JP2010216285A - Control device for multi-cylinder internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit deterioration of exhaust emission control catalysts in a multi-cylinder internal combustion engine performing reduced-number-of-cylinder operation. <P>SOLUTION: Exhaust manifolds 36a, 36b communicate with an A bank and a B bank forming the multi-cylinder internal combustion engine, respectively. The exhaust emission control catalysts 34a, 34b are arranged in the exhaust manifolds 36a, 36b, respectively. In the internal combustion engine, the reduced-number-of-cylinder operation in which fuel injection to a cylinder group forming the A bank is stopped and an operating state of the same is put in a resting state and all-cylinder operation in which fuel is injected to all cylinders is selectively performed based on an engine operating state. When the catalyst temperature Tcat of the exhaust emission control catalysts 34a is equal to or higher than a first predetermined temperature α, the all-cylinder operation is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is applied to an internal combustion engine having a plurality of cylinder groups connected to different exhaust purification catalysts, and stops fuel injection to one of the plurality of cylinder groups when an execution condition is satisfied. The present invention relates to a control device for a multi-cylinder internal combustion engine that performs a reduced-cylinder operation in which a cylinder operation is in a pause state.

An internal combustion engine having a V-type cylinder arrangement has two banks and a separate exhaust purification catalyst is provided for each bank.
In an internal combustion engine having such a V-type cylinder arrangement, when the output of the internal combustion engine is not required, such as during idle operation or deceleration, the fuel injection to the cylinder group forming one bank is stopped and the operation is performed. The fuel consumption amount and the exhaust gas amount are reduced by executing a reduced-cylinder operation (one-bank operation) that pauses (see, for example, Patent Document 1).

JP 2006-322371 A

  By the way, when such a reduced-cylinder operation is executed, air containing a large amount of oxygen flows into the exhaust purification catalyst connected to the cylinder group of the bank. When air containing a large amount of oxygen flows into the exhaust purification catalyst in this manner, the oxygen burns in the exhaust purification catalyst, and the exhaust purification catalyst may rise in temperature excessively, thereby promoting deterioration. In particular, when the reduced-cylinder operation is performed after the high-load operation, the exhaust purification catalyst is in a high temperature state, so that the deterioration of the exhaust purification catalyst is further facilitated.

  This situation is not limited to the case where the reduced cylinder operation is performed in the internal combustion engine having the V-type cylinder arrangement described above, but the internal combustion engine having a plurality of cylinder groups connected to different exhaust purification catalysts. This is generally common even when a reduced-cylinder operation is executed in which the operation of a specific cylinder group is suspended.

  The present invention has been made in view of the above-described circumstances, and suppresses deterioration of the exhaust purification catalyst in a multi-cylinder internal combustion engine in which separate exhaust purification catalysts are arranged in a plurality of cylinder groups to perform reduced-cylinder operation. The purpose is to do.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is applied to an internal combustion engine having a plurality of cylinder groups connected to different exhaust purification catalysts, and stops fuel injection to one of the cylinder groups to perform cylinder operation. In a control device for a multi-cylinder internal combustion engine that selectively executes a reduced-cylinder operation in a resting state and an all-cylinder operation in which fuel is injected into all cylinders based on the engine operating state, the catalyst temperature of the exhaust purification catalyst is estimated The gist of the present invention is to have a catalyst temperature estimation means, and execute the all-cylinder operation when the catalyst temperature estimated by the catalyst temperature estimation means is equal to or higher than the first predetermined temperature.

  According to this configuration, the all-cylinder operation is performed when the catalyst temperature becomes equal to or higher than the first predetermined temperature and the exhaust purification catalyst may rise in temperature due to the supply of oxygen and the deterioration thereof may be promoted. That is, the selection of the reduced-cylinder operation is prohibited in the cylinder connected to the exhaust purification catalyst. As a result, it is possible to suppress the introduction of oxygen through the cylinder that has become inactive to the exhaust purification catalyst that has reached the first predetermined temperature or more, and to suppress deterioration thereof.

  According to a second aspect of the present invention, in the control device for a multi-cylinder internal combustion engine according to the first aspect, the catalyst temperature of the exhaust purification catalyst estimated by the catalyst temperature estimating means is lower than the first temperature. The gist is to execute the all-cylinder operation when the temperature is lower than a preset second predetermined temperature.

  As described above, when exhaust gas containing a large amount of oxygen is introduced into the exhaust purification catalyst when the temperature of the exhaust purification catalyst is high to some extent, this oxygen is burned by the catalytic function of the exhaust purification catalyst, The temperature of the exhaust purification catalyst increases. On the other hand, if the reduced-cylinder operation is executed when the temperature of the exhaust purification catalyst is low, such as before the warm-up is completed, the temperature of the exhaust purification catalyst also decreases as the exhaust temperature decreases. When the temperature of the exhaust purification catalyst decreases in this way, the catalyst function decreases, so that the exhaust properties may deteriorate when the all-cylinder operation is resumed. In this respect, according to the same configuration, the all-cylinder operation is performed in a state where the purification function of the exhaust purification catalyst is low, that is, the execution of the reduced-cylinder operation is prohibited. Deterioration of exhaust properties can be suppressed.

  According to a third aspect of the present invention, in the control device for a multi-cylinder internal combustion engine according to the first or second aspect, the multi-cylinder internal combustion engine has a V-type cylinder arrangement. The gist is that the exhaust purification catalyst and the fuel injection system are separately provided in the bank, and the fuel injection to each cylinder belonging to one of the banks is stopped when the reduced cylinder operation is executed.

  The above-described configuration can be applied to a multi-cylinder internal combustion engine having a V-type cylinder arrangement as in the third aspect of the invention, and by stopping fuel injection to the cylinders belonging to one of the banks. Reduced cylinder operation can be performed.

The schematic diagram which shows schematic structure of the multicylinder internal combustion engine to which the control apparatus concerning this Embodiment is applied. The schematic diagram which shows schematic structure of the intake system of the multicylinder internal combustion engine to which the control apparatus concerning this Embodiment is applied, and an exhaust system. The flowchart which shows the execution process procedure of the reduced cylinder driving | running concerning this Embodiment. The timing chart which shows the time transition of the exhaust purification catalyst temperature concerning this Embodiment, and the operating state of A bank.

  Hereinafter, an embodiment embodying a control device for a multi-cylinder internal combustion engine according to the present invention will be described with reference to FIGS. First, a schematic configuration of a multi-cylinder internal combustion engine and its control device according to the present embodiment will be described with reference to FIGS.

  As shown in FIG. 2, the multi-cylinder internal combustion engine according to the present embodiment is a V-type 8-cylinder internal combustion engine having two banks (A bank and B bank) and each bank having four cylinders. is there. Since the basic structure of each bank of the internal combustion engine is the same, only the basic structure of the A bank will be described below, and the description of the basic structure of the B bank will be omitted. Further, in the following description, the same components in each bank are given the same numbers as the reference numerals, and in order to distinguish them, “a” is added to the end of the components in the A bank, “B” is added to the end of B bank components. In addition, only the number is attached | subjected as a code | symbol about the component which does not need to distinguish for every bank.

  FIG. 1 shows a schematic configuration of the cylinder 11a of the A bank. As shown in FIG. 1, combustion chambers 16a are formed in each cylinder 11a (shown in FIG. 1) of the A bank, and the combustion chambers 16a, the intake branch passage 32a, and the exhaust branch are formed. An intake valve 18a and an exhaust valve 19a are provided to communicate and block the passage 33a. Each cylinder 11a is provided with an in-cylinder injection valve 15a that directly injects fuel toward the inside of the combustion chamber 16a, specifically, near the top surface of the piston 12a, and exists in the combustion chamber 16a. Spark plugs 14a for igniting the air-fuel mixture are provided.

  In each combustion chamber 16a, an ignition plug 14a ignites the air-fuel mixture composed of intake air and injected fuel. By this ignition operation, the air-fuel mixture burns, the piston 12a reciprocates, and the crankshaft 13a rotates. Then, the air-fuel mixture after combustion is sent out from each combustion chamber 16a to the exhaust branch passage 33a as exhaust. The driving modes of the in-cylinder injection valve 15a, the spark plug 14a, and the throttle valve 37 are all controlled by the electronic control unit 60. The electronic control unit 60 determines the driving mode of the in-cylinder injection valve 15a and the like based on the detection values of various sensors such as the engine rotation speed sensor 71 and the accelerator sensor 72.

  Next, the structure of each bank will be described with reference to FIG. 2 showing a schematic configuration of an intake system and an exhaust system of the multi-cylinder internal combustion engine according to the present embodiment. As shown in FIG. 2, the intake passage 31 is branched into two passages on the downstream side in the intake flow direction of the throttle valve 37 (hereinafter simply referred to as the downstream side), one of which (the intake collecting passage 35a) is The other bank (intake air collecting passage 35b) is connected to the B bank. The intake air collecting passage 35a is further branched into four intake branch passages 32a. These intake branch passages 32a are connected to the respective cylinders 11a. The intake air introduced into the internal combustion engine according to the present embodiment is metered by the throttle valve 37 and then introduced into each cylinder 11a through the intake manifold passage 35a and each intake branch passage 32a.

  Further, the exhaust branch passages 33a communicating with the respective cylinders 11a are gathered at the downstream portion to form an exhaust gather passage 36a. The exhaust collecting passage 36a merges with the exhaust collecting passage 36b corresponding to the B bank at the downstream portion thereof. Exhaust purification catalysts 34a and 34b are provided for each bank corresponding to the exhaust collecting passages 36a and 36b.

  The exhaust discharged from each cylinder 11a is purified through an exhaust purification catalyst 34a provided in the exhaust collecting passage 36a and then discharged to the outside. The exhaust purification catalyst 34a oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust and nitrogen oxides (NOx) in the exhaust in a state where combustion near the stoichiometric air-fuel ratio is performed. ) To purify the exhaust gas. A catalyst temperature sensor 70 a that detects the temperature and outputs the detected value to the electronic control unit 60 is attached to the exhaust purification catalyst 34 a. Similarly, a catalyst temperature sensor 70b is attached to the exhaust purification catalyst 34b of the B bank.

  The electronic control unit 60 stops the fuel injection to each cylinder 11a of the A bank and stops the operation of each cylinder 11a of the A bank based on the detection values of various sensors such as the engine speed sensor 71 and the accelerator sensor 72. A cylinder operation (one bank operation) and an all cylinder operation in which fuel is injected into all cylinders are selectively executed. Specifically, the electronic control unit 60 selects the reduced-cylinder operation when the engine required output is small, such as during engine low / medium load operation, while reducing the cylinder operation when the engine required output is large, such as during engine high load. Is prohibited and all-cylinder operation is selected. In each cylinder 11a of the A bank that has transitioned to the inactive state, the intake air introduced into the combustion chamber 16a when the intake valve 18a is opened is not used for combustion, and the piston 12a reciprocates and the exhaust valve 19a As the valve is opened, it is discharged to the exhaust branch passage 33a. In addition, in each cylinder 11a of the A bank that has shifted to the rest state in this way, both ignition by the spark plug 14a and fuel injection by the in-cylinder injection valve 15a are stopped.

  By the way, when each cylinder 11a in the A bank shifts to a resting state with the execution of the reduced cylinder operation, air containing oxygen flows into the exhaust purification catalyst 34a. When oxygen is supplied to the exhaust purification catalyst 34a in this way, oxygen is combusted in the exhaust purification catalyst 34a, and the catalyst temperature Tcat rises excessively, and its deterioration may be promoted. In particular, after the high load operation, the catalyst temperature Tcat is in a high state, and thus the deterioration of the exhaust purification catalyst 34a is further facilitated. Therefore, in the present embodiment, when the catalyst temperature Tcat of the exhaust purification catalyst 34a is equal to or higher than the temperature (first predetermined temperature α) at which the deterioration is promoted in the presence of oxygen, the engine operating state Regardless of this, selection of reduced cylinder operation is prohibited.

  On the other hand, if the reduced-cylinder operation is executed when the catalyst temperature Tcat of the exhaust purification catalyst 34a is lower than the temperature at which the function can be performed (second catalyst temperature β), such as before the warm-up operation, the exhaust temperature As the temperature decreases, the catalyst temperature Tcat of the exhaust purification catalyst 34a also decreases. Thus, when the temperature of the exhaust purification catalyst 34a is lowered, the catalytic function is lowered, so that the exhaust property may be deteriorated when the all-cylinder operation is resumed. Therefore, in the present embodiment, when the catalyst temperature Tcat of the exhaust purification catalyst 34a is lower than the second catalyst temperature β, such as before the warm-up operation, the engine operation state is set for the purpose of early warming up of the exhaust purification catalyst 34a. Regardless, all-cylinder operation is performed. When the catalyst temperature Tcat of the exhaust purification catalyst 34a becomes higher than the second predetermined temperature β, either the reduced cylinder operation or the all cylinder operation is selected based on the engine operation state. The first predetermined temperature α and the second predetermined temperature β are both values determined in advance by experiments or the like, and the first predetermined temperature α is set to a value lower than the second predetermined temperature β. Yes.

  Hereinafter, the execution processing procedure of such reduced-cylinder operation will be described with reference to FIG. The series of processes shown in this flowchart is performed by the electronic control device 60 at regular intervals.

  First, in this series of processes, the catalyst temperature Tcat of the exhaust purification catalyst 34a is read by the catalyst temperature sensor 70a (step S100). Next, it is determined whether or not an execution condition for reduced-cylinder operation is satisfied based on the engine operation state (step S101). That is, when the engine operating state is in the low / medium load state, it is determined that the condition for executing the reduced cylinder operation is satisfied. On the other hand, when the engine operating state is in a high load state, it is determined that the condition for executing the reduced cylinder operation is not satisfied.

  If it is determined based on the engine operation state that the execution condition for reduced cylinder operation is not satisfied (step S101: NO), all cylinder operation is executed (step S102). That is, the selection of the reduced cylinder operation is prohibited, and this process is temporarily ended.

  On the other hand, when it is determined that the condition for executing the reduced cylinder operation is satisfied based on the engine operating state (step S101: YES), the catalyst temperature Tcat of the exhaust purification catalyst 34a is equal to or higher than the second predetermined temperature β. And whether the temperature is lower than the first predetermined temperature α is determined (step S103).

  When it is determined that the catalyst temperature Tcat of the exhaust purification catalyst 34a is equal to or higher than the second predetermined temperature β and lower than the first predetermined temperature α (step S103: YES), the reduced-cylinder operation is selected. That is, the cylinders 11a in the A bank are shifted to the inactive state, while the cylinders 11b in the B bank are maintained in the operating state (step S104). After the reduced-cylinder operation is selected in this way, this process is temporarily terminated.

  On the other hand, when it is determined that the catalyst temperature Tcat of the exhaust purification catalyst 34a is lower than the second predetermined temperature β or higher than the first predetermined temperature α (step S103: NO), the all-cylinder operation is executed. (Step S102), this process is temporarily terminated.

  FIG. 4 shows (a) whether or not execution conditions for reduced-cylinder operation based on the engine operating state are satisfied when the reduced-cylinder operation shown in the flowchart of FIG. 3 is executed, (b) transition of the catalyst temperature Tcat of the exhaust purification catalyst 34a, (C) An example of transition of the operating state of A bank is shown.

  As shown in FIG. 4, when the engine operation is started, the catalyst temperature Tcat of the exhaust purification catalyst 34a increases. When the condition for executing the reduced cylinder operation is satisfied based on the engine operating state, it is determined whether or not the execution condition for the reduced cylinder operation is satisfied based on the catalyst temperature Tcat of the exhaust purification catalyst 34a (timing t1). Here, since the catalyst temperature Tcat of the exhaust purification catalyst 34a is lower than the second predetermined temperature β, the selection of the reduced cylinder operation is prohibited, and the all cylinder operation is executed. For this reason, each cylinder 11a of A bank is maintained in an operating state. Then, when the catalyst temperature Tcat of the exhaust purification catalyst 34a rises with the engine operation and becomes equal to or higher than the second predetermined temperature β, the reduced-cylinder operation is selected (timing t2). At this time, each cylinder 11a in the A bank shifts to a deactivated state, and each cylinder 11b in the B bank is maintained in an operating state. As the engine operates, the catalyst temperature Tcat of the exhaust purification catalyst 34a further increases (timing t2 to t3). When the catalyst temperature Tcat of the exhaust purification catalyst 34a becomes equal to or higher than the first predetermined temperature α, the reduced-cylinder operation is interrupted and the all-cylinder operation is executed. For this reason, each cylinder 11a of A bank shifts to an operating state (timing t3). When the catalyst temperature Tcat of the exhaust purification catalyst 34a decreases and becomes lower than the first predetermined temperature α as a result of such all-cylinder operation, the reduced-cylinder operation is selected again, and the cylinders 11a in the A bank are in a resting state. Transition (timing t4). When the engine operating state shifts from a high load to a low load and the execution condition of the reduced cylinder operation based on the engine operating state is not satisfied, the all cylinder operation is selected regardless of the catalyst temperature Tcat of the exhaust purification catalyst 34a. Then, each cylinder 11a of the A bank shifts to an operating state (timing t5).

According to this embodiment described above, the following effects can be obtained.
(1) When the catalyst temperature Tcat of the exhaust purification catalyst 34a is equal to or higher than the first predetermined temperature α and there is a risk that deterioration will be accelerated by the supply of oxygen, the reduced-cylinder operation is prohibited and the all-cylinder operation is executed. Is done. Thereby, it is possible to suppress the introduction of oxygen through the cylinders 11a in the deactivated state with respect to the exhaust purification catalyst 34a that has become the first predetermined temperature α or higher, and to suppress the deterioration thereof. become.

  (2) When the reduced-cylinder operation is executed when the catalyst temperature Tcat of the exhaust purification catalyst 34a is low, such as before the warm-up is completed, the temperature of the exhaust purification catalyst 34a is also lowered with a decrease in the exhaust temperature. Become. Thus, when the temperature of the exhaust purification catalyst 34a is lowered, the catalytic function is lowered, so that the exhaust property may be deteriorated when the all-cylinder operation is resumed. In this regard, according to the same configuration, the execution of the reduced-cylinder operation in a state where the purification function of the exhaust purification catalyst 34a is low is prohibited, so that the exhaust property due to the decrease in the catalyst temperature Tcat of the exhaust purification catalyst 34a. Deterioration can be suppressed.

In addition, embodiment described above can be implemented in the aspect which changed the form suitably as follows.
In addition, when the catalyst temperature Tcat of the exhaust purification catalyst 34a is lower than the second predetermined temperature β and when it is equal to or higher than the first predetermined temperature α, the reduced-cylinder operation is prohibited. The reduced-cylinder operation may be prohibited only when α is equal to or higher than the first predetermined temperature. Even in this embodiment, the effects described in (1) above can be achieved.

  In the above embodiment, the operation of each cylinder 11a in the A bank is suspended during the reduced cylinder operation. However, the bank to be deactivated in this way may be changed periodically between the A bank and the B bank.

  In the above embodiment, the catalyst temperature Tcat of the exhaust purification catalyst 34a is detected by the catalyst temperature sensor 70a. However, the present embodiment is not limited to this, and is estimated based on the engine operating state. May be. Even in such an embodiment, the operational effects according to the above embodiment can be achieved.

  In the above-described embodiment, the V-type 8-cylinder internal combustion engine in which each bank has four cylinders has been described. However, the present embodiment is not limited to this. The present invention may be applied to an internal combustion engine having a plurality of cylinder groups connected to different exhaust purification catalysts so long as a reduced-cylinder operation for stopping the operation of a specific cylinder group is executed. That is, as described above, the catalyst temperature Tcat of the exhaust purification catalyst connected to the cylinder that has transitioned to the inactive state is detected, and it is determined whether or not the conditions for executing the reduced cylinder operation are satisfied according to the catalyst temperature Tcat. Whether or not the execution condition for the reduced cylinder operation is satisfied can be determined. Also in the present embodiment, the operational effects according to the above (1) and (2) can be achieved.

  11a ... cylinder, 11b ... cylinder, 12a ... piston, 13a ... crankshaft, 14a ... spark plug, 15a ... cylinder injection valve, 16a ... combustion chamber, 18a ... intake valve, 19a ... exhaust valve, 31 ... intake passage, 32a ... intake branch passage, 33a ... exhaust branch passage, 34a ... exhaust purification catalyst, 34b ... exhaust purification catalyst, 35a ... intake collecting passage, 35b ... intake collecting passage, 36a ... exhaust collecting passage, 36b ... exhaust collecting passage, 37 ... throttle Valve: 60 ... Electronic control device, 70a ... Catalyst temperature sensor, 70b ... Catalyst temperature sensor, 71 ... Engine rotational speed sensor, 72 ... Accelerator sensor.

Claims (3)

This is applied to an internal combustion engine having a plurality of cylinder groups connected to different exhaust purification catalysts, and a reduced-cylinder operation in which the cylinder operation is stopped by stopping fuel injection for one of the cylinder groups and all In a control device for a multi-cylinder internal combustion engine that selectively executes all-cylinder operation for injecting fuel into cylinders based on the engine operation state,
A catalyst temperature estimating means for estimating a catalyst temperature of the exhaust purification catalyst, and when the catalyst temperature estimated by the catalyst temperature estimating means is equal to or higher than a first predetermined temperature, all-cylinder operation is executed. A control device for a multi-cylinder internal combustion engine. The control apparatus for a multi-cylinder internal combustion engine according to claim 1,
All-cylinder operation is performed when the catalyst temperature of the exhaust purification catalyst estimated by the catalyst temperature estimation means is lower than a second predetermined temperature that is preset to a temperature lower than the first temperature. A control device for a multi-cylinder internal combustion engine. The control apparatus for a multi-cylinder internal combustion engine according to claim 1 or 2,
The multi-cylinder internal combustion engine has a V-type cylinder arrangement, and the exhaust purification catalyst and the fuel injection system are separately provided in each bank of the internal combustion engine. A control apparatus for a multi-cylinder internal combustion engine, characterized in that fuel injection to each cylinder belonging to is stopped.

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