a variable cylinder internal combustion engine. In the internal combustion engine 10, during cylinder reduction operation, the two cylinders are deactivated, and the remaining two cylinders cause combustion of the air-fuel mixture. The two cylinders to be deactivated can be arbitrarily selected and set. In the following, the cylinder 16 that is in the inactive state may be referred to as the inactive cylinder, and the cylinder that is in the active state may be referred to as the active cylinder.

  Since the internal combustion engine 10 has substantially the same configuration with respect to all the cylinders 16, the overall configuration of the internal combustion engine 10 will be described here focusing on any one cylinder 16. An intake port facing each combustion chamber 14 is opened and closed by an intake valve Vi and connected to the intake manifold 20. A surge tank 22 and an intake pipe 24 are sequentially connected to the upstream side of the intake manifold 20. The intake pipe 24 is connected to an air intake (not shown) via an air cleaner 26. A throttle valve 28 (which is an electronically controlled throttle valve driven by an actuator 27 in this embodiment) is incorporated in the middle of the intake pipe 24 (between the surge tank 22 and the air cleaner 26). For example, each of the intake port, the intake manifold 20, the surge tank 22, and the intake pipe 24 defines a part of the intake passage 30.

  On the other hand, an exhaust port facing each combustion chamber 14 is opened and closed by an exhaust valve Ve and connected to an exhaust manifold 32, and an exhaust pipe 34 is connected to the exhaust manifold 32 on the downstream side. Connected to the exhaust pipe 34 are a front-stage catalyst device 36 including a three-way catalyst and a rear-stage catalyst device 38 including a NOx storage reduction catalyst. For example, each of the exhaust port, the exhaust manifold 32 and the exhaust pipe 34 defines a part of the exhaust passage 40.

  The internal combustion engine 10 is provided with an exhaust gas recirculation (EGR) device (EGR device) 42 that guides part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30. The EGR device 42 is provided in the EGR passage 46 defined by the EGR pipe 44 so as to guide a part of the exhaust gas flowing through the exhaust passage 40 to the intake passage 30 and the EGR passage 46 (here, driven by the actuator 47). Electronically controlled EGR valve) EGR valve 48. An EGR cooler 50 for cooling the recirculated exhaust gas (EGR gas) is provided in the EGR passage 46.

  The intake valve Vi and the exhaust valve Ve are opened and closed by a valve operating mechanism having a variable valve timing and / or a variable lift function, respectively. The valve operating mechanism including the drive mechanism 52 for the intake valve Vi and the drive mechanism 54 for the exhaust valve Ve synchronizes the intake valve Vi and the exhaust valve Ve with the rotation of the crankshaft to which the piston 18 is connected via a connecting rod. Thus, the mechanism can be individually controlled at an arbitrary opening degree and timing. Further, the valve operating mechanism is a mechanism capable of maintaining each intake / exhaust valve Vi, Ve independently in a dormant state, for example, a closed state. Specifically, the drive mechanism 52 for the intake valve Vi and the drive mechanism 54 for the exhaust valve Ve each include a separately provided solenoid. That is, the intake valve Vi and the exhaust valve Ve are respectively electromagnetically driven valves. The intake valve Vi and the exhaust valve Ve are configured to be able to realize a valve overlap that opens simultaneously. However, instead of such a configuration, the valve timing and cam profile can be set arbitrarily by switching, for example, a plurality of types of cams applied to a single valve as a valve operating mechanism of the intake valve Vi and the exhaust valve Ve. It is also possible to use a variable valve timing mechanism (VVT) that can be changed to

  Further, each cylinder 16 of the internal combustion engine 10 has a spark plug 56. The spark plug 56 is disposed in the cylinder head so as to face the corresponding combustion chamber 14.

  Further, as shown in FIG. 1, the internal combustion engine 10 includes an injector 58, and the injector 58 is disposed in the cylinder head so as to face the corresponding combustion chamber 14. In the internal combustion engine 10, fuel such as gasoline is directly injected from each injector 58 toward each combustion chamber 14 in a state where air is sucked into each combustion chamber 14.

  The throttle valve 28, the EGR valve 48, the driving mechanisms 52 and 54 included in the valve operating mechanism, the ignition plugs 56, the injectors 58, and the like are electrically connected to the ECU 60 that substantially functions as a control device for the internal combustion engine 10. It is connected to the. The ECU 60 includes a CPU, a ROM, a RAM, an input / output port, etc., all not shown. Various sensors are electrically connected to the ECU 60 via an A / D converter or the like, for example, an air flow meter 62 for detecting an intake air amount. The ECU 60 uses various maps stored in a storage device such as a ROM and the throttle valve 28 and the EGR valve 48 so that a desired output is obtained based on detection values obtained using various sensors. The drive mechanisms 52 and 54, the spark plugs 56, the injectors 58 and the like are controlled.

As shown in FIG. 1, the sensors connected to the ECU 60 include a crank position sensor 64. The crank position sensor 64 is a magnetic sensor or a photoelectric sensor including a rotor plate (signal plate) fixed to the crankshaft, and provides a pulse signal indicating the rotation angle of the crankshaft to the ECU 60 every minute time. In addition, the internal combustion engine 10 has in-cylinder pressure sensors 66 including semiconductor elements, piezoelectric elements, optical fiber detection elements, and the like corresponding to the number of cylinders. Each in-cylinder pressure sensor 66 is disposed in the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 14, and is electrically connected to the ECU 60. Each in-cylinder pressure sensor 66 outputs an electric signal corresponding to the pressure in the combustion chamber 14, that is, the in-cylinder pressure. Output signals from the in-cylinder pressure sensors 66 are sequentially given to the ECU 60 at predetermined time intervals (predetermined crank angles), converted into pressure values, and associated with the crank angle by a predetermined amount in a predetermined storage area of the ECU 60. Stored and retained. Further, a throttle opening sensor 67 for detecting the opening of the throttle valve 28 (throttle opening) is provided. Further, an intake pressure sensor 68 is provided to detect the pressure in the intake passage 30, that is, the intake pressure. Further, the knock sensor 70 for detecting the occurrence of knocking in the internal combustion engine 10, the position sensor 71 for detecting the opening degree (EGR opening degree) of the EGR valve 48, and the temperature of the cooling water in the EGR cooler 50 are set. An EGR cooler water temperature sensor 72 for detecting, a water temperature sensor (not shown) for detecting the temperature of the cooling water of the internal combustion engine 10, and an accelerator position sensor (not shown) for detecting the opening of the accelerator pedal. Is provided. A vehicle speed sensor for detecting the speed (vehicle speed) of the vehicle on which the internal combustion engine 10 is mounted is also provided. Further, an air-fuel ratio sensor (A / F sensor) 74 is provided in the exhaust passage 40. The A / F sensor 74 outputs an electric signal corresponding to the air-fuel ratio in the exhaust gas in the exhaust passage to the ECU 60. Further, an O ₂ sensor 76 is provided in the exhaust passage 40. The O ₂ sensor 76 outputs an electrical signal corresponding to the oxygen concentration in the exhaust gas to the ECU 60.

  The ROM of the ECU 60 has a routine for fuel injection control, a routine for determining the opening / closing timing of the intake valve Vi and the exhaust valve Ve and controlling them, a routine for controlling the ignition timing, a routine for controlling the throttle valve, an internal combustion engine Data such as a routine for changing the number of operating cylinders and maps used for them are stored.

  The ECU 60 executes fuel injection control, ignition control, intake valve opening / closing control, exhaust valve opening / closing control, throttle control, variable cylinder control, and the like according to application programs such as the various routines stored in the ROM or the like.

  In the variable cylinder control, the ECU 60 changes the number of operating cylinders according to the operating state of the internal combustion engine 10. Here, when the operation state of the internal combustion engine 10 is in the low load operation region, the ECU 60 reduces the number of operating cylinders to reduce the internal combustion engine 10 and the operation state of the internal combustion engine 10 is in the medium and high load operation region. When all the cylinders 16 are operated, the internal combustion engine 10 is operated in all cylinders. Note that the boundary between the reduced-cylinder operation region and the all-cylinder operation region, that is, the switching timing from one of the reduced-cylinder operation and the all-cylinder operation to the other is not limited to be determined in this way and can be set variously.

  Here, in the cylinder 16 which is not operated, that is, the idle cylinder, in addition to fuel injection and ignition not being performed, the intake valve Vi and the exhaust valve Ve are both closed. However, the present invention allows the intake valve Vi and / or the exhaust valve Ve to be opened or opened / closed in the idle cylinder as in the case of operation.

  The air amount control means for controlling the amount of air flowing into the cylinder 16 includes a part of the ECU 60. This air amount control means is based on the difference between the pre-switching torque and the post-switching torque based on a target air amount ratio, which will be described later, used for control when switching from one to the other of all-cylinder operation and reduced-cylinder operation. And updating means for updating to suppress torque fluctuation. The update means includes a part of the ECU 60. Further, the torque calculation means for calculating the torque based on the output signal from the in-cylinder pressure sensor 66 includes a part of the ECU 60. Here, the torque detection means includes the in-cylinder pressure sensor 66 and such torque calculation means, but may be configured differently. Further, the ignition timing control means includes a part of the ECU 60. Further, the EGR control means includes a part of the ECU 60.

  Hereinafter, switching control between all-cylinder operation and reduced-cylinder operation will be described in detail.

  First, the case where the internal combustion engine 10 is switched from the full cylinder operation to the reduced cylinder operation will be described with reference to FIGS. In the following, when the internal combustion engine 10 is switched from full cylinder operation to reduced cylinder operation, fuel injection control, ignition control, intake valve opening / closing control, exhaust valve opening / closing control, air amount for controlling the amount of air flowing into the cylinder 16 The throttle control and variable cylinder control substantially corresponding to the control will be described in combination. The control described below is preferably applied to each cylinder 16 as much as possible.

  FIG. 2 is a flowchart relating to switching from all-cylinder operation to reduced-cylinder operation, and FIG. 3 is a time conceptually showing changes in various values on the same time axis when switching control is performed according to FIG. It is a chart. In the state where the all-cylinder operation is being executed, the internal combustion engine 10 is switched from the all-cylinder operation to the reduced-cylinder operation based on the flowchart of FIG.

  The ECU 60 proceeds to the routine shown in FIG. 2 when the above switching condition from the all-cylinder operation to the reduced-cylinder operation is satisfied during engine control according to the main routine. Note that switching from all-cylinder operation to reduced-cylinder operation is mainly determined based on the engine rotation speed and the engine load. Here, as described above, the operation state of the internal combustion engine 10 is in the middle and high load operation region. It is executed when shifting from low to high load operation region. The engine load is associated with at least one of a throttle opening, an accelerator opening, an intake pressure, and the like. However, when the above switching condition from full cylinder operation to reduced cylinder operation is satisfied (at time t1 in FIG. 3), in addition to proceeding to the routine of FIG. 2, the actuator 47 is operated so that the EGR valve 48 is closed. A signal is output.

  When the condition for switching from all-cylinder operation to reduced-cylinder operation is satisfied, a target torque is set in step S201. The target torque is the output torque of the internal combustion engine 10 when the switching condition is satisfied. This is to prevent torque fluctuation with respect to the output from the internal combustion engine 10 when shifting from full cylinder operation to reduced cylinder operation. The output torque in the internal combustion engine 10 is calculated based on the output signal from the in-cylinder pressure sensor 66, and here, it is the indicated torque (the sum of the indicated torques for all cylinders). Note that the output torque of the internal combustion engine 10 when the switching condition that is the target torque is satisfied is also stored as the pre-switching torque.

  Then, in the next step S203, it is determined whether or not the EGR rate is equal to or less than a predetermined EGR rate. Here, the EGR rate is estimated from the opening degree of the EGR valve 48 (EGR opening degree) and the valve timings of the intake and exhaust valves Vi and Ve. The EGR rate may be calculated based on an output signal from the in-cylinder pressure sensor 66. The predetermined EGR rate may be zero, may be arbitrarily determined, and may be determined so as not to cause torque shock or misfire by switching from all-cylinder operation to reduced-cylinder operation. Step S203 is repeated until the EGR rate becomes equal to or lower than the predetermined EGR rate.

  Since the EGR rate is equal to or lower than the predetermined EGR rate, if an affirmative determination is made in step S203, step S205 is executed. In step S205, throttle control is executed so that the throttle opening increases. Here, an operation signal is output to the throttle actuator 27 so that the throttle opening is fully opened (at time t2 in FIG. 3). By opening the throttle valve 28 as described above, the amount of air charged in the cylinder 16 is increased. The increase in the air amount is performed so that the air amount flowing into the cylinder 16 becomes a target air amount described later. On the other hand, before the throttle valve 28 is controlled in this way, preferably immediately before, the amount of air that is filled (or filled) in one cylinder 16 (the amount of air before switching) is detected and stored. . The detection of the amount of air filled in the cylinder 16 is performed by searching for data (not shown) or performing calculation based on an output signal from the air flow meter 62. Note that the amount of air filled in the cylinder 16 may be calculated based on an output signal from the in-cylinder pressure sensor 66. In addition, before the throttle valve 28 is controlled as described above, preferably the immediately preceding torque may be obtained as described above, and may be set as the above-described pre-switching torque. However, the torque immediately before, preferably immediately before the throttle valve 28 is controlled is approximately equal to the output torque of the internal combustion engine 10 when the switching condition is satisfied.

  Next, in step S207, the ignition timing is retarded. This is intended to execute the ignition timing control for retarding the ignition timing until step S211 described later is reached. The ignition timing is retarded by a predetermined retardation amount so that torque increase, that is, torque fluctuation does not occur as a result of the throttle control performed in step S205. The predetermined retardation amount is determined based on a total retardation amount stored in advance based on experiments or the like. Specifically, data on the total retardation amount for various pre-switching torques is stored and saved. Preferably, the total retard amount data is also related to the air amount before switching as described above. The predetermined total retardation amount is read by searching the data with the pre-switching torque and the pre-switching air amount detected as described above. The predetermined total retardation amount read is a predetermined switching period (for example, equivalent to three to four combustion cycles) for switching from all-cylinder operation to reduced-cylinder operation (between t2 and t3 in FIG. 3). Since this is the total retard amount of the ignition timing at, it is divided into three equal parts or four equal parts. Thereby, a predetermined retardation amount for one combustion cycle is derived. Thus, the ignition timing control is performed so that the ignition timing is retarded linearly. Such a change in the predetermined retardation amount corresponds to a change in the amount of air flowing into the cylinder 16. The predetermined retardation amount is further corrected by the detected torque or the like so that the output torque of the internal combustion engine 10 matches the target torque.

  Next, in step S209, it is determined whether or not the air amount flowing into the cylinder 16 has reached the target air amount. The target air amount is approximately twice the above-described air amount before switching. This corresponds to the fact that the number of operating cylinders is reduced by half by shifting to the reduced cylinder operation. For example, when the number of operating cylinders is reduced to a quarter due to the shift to the reduced cylinder operation, the target air amount may be about four times the pre-switching air amount. Specifically, the target air amount is obtained by the product of the pre-switching air amount detected as described above and a predetermined value that is determined and stored in advance through experiments. Here, the predetermined value is initially set to 2, and is corrected and updated as will be described later. As can be understood from the above description, this predetermined value is a switching period that is a ratio of the amount of air flowing into one working cylinder 16 before switching and the amount of air flowing into one working cylinder 16 after switching. This corresponds to the target value of the air amount ratio before and after (between t2 and t3 in FIG. 3). The target value of the air amount ratio is referred to as a target air amount ratio. As described above, the amount of air flowing into the cylinder 16 can be detected based on the output signal from the air flow meter 62 or can be detected based on the output signal from the in-cylinder pressure sensor 66. If a negative determination is made in step S209, step S207 and step S209 are repeated.

  If an affirmative determination is made in step S209, switching to reduced-cylinder operation is executed in step S211 (at time t3 in FIG. 3). Switching from all-cylinder operation to reduced-cylinder operation is achieved by closing the intake and exhaust valves Vi and Ve as described above in addition to prohibiting fuel injection in the cylinder 16 that is deactivated. Is done. Then, while maintaining the output torque of the internal combustion engine 10 at the target torque, the internal combustion engine control according to the operating state is executed. Specifically, various controls are performed on the cylinder 16 that continues to operate so that the throttle opening becomes the target throttle opening, the ignition timing becomes the target ignition timing, and the EGR rate becomes the target EGR rate. These target values are determined so that, in principle, torque shock does not occur by switching from all-cylinder operation to reduced-cylinder operation, but the target throttle opening is determined so that the amount of air flowing into the cylinder 16 does not change. (See FIG. 3). That is, the throttle control is executed so that the air amount at the completion of switching matches the target air amount. In this way, the switching from the all cylinder operation to the reduced cylinder operation is completed.

  For learning and updating various values described below, the output torque of the internal combustion engine 10 immediately before switching from all-cylinder operation to reduced-cylinder operation and the output torque of the internal combustion engine 10 after switching, preferably immediately after switching, are detected. And memorized. Hereinafter, the output torque of the internal combustion engine 10 immediately before the switching is referred to as the immediately preceding torque, and the output torque of the internal combustion engine 10 after the switching is referred to as the post-switching torque. Further, after switching from the full cylinder operation to the reduced cylinder operation, the amount of air flowing into one active cylinder 16 is detected and stored preferably immediately after. This air amount is referred to as a post-switching air amount. Further, the total retard amount of the ignition timing retarded with respect to the switching from the all cylinder operation to the reduced cylinder operation is calculated. This total retardation amount is referred to as a new total retardation amount.

  After switching from all-cylinder operation to reduced-cylinder operation, the predetermined total retardation amount read in step S207 and the predetermined value used to set the target air amount in step S209 are updated.

  The new total retardation amount is corrected according to the difference between the pre-switching torque detected and set as described above and the immediately preceding torque. The new total retardation amount is corrected based on the difference between the torque before switching and the torque immediately before switching. Specifically, the new total retardation amount after correction is such that the ratio between the torque before switching and the immediately preceding torque has a corresponding relationship with the ratio between the new total retardation amount and the corrected new total retardation amount. Calculated. Then, the data corresponding to the predetermined total retardation amount read in step S207 is updated (rewritten) with the corrected new total retardation amount. Based on the data updated in this way, switching control from the all-cylinder operation to the reduced-cylinder operation from the next time is executed.

  On the other hand, the predetermined value used for setting the target air amount in step S209, that is, the target air amount ratio, is the difference between the pre-switching torque and the post-switching torque detected and set as described above (before and after the switching period). Updated based on the difference in torque). Specifically, first, an air amount ratio, which is a ratio between the obtained air amount before switching and air amount after switching, is corrected according to the difference in torque before and after the switching period. The air amount ratio (pre-switching air amount / post-switching air amount) is corrected so that the torque ratio (pre-switching torque / post-switching torque) having a corresponding relationship is 1, in other words, the torque fluctuation is suppressed. . Then, the predetermined value used for setting the target air amount in step S209 is updated by the reciprocal of the corrected air amount ratio. That is, the target air amount ratio is updated based on the difference in torque before and after the switching period. Based on the data updated in this way, switching control from the all-cylinder operation to the reduced-cylinder operation from the next time is executed.

  Here, the EGR rate is lowered to the predetermined EGR rate by t2 as described above, but may be gradually reduced to t3 as shown by the dotted line in FIG. The reduction rate of the EGR rate or the like may be set in consideration of the NOx concentration of the exhaust gas.

  Next, switching from reduced-cylinder operation to all-cylinder operation will be described with reference to FIGS. 4 and 5. In the following, fuel injection control, ignition control, intake valve opening / closing control, exhaust valve opening / closing control, when switching from reduced-cylinder operation to all-cylinder operation, as in the description related to switching from all-cylinder operation to reduced-cylinder operation, The throttle control and variable cylinder control will be described in combination. However, switching from reduced-cylinder operation to all-cylinder operation is performed based on the same inventive concept as switching from all-cylinder operation to reduced-cylinder operation. Therefore, in general, the control when switching between them is similar. Therefore, focusing on the difference in switching between them, hereinafter, switching from reduced-cylinder operation to all-cylinder operation will be described with some omissions. The control described below is preferably applied to each cylinder 16 as much as possible.

  FIG. 4 is a flowchart relating to switching from reduced-cylinder operation to all-cylinder operation, and FIG. 5 is a time conceptually showing changes in various values on the same time axis when switching control is performed according to FIG. It is a chart. In a state where the internal combustion engine 10 is executing the reduced cylinder operation, switching from the reduced cylinder operation to the all cylinder operation is executed based on the flowchart of FIG.

  The ECU 60 proceeds to the routine shown in FIG. 4 when the above switching condition from the reduced-cylinder operation to the all-cylinder operation is satisfied during engine control according to the main routine. However, when the switching condition from the reduced cylinder operation to the all cylinder operation is satisfied (at time t11 in FIG. 5), in addition to proceeding to the routine of FIG. 4, the actuator 47 is operated so that the EGR valve 48 is closed. A signal is output.

  When the switching condition from the reduced cylinder operation to the all cylinder operation is satisfied, the target torque is set in step S401. The target torque is the output torque of the internal combustion engine 10 when the switching condition is satisfied, as described with respect to step S201 above. This is to prevent torque fluctuation with respect to the output from the internal combustion engine 10 when shifting from the reduced cylinder operation to the all cylinder operation. The target torque that is the output torque of the internal combustion engine 10 when the switching condition is satisfied is similarly stored as the torque before switching.

  Then, in step S403, it is determined whether or not the EGR rate is equal to or less than a predetermined EGR rate, as in step S203. Here, calculation, estimation, and the like of the EGR rate are as described for step S203 above.

  Since the EGR rate has become equal to or less than the predetermined EGR rate, if an affirmative determination is made in step S403, step S405 is executed. In step S405, all the cylinders 16 are operated and the throttle opening is reduced. The operation of all the cylinders 16 is achieved by resuming fuel injection and ignition in the deactivated cylinder while resuming the opening / closing drive of the intake / exhaust valves Vi and Ve of the deactivated cylinder. Here, an operation signal is output to the throttle actuator 27 so that the throttle opening becomes a predetermined small opening (at t12 in FIG. 5). By reducing the throttle opening, the amount of air flowing into the working cylinder 16 can be reduced. This reduction in the air amount is performed so that the air amount flowing into the working cylinder 16 becomes the target air amount. On the other hand, the air amount before switching, preferably immediately before switching, is detected and stored before the throttle valve 28 is controlled in the same manner as described in connection with step S205.

  Next, in step S407, the ignition timing is retarded. This is closely related to step S405, and it is intended that ignition timing control for retarding the ignition timing is executed until step S411 described later is reached. However, in step S407, unlike in step S207, the ignition timing is retarded discontinuously by a predetermined second total retardation amount. Then, the ignition timing is controlled so that the retard amount decreases by a predetermined second retard amount. Note that the predetermined second total retardation amount and the predetermined second retardation amount are amounts corresponding to the predetermined total retardation amount and the predetermined retardation amount, respectively, and the predetermined total retardation amount and the predetermined retardation amount. It is defined in the same way as the angular amount, and learned and updated in the same way. The predetermined second total retardation amount is a predetermined switching period (e.g., corresponding to three to four combustion cycles) relating to switching from reduced cylinder operation to all cylinder operation (between t12 and t13 in FIG. 5). Since this is the total retard amount of the ignition timing at, it is divided into three equal parts or four equal parts. Thereby, the predetermined second retardation amount for one combustion cycle is derived.

  Next, in step S409, it is determined whether or not the air amount flowing into the working cylinder 16 has reached the target air amount. The target air amount is about 0.5 times the air amount before switching described above. This corresponds to the fact that the number of operating cylinders is doubled by shifting to the all-cylinder operation. For example, when the number of operating cylinders is increased four times due to the shift to all cylinder operation, the target air amount may be set to about 0.25 times the air amount before switching. Here, the setting of the target air amount and the setting, learning, and updating of a predetermined value (corresponding to the target air amount ratio) are the same as those of the predetermined value in step S209.

  If an affirmative determination is made in step S409, complete switching to all-cylinder operation is executed in step S411 (at time t13 in FIG. 5). Since all cylinders 16 are already in operation, various cylinders 16 are selected so that the throttle opening is the target throttle opening, the ignition timing is the target ignition timing, and the EGR rate is the target EGR rate. The control is executed. However, these target values are determined so that torque shock does not occur by switching from all-cylinder operation to reduced-cylinder operation. Thus, the switching from the reduced cylinder operation to the all cylinder operation is completed. Note that the torque after complete switching from the reduced-cylinder operation to the all-cylinder operation in step S411 is detected and stored as the post-switching torque. Further, after such switching, the amount of air flowing into one working cylinder 16 immediately after switching, that is, the amount of air after switching is detected and stored.

  The various values (including the target air amount ratio) used when switching from reduced-cylinder operation to all-cylinder operation are also the same as the various values used when switching from all-cylinder operation to reduced-cylinder operation. Updated.

  Here, the EGR rate is lowered to the predetermined EGR rate by t12 as described above, but may be reduced by t13 as shown by the dotted line in FIG. The reduction rate of the EGR rate may be set in consideration of the NOx concentration of the exhaust gas.

  As described above, when switching between all-cylinder operation and reduced-cylinder operation, the ratio of the amount of air flowing into one working cylinder before switching and the amount of air flowing into one working cylinder after switching. The amount of air flowing into the cylinder 16 is controlled so that the air amount ratio becomes the target air amount ratio. In this air amount control, the target air amount ratio is not set to a fixed value, but is updated based on the torque difference before and after the switching period (between t2 and t3 in FIG. 3 and between t12 and t13 in FIG. 5). Then, switching between the all-cylinder operation and the reduced-cylinder operation from the next time is executed using the updated target air amount ratio. Then, EGR control and ignition timing control are combined so that torque fluctuation suppression by the air amount control can be executed more appropriately.

  As described above, in the present embodiment, the value used in the control when switching between the all cylinder operation and the reduced cylinder operation is updated using various values obtained by the actual switching control of the internal combustion engine 10. Therefore, for example, even if the intake characteristics vary between cylinders or the characteristics of the internal combustion engine change due to deposit accumulation, torque fluctuations when switching between all-cylinder operation and reduced-cylinder operation are appropriately suppressed. It becomes possible to continue. Therefore, by switching between all-cylinder operation and reduced-cylinder operation, it is possible to prevent the driver from feeling uncomfortable or uncomfortable.

  Note that the above-mentioned various values when switching between all-cylinder operation and reduced-cylinder operation, for example, the predetermined value described in relation to steps S209 and S409, that is, the target air amount ratio, is the number of operating cylinders during reduced-cylinder operation. In an internal combustion engine that changes a plurality of times, it may be changed according to the number of operating cylinders during the reduced-cylinder operation. For example, in an internal combustion engine in which the total number of cylinders is four, when a reduced cylinder operation is performed using only two cylinders, and when a reduced cylinder operation is performed using only one cylinder, the predetermined value or the like Various values may be determined for each case.

  In the above embodiment, the internal combustion engine is a spark ignition type internal combustion engine, but may be a compression ignition type internal combustion engine. Further, the number of cylinders and the cylinder arrangement of the internal combustion engine are arbitrary. The present invention can be applied to various internal combustion engines having two or more cylinders capable of switching between full cylinder operation and reduced cylinder operation.

  In addition, although the present invention has been described with a certain degree of specificity in the above-described embodiments and modifications thereof, the present invention is not limited to these, and the spirit and scope of the invention described in the scope of the claims. It should be understood that various modifications and changes can be made without leaving. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Combustion chamber 28 Throttle valve 48 EGR valve 56 Spark plug 66 In-cylinder pressure sensor Vi Intake valve Ve Exhaust valve

Claims (4)

In a control device for a variable cylinder internal combustion engine capable of switching between full cylinder operation and reduced cylinder operation,
Air amount control means for controlling the amount of air flowing into a cylinder, and when switching from one to the other of all-cylinder operation and reduced-cylinder operation, the amount of air that flows into one working cylinder before switching And air amount control means for controlling the air amount so that the air amount ratio, which is the ratio of the air amount flowing into one working cylinder after switching, becomes the target air amount ratio,
The air amount control means includes an update means for updating the target air amount ratio so as to suppress torque fluctuation based on a difference between the pre-switching torque and the post-switching torque. Control device. An in-cylinder pressure sensor;
Torque calculating means for calculating torque based on an output signal from the in-cylinder pressure sensor,
2. The control device for a variable cylinder internal combustion engine according to claim 1, wherein the torque calculating means calculates the pre-switching torque and the post-switching torque, respectively.   Ignition timing control means for controlling the ignition timing so as to suppress torque fluctuations corresponding to the control of the air amount by the air amount control means when switching from one to the other of all cylinder operation and reduced cylinder operation The control apparatus for a variable cylinder internal combustion engine according to claim 1, further comprising:   When switching from one to the other of all-cylinder operation and reduced-cylinder operation, the EGR rate is set before the air amount control means controls the air amount so that the air amount ratio becomes the target air amount ratio. 4. The control apparatus for a variable cylinder internal combustion engine according to claim 1, further comprising EGR control means for reducing the EGR rate to a predetermined EGR rate or less.

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