Control apparatus and method for internal combustion engine

Abstract

A control apparatus for an internal combustion engine that includes right and left banks, first and second catalysts provided in the right and left exhaust pipes, respectively, and a downstream catalyst provided in a common exhaust pipe downstream of the upstream catalysts is adapted to alternately switch execution of catalyst degradation minimization and execution of fuel cut between the two banks if at least one of the temperature of the first catalyst and temperature of the second catalyst is higher than a predetermined value during deceleration of the internal combustion engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a view showing the configuration of a system according to the first exemplary embodiment of the invention;

FIG. 2 is a flowchart showing a control routine executed in the first exemplary embodiment of the invention;

FIG. 3A to FIG. 3E are time charts illustrating the method for counting the total fuel-cut time and the timing for switching the bank in which execution of fuel-cut is prohibited;

FIG. 4A to FIG. 4J are charts illustrating the states of the upstream and downstream catalysts when fuel-cut is being executed in the right bank and the catalyst degradation minimization control is being executed in the left bank while the condition for executing fuel cut is in effect;

FIG. 5 is a flowchart showing a control routine executed in the second exemplary embodiment of the invention;

FIG. 6A to FIG. 6C are diagrams illustrating the concept of the catalyst stress calculated in step 200 in the control routine shown in FIG. 5;

FIG. 7 is a flowchart showing a control routine executed in the third exemplary embodiment of the invention;

FIG. 8 is a diagram illustrating the relation between the degree of catalyst degradation and the maximum adsorbed oxygen amount Cmax;

FIG. 9 is a diagram illustrating the relation between the value of the threshold T_C and the vehicle running time; and

FIG. 10 is a flowchart showing a control routine executed in the fourth exemplary embodiment of the invention.

Claims

1. A control apparatus for an internal combustion engine including: a first cylinder group; a second cylinder group; a first exhaust passage provided for the first cylinder group; a second exhaust passage provided for the second cylinder group; a first upstream catalyst provided in the first exhaust passage; a second upstream catalyst provided in the second exhaust passage; and a downstream catalyst provided in a third exhaust passage provided downstream of a confluence of the first exhaust passage and the second exhaust passage, the confluence being located downstream of the first upstream catalyst and the second upstream catalyst, the control apparatus comprising: a fuel supply suspending portion that suspends supply of fuel to at least one of the first cylinder group and the second cylinder group under a predetermined state of the internal combustion engine;a fuel supply suspension prohibiting portion that prohibits execution of the fuel supply suspension control by the fuel supply suspending portion when at least one of a temperature of the first upstream catalyst and a temperature of the second upstream catalyst is higher than a predetermined value; anda fuel supply suspension prohibition switching portion that alternately switches the cylinder group in which the fuel supply suspension prohibiting control is executed by the fuel supply suspension prohibiting portion between the first cylinder group and the second cylinder group.

2. The control apparatus according to claim 1, wherein: the internal combustion engine is a V-type multi-cylinder engine;the first cylinder group is in a first bank of the V-type multi-cylinder engine; andthe second cylinder group is in a second bank of the V-type multi-cylinder engine.

3. The control apparatus according to claim 1, further comprising: an air-fuel ratio controlling portion that controls an air-fuel ratio in the cylinder group in which the fuel supply suspension prohibiting control is executed by the fuel supply suspension prohibiting portion to a stoichiometric air-fuel ratio.

4. The control apparatus according to claim 1, further comprising: a fuel supply suspension time calculating portion that calculates a total time of the fuel supply suspending control by the fuel supply suspending portion, wherein the fuel supply suspension prohibition switching portion switches the cylinder group in which the fuel supply suspending control is executed from one of the first cylinder group and the second cylinder group to the other if the total time calculated by the fuel supply suspension time calculating portion is longer than a predetermined value.

5. The control apparatus according to claim 1, further comprising: a first oxygen concentration obtaining portion that obtains an oxygen concentration in the first upstream catalyst;a second oxygen concentration obtaining portion that obtains an oxygen concentration in the second upstream catalyst; anda running time obtaining portion that obtains a running time, wherein the fuel supply suspension prohibition switching portion switches the cylinder group for the fuel supply suspension based on a reference value reflecting at least one of a catalyst temperature in the cylinder group in which the fuel supply suspending control is being executed, an oxygen concentration in the same cylinder group, and a running time.

6. The control apparatus according to claim 1, further comprising: a first catalyst degradation degree estimating portion that estimates the degree of degradation of the first upstream catalyst;a second catalyst degradation degree estimating portion that estimates the degree of degradation of the second upstream catalyst; anda degradation degree comparing portion that compares the degree of degradation of the first upstream catalyst and the degree of degradation of the second upstream catalyst, wherein the fuel supply suspension prohibiting portion executes the fuel supply suspension prohibiting control in the cylinder group with the catalyst that the degradation degree comparing portion determines to have degraded to a higher degree.

7. The control apparatus according to claim 1, further comprising: an EGR control portion that controls the amount of re-circulated exhaust gas, wherein the EGR control portion makes the amount of re-circulated exhaust gas for the cylinder group in which the fuel supply suspension prohibiting control is executed larger than the amount of re-circulated exhaust gas for the other cylinder group.

8. The control apparatus according to claim 1, wherein the fuel supply suspending portion suspends supply of fuel to at least one of the first cylinder group and the second cylinder group during deceleration of the internal combustion engine.

9. The control apparatus according to claim 1, wherein the fuel supply suspension prohibiting portion estimates the temperature of the first upstream catalyst based on at least one of the amount of intake air supplied to the first cylinder group and the engine speed in the first cylinder group, and estimates the temperature of the second upstream catalyst based on at least one of the amount of intake air supplied to the second cylinder group and the engine speed in the second cylinder group.

10. The control apparatus according to claim 6, further comprising: a first oxygen concentration obtaining portion that obtains an oxygen concentration in the first upstream catalyst;a second oxygen concentration obtaining portion that obtains an oxygen concentration in the second upstream catalyst; anda degradation degree comparing portion that compares the degree of degradation of the first upstream catalyst and the degree of degradation of the second upstream catalyst, wherein:the first catalyst degradation degree estimating portion calculates a maximum adsorbed oxygen amount of the first upstream catalyst based on a target air-fuel ratio for the first cylinder group and the oxygen concentration in the first upstream catalyst that is obtained by the first oxygen concentration obtaining portion, and estimates the degree of degradation of the first upstream catalyst based on the maximum adsorbed oxygen amount of the first upstream catalyst; andthe second catalyst degradation degree estimating portion calculates a maximum adsorbed oxygen amount of the second upstream catalyst based on a target air-fuel ratio for the second cylinder group and the oxygen concentration in the second upstream catalyst that is obtained by the second oxygen concentration obtaining portion, and estimates the degree of degradation of the second upstream catalyst based on the maximum adsorbed oxygen amount of the second upstream catalyst.

11. The control apparatus according to claim 10, wherein: the first catalyst degradation degree estimating portion makes the degree of degradation of the first upstream catalyst higher as the maximum adsorbed oxygen amount of the first upstream catalyst is smaller; andthe second catalyst degradation degree estimating portion makes the degree of degradation of the second upstream catalyst higher as the maximum adsorbed oxygen amount of the second upstream catalyst is smaller.

12. A control method for an internal combustion engine including: a first cylinder group; a second cylinder group; a first exhaust passage provided for the first cylinder group; a second exhaust passage provided for the second cylinder group; a first upstream catalyst provided in the first exhaust passage; a second upstream catalyst provided in the second exhaust passage; and a downstream catalyst provided in a third exhaust passage provided downstream of a confluence of the first exhaust passage and the second exhaust passage, the confluence being located downstream of the first upstream catalyst and the second upstream catalyst, the control method comprising: suspending supply of fuel to at least one of the first cylinder group and the second cylinder group under a predetermined state of the internal combustion engine;prohibiting execution of the fuel supply suspension control when at least one of a temperature of the first upstream catalyst and a temperature of the second upstream catalyst is higher than a predetermined value; andalternately switching the cylinder group in which the fuel supply suspension prohibiting control is executed between the first cylinder group and the second cylinder group.

13. A control apparatus for an internal combustion engine including: a first cylinder group; a second cylinder group; a first exhaust passage provided for the first cylinder group; a second exhaust passage provided for the second cylinder group; a first upstream catalyst provided in the first exhaust passage; a second upstream catalyst provided in the second exhaust passage; and a downstream catalyst provided in a third exhaust passage provided downstream of a confluence of the first exhaust passage and the second exhaust passage, the confluence being located downstream of the first upstream catalyst and the second upstream catalyst, the control apparatus comprising:fuel supply suspending means for suspending supply of fuel to at least one of the first cylinder group and the second cylinder group under a predetermined state of the internal combustion engine;fuel supply suspension prohibiting means for prohibiting execution of the fuel supply suspension control by the fuel supply suspending means when at least one of a temperature of the first upstream catalyst and a temperature of the second upstream catalyst is higher than a predetermined value; andfuel supply suspension prohibition switching means for alternately switching the cylinder group in which the fuel supply suspension prohibiting control is executed by the fuel supply suspension prohibiting means between the first cylinder group and the second cylinder group.