JP4725653B2 - Operation control device for multi-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to an operation control device for a multi-cylinder internal combustion engine. In particular, the present invention is intended to prolong the duration of the reduced-cylinder operation for a multi-cylinder internal combustion engine capable of executing a reduced-cylinder operation in which the operation of some cylinders is stopped according to the load of the internal combustion engine. Regarding improvements.

  Conventionally, as disclosed in, for example, Patent Documents 1 to 3 below, a reduced-cylinder operation for improving the fuel consumption rate by stopping the operation of some cylinders when the engine is not loaded is performed. A viable multi-cylinder engine is known.

  For example, in a state where there is a surplus output, such as during idling operation of the engine, the load applied to each cylinder is small, so intake / exhaust loss increases and there is a concern about deterioration in combustion efficiency. For this reason, the fuel supply to some cylinders (for example, the cylinders in one bank in the case of a V-type engine) is stopped, and the cylinders are deactivated (deactivated) so that the fuel is not supplied. The combustion efficiency is increased by increasing the load of the supplied operating cylinder (cylinder of the other bank). Thereby, improvement of a fuel consumption rate and reduction of fuel consumption can be aimed at.

  Note that, in Patent Document 1, when shifting from the above-described reduced-cylinder operation to an all-cylinder operation (an operation for supplying fuel to all cylinders), exhaust that leads to a cylinder that has been inactive (stopped cylinder) until then. It is disclosed that when the temperature of the catalyst provided in the system is lower than the activation temperature, the ignition timing in the combustion stroke of the cylinder is retarded. Thus, the exhaust gas emission is improved by raising the catalyst temperature early.

  Further, in Patent Document 2, during the reduced-cylinder operation, the temperature of the catalyst provided in the exhaust system connected to the deactivated cylinder becomes lower than a predetermined temperature (the temperature at which the catalyst is assumed to be surely activated). In some cases, reduced-cylinder operation is prohibited. That is, by shifting to all-cylinder operation as the catalyst temperature decreases, the exhaust emission at the time of returning to all-cylinder operation due to the catalyst temperature decreasing to the activation temperature or less is prevented.

  Furthermore, Patent Document 3 discloses that when performing catalyst early warm-up control, ignition delay is performed to raise the exhaust gas temperature, and at this time, fuel injection to some cylinders is stopped to reduce cylinder operation. Is disclosed.

JP-A-2005-351134 JP 2001-227369 A JP 2001-182601 A

  By the way, in an engine capable of performing the above-described reduced cylinder operation, as disclosed in Patent Document 1 and Patent Document 2, an exhaust system catalyst (hereinafter referred to as a cylinder that is inactive during the reduced cylinder operation) , Referred to as a deactivated cylinder side catalyst) and an exhaust system catalyst (hereinafter referred to as an active cylinder side catalyst) connected to a cylinder (operating cylinder) that continues to operate, This may cause problems.

  That is, even if the temperature of the idle cylinder side catalyst is equal to or higher than the lower limit of the activation temperature (for example, 450 ° C.) Is not sufficiently high (for example, a situation in which the temperature is only about 50 ° C. higher than the lower limit of the activation temperature of the catalyst), the catalyst temperature decreases to near the lower limit of the activation temperature within a short time after the start of the reduced cylinder operation. As a result, all-cylinder operation must be restored.

  In particular, in the engine in which the intake and exhaust valves of the deactivated cylinder during the reduced-cylinder operation are opened and closed in the same manner as during all-cylinder operation, air (same as the outside air) Therefore, the amount of decrease in the catalyst temperature per unit time tends to be large, and the above problem is promoted.

  In such a case, the duration of the reduced-cylinder operation becomes extremely short, and it becomes difficult to fully utilize the merit of the engine system capable of executing this reduced-cylinder operation. As a result, there is a possibility that the effect of improving the fuel consumption rate and the effect of reducing the fuel consumption cannot be fully achieved.

  This problem may also occur in each of the above patent documents. That is, in Patent Document 1, the catalyst temperature is raised by retarding the ignition timing after shifting from reduced-cylinder operation to all-cylinder operation. In this method, the temperature of the deactivated cylinder-side catalyst during reduced-cylinder operation is used. It is not possible to lengthen the time for maintaining the temperature at the activation temperature to prolong the duration of the reduced-cylinder operation.

  Further, Patent Document 2 simply prohibits the reduced-cylinder operation when the temperature of the catalyst becomes lower than a predetermined temperature. Also in this method, the temperature of the deactivated cylinder-side catalyst during the reduced-cylinder operation is activated. The time for maintaining the temperature cannot be extended.

  In addition, the exhaust system configuration disclosed in Patent Document 3 is because all cylinders are connected to the same catalyst (because the deactivated cylinder side catalyst and the active cylinder side catalyst are not independent configurations), the reduced cylinder operation is performed. The above-mentioned problem that the temperature of a part of the catalyst is lowered during execution does not occur. That is, the exhaust system structure targeted by the present invention is not achieved.

  The present invention has been made in view of such a point, and an object of the present invention is to maintain a high temperature of the deactivated cylinder side catalyst during the reduced-cylinder operation with respect to the multi-cylinder internal combustion engine capable of performing the reduced-cylinder operation. An object of the present invention is to provide an operation control device for a multi-cylinder internal combustion engine that can ensure a long duration of the reduced-cylinder operation.

-Principle of solving the problem-
The solution principle of the present invention taken in order to achieve the above object is that the catalyst temperature of the exhaust system that leads to the cylinder that is inactive in the reduced cylinder operation (scheduled cylinder) is preset. Control that is set to a high value is executed, and then the reduced-cylinder operation is started. For this reason, it is possible to lengthen the time until the catalyst temperature decreases to near the lower limit of the activation temperature during the reduced-cylinder operation, and to obtain a longer duration of the reduced-cylinder operation.

-Solution-
Specifically, the present invention provides a first catalyst provided in a first exhaust passage connected to some cylinders of the plurality of cylinders, and a second catalyst provided in a second exhaust passage connected to other cylinders. And an operation control device for a multi-cylinder internal combustion engine that can perform a reduced cylinder operation that deactivates some of the cylinders when a predetermined reduced cylinder operation execution condition is satisfied. This multi-cylinder internal combustion engine operation control device is provided with catalyst temperature recognition means and catalyst preheating operation execution means. The catalyst temperature recognizing means detects or estimates the temperature of the first catalyst. Further, the catalyst preheating operation execution means is configured such that when the reduced cylinder operation execution condition is satisfied, the temperature of the first catalyst detected or estimated by the catalyst temperature recognition means is the lower limit value of the activation temperature of the first catalyst. When the temperature is lower than the preheating required temperature set as a value higher than a predetermined value, the temperature of the first catalyst is raised to the preheating required temperature or higher prior to the execution of the reduced cylinder operation. The catalyst preheating operation is performed. The catalyst preheating operation retards the ignition timing of the spark plugs of the some cylinders that are inoperative during the reduced cylinder operation prior to the execution of the reduced cylinder operation. By gradually increasing the timing retard amount, the amount of kinetic energy that contributes to the torque generation of the internal combustion engine out of the energy generated by the combustion of the air-fuel mixture is gradually reduced and the catalyst is preheated. Gradually increase the amount of thermal energy that contributes. If the temperature of the first catalyst rises to the preheating required temperature or more by the catalyst preheating operation while the reduced cylinder operation execution condition is satisfied, the catalyst preheating operation is terminated and decreased. The cylinder operation is started.

  Here, “part of the cylinders” that are inactive during the reduced-cylinder operation is a concept that includes not only a single cylinder but also a plurality of cylinders (for example, one bank of a V-type engine). . Further, as the catalysts arranged independently by being provided in different exhaust passages, not only the first catalyst and the second catalyst but also three or more types of catalysts may be arranged independently of each other. .

  According to the above specific matter, when the reduced cylinder operation execution condition is satisfied during the execution of the all cylinder operation, the temperature of the first catalyst is detected or estimated by the catalyst temperature recognition means. When the temperature of the first catalyst is lower than the predetermined preheating required temperature, the reduced cylinder operation is not started immediately after the reduced cylinder operation execution condition is satisfied, but first, the first cylinder is started. A catalyst preheating operation is performed to raise the temperature of the catalyst above the preheating required temperature. Then, after the temperature of the first catalyst has sufficiently increased to the preheating required temperature or higher by executing this catalyst preheating operation, the reduced cylinder operation is started. That is, since the reduced-cylinder operation is started in a state where the temperature of the first catalyst is relatively high, even if the temperature of the first catalyst gradually decreases during the reduced-cylinder operation, that temperature However, it is possible to lengthen the time for the temperature to decrease to a temperature (for example, the activation temperature lower limit value) that requires the return of all cylinder operation. As a result, it is possible to obtain a longer duration of reduced-cylinder operation and to fully utilize the merits of the engine system that enables the reduced-cylinder operation, and to improve the fuel consumption rate and fuel consumption. A reduction effect can be sufficiently achieved.

Further, since the retard the ignition timing of the spark plug as a catalyst preliminary heating operation, slow even combustion start timing in the combustion stroke (nonworking become cylinder when the transition to the reduced-cylinder operation) the part of the cylinder As the engine is turned, the combustion becomes slow, and a part of the air-fuel mixture is combusted in the exhaust passage (first exhaust passage). For this reason, the temperature of the first catalyst can be rapidly increased by significantly increasing the gas temperature in the exhaust system. Accordingly, it is possible to sufficiently raise the temperature of the first catalyst to the preheating required temperature or more in a short time, and the fuel supplied during the catalyst preheating operation period can be effectively increased. It is possible to contribute to an increase in temperature of one catalyst. As a result, the amount of fuel used for the catalyst preheating operation can be kept relatively small, and the fuel consumption is not significantly increased.

When the reduced cylinder operation execution condition is satisfied and the catalyst preheating operation is started, at the initial stage, the retard amount of the ignition timing of the spark plug is relatively small, and most of the energy generated by the combustion of the air-fuel mixture is Is kinetic energy that contributes to torque generation of the internal combustion engine, and part of it is used as thermal energy that contributes to catalyst preheating (heating of the first catalyst). After that, as the retard amount of the ignition timing of the spark plug gradually increases, the amount of kinetic energy that contributes to the torque generation of the internal combustion engine among the energy generated by the combustion of the air-fuel mixture gradually decreases. On the other hand, the amount of heat energy contributing to catalyst preheating gradually increases. When the temperature of the first catalyst reaches the preheating required temperature or more, the catalyst preheating operation is finished and the reduced cylinder operation is started. In this way, when switching from full cylinder operation to reduced cylinder operation, the torque of the internal combustion engine gradually decreases during the catalyst preheating operation, so that sudden torque fluctuations occur during this operation switching. The vibration (shock) at the time of switching operation can be hardly generated. That is, the operation can be switched without making the vehicle occupant aware of the change from the all-cylinder operation to the reduced-cylinder operation, and drastic improvement in drivability can be achieved. As described above, according to this solution, it is possible to realize an unprecedented switching operation from all cylinder operation to reduced cylinder operation, which hardly causes vibration at the time of operation switching, and the duration of reduced cylinder operation. It is possible to achieve both the effect of improving the fuel consumption rate and the effect of reducing the fuel consumption by obtaining a longer time.

  Examples of the configuration for switching from the reduced-cylinder operation to the all-cylinder operation include the following. That is, when the temperature of the first catalyst falls to a predetermined all-cylinder operation return temperature during the reduced-cylinder operation, the reduced-cylinder operation is switched to the all-cylinder operation. The all-cylinder operation return temperature is set to a temperature that is higher than the lower limit of the activation temperature of the first catalyst and lower than the preheating required temperature (the activity of the first catalyst). Lower temperature limit <all cylinder operation return temperature <required preheating temperature).

  Thus, each temperature is set (the preheating required temperature is set higher than the all-cylinder operation return temperature, and the all-cylinder operation return temperature is set higher than the activation temperature lower limit value of the first catalyst). Therefore, during the reduced-cylinder operation, the time until the catalyst temperature decreases to near the lower limit of the activation temperature is prolonged, and the exhaust emission is prevented from deteriorating when the reduced-cylinder operation is switched to the all-cylinder operation. It becomes possible to achieve both.

  In the present invention, at the start of the reduced-cylinder operation, control is performed in which the catalyst temperature of the exhaust system connected to the cylinder that is inactive in the reduced-cylinder operation is set in advance, and then the reduced-cylinder operation is started. I have to. For this reason, it is possible to prolong the time until the catalyst temperature decreases to near the lower limit of the activation temperature during the reduced-cylinder operation. In addition, the fuel consumption can be sufficiently reduced.

It is a figure which shows schematic structure inside the engine which looked at the V-type engine which concerns on embodiment from the direction along the axial center of a crankshaft. It is a system block diagram which shows the outline of an engine, an intake / exhaust system, and a control system. It is a block diagram which shows the control system of an engine. It is a flowchart figure which shows the operation | movement procedure of driving | operation switching control.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment demonstrates the case where this invention is applied to the vehicle carrying a V type 6 cylinder gasoline engine as an internal combustion engine.

  Before describing the control at the time of switching to the reduced-cylinder operation, which is the characteristic feature of this embodiment, the overall engine configuration and control block will be described.

-Description of overall engine configuration-
FIG. 1 is a diagram showing a schematic configuration inside an engine when a V-type engine E according to the present embodiment is viewed from a direction along the axis of a crankshaft C. FIG. 2 is a system configuration diagram showing an outline of the engine E, intake / exhaust system, and control system.

  As shown in these drawings, the V-type engine E has a pair of banks 2L and 2R protruding in a V-shape at the upper part of the cylinder block 1. Each bank 2L, 2R includes a cylinder head 3L, 3R installed at the upper end of the cylinder block 1 and a head cover 4L, 4R attached to the upper end thereof. The cylinder block 1 is provided with a plurality of cylinders 5L, 5R,... (For example, three in each bank 2L, 2R) with a predetermined sandwich angle (for example, 90 °). The pistons 51L, 51R,... The pistons 51L, 51R,... Are connected to the crankshaft C through connecting rods 52L, 52R,. Further, a crankcase 6 is attached to the lower side of the cylinder block 1, and a space extending from the lower part in the cylinder block 1 to the inside of the crankcase 6 is a crank chamber 61. An oil pan 62 serving as an oil reservoir is disposed further below the crankcase 6.

  The cylinder heads 3L and 3R are respectively assembled with intake valves 32L and 32R for opening and closing the intake ports 31L and 31R and exhaust valves 34L and 34R for opening and closing the exhaust ports 33L and 33R. The valves 32L, 32R, 34L, and 34R are opened and closed by the rotation of the cam shafts 35L, 35R, 36L, and 36R disposed in the cam chambers 41L and 41R formed between the head covers 4L and 4R. To be done.

  Further, the cylinder heads 3L and 3R of the engine E according to the present embodiment have a divided structure. Specifically, the cylinder heads 3L and 3R are constituted by cylinder head bodies 37L and 37R attached to the upper surface of the cylinder block 1 and camshaft housings 38L and 38R assembled on the upper side of the cylinder head bodies 37L and 37R.

  On the other hand, intake manifolds 7L and 7R corresponding to the banks 2L and 2R are disposed on the inner side (between banks) of the banks 2L and 2R, and the downstream ends of the intake manifolds 7L and 7R correspond to the respective banks. It communicates with the intake ports 31L, 31R,. The intake manifolds 7L and 7R are connected to an intake pipe 73 having a surge tank 71 (see FIG. 2) common to each bank and a throttle valve 72, and an air cleaner 74 is provided upstream of the intake pipe 73. Is provided. Thereby, the air introduced into the intake pipe 73 from the air cleaner 74 is introduced into the intake manifolds 7L and 7R through the surge tank 71.

  The intake ports 31L and 31R of the cylinder heads 3L and 3R are respectively provided with injectors 75L and 75R. When fuel is injected from the injectors 75L and 75R, the air introduced into the intake manifolds 7L and 7R. Then, the fuel injected from the injectors 75L and 75R is mixed to form an air-fuel mixture, which is introduced into the combustion chambers 76L and 76R when the intake valves 32L and 32R are opened.

  Spark plugs 77L and 77R are disposed at the tops of the combustion chambers 76L and 76R. In the combustion chambers 76L and 76R, the combustion pressure of the air-fuel mixture accompanying the ignition of the spark plugs 77L and 77R is transmitted to the pistons 51L and 51R, causing the pistons 51L and 51R to reciprocate. The reciprocating motion of the pistons 51L and 51R is transmitted to the crankshaft C via the connecting rods 52L and 52R, converted into rotational motion, and taken out as the output of the engine E. The camshafts 35L, 35R, 36L, and 36R are driven to rotate by the power extracted from the crankshaft C being transmitted by the timing chain, and by this rotation, the valves 32L, 32R, 34L, and 34R are opened and closed. Let it be done.

  The air-fuel mixture after combustion becomes exhaust gas and is discharged to the exhaust manifolds 8L and 8R when the exhaust valves 34L and 34R are opened. Exhaust pipes 81L and 81R are connected to the exhaust manifolds 8L and 8R, respectively, and catalytic converters 82L and 82R incorporating a three-way catalyst or the like are attached to the exhaust pipes 81L and 81R. By passing the exhaust gas through the catalytic converters 82L and 82R, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxide components (NOx) contained in the exhaust gas are purified. . Further, the downstream ends of the exhaust pipes 81L and 81R are joined and connected to the muffler 83.

-Description of control block-
The operating state of the engine E is controlled by an engine ECU (Electronic Control Unit) 9. As shown in FIG. 3, the engine ECU 9 includes a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, a backup RAM 94, and the like.

  The ROM 92 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 91 executes arithmetic processing based on various control programs and maps stored in the ROM 92.

  The RAM 93 is a memory that temporarily stores calculation results in the CPU 91, data input from each sensor, and the backup RAM 94 is a non-volatile memory that stores data to be saved when the engine E is stopped. is there. The ROM 92, CPU 91, RAM 93, and backup RAM 94 are connected to each other via a bus 97, and are connected to an external input circuit 95 and an external output circuit 96.

The external input circuit 95 includes a water temperature sensor 101, an air flow meter 102, an intake air temperature sensor 103, an A / F sensor 104a, an O ₂ sensor 104b, a throttle position sensor 105, a crank angle sensor 106, a cam angle sensor 107, a knock sensor 108, An intake pressure sensor 109, an accelerator opening sensor 110, and the like are connected. On the other hand, the external output circuit 96 is connected to the injectors 75L and 75R, the igniter 111, a throttle motor 72a for driving the throttle valve 72, and the like.

  The water temperature sensor 101 detects the temperature of the cooling water flowing in the water jacket 11 formed in the cylinder block 1 and transmits the cooling water temperature signal to the engine ECU 9.

  The air flow meter 102 detects the intake air amount and transmits the intake air amount signal to the engine ECU 9.

  The intake air temperature sensor 103 is arranged on the downstream side of the air cleaner 74, detects the intake air temperature, and transmits the intake air temperature signal to the engine ECU 9.

  The A / F sensor 104a is disposed on the upstream side of each of the catalytic converters 82L and 82R. For example, a limiting current type oxygen concentration sensor is applied. The A / F sensor 104a generates an output voltage corresponding to the air-fuel ratio over a wide air-fuel ratio region, and transmits the voltage signal to the engine ECU 9.

The O ₂ sensor 104b is disposed on the downstream side of each of the catalytic converters 82L and 82R. For example, an electromotive force type (concentration cell type) oxygen concentration sensor is applied. The O ₂ sensor 104b determines whether or not the air-fuel ratio in the exhaust is at the stoichiometric air-fuel ratio, and transmits a determination signal to the engine ECU 9.

  The throttle position sensor 105 detects the opening of the throttle valve 72 and transmits a throttle opening detection signal to the engine ECU 9.

  The crank angle sensor 106 is disposed in the vicinity of the crankshaft C and detects the rotation angle (crank angle CA) and the rotation speed (engine rotation speed NE) of the crankshaft C. Specifically, the crank angle sensor 106 outputs a pulse signal every predetermined crank angle (for example, 30 °). As an example of a crank angle detection method by the crank angle sensor 106, external teeth are formed at intervals of 30 ° on the outer peripheral surface of a rotor (NE rotor) 106a that is integrally rotated with the crankshaft C, and the external teeth face each other. Then, the crank angle sensor 106 formed of an electromagnetic pickup is disposed. When the external teeth pass near the crank angle sensor 106 as the crankshaft C rotates, the crank angle sensor 106 generates an output pulse. In addition, as this NE rotor 106a, what the external tooth formed in an outer peripheral surface is formed every 10 degrees may be applied. In this case, frequency division is performed in the engine ECU 9 to generate output pulses every 30 ° CA.

  The cam angle sensor 107 is disposed in the vicinity of the intake camshafts 35L and 35R, and is used as a cylinder discrimination sensor by outputting a pulse signal corresponding to the compression top dead center (TDC) of the first cylinder, for example. Is done. That is, the cam angle sensor 107 outputs a pulse signal for each rotation of the intake camshafts 35L and 35R. As an example of a cam angle detection method by the cam angle sensor 107, external teeth are formed at one place on the outer peripheral surface of the rotor integrally formed with the intake camshafts 35L and 35R, and the external teeth are electromagnetically faced. The cam angle sensor 107 constituted by a pickup is arranged so that when the external teeth pass in the vicinity of the cam angle sensor 107 as the intake cam shafts 35L and 35R rotate, the cam angle sensor 107 generates an output pulse. It has become. Since the rotor rotates at half the rotational speed of the crankshaft C, an output pulse is generated every time the crankshaft C rotates 720 °. In other words, an output pulse is generated each time a specific cylinder reaches the same stroke (for example, when the first cylinder reaches compression top dead center).

  The knock sensor 108 is a vibration type sensor that is disposed in each of the banks 2L and 2R and detects vibrations of the engine transmitted to the cylinder block 1 by a piezoelectric element type (piezo element type) or an electromagnetic type (magnet, coil). Then, an output signal corresponding to the magnitude of vibration of the cylinder block 1 is transmitted to the engine ECU 9.

  The intake pressure sensor 109 is attached to the surge tank 71, detects the pressure in the intake pipe 73 (intake pipe pressure), and transmits the intake pressure signal to the engine ECU 9.

  The accelerator opening sensor 110 outputs a detection signal corresponding to the amount of depression of the accelerator pedal (accelerator opening), and recognizes the operation speed of the accelerator by recognizing the amount of change in the accelerator opening per unit time. It can be done.

  And engine ECU9 controls various parts of engine E including ignition timing control etc. by controlling each part, such as igniter 111, injectors 75L and 75R, and throttle motor 72a, based on the output signal of the above-mentioned various sensors 101-110. Execute.

  As an example, as a basic control of the ignition timing of the ignition plugs 77L and 77R by the igniters 111 and 111, the advance correction of the ignition timing is performed so that the ignition timing approaches MBT (Minimum Spark Advance for Best Torque). When knocking is detected by the knock sensors 108, 108, the control is performed such that the knocking is eliminated by correcting the retard of the ignition timing.

As fuel injection control for the injectors 75L and 75R, the target air-fuel ratio is calculated based on the engine load, the engine speed, etc., and the target air-fuel ratio is obtained based on the intake air amount detected by the air flow meter 102. Thus, control of the fuel injection amount (control of the valve opening time of the injectors 75L and 75R) is performed. At this time, the oxygen concentration in the exhaust gas is calculated based on the outputs of the A / F sensor 104a and the O ₂ sensor 104b, and the actual air-fuel ratio obtained from the calculated oxygen concentration is determined as the target air-fuel ratio (for example, the theoretical air-fuel ratio). The air-fuel ratio feedback control is performed such that the fuel injection amount by the injectors 75L and 75R is controlled so as to coincide with the (fuel ratio).

  Further, as the drive control of the throttle motor 72a, the opening degree of the throttle valve 72 which is the intake air amount for obtaining the requested engine output is obtained based on the opening degree of the accelerator pedal operated by the driver. In addition, the drive amount of the throttle motor 72a is controlled.

  The engine ECU 9 is also configured to execute reduced cylinder operation control, which will be described later. Hereinafter, this reduced-cylinder operation will be described.

-Reduced cylinder operation-
The V-type engine E according to the present embodiment has a reduced-cylinder operation in which the operation of the cylinder group (three cylinders in this embodiment) belonging to one of the left bank 2L and the right bank 2R (for example, the left bank 2L) is suspended. It is possible. In other words, when the engine E is idling, the load applied to each cylinder is small in a state where there is a surplus output, and intake / exhaust loss increases and there is a concern about deterioration in combustion efficiency. For this reason, when there is no load or light load, the fuel supply to the cylinders in one bank is cut off, and the reduced cylinder operation is performed to stop these cylinders, and the cylinders in which fuel is supplied (the cylinders in the other bank) The fuel consumption rate is improved by increasing the operation load and increasing the operation efficiency.

  Specific operations of this reduced-cylinder operation are based on the engine speed calculated based on the output signal from the crank angle sensor 106, the opening of the throttle valve 72 detected by the throttle position sensor 105, and the like. It is determined whether the engine E is in a no-load state or a light load state such as idling operation, and when the engine E is in a no-load state or a light load state, it is determined that the reduced-cylinder operation execution condition is satisfied. .

  In the present embodiment, the operation of the three cylinders of the left bank 2L is always stopped when the reduced cylinder operation is executed. Although the reason is not shown in the drawing, the evaporated fuel generated in the fuel tank is introduced into the intake manifold 7R of the right bank 2R, and since this evaporated fuel needs to be processed, the right bank 2R This is to continue operation of the three cylinders.

  Note that the reduced-cylinder operation is not limited to this, and at the time of transition to reduced-cylinder operation, the bank that was operating during the previous reduced-cylinder operation is used as the suspension bank, and the bank that was stopped during the previous reduced-cylinder operation is operated. You may make it drive | operate as a bank. That is, every time the reduced-cylinder operation is started, the bank to be paused is switched alternately, so that the cumulative operation time of each cylinder is made uniform, and the life of the engine E is extended.

  In the present embodiment, during the reduced-cylinder operation, the intake valve 32L and the exhaust valve 34L of the deactivated cylinder are opened and closed in the same manner as during all-cylinder operation. Thus, the engine E according to the present embodiment can be constructed without requiring a large design change from the conventional engine that does not execute the reduced-cylinder operation.

  During the reduced-cylinder operation, the intake valve 32L and the exhaust valve 34L of the deactivated cylinder may be fully closed. According to this, the pumping loss due to the reciprocating motion of the piston 51L in the idle cylinder can be reduced, and the efficiency of the engine E can be improved.

-Operation switching control-
Next, a control operation that characterizes the present embodiment for switching the operation between the all cylinder operation and the reduced cylinder operation will be described.

  Specifically, when the above-described reduced-cylinder operation execution condition is satisfied, the exhaust pipe (exhaust gas constituting the first exhaust passage) connected to the three cylinders of the left bank 2L, that is, the cylinder that is deactivated during the reduced-cylinder operation. Tube) When the temperature of the catalytic converter 82L provided in 81L is estimated and this temperature is lower than the predetermined preheating required temperature, the temperature of the catalytic converter 82L is increased prior to the execution of the reduced cylinder operation. Catalyst preheating operation is performed (perform catalyst preheating operation by the catalyst preheating operation execution means).

  In the following description, the catalytic converter 82L provided in the exhaust pipe 81L connected to the three cylinders of the left bank 2L that is inactive during the reduced cylinder operation is referred to as a first catalytic converter (first catalyst) 82L, and the reduced cylinder The catalytic converter 82R provided in the exhaust pipe (exhaust pipe constituting the second exhaust passage) 81R connected to the three cylinders of the right bank 2R that continues operation even during operation is replaced with the second catalytic converter (second catalyst). ) 82R.

  FIG. 4 is a flowchart showing the procedure of the operation switching control for switching the operation between the all cylinder operation and the reduced cylinder operation. The routine shown in FIG. 4 is executed every predetermined time or every predetermined angle rotation of the crankshaft C.

  First, in step ST1, it is determined whether the reduced cylinder operation execution condition is satisfied. As described above, the reduced-cylinder operation execution condition includes whether or not the engine E is in a no-load state or a light load state such as idling operation, and the temperature of the cooling water detected by the water temperature sensor 101 is a predetermined temperature. It is mentioned whether it is (for example, 50 degreeC) or more. In the present embodiment, the reduced cylinder operation execution condition determined in step ST1 does not include the temperature condition of the first catalytic converter 82L. That is, regardless of the temperature of the first catalytic converter 82L, if other reduced-cylinder operation execution conditions are satisfied, YES is determined in this step ST1.

  When the reduced cylinder operation execution condition is not satisfied, NO is determined in step ST1, and the process proceeds to step ST7 to continue the all cylinder operation. If NO is determined in step ST1 during execution of the reduced cylinder operation, the all cylinder operation is restored.

  On the other hand, if the reduced cylinder operation execution condition is satisfied, YES is determined in step ST1, and the process proceeds to step ST2. In this step ST2, it is determined whether or not the current operation state of the engine E is all-cylinder operation. That is, whether or not the reduced-cylinder operation execution condition has been satisfied from the state in which all-cylinder operation has been performed because the reduced-cylinder operation execution condition has not been satisfied until then, or the catalyst preheating operation described later It is determined whether or not it is in a state in which all cylinder operation is being performed since it has not yet been shifted to the reduced cylinder operation.

  If the engine E is operating in all cylinders and the determination in step ST2 is YES, the process proceeds to step ST3, and whether the temperature of the first catalytic converter 82L is lower than a predetermined preheating required temperature (A). Determine whether or not. That is, if the shift to the reduced cylinder operation is performed as it is, the temperature of the first catalytic converter 82L decreases to the vicinity of the lower limit of the activation temperature within an extremely short time, and it is necessary to switch to the all cylinder operation at an early stage. It is determined whether or not.

  The preheating necessary temperature (A) is set to a value that is higher by about 150 ° C. than the lower limit of the activation temperature of the first catalytic converter 82L (for example, 450 ° C.). These values are not limited to this.

  The temperature of the first catalytic converter 82L is estimated from the current engine operating state. Specifically, a catalyst temperature estimation map for estimating the temperature of the first catalytic converter 82L from the engine speed and the engine load (throttle valve opening etc.) is stored in the ROM 92. The temperature of the first catalytic converter 82L is estimated by fitting the current engine speed and engine load (catalyst temperature estimation operation by the catalyst temperature recognition means). Further, the temperature estimation operation of the first catalytic converter 82L may be estimated from the exhaust gas temperature. For example, exhaust gas temperature sensors are provided upstream and downstream of the first catalytic converter 82L, respectively, and the temperature of the first catalytic converter 82L is estimated based on the exhaust gas temperatures detected by these exhaust gas temperature sensors. Further, the temperature of the first catalytic converter 82L may be directly detected by using a means such as a thermistor (catalyst temperature detection operation by the catalyst temperature recognition means).

  When the temperature of the first catalytic converter 82L is equal to or higher than the preheating required temperature (when NO is determined in step ST3), the process proceeds to step ST6, and the first catalytic converter is shifted to the reduced cylinder operation as it is. The reduced-cylinder operation is executed on the assumption that a sufficient time can be secured until the temperature of 82L drops to near the lower limit of the activation temperature. That is, the fuel injection to each cylinder of the left bank 2L is stopped, and the operation of these cylinders is stopped.

  On the other hand, if the temperature of the first catalytic converter 82L is lower than the preheating required temperature and YES is determined in step ST3, the process proceeds to step ST4 to perform the catalyst preheating operation. Specifically, as the catalyst preheating operation, the ignition of the spark plugs 77L provided in these cylinders is continued while the operation of all cylinders is continued, that is, the fuel injection to each cylinder of the left bank 2L is continued. Delay the timing.

  More specifically, the retard amount of the ignition timing is gradually increased. For example, every 10 revolutions of the crankshaft C, the ignition timing is shifted to the retard side by 1 ° CA (1 ° in crank angle). This value is not limited to this, but is obtained in advance by experiments, simulations, or the like.

  As a result, the combustion start timing in the combustion stroke of these cylinders (cylinders that are deactivated when transitioning to reduced cylinder operation: cylinders to be deactivated) is retarded and the combustion becomes slow, and part of the mixture Will burn in the exhaust pipe 81L. For this reason, the temperature of the first catalytic converter 82L can be rapidly increased by greatly increasing the gas temperature in the exhaust system provided with the first catalytic converter 82L.

  Also, by gradually increasing the retard amount of the ignition timing, the amount of kinetic energy contributing to the torque generation of the engine E out of the energy generated by the combustion of the air-fuel mixture in these cylinders is gradually reduced. At the same time, the amount of thermal energy contributing to the preheating of the first catalytic converter 82L is gradually increased. That is, when the reduced-cylinder operation execution condition is satisfied and the catalyst preheating operation is started, at the initial stage, the retard amount of the ignition timing of the spark plug 77L is relatively small, and the energy generated by the combustion of the air-fuel mixture is large. The portion becomes kinetic energy that contributes to the torque generation of the engine E, and a portion thereof is used as thermal energy that contributes to preheating of the first catalytic converter 82L. Thereafter, as the retard amount of the ignition timing of the spark plug 77L gradually increases, the amount of kinetic energy that contributes to the torque generation of the engine E among the energy generated by the combustion of the air-fuel mixture gradually decreases. On the other hand, the amount of thermal energy contributing to the preliminary heating of the first catalytic converter 82L gradually increases. That is, in this catalyst preheating operation, the torque of the engine E is gradually reduced while gradually increasing the preheating capability of the first catalytic converter 82L.

  In this case, the lower limit value of the torque of the engine E (the lower limit value of the torque of the engine E during the catalyst preheating operation) that is changed so as to be gradually decreased is the time of transition from the all-cylinder operation described later to the reduced cylinder operation. The ignition timing maximum retard amount is defined so as to substantially match the torque of the engine E (the torque of the engine E when only three cylinders are operating in a no-load state or a light load state).

  While such a catalyst preheating operation is performed and the reduced-cylinder operation execution condition is satisfied, the operations of step ST1 to step ST4 are repeated. If the temperature of the first catalytic converter 82L becomes equal to or higher than the preheating required temperature while the reduced-cylinder operation execution condition is satisfied, NO is determined in step ST3, and the process proceeds to step ST6. In this step ST6, when the temperature of the first catalytic converter 82L has reached the preheating required temperature or more, the catalyst preheating operation is finished and the reduced cylinder operation is executed.

  At this time, as described above, since the torque of the engine E is gradually reduced during the catalyst preheating operation, the sudden torque fluctuation at the time of switching from the full cylinder operation to the reduced cylinder operation is eliminated. The vibration (shock) at the time of operation switching can be hardly generated. That is, the operation can be switched without making the vehicle occupant aware of the change from the all-cylinder operation to the reduced-cylinder operation, and drastic improvement in drivability can be achieved.

  As described above, in the state where the reduced-cylinder operation is started, when the reduced-cylinder operation execution condition is not satisfied due to an increase in the engine load or the like, NO is determined in step ST1, and the process proceeds to step ST7. To perform all-cylinder operation. That is, the reduced-cylinder operation is switched to the all-cylinder operation when the reduced-cylinder operation execution condition is not satisfied.

  Further, in the state where the reduced cylinder operation is being executed, a NO determination is made in step ST2, and the process proceeds to step ST5, in which whether or not the temperature of the first catalytic converter 82L is lower than a predetermined all-cylinder operation return temperature (B). Determine whether. That is, it is determined whether or not the temperature of the first catalytic converter 82L has decreased to near the activation temperature lower limit value.

  The all-cylinder operation return temperature (B) is set to a value about 50 ° C. higher than the activation temperature lower limit (for example, 450 ° C.) of the first catalytic converter 82L. These values are not limited to this.

  If the temperature of the first catalytic converter 82L is equal to or higher than the all-cylinder operation return temperature (NO in step ST5), the reduced-cylinder operation is continued as it is.

  On the other hand, if the temperature of the first catalytic converter 82L is lower than the all-cylinder operation return temperature and the determination in step ST5 is YES, the process goes to step ST7 in order to avoid deterioration of exhaust emission when all cylinders return to operation. Move to run all cylinders.

  As described above, in this embodiment, when the reduced-cylinder operation execution condition is satisfied during the execution of the all-cylinder operation, if the temperature of the first catalytic converter 82L is lower than the preheating required temperature, Instead of starting the reduced cylinder operation immediately after the reduced cylinder operation execution condition is satisfied, first, the catalyst preheating operation is executed to raise the temperature of the first catalytic converter 82L to the preheating required temperature or higher. Then, after the temperature of the first catalytic converter 82L has risen to the preheating required temperature or higher by executing this catalyst preheating operation, the reduced cylinder operation is started. For this reason, since the reduced-cylinder operation is started in a state where the temperature of the first catalytic converter 82L is relatively high, even if the temperature of the first catalytic converter 82L gradually decreases during the reduced-cylinder operation. Thus, it is possible to prolong the time during which the temperature decreases to a temperature that requires the return of all cylinder operation (the above-mentioned all cylinder operation return temperature). As a result, the duration of reduced-cylinder operation can be obtained longer, and the advantages of an engine system that can perform reduced-cylinder operation can be fully utilized, improving the fuel consumption rate and reducing fuel consumption. The effect can be sufficiently achieved.

  Further, in the present embodiment, the torque of the engine E is gradually reduced during the catalyst preheating operation, so that vibration at the time of switching the operation from the full cylinder operation to the reduced cylinder operation hardly occurs. It is also possible to realize a switching operation from unprecedented all-cylinder operation to reduced cylinder operation.

(Modification of catalyst preheating operation)
Next, a modified example of the catalyst preheating operation will be described. In the above-described embodiment, as the catalyst preheating operation, the ignition timing of the cylinder (non-operation scheduled cylinder) that is inoperative in the reduced cylinder operation is retarded. Instead, it is also within the scope of the technical idea of the present invention to perform a catalyst preheating operation as described below.

  First, the ignition of the spark plug 77L is not performed for a cylinder (cylinder scheduled to be deactivated) that is inactive in the reduced cylinder operation. That is, during the catalyst preheating operation, only the fuel is supplied to the cylinders scheduled to be stopped so that the ignition of the spark plug 77L is not executed.

  According to this, most of the air-fuel mixture in the cylinder to be deactivated is sent to the exhaust pipe 81L as unburned gas, and is combusted (oxidation reaction) by receiving heat energy in the first catalytic converter 82L. Also in this case, similarly to the catalyst preheating operation in the above-described embodiment, the temperature of the first catalytic converter 82L can be raised to the preheating required temperature or higher in a short time. Further, in this case, since almost the entire amount of fuel supplied during the catalyst preheating operation period can contribute to the temperature increase of the first catalytic converter 82L, the amount of fuel used for the catalyst preheating operation is required. Can be minimized.

  When performing the catalyst preheating operation in which the spark plug 77L is not ignited as described above, a certain amount of thermal energy needs to be present in the first catalytic converter 82L. The above operation is performed in a state in which the temperature of 82L is detected or estimated and it is confirmed that sufficient thermal energy exists to combust the air-fuel mixture in the first catalytic converter 82L. become. That is, the preheating required temperature (A) is set to a temperature at which the air-fuel mixture can be combusted inside the first catalytic converter 82L.

  Further, as another modification of the catalyst preheating operation, when the engine E is an in-cylinder direct injection gasoline engine, an injector 75L that supplies fuel to a cylinder (non-operation scheduled cylinder) that is inactive in the reduced-cylinder operation. It is also possible to control the fuel injection timing.

  That is, the fuel injection timing from the injector 75L is retarded. For example, when the fuel injection timing is retarded until approximately the same timing as the ignition timing of the spark plug 77L, the combustion start timing shifts to the retard side in the cylinder to be stopped. Further, when the fuel injection timing is retarded to the retard side with respect to the ignition timing of the spark plug 77L, combustion is not performed in the cylinder. In any of these cases, the air-fuel mixture burns in the exhaust pipe 81L or the first catalytic converter 82L, so that the temperature of the first catalytic converter 82L can be rapidly increased. The same effect can be achieved.

  Further, after the start of the catalyst preheating operation, the retard amount of the fuel injection timing may be gradually increased. For example, every 10 revolutions of the crankshaft C, the fuel injection timing is shifted to the retard side by 1 ° CA. This value is not limited to this, but is obtained in advance by experiments, simulations, or the like.

-Other embodiments-
In the embodiment described above, the case where the present invention is applied to the V-type engine E for automobiles has been described. The present invention is not limited to this, and can be applied to a horizontally opposed engine for automobiles, an in-line engine for automobiles, and the like. Moreover, it is applicable not only to a gasoline engine but also to a diesel engine. When applied to a diesel engine, this type of engine generally does not include a spark plug, and as described in the above-described modification, the catalyst preliminary is controlled by controlling the fuel injection timing from the injector to the retard side. A heating operation will be performed. In the present invention, the number of cylinders of the engine, the fuel injection method, and other specifications of the engine E are not particularly limited.

  In the above embodiment, as the catalyst preheating operation, the ignition timing of the cylinder to be stopped is gradually retarded. The present invention is not limited to this, and at the same time when the catalyst preheating operation is started, the ignition timing of the cylinder to be stopped is greatly shifted to the retard side, and the ignition timing is maintained (the temperature of the first catalytic converter 82L becomes the preheating required temperature). May be maintained until it reaches.

  The present invention can be applied to control when switching from full-cylinder operation to reduced-cylinder operation in an engine mounted on an automobile and capable of executing reduced-cylinder operation.

77L Spark plug
81L exhaust pipe (first exhaust passage)
81R Exhaust pipe (second exhaust passage)
82L first catalytic converter (first catalyst)
82R Second catalytic converter (second catalyst)
E engine (multi-cylinder internal combustion engine)

Claims (2)

A first catalyst provided in a first exhaust passage connected to some cylinders of the plurality of cylinders, and a second catalyst provided in a second exhaust passage connected to other cylinders; In the operation control device for a multi-cylinder internal combustion engine capable of executing reduced-cylinder operation for disabling some of the cylinders when the reduced-cylinder operation execution condition is satisfied,
Catalyst temperature recognition means for detecting or estimating the temperature of the first catalyst;
When the reduced-cylinder operation execution condition is satisfied, the temperature of the first catalyst detected or estimated by the catalyst temperature recognition means is set as a value higher than the lower limit value of the activation temperature of the first catalyst by a predetermined value. If it is less than has been preheated required temperature, the catalyst preheating for executing catalyst preliminary heating operation for increasing the temperature of the first catalyst than the preheating temperature required prior to the execution of the reduced-cylinder operation Operation execution means ,
The catalyst preheating operation retards the ignition timing of the spark plugs of the some cylinders that are inactive during the reduced cylinder operation prior to the execution of the reduced cylinder operation. By gradually increasing the retard amount, the amount of kinetic energy that contributes to the torque generation of the internal combustion engine among the energy generated by the combustion of the air-fuel mixture is gradually reduced and contributes to catalyst preheating. Gradually increasing the amount of thermal energy,
If the temperature of the first catalyst rises above the preheating required temperature by the catalyst preheating operation while the reduced cylinder operation execution condition is satisfied, the catalyst preheating operation is terminated and the cylinder reducing operation is completed. operation control device for a multi-cylinder internal combustion engine, characterized in that has a configuration but is initiated. In the multi-cylinder internal combustion engine operation control device according to claim 1,
When the temperature of the first catalyst falls to a predetermined all-cylinder operation return temperature during the reduced-cylinder operation, the reduced-cylinder operation is switched to the all-cylinder operation.
The all-cylinder operation return temperature is set to a temperature that is higher than the lower limit of the activation temperature of the first catalyst and lower than the preheating required temperature. Operation control device.

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