JP2017203424A - Control unit of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of oxygen occluded by a three-way catalyst in an execution period of a fuel cut process.SOLUTION: A control unit is applied to an internal combustion engine including a nitrogen enrichment device arranged in an intake passage, and a three-way catalyst arranged in an exhaust passage. The control unit carries out a nitrogen enrichment process which is a process of controlling the nitrogen enrichment device so that, in a period from a start to an end of a fuel cut process, a nitrogen ratio of intake air is made higher, thereby reducing an oxygen amount occluded by the three-way catalyst in the fuel cut period.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device applied to an internal combustion engine provided with a nitrogen enrichment device.

In a spark ignition type internal combustion engine in which a three-way catalyst having an oxygen storage capacity (OSC) is disposed in an exhaust passage, when a fuel cut process is performed during the operation of the internal combustion engine, the three-way catalyst The oxygen storage capacity of the catalyst increases rapidly. Therefore, the oxygen storage amount of the three-way catalyst at the end of the fuel cut process may be excessively increased. In such a case, if the internal combustion engine is stoichiometrically operated (operation for burning the air-fuel mixture in the vicinity of the theoretical air-fuel ratio) immediately after the fuel cut processing is finished, the three-way catalyst becomes a lean atmosphere, and the NO _X purification performance is improved. descend. For such a problem, the three-way catalyst is prevented from becoming a lean atmosphere by performing a rich operation (operation for combusting a rich air-fuel ratio mixture) for a predetermined period from the end of the fuel cut processing. Techniques have been proposed (see, for example, Patent Document 1).

JP 2003-013777 A JP 2013-227926 A JP 2011-069339 A JP 2005-105993 A JP 2015-0104089 A

  By the way, according to the above-described prior art, as the oxygen storage amount of the three-way catalyst at the end of the fuel cut process increases, it is necessary to lengthen the time during which the internal combustion engine is richly operated after the fuel cut process ends. When the period during which the internal combustion engine is richly operated becomes longer, there is a problem that the fuel consumption rate (fuel consumption per unit output) of the internal combustion engine increases accordingly.

  The present invention has been made in view of the above-described problems, and an object thereof is to suppress the amount of oxygen occluded in the three-way catalyst during the fuel cut process.

  In order to solve the above-described problems, the present invention provides an internal combustion engine including a nitrogen enrichment device disposed in an intake passage and a three-way catalyst disposed in an exhaust passage. The amount of oxygen flowing into the three-way catalyst per unit time was reduced by increasing the nitrogen ratio of the intake air with a nitrogen enrichment device.

Specifically, the present invention is arranged in an intake passage of an internal combustion engine, by adding nitrogen gas to the intake air that is a gas flowing through the intake passage, or by removing at least a part of oxygen contained in the intake air. A nitrogen enricher that increases the nitrogen ratio, which is the ratio of the amount of nitrogen contained in the intake air with respect to the amount of oxygen contained in the intake air, and an exhaust gas air-fuel ratio disposed in the exhaust passage of the internal combustion engine A three-way catalyst that stores oxygen in the exhaust gas and releases the oxygen that has been stored when the air-fuel ratio of the exhaust gas is a rich air-fuel ratio. is there. The controller enriches the nitrogen in order to increase the nitrogen ratio of the intake air during the period from the start to the end of the fuel cut process, which is a process for temporarily stopping fuel injection during the operation of the internal combustion engine. A nitrogen enrichment process, which is a process for controlling the apparatus, was performed.

  When the nitrogen enrichment process is executed in a period from the start to the end of the fuel cut process (hereinafter referred to as “fuel cut period”), the internal combustion is performed per unit time (for example, per cycle). The amount of oxygen inhaled into the engine is reduced.

  For example, when the nitrogen enrichment device is a device that adds nitrogen gas to the intake air, when the nitrogen enrichment process is executed during the fuel cut period, the amount of air taken into the internal combustion engine per unit time is The amount decreases by the amount of nitrogen gas sucked into the internal combustion engine per unit time. In the fuel cut period, when the amount of air sucked into the internal combustion engine per unit time decreases, the amount of oxygen sucked into the internal combustion engine per unit time decreases accordingly.

  Further, in the case where the nitrogen enrichment device is a device that removes at least a part of oxygen contained in the intake air, when the nitrogen enrichment process is performed during the fuel cut period, the nitrogen enrichment device performs oxygen content. The intake air after having been reduced is taken into the internal combustion engine. As a result, during the fuel cut period, the amount of oxygen taken into the internal combustion engine per unit time decreases.

  As described above, when the nitrogen enrichment process is performed during the fuel cut period, the amount of oxygen sucked into the internal combustion engine per unit time decreases, and accordingly, the exhaust gas is discharged from the internal combustion engine per unit time. The amount of oxygen produced is also reduced. As a result, in the fuel cut period, the amount of oxygen flowing into the three-way catalyst per unit time decreases, and accordingly, the amount of oxygen stored in the three-way catalyst per unit time also decreases. Therefore, when the nitrogen enrichment process is performed during the fuel cut period, the amount of oxygen stored in the three-way catalyst during the fuel cut period can be reduced. If the amount of oxygen occluded in the three-way catalyst during the fuel cut period decreases, when fuel injection is resumed at the end of the fuel cut process, the time required for rich operation of the internal combustion engine is shortened, or the internal combustion engine is Since it is not necessary to perform the rich operation (that is, the internal combustion engine can be immediately operated after the fuel cut process is completed), it is possible to suppress an increase in the fuel consumption rate. The method of executing the nitrogen enrichment process during the fuel cut period is not limited to the method of continuously executing the nitrogen enrichment process during the entire fuel cut period, and the nitrogen enrichment process during the fuel cut period. It may be a method of intermittently performing the oxidization process or a method of executing the nitrogen enrichment process in at least a part of the fuel cut period.

  Here, when the fuel cut process is ended, the nitrogen enrichment process is also ended, but when the fuel injection is resumed with the end of the fuel cut process, the internal combustion engine is stopped. The intake air to be sucked becomes a gas whose nitrogen ratio is increased immediately before the end of the fuel cut process. Here, if the nitrogen enrichment device is a device that adds nitrogen gas to the intake air, the amount of air taken into the intake passage from the atmosphere (intake air amount) and the amount of oxygen taken into the internal combustion engine are correlated. . Therefore, when fuel injection is resumed with the end of the fuel cut processing, even if the gas whose nitrogen ratio has been increased by the nitrogen enrichment device is being sucked into the internal combustion engine, the amount of intake air is used as a parameter for the fuel. A known method of determining the injection amount can be used. However, when the nitrogen enrichment device is a device that removes a part of oxygen contained in the intake air, the intake air amount and the oxygen amount actually taken into the internal combustion engine are not correlated. Therefore, when the fuel injection is resumed with the end of the fuel cut process, if the above-described known method is used, the fuel injection is compared with the fuel amount suitable for the oxygen amount actually sucked into the internal combustion engine. The amount can be large.

  Therefore, in the case where the nitrogen enrichment device is a device that removes at least a part of oxygen contained in the intake air, the control device is configured such that when fuel injection is resumed with the end of the fuel cut processing. The fuel injection amount may be calculated based on the amount of oxygen removed from the intake air by the nitrogen enrichment device before the end of the fuel cut process. According to such a configuration, when the fuel injection is restarted with the end of the fuel cut process, the fuel injection amount increases as compared with the amount suitable for the amount of oxygen sucked into the internal combustion engine. Can be suppressed.

  According to the present invention, it is possible to suppress the amount of oxygen stored in the three-way catalyst during the fuel cut process.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. F / C flag, on / off of nitrogen enrichment apparatus, oxygen concentration of exhaust gas flowing into the three-way catalyst, and oxygen storage amount of the three-way catalyst when the nitrogen enrichment process is executed during the fuel cut period 6 is a timing chart showing changes with time of rich operation on / off. It is a flowchart which shows the process routine which ECU performs when a nitrogen enrichment process is performed. It is a figure which shows the relationship between the coefficient for correct | amending the differential pressure | voltage of a nitrogen enriched film, and the amount of intake air.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is an internal combustion engine mounted on a vehicle, and is a 4-stroke cycle spark ignition type internal combustion engine (gasoline engine) having a plurality of cylinders 2. Although FIG. 1 shows an example in which the number of cylinders is four, the number may be three or less, or may be five or more. Each cylinder 2 of the internal combustion engine 1 is provided with a spark plug 3 for generating a spark in the cylinder 2 and a fuel injection valve 4 for injecting fuel into an intake port (not shown). The fuel injection valve 4 may be configured to inject fuel into the cylinder 2.

  The internal combustion engine 1 is connected to the intake passage 5. The intake passage 5 is a passage for guiding air taken in from the atmosphere to each cylinder 2. An air cleaner box 50 for collecting dust and the like in the air is attached in the vicinity of the upstream end of the intake passage 5. A throttle valve 51 for adjusting the amount of air flowing through the intake passage 5 is attached to the intake passage 5 downstream of the air cleaner box 50. The intake passage 5 between the throttle valve 51 and the air cleaner box 50 flows through the intake passage 5 and an intake air temperature sensor 52 that outputs an electrical signal correlated with the temperature of the air flowing through the intake passage 5. An air flow meter 53 that outputs an electrical signal correlated with the air amount (intake air amount) is attached.

The internal combustion engine 1 is connected to the exhaust passage 6. The exhaust passage 6 is a passage for circulating burned gas (exhaust gas) burned in the cylinder 2. A three-way catalyst 60 is disposed in the middle of the exhaust passage 6. The three-way catalyst 60 includes hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides contained in the exhaust when the air-fuel ratio of the exhaust flowing into the three-way catalyst 60 is in the vicinity of the theoretical air-fuel ratio. This is a catalyst for purifying (NO _x ). The three-way catalyst 60 stores oxygen in the exhaust when the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 60 is a lean air-fuel ratio, and the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 60 When the air-fuel ratio is rich, it has an oxygen storage capacity for releasing the stored oxygen. An oxygen concentration sensor 61 that outputs an electrical signal that correlates with the oxygen concentration of the exhaust gas is attached to the exhaust passage 6 upstream of the three-way catalyst 60 described above.

  Further, the internal combustion engine 1 includes a nitrogen enrichment device 54. The nitrogen enrichment device 54 is a device that is disposed in the intake passage 5 and increases the ratio of the amount of nitrogen contained in intake air (nitrogen ratio) to the amount of oxygen contained in intake air. Specifically, the nitrogen enrichment device 54 is a device that adds nitrogen gas to the gas (intake air) flowing through the intake passage 5. As the nitrogen gas here, nitrogen gas stored in a tank (not shown) is used.

The internal combustion engine 1 configured as described above is provided with an ECU (Electronic Control Unit) 7 as a “control device” according to the present invention. ECU7 is CPU, ROM, R
It consists of AM, backup RAM, etc. The ECU 7 configured as described above is electrically connected to various sensors such as the accelerator position sensor 9, the crank position sensor 10, and the water temperature sensor 8 in addition to the intake air temperature sensor 52, the air flow meter 53, and the oxygen concentration sensor 61 described above. Connected so that the output signals of these various sensors can be input. The water temperature sensor 8 is a sensor that outputs an electrical signal correlated with the temperature of the cooling water circulating through the internal combustion engine 1. The accelerator position sensor 9 is a sensor that outputs an electrical signal correlated with the amount of operation of the accelerator pedal (accelerator opening). The crank position sensor 10 is a sensor that outputs an electrical signal correlated with the rotational position of the engine output shaft (crankshaft) of the internal combustion engine 1.

  The ECU 7 is also electrically connected to various devices such as the ignition plug 3, the fuel injection valve 4, the throttle valve 51, and the nitrogen enrichment device 54 described above, and can control the operating state of these various devices. Yes. For example, the ECU 7 calculates a target fuel injection amount, a target fuel injection timing, a target ignition timing, a target throttle opening, and the like based on the output signals of the various sensors described above, and in accordance with these various target values, the fuel injection valve 4. Control the spark plug 3, the throttle valve 51, and the like.

  Further, the ECU 7 stops the operation of the fuel injection valve 4 when a predetermined fuel cut start condition is satisfied, and restarts the operation of the fuel injection valve 4 when a predetermined fuel cut end condition is satisfied, A fuel cut process for temporarily stopping the combustion of the air-fuel mixture in the internal combustion engine 1 is executed. The fuel cut start condition here is that (1) the engine rotational speed calculated based on the output signal of the crank position sensor 10 is equal to or higher than a predetermined first rotational speed, and (2) the internal combustion engine 1 is warmed up. That the three conditions are satisfied, (3) the three-way catalyst 60 is in the active state, and (4) the output signal (accelerator opening) of the accelerator position sensor 9 is zero. . Further, the fuel cut end condition is that (5) the engine rotational speed is equal to or lower than a predetermined second rotational speed (a rotational speed lower than the first rotational speed and higher than the idle rotational speed), or (6) the accelerator is opened. That is, at least one of the conditions that the degree is greater than 0 is satisfied. When the fuel cut process is executed according to the above-described conditions, the fuel consumption rate of the internal combustion engine 1 can be reduced.

By the way, in the period from the start to the end of the fuel cut process (fuel cut period), the air sucked into the cylinder 2 of the internal combustion engine 1 is discharged into the exhaust passage 6 as it is. Therefore, during the fuel cut period, the amount of oxygen flowing into the three-way catalyst 60 per unit time is larger than the period during which the fuel cut process is not performed (the period in which the fuel is burned in the internal combustion engine 1). Accordingly, the amount of oxygen stored in the three-way catalyst 60 per unit time increases. As a result, the oxygen storage amount of the three-way catalyst 60 at the end of the fuel cut process may become excessive. In such a case, when the internal combustion engine 1 immediately after the end of the fuel cut process is stoichiometric operation, the three-way catalyst 60 becomes a lean atmosphere, NO _X purifying performance degrades.

  For the above-described problem, when the oxygen storage amount of the three-way catalyst 60 at the end of the fuel cut processing exceeds a predetermined threshold, the oxygen storage amount of the three-way catalyst 60 after the fuel cut processing is ended is A method of suppressing the three-way catalyst 60 from entering a lean atmosphere by causing the internal combustion engine 1 to perform a rich operation during a period until the predetermined threshold value is reached is conceivable. However, as the oxygen storage amount of the three-way catalyst 60 at the end of the fuel cut process increases, the rich operation time needs to be lengthened. Therefore, the fuel consumption rate of the internal combustion engine 1 may increase accordingly.

  Therefore, in the present embodiment, the three-way catalyst 60 occludes during the fuel cut period by executing a process (nitrogen enrichment process) for adding nitrogen gas from the nitrogen enrichment device 54 to the intake air during the fuel cut period. I tried to keep the amount of oxygen released. Hereinafter, the execution procedure of the nitrogen enrichment process in the present embodiment will be described.

  FIG. 2 shows the fuel cut flag (F / C flag), the ON / OFF of the nitrogen enrichment device 54, and the exhaust gas flowing into the three-way catalyst 60 when the nitrogen enrichment process is executed during the fuel cut period. 4 is a timing chart showing temporal changes in oxygen concentration, oxygen storage amount of a three-way catalyst 60, and on / off of rich operation. The F / C flag here is a flag that is turned on when the fuel cut start condition is satisfied and is turned off when the fuel cut end condition is satisfied.

  Here, t1 in FIG. 2 indicates the timing at which the fuel cut start condition is satisfied. T2 in FIG. 2 is a timing at which the fuel cut end condition is satisfied, and indicates a timing at which the rich operation is started. T3 in FIG. 2 indicates the end timing of the rich operation when the nitrogen enrichment process is executed (this example). T4 in FIG. 2 indicates the end timing of the rich operation when the nitrogen enrichment process is not executed (conventional). Also, the alternate long and short dash line in the third to fifth timing charts in FIG. 2 indicates the exhaust oxygen concentration, the oxygen storage amount, and the rich operation on / off when the nitrogen enrichment process is not performed. Respectively.

  As shown in FIG. 2, when the fuel cut start condition is satisfied and the F / C flag is turned on (t1 in FIG. 2), the ECU 7 operates (turns on) the nitrogen enrichment device 54, The addition of nitrogen gas from the nitrogen enricher 54 to the intake air is started. Thereafter, when the fuel cut termination condition is satisfied and the F / C flag is turned off (t2 in FIG. 2), the ECU 7 stops (turns off) the operation of the nitrogen enriching device 54, and the nitrogen rich Addition of nitrogen gas from the gasification device 54 to the intake air is terminated.

When the nitrogen enrichment process is executed by the above-described method, the gas sucked into the cylinder 2 is a mixed gas of air and nitrogen gas in the fuel cut period (t1-t2 in FIG. 2). Therefore, the amount of air sucked into the internal combustion engine 1 per cycle is reduced by the amount of nitrogen gas sucked into the internal combustion engine 1 per cycle. Accordingly, the amount of air discharged from the internal combustion engine 1 per cycle also decreases by the amount of nitrogen gas discharged from the internal combustion engine 1 per cycle. Thus, when the amount of air discharged from the internal combustion engine 1 per cycle decreases, the amount of oxygen discharged from the internal combustion engine 1 per cycle decreases. Therefore, the oxygen concentration of the exhaust gas flowing into the three-way catalyst 60 during the fuel cut period is smaller when it is executed than when the nitrogen enrichment process is not executed. As a result, when the nitrogen enrichment process is executed, the three-way catalyst 6 per cycle is compared with the case where the nitrogen enrichment process is not executed.
The amount of oxygen flowing into zero decreases. The increase in the oxygen storage amount during the fuel cut period is smaller when the nitrogen enrichment process is not performed than when the nitrogen enrichment process is not performed. Therefore, when the rich operation after the end of the fuel cut process is executed, the timing at which the oxygen storage amount becomes equal to or less than the predetermined threshold is executed from the case where the nitrogen enrichment process is not executed (t4 in FIG. 2). The case (t3 in FIG. 2) is faster. That is, when the nitrogen enrichment process is executed, the rich operation time after the fuel cut process is completed is shorter than when the nitrogen enrichment process is not executed. Thereby, the increase in the fuel consumption rate resulting from rich operation can be suppressed to a small extent.

  Note that FIG. 2 shows an example in which the oxygen storage amount at the end of the fuel cut process exceeds a predetermined threshold value. However, by executing the nitrogen enrichment process described above, the three-way catalyst 60 is in the fuel cut period. If the amount of stored oxygen decreases, the oxygen storage amount at the end of the fuel cut process may fall below a predetermined threshold. In such a case, it is not necessary to perform the rich operation of the internal combustion engine 1 after the fuel cut process is completed, so that an increase in the fuel consumption rate due to the rich operation can be avoided.

  Hereafter, the execution procedure of the nitrogen enrichment process in this embodiment is demonstrated along FIG. FIG. 3 is a flowchart showing a processing routine executed by the ECU 7 when the nitrogen enrichment process is executed. This processing routine is stored in advance in the ROM of the ECU 7 and is periodically executed by the ECU 7 during operation of the internal combustion engine 1.

  In the processing routine of FIG. 3, the ECU 7 first determines whether or not the fuel cut start condition described above is satisfied in the processing of S101. If a negative determination is made in the processing of S101, the ECU 7 ends the execution of this processing routine. On the other hand, when an affirmative determination is made in the process of S101, the ECU 7 proceeds to the process of S102.

  In the process of S102, the ECU 7 turns on the F / C flag. Next, the ECU 7 proceeds to the process of S103, and executes the fuel cut process by stopping the operation of the fuel injection valve 4 and the operation of the spark plug 3. Then, the ECU 7 proceeds to the process of S104 and starts the nitrogen enrichment process by starting the addition of nitrogen gas from the nitrogen enrichment device 54 to the intake air.

In the process of S105, the ECU 7 calculates the oxygen storage amount ΣO ₂ of the three-way catalyst 60. Specifically, the ECU 7 first sets the measured value of the oxygen concentration sensor 61 and the exhaust flow rate (the sum of the intake air amount detected by the air flow meter 53 and the addition amount of nitrogen gas) as a parameter per unit time. The amount of oxygen ΔO ₂ stored in the three-way catalyst 60 is calculated. Subsequently, ECU 7, by adding the amount of oxygen delta O.D. ₂ to the immediately preceding value NA: 0.75, o ₂ old oxygen storage amount NA: 0.75, o _2, and calculates the oxygen storage amount NA: 0.75, o ₂ of the three-way catalyst 60. When the oxygen storage amount ΣO ₂ is larger than the saturated storage amount of the three-way catalyst 60, the saturated storage amount is set to the oxygen storage amount ΣO ₂ .

  In the process of S106, the ECU 7 determines whether or not the fuel cut end condition is satisfied. If a negative determination is made in the process of S106, the ECU 7 returns to the process of S105. On the other hand, if an affirmative determination is made in the process of S106, the ECU 7 proceeds to the process of S107.

  In the process of S107, the ECU 7 ends the nitrogen enrichment process by terminating the addition of nitrogen gas from the nitrogen enrichment device 54 to the intake air. Subsequently, the ECU 7 proceeds to the process of S108 and switches the F / C flag from on to off.

In the process of S109, the ECU 7 determines whether or not the oxygen storage amount ΣO ₂ calculated in the process of S105 is larger than the predetermined threshold ΣO ₂ thr described above. Here, the predetermined threshold ΣO ₂ thr is determined when the internal combustion engine 1 is stoichiometrically operated when the oxygen storage amount ΣO ₂ of the three-way catalyst 60 exceeds the predetermined threshold ΣO ₂ thr. The value is assumed to be a lean atmosphere, and is a value obtained experimentally in advance.

  When an affirmative determination is made in the process of S109, the ECU 7 proceeds to the process of S110, and ends the fuel cut process by resuming the operation of the fuel injection valve 4 and the operation of the spark plug 3. At that time, the ECU 7 causes the internal combustion engine 1 to perform a rich operation by setting the target air-fuel ratio of the air-fuel mixture to a rich air-fuel ratio. By the way, the gas (combustion gas) used for combustion in the cylinder 2 immediately after the end of the fuel cut processing is a gas containing nitrogen gas added from the nitrogen enrichment device 54. However, the amount of oxygen contained in the combustion gas correlates with the amount of air measured by the air flow meter 53. Therefore, the ECU 7 may determine the target fuel injection amount based on the target air-fuel ratio and the output signal value of the air flow meter 53.

In the process of S111, the ECU 7 calculates the oxygen storage amount ΣO ₂ of the three-way catalyst 60. Specifically, the ECU 7 first calculates the oxygen amount ΔO ₂ ′ released from the three-way catalyst 60 per unit time using the air-fuel ratio of the air-fuel mixture and the exhaust gas flow rate as parameters. At that time, the correlation between the air-fuel ratio of the air-fuel mixture, the exhaust gas flow rate, and the oxygen amount ΔO ₂ ′ released from the three-way catalyst 60 per unit time is obtained experimentally in advance, and the correlation is mapped. To do. Then, the ECU 7 derives the oxygen amount ΔO ₂ ′ released from the three-way catalyst 60 per unit time by accessing the map as the air-fuel ratio of the air-fuel mixture, the exhaust gas flow rate, and the arguments. Then, ECU 7, by subtracting the amount of oxygen delta O.D. ₂ 'from the previous value NA: 0.75, o ₂ old oxygen storage amount NA: 0.75, o _2, and calculates the oxygen storage amount NA: 0.75, o ₂ of the three-way catalyst 60.

In the process of S112, the ECU 7 determines whether or not the oxygen storage amount ΣO ₂ calculated in the process of S111 has decreased below the predetermined threshold ΣO ₂ thr. If a negative determination is made in the process of S112, the ECU 7 returns to the process of S111. On the other hand, when a positive determination is made in the process of S112, the ECU 7 proceeds to the process of S113.

  In the process of S113, the ECU 7 switches the operation state of the internal combustion engine 1 from the rich operation to the stoichiometric operation by switching the target air-fuel ratio of the air-fuel mixture from the rich air-fuel ratio to the stoichiometric air-fuel ratio. If a negative determination is made in the process of S109, the ECU 7 skips the processes of S110-S112 and executes the process of S113 because there is no need to make the internal combustion engine 1 perform a rich operation after the fuel cut process is completed. It shall be.

  When the nitrogen enrichment process is executed according to the procedure described above, the amount of oxygen stored in the three-way catalyst 60 during the fuel cut period decreases. Therefore, the time during which the internal combustion engine 1 is richly operated after the fuel cut processing is completed is shortened, or it is not necessary to perform the rich operation. Therefore, it is possible to suppress an increase in the fuel consumption rate resulting from the rich operation of the internal combustion engine 1 after the fuel cut process is completed, or it is possible to avoid an increase in the fuel consumption rate.

  In the present embodiment, the example in which the nitrogen enrichment process is continuously performed in the entire fuel cut period has been described. However, the nitrogen enrichment process may be intermittently performed in the fuel cut period, or the fuel may be performed. The nitrogen enrichment process may be continuously performed during at least a part of the cut period.

<Other embodiments>
In the above-described embodiments, as the nitrogen enrichment apparatus according to the present invention, an apparatus for adding nitrogen gas to the intake air has been described as an example. However, an apparatus for removing at least a part of oxygen contained in the intake air can also be used. Specifically, a nitrogen-rich film that is provided in the middle of the intake passage 5 and separates oxygen from the air taken into the intake passage 5, and an adjustment mechanism that adjusts the differential pressure across the nitrogen-rich film. A nitrogen enrichment apparatus comprising a bypass passage that bypasses the nitrogen enriched membrane, and a flow path switching valve that conducts either the nitrogen enriched membrane or the bypass passage can be used. In that case, the ECU 7 controls the flow path switching valve so that the bypass passage is conducted when the nitrogen enrichment process is not executed and the nitrogen enriched film is conducted when the nitrogen enrichment process is executed. Control is sufficient.

  In an internal combustion engine having a membrane separation type nitrogen enrichment apparatus as described above, a gas (combustion gas) used for combustion in the cylinder 2 at the time of rich operation or stoichiometric operation immediately after the end of the fuel cut processing is nitrogen-rich. The oxygen content is reduced by the gasification device. Therefore, the amount of oxygen contained in the combustion gas does not correlate with the amount of air measured by the air flow meter 53. Therefore, in an internal combustion engine equipped with a membrane separation type nitrogen enrichment device, it is necessary to determine the target fuel injection amount immediately after the end of the fuel cut process in consideration of the amount of oxygen removed by the nitrogen enrichment device. .

Here, the amount of oxygen removed by the membrane separation type nitrogen enricher increases as the differential pressure across the nitrogen enriched membrane increases. Therefore, the ECU 7 may be configured such that the target fuel injection amount becomes smaller as the front-rear differential pressure adjusted by the adjustment mechanism when the nitrogen enrichment process is performed is larger. For example, the ECU 7 corrects the measured value (intake air amount) Ga of the air flow meter 53 according to the following equation (1), and corrects the intake air amount Ga ′ after correction and the target air-fuel ratio (rich air-fuel ratio or stoichiometric air-fuel ratio). ) As a parameter and the target fuel injection amount may be calculated.
Ga ′ = Ga * k (1)

  In addition, as shown in FIG. 4, k in the above equation (1) is a coefficient that is larger than 0 and equal to or smaller than 1, and is determined so as to decrease as the front-rear differential pressure of the nitrogen-enriched film increases. Is a coefficient.

  Further, the calculation of the target fuel injection amount by the method as described above is performed in a period from when the fuel injection accompanying the end of the fuel cut process is restarted until a predetermined number of cycles elapses. The predetermined number of cycles at that time may be determined according to the amount of gas sucked into the internal combustion engine 1 per cycle and the volume of the intake passage 5 downstream from the nitrogen enricher.

  As described above, when the target fuel injection amount is calculated, the fuel injection amount at the time of the rich operation or the stoichiometric operation immediately after the end of the fuel cut process is set to an amount suitable for the amount of oxygen contained in the combustion gas. it can.

1 Internal combustion engine 2 Cylinder 3 Spark plug 4 Fuel injection valve 5 Intake passage 6 Exhaust passage 7 ECU
10 Crank Position Sensor 51 Throttle Valve 53 Air Flow Meter 54 Nitrogen Enrichment Device 60 Exhaust Purification Catalyst 540 Nitrogen Injection Valve

Claims (2)

Oxygen contained in the intake air by adding nitrogen gas to the intake air that is disposed in the intake passage of the internal combustion engine and flowing through the intake passage, or by removing at least part of the oxygen contained in the intake air A nitrogen enrichment device that increases a nitrogen ratio, which is a ratio of the amount of nitrogen contained in the intake air with respect to the amount of
Oxygen stored in the exhaust passage of the internal combustion engine is stored when the air-fuel ratio of the exhaust gas is lean, and the stored oxygen is stored when the air-fuel ratio of the exhaust gas is rich. A three-way catalyst to be released,
A control device applied to an internal combustion engine comprising:
The control device is configured to increase the nitrogen ratio of the intake air in a period from the start to the end of a fuel cut process that is a process of temporarily stopping fuel injection during the operation of the internal combustion engine. A control apparatus for an internal combustion engine, which performs a nitrogen enrichment process, which is a process for controlling the synthesizer. The nitrogen enrichment device is a device that reduces the amount of oxygen contained in the intake air,
When the fuel injection is resumed at the end of the fuel cut process, the control device is configured to perform fuel based on the amount of oxygen removed from the intake air by the nitrogen enrichment device before the end of the fuel cut process. 2. The control apparatus for an internal combustion engine according to claim 1, wherein an injection amount is calculated.

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