JP2005264927A - Internal combustion engine and its operation control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of a catalyst during fuel injection stop. <P>SOLUTION: This internal combustion engine is such a reciprocating internal combustion engine that a mixture of air A and fuel is burnt in a cylinder 1s. The mixture after burnt in the cylinder 1s is exhausted as exhaust gas Ex. The exhaust gas Ex is purified by the catalyst 12. When fuel injection from a cylinder injection valve 3 is stopped during speed reducing operation of the internal combustion engine 1, an EGR valve 14 is opened to recirculate the exhaust gas Ex into an intake passage 8i and a throttle valve 16 and an ISC valve 17 are closed to make the air to be introduced from the intake passage 8i into the internal combustion engine 1 zero. Then, the fuel injection from the cylinder injection valve 3 is stopped. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine capable of suppressing deterioration of a catalyst when fuel injection is stopped, and an operation control device for the internal combustion engine.

  An internal combustion engine mounted on a vehicle such as a passenger car or a truck is generally provided with a catalyst for purifying exhaust gas generated after burning fuel. The catalyst is purified by oxidizing and reducing harmful components in the exhaust gas. This catalyst generally tends to deteriorate at a high temperature. In particular, the deterioration of the catalyst easily proceeds in an atmosphere where high temperature and oxygen are present (hereinafter referred to as high temperature lean). In the case of an internal combustion engine mounted on a vehicle or the like, for example, when the accelerator is closed as in a deceleration operation, the fuel consumption is reduced by stopping the supply of fuel to the internal combustion engine. However, if fuel injection is stopped at the time of deceleration, exhaust gas that has become lean at high temperature flows into the catalyst, which promotes deterioration of the catalyst.

  In order to solve such a problem, Patent Document 1 includes a communication passage that connects an exhaust gas passage upstream of the catalyst and an intake passage of the internal combustion engine, and when the internal combustion engine is decelerating and when fuel injection is stopped, the exhaust gas passage is provided. A technique for providing an opening / closing means for opening a communication passage so as to communicate with the intake passage is disclosed. Patent Document 2 also provides an EGR means for returning exhaust gas to the intake side and an EGR amount increasing means in the middle of the exhaust gas passage so that the amount of exhaust gas returned to the intake side when the internal combustion engine is decelerated and when fuel injection is stopped. Techniques for increasing are disclosed.

JP-A-9-209844 JP 7-293230 A

  By the way, with the techniques disclosed in Patent Document 1 and Patent Document 2, the amount of high-temperature exhaust gas flowing into the catalyst can be reduced by recirculating the exhaust gas to the intake side. However, it is insufficient for reducing the concentration of oxygen contained in the exhaust gas, and there is room for further improvement in suppressing deterioration of the catalyst. Therefore, the present invention has been made in view of the above, and an internal combustion engine that can suppress deterioration of the catalyst by reducing the oxygen concentration of the exhaust gas introduced into the catalyst when fuel injection to the internal combustion engine is stopped, and An object of the present invention is to provide an operation control device for an internal combustion engine.

  In order to solve the above-described problems and achieve the object, the present inventors have conducted intensive research. As a result, there is new air introduced into the internal combustion engine from the intake passage when the fuel injection to the internal combustion engine is stopped. Pay attention. The throttle valve of the internal combustion engine is closed when the internal combustion engine is decelerated and fuel injection is stopped. However, in general, in an internal combustion engine, in order to control the idling speed, even when the throttle valve is completely closed, air corresponding to the idling operation of the internal combustion engine flows into the internal combustion engine through the intake passage. The present inventors have found that the oxygen concentration in the exhaust gas is increased by the air, and the exhaust gas that has been made lean at high temperature flows into the catalyst, thereby promoting the deterioration of the catalyst. The present invention has been completed from this viewpoint.

  An internal combustion engine according to the present invention is an internal combustion engine that burns a mixture of air and fuel in a combustion chamber, and introduces air to an intake port provided in the combustion chamber and introduces air into the combustion chamber; A fuel injection valve that injects fuel for forming the air-fuel mixture, a catalyst that purifies the exhaust gas after the air-fuel mixture burns, and an exhaust gas recirculation passage that recirculates the exhaust gas to the combustion chamber, When the fuel injection from the fuel injection valve is stopped, the exhaust gas is recirculated and the fuel injection is stopped after the introduction of air into the combustion chamber is stopped.

  When the fuel injection is stopped, the internal combustion engine stops the introduction of air into the internal combustion engine and recirculates the exhaust gas to the combustion chamber. Thereby, since the oxygen concentration of the exhaust gas introduced into the catalyst can be reduced, leaning of the exhaust gas can be suppressed and deterioration of the catalyst can be suppressed. In order to recirculate the exhaust gas to the combustion chamber, for example, there is a method in which air is led to an intake port provided in the combustion chamber and recirculated through an intake passage through which air is introduced into the combustion chamber.

  The internal combustion engine according to the present invention is characterized in that, in the internal combustion engine, the flow rate of the exhaust gas recirculated to the combustion chamber is changed.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, since the internal combustion engine changes the flow rate of the exhaust gas recirculated to the combustion chamber, the engine brake performance during deceleration of a vehicle or the like equipped with the internal combustion engine can be changed.

  The internal combustion engine according to the present invention is characterized in that, in the internal combustion engine, the flow rate of the exhaust gas recirculated to the combustion chamber is substantially the same as the intake air amount when the internal combustion engine is idling.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, in this internal combustion engine, the flow rate of the exhaust gas recirculated to the combustion chamber is set to be substantially the same as the intake air amount when the internal combustion engine is idling. Thereby, the engine braking performance at the time of deceleration of the vehicle etc. which mounts this internal combustion engine is maintainable.

  In the internal combustion engine according to the next aspect of the present invention, after the introduction of air into the combustion chamber is stopped in the internal combustion engine, the amount of fuel is increased more than when a condition for stopping fuel injection from the fuel injection valve is satisfied. Then, the fuel is injected from the fuel injection valve.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine increases the amount of fuel and injects it from the fuel injection valve before executing the stop of the fuel injection, compared to when the condition for stopping the fuel injection is satisfied. As a result, oxygen contained in the air remaining in the intake passage or the like can be consumed, so that deterioration of the catalyst can be suppressed.

  In the internal combustion engine according to the next aspect of the present invention, after the first predetermined period elapses after the introduction of air into the combustion chamber is stopped in the internal combustion engine, fuel injection from the fuel injection valve is performed. The fuel is increased from the time when the condition for stopping is satisfied, and the fuel is injected from the fuel injection valve.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine increases the amount of fuel and injects the fuel from the fuel injection valve after the first predetermined period before the stop of the fuel injection is executed, compared to when the condition for stopping the fuel injection is satisfied. In this way, by waiting for the first predetermined period to elapse, fuel can be injected in consideration of the air flowing into the intake passage through the throttle valve after the air introduction is stopped. As a result, oxygen contained in the air remaining in the intake passage or the like can be consumed more sufficiently, the exhaust gas introduced into the catalyst can be made rich, and the deterioration of the catalyst can be suppressed.

  In the internal combustion engine according to the next aspect of the present invention, in the internal combustion engine, the recirculation of the exhaust gas is stopped until the introduction of air into the combustion chamber is stopped and the first predetermined period and the predetermined second predetermined period have elapsed. And then the exhaust gas is recirculated to the combustion chamber.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine stops the exhaust gas recirculation until a first predetermined period and a predetermined second predetermined period have elapsed. As a result, an increase in the concentration of exhaust gas in the intake passage can be suppressed, so that the period during which oxygen contained in the air remaining in the intake passage and the like can be combusted becomes longer. As a result, more oxygen contained in the air remaining in the intake passage or the like can be consumed, so that deterioration of the catalyst can be further suppressed.

  The internal combustion engine according to the present invention is characterized in that the fuel injection from the fuel injection valve is stopped after a predetermined third predetermined period has elapsed since the start of the recirculation of the exhaust gas.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine stops fuel injection after elapse of a predetermined third predetermined period from the start of the exhaust gas recirculation. As a result, the air remaining in the intake passage can be combusted in the combustion chamber, and fuel injection can be stopped from the combustion chamber in which the air remaining in the intake passage cannot be combusted due to an increase in exhaust gas.

  In the internal combustion engine according to the next aspect of the present invention, the period from when the introduction of air into the combustion chamber is stopped until the fuel injection from the fuel injection valve is stopped is before the introduction of air into the combustion chamber is stopped. Rather, the ignition timing is retarded.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, this internal combustion engine retards the ignition timing during the period from when the introduction of air into the combustion chamber is stopped to when the fuel injection is stopped before the stop of the introduction of air into the combustion chamber. As a result, torque fluctuation when the amount of fuel is increased in order to consume oxygen in the air remaining in the intake passage or the like can be reduced, and deterioration of drivability can be suppressed.

  In the internal combustion engine according to the present invention, the internal combustion engine estimates a time from when the exhaust gas starts to recirculate until the exhaust gas reaches the intake port, and the exhaust gas reaches the intake port and the exhaust gas reaches the intake port. The fuel injection to the combustion chamber is stopped either at a timing when exhaust gas is taken into the combustion chamber or after the third predetermined time has elapsed.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Furthermore, this internal combustion engine estimates the time from when exhaust gas recirculation is started until the exhaust gas reaches the intake port. Then, fuel injection to the cylinder is stopped at a timing when exhaust gas is taken into the combustion chamber. Thereby, misfire due to the recirculation of the exhaust gas can be suppressed, and the amount of air mixed in the exhaust gas taken into the combustion chamber can be reduced. As a result, the deterioration of the exhaust gas can be suppressed more reliably and the deterioration of the catalyst can be suppressed.

  In the internal combustion engine according to the present invention, the internal combustion engine estimates a time from when the exhaust gas starts to recirculate until the exhaust gas reaches the intake port, and more than the timing at which fuel injection is stopped. The exhaust gas starts to recirculate as soon as the exhaust gas reaches the intake port.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine starts recirculation of the exhaust gas earlier than the timing at which fuel injection is stopped until the exhaust gas reaches the intake port. As a result, misfire due to the recirculation of the exhaust gas can be suppressed more reliably, and the amount of air mixed into the exhaust gas taken into the combustion chamber can be further reduced. As a result, it is possible to further suppress the deterioration of the catalyst by suppressing the lean exhaust gas.

  The internal combustion engine according to the present invention is characterized in that in the internal combustion engine, the exhaust gas discharged from the catalyst is recirculated to the combustion chamber.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, since the internal combustion engine recirculates the exhaust gas after leaving the catalyst to the intake passage, the exhaust gas purified by the catalyst can be recirculated to the intake side of the internal combustion engine. Thereby, since the dirt of the valve which controls the recirculation of the exhaust gas can be suppressed, deterioration with time of the valve can also be suppressed.

  In the internal combustion engine according to the present invention, when the internal combustion engine is forcibly returned from a state in which fuel injection is stopped to a state in which fuel is injected again, air introduction into the combustion chamber is started. Then, the time for the air to reach the intake port provided in the combustion chamber is estimated, and fuel is injected from the combustion chamber in which the air reaches the intake port.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Furthermore, this internal combustion engine injects fuel in order from the combustion chamber where air is predicted to reach the intake port. As a result, when returning from the stop of fuel injection, the occurrence of misfire due to lack of oxygen can be suppressed, and the discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  In the internal combustion engine according to the next aspect of the present invention, in the internal combustion engine, for a predetermined period from the start of air introduction into the combustion chamber, a larger amount of air than the air amount determined from the operating conditions of the internal combustion engine is supplied. It introduce | transduces into the said combustion chamber, It is characterized by the above-mentioned.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, the internal combustion engine introduces a larger amount of air into the combustion chamber than the amount of air determined from the operating conditions of the internal combustion engine for a predetermined period after the start of air introduction into the combustion chamber. As a result, exhaust gas remaining in the intake passage or the like can be scavenged, and therefore, when returning from the stop of fuel injection, misfire due to lack of oxygen can be suppressed, and discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  In the internal combustion engine according to the present invention, when the internal combustion engine naturally returns from the state in which fuel injection is stopped to the state in which fuel is injected again, air introduction into the combustion chamber is started at the same time. Alternatively, after the introduction of air into the combustion chamber is started, the recirculation of the exhaust gas is stopped, and after a predetermined period has elapsed since the recirculation of the exhaust gas is stopped, the fuel injection from the fuel injection valve is performed. It is characterized by starting.

  Since the internal combustion engine has the same configuration as the internal combustion engine, the same operation and effect as the internal combustion engine are achieved. Further, since the internal combustion engine starts fuel injection after a predetermined period has elapsed after stopping the recirculation of the exhaust gas, the exhaust gas remaining in the intake passage or the like can be scavenged. As a result, in returning from the stop of fuel injection, the occurrence of misfire due to lack of oxygen can be suppressed, and the discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  An internal combustion engine operation control apparatus according to the present invention is used for operation control of an internal combustion engine having means for combusting a mixture of air and fuel in a combustion chamber and returning exhaust gas to the combustion chamber. A fuel cut condition determining unit that determines whether or not fuel injection to the internal combustion engine is stopped; and when the fuel injection is stopped, the exhaust gas is recirculated to the combustion chamber, and An exhaust gas recirculation control unit for stopping the intake of air from the intake passage; and a fuel cut control unit for stopping fuel injection to the internal combustion engine after executing the recirculation of the exhaust gas and stopping the intake of air from the intake passage; It is characterized by including.

  This operation control device for an internal combustion engine controls to stop the introduction of air into the internal combustion engine and return the exhaust gas to the combustion chamber when the fuel injection is stopped. Thereby, since the oxygen concentration of the exhaust gas introduced into the catalyst can be reduced, leaning of the exhaust gas can be suppressed and deterioration of the catalyst can be suppressed.

  The operation control apparatus for an internal combustion engine according to the present invention is characterized in that the operation control apparatus for the internal combustion engine further includes an exhaust gas recirculation amount calculation unit for obtaining an amount of the exhaust gas recirculated to the combustion chamber.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the internal combustion engine operation control device can determine the amount of exhaust gas recirculated to the combustion chamber. As a result, the flow rate of the exhaust gas recirculated to the intake passage can be changed, so that the engine brake performance during deceleration of a vehicle or the like equipped with the internal combustion engine can be changed.

  In the internal combustion engine operation control apparatus according to the next aspect of the present invention, the amount of the exhaust gas recirculated to the combustion chamber is substantially the same as the intake air amount when idling the internal combustion engine. It is characterized by doing.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device for the internal combustion engine controls the flow rate of the exhaust gas recirculated to the combustion chamber to be substantially the same as the intake air amount when the internal combustion engine is idling. Thereby, the engine braking performance at the time of deceleration of the vehicle etc. which mounts this internal combustion engine is maintainable.

  The internal combustion engine operation control apparatus according to the present invention is the internal combustion engine operation control apparatus, wherein the fuel cut control unit stops fuel introduction from the fuel injection valve after stopping air introduction into the combustion chamber. The fuel is injected from the fuel injection valve after increasing the amount of fuel compared to when the condition for stopping the injection is satisfied.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device for the internal combustion engine increases the amount of fuel and injects it from the fuel injection valve before stopping the fuel injection, compared to when the condition for stopping the fuel injection is satisfied. As a result, oxygen contained in the air remaining in the intake passage or the like can be consumed, so that deterioration of the catalyst can be suppressed.

  The internal combustion engine operation control device according to the next aspect of the present invention is the internal combustion engine operation control device, wherein after the first predetermined period has elapsed since the introduction of air into the combustion chamber was stopped, The fuel is increased from the time when the condition for stopping the fuel injection from the fuel injection valve is satisfied, and the fuel is injected from the fuel injection valve.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control apparatus for the internal combustion engine increases the amount of fuel and injects it from the fuel injection valve after the first predetermined period before stopping the fuel injection than when the condition for stopping the fuel injection is satisfied. In this manner, by waiting for the first predetermined period to elapse, fuel can be injected in consideration of the air flowing into the intake passage through the throttle valve after the air introduction is stopped. As a result, the oxygen contained in the air remaining in the intake passage or the like is more sufficiently consumed, the exhaust gas introduced into the catalyst is made rich, and deterioration of the catalyst can be suppressed.

  In the internal combustion engine operation control apparatus according to the present invention, in the operation control apparatus for the internal combustion engine, the exhaust gas recirculation control unit stops the introduction of air into the combustion chamber, and the first predetermined period and the predetermined time are determined. The exhaust gas recirculation is stopped until the second predetermined period elapses, and then the exhaust gas is recirculated to the combustion chamber.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device for the internal combustion engine stops the recirculation of the exhaust gas until a first predetermined period and a predetermined second predetermined period elapse. As a result, an increase in the concentration of exhaust gas in the intake passage can be suppressed, so that the period during which oxygen contained in the air remaining in the intake passage and the like can be combusted becomes longer. As a result, more oxygen contained in the air remaining in the intake passage or the like can be consumed, so that deterioration of the catalyst can be further suppressed.

  The internal combustion engine operation control apparatus according to the next aspect of the present invention is the internal combustion engine operation control apparatus, wherein the fuel cut control unit is configured to start a recirculation of the exhaust gas after a predetermined third predetermined period has elapsed. The fuel injection from the fuel injection valve is stopped.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control apparatus for the internal combustion engine stops the fuel injection after the elapse of a predetermined third predetermined period after starting the recirculation of the exhaust gas. As a result, the air remaining in the intake passage can be combusted in the combustion chamber, and fuel injection can be stopped from the combustion chamber in which the air remaining in the intake passage cannot be combusted due to an increase in exhaust gas.

  In the internal combustion engine operation control apparatus according to the next aspect of the present invention, in the internal combustion engine operation control apparatus, a period from when the fuel cut control unit stops introduction of air into the combustion chamber to when fuel injection is stopped. The ignition timing is retarded from before the air introduction into the combustion chamber is stopped.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device of the internal combustion engine retards the ignition timing during a period from when the introduction of air into the combustion chamber is stopped to when the fuel injection is stopped before before the introduction of air into the combustion chamber is stopped. . As a result, torque fluctuation when the amount of fuel is increased in order to consume oxygen in the air remaining in the intake passage or the like can be reduced, and deterioration of drivability can be suppressed.

  The operation control device for an internal combustion engine according to the next aspect of the present invention is the operation control device for the internal combustion engine, wherein the exhaust gas to be recirculated from the start of the recirculation of the exhaust gas until the exhaust gas reaches the intake port of the combustion chamber. An exhaust gas arrival time calculation unit that estimates time, and the fuel cut control unit predicts a combustion chamber in which the exhaust gas reaches the intake port from a time until the exhaust gas reaches the intake port, and the combustion The fuel injection into the combustion chamber is stopped at a timing when the exhaust gas can be taken into the chamber.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device for the internal combustion engine estimates the time from when the exhaust gas recirculation is started until the exhaust gas reaches the intake port. Then, the fuel injection to the cylinder is controlled to stop at the timing when the exhaust gas can be taken into the combustion chamber. Thereby, misfire due to the recirculation of the exhaust gas can be suppressed, and the amount of air mixed in the exhaust gas taken into the combustion chamber can be reduced. As a result, the deterioration of the exhaust gas can be suppressed more reliably and the deterioration of the catalyst can be suppressed.

  In the internal combustion engine operation control apparatus according to the next aspect of the present invention, the internal combustion engine operation control apparatus further includes a time period from when the exhaust gas starts to recirculate until the exhaust gas reaches the intake port of the combustion chamber. An exhaust gas arrival time calculation unit for estimating, and the exhaust gas recirculation control unit starts recirculation of the exhaust gas earlier than the timing of stopping fuel injection by the time until the exhaust gas reaches the intake port. The recirculation start time of the exhaust gas is determined.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device of the internal combustion engine performs control so that the exhaust gas starts to be recirculated earlier than the timing of stopping the fuel injection by the time until the exhaust gas reaches the intake port. As a result, misfire due to the recirculation of the exhaust gas can be suppressed more reliably, and the amount of air mixed into the exhaust gas taken into the combustion chamber can be further reduced. As a result, it is possible to further suppress the deterioration of the catalyst by suppressing the lean exhaust gas.

  In the internal combustion engine operation control device according to the next aspect of the present invention, when the internal combustion engine operation control device further forcibly returns from the state where the fuel injection is stopped to the state where the fuel is injected again, An air arrival time calculation unit for estimating a time for air to reach an intake port provided in the combustion chamber after air introduction into the combustion chamber is started, and the fuel cut control unit calculates the air arrival time Based on the time estimated by the unit, fuel is injected from the combustion chamber in which air reaches the intake port.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Further, the operation control device for the internal combustion engine estimates the time for the air to reach the intake port, and injects fuel in order from the combustion chamber where the air is predicted to reach the intake port. As a result, when returning from the stop of fuel injection, the occurrence of misfire due to lack of oxygen can be suppressed, and the discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  The internal combustion engine operation control apparatus according to the present invention is the internal combustion engine operation control apparatus, further comprising an introduction air amount control unit for controlling the amount of air introduced into the combustion chamber, and the air to the combustion chamber During a predetermined period after the start of introduction, a larger amount of air than the amount of air determined from the operating conditions of the internal combustion engine is introduced into the combustion chamber.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Furthermore, the internal combustion engine operation control device introduces an amount of air larger than the amount of air determined from the operating conditions of the internal combustion engine for a predetermined period after the introduction of air into the combustion chamber. As a result, exhaust gas remaining in the intake passage or the like can be scavenged, and therefore, when returning from the stop of fuel injection, misfire due to lack of oxygen can be suppressed, and discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  The operation control device for an internal combustion engine according to the next aspect of the invention provides the exhaust gas recirculation control when the operation control device for the internal combustion engine naturally returns from a state where fuel injection is stopped to a state where fuel is injected again. The unit stops the recirculation of the exhaust gas at the same time as the start of air introduction into the combustion chamber or after the start of the air introduction into the combustion chamber, and the fuel cut control unit stops the recirculation of the exhaust gas. The fuel injection from the fuel injection valve is started after a predetermined period of time has elapsed.

  Since this internal combustion engine operation control device has the same configuration as the internal combustion engine operation control device, the same operation and effect as the internal combustion engine operation control device can be obtained. Furthermore, since the operation control device of the internal combustion engine starts fuel injection after a predetermined period has elapsed after stopping the recirculation of the exhaust gas, the exhaust gas remaining in the intake passage or the like can be scavenged. As a result, in returning from the stop of fuel injection, the occurrence of misfire due to lack of oxygen can be suppressed, and the discharge of unburned fuel can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed.

  According to the internal combustion engine of the present invention, when fuel injection is stopped, the introduction of air to the internal combustion engine is stopped and the exhaust gas is recirculated to the intake side. Thereby, since the oxygen concentration of the exhaust gas introduced into the catalyst can be reduced, leaning of the exhaust gas can be suppressed and deterioration of the catalyst can be suppressed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention described below. In addition, constituent elements disclosed in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. Further, the present invention can be preferably applied to a reciprocating internal combustion engine, but is not limited thereto. The present invention is particularly preferable for an internal combustion engine mounted on a vehicle such as a passenger car, a bus, or a truck.

  In the present invention, when stopping fuel injection at the time of deceleration or the like, the exhaust gas of the internal combustion engine is recirculated to the combustion chamber. An example in which the exhaust gas of the internal combustion engine is recirculated to the intake passage of the internal combustion engine will be described below. . The present invention is not limited as long as the exhaust gas can be recirculated to the combustion chamber, and the exhaust gas may be recirculated not only from the intake passage but also from the exhaust passage of the internal combustion engine to the combustion chamber through the exhaust valve.

  When the internal combustion engine according to the first embodiment stops fuel injection at the time of deceleration or the like, the exhaust gas is recirculated to the combustion chamber via the intake passage of the internal combustion engine, and the introduction of air is stopped to introduce the catalyst into the catalyst. This is characterized in that the lean exhaust gas is prevented from being leaned and the temperature of the exhaust gas is lowered.

  FIG. 1 is an explanatory diagram illustrating one cylinder of the internal combustion engine according to the first embodiment. The internal combustion engine 1 according to the first embodiment is a spark ignition reciprocating internal combustion engine using gasoline as fuel. Further, the number of cylinders of the internal combustion engine 1 is not particularly limited. The internal combustion engine 1 is a so-called port injection type internal combustion engine and includes a port injection valve 2. The port injection valve 2 injects fuel F into an intake pipe 4i for introducing air into the combustion chamber 1b in the cylinder 1s to form an air-fuel mixture. Here, the combustion chamber 1b refers to a space in which a mixture of fuel and air burns. In a reciprocating internal combustion engine, the combustion chamber 1b is a space surrounded by the piston 5 and the cylinder head 1h in the cylinder 1s. That is, in the reciprocating internal combustion engine, the combustion chamber 1b is in the cylinder 1s. Then, the exhaust gas is recirculated into the combustion chamber 1b, the air is introduced, or the air-fuel mixture is introduced. The exhaust gas is recirculated into the cylinder 1s, the air is introduced, or the air-fuel mixture is introduced. Is synonymous with

  The intake pipe 4i is a part that forms part of the intake passage and guides the air A to the intake valve 10i. Note that the present invention is also applied to a so-called direct injection internal combustion engine in which the fuel injection is directly injected into the combustion chamber 1b in the cylinder 1s by the in-cylinder injection valve 3 indicated by the dotted line in FIG. Is applicable. The present invention can also be applied to a so-called dual port type internal combustion engine including the port injection valve 2 and the in-cylinder injection valve 3.

  The intake pipe 4i is connected to the intake passage 8i, and air is introduced from the intake passage 8i. An air cleaner 19, an air flow sensor 43, and a throttle valve 16 are arranged in the intake passage 8i from the outside air side. The throttle valve 16 includes a butterfly valve 16b. The butterfly valve 16b changes the cross-sectional area of the flow path in the throttle valve 16 to adjust the amount of air supplied to the internal combustion engine 1. The intake passage 8i is provided with a bypass passage 18 that bypasses the throttle valve 16 and flows air to the intake passage 8i. An ISC (Idling Speed Control) valve 17 is disposed in the bypass passage 18 and controls the engine speed NE of the internal combustion engine 1 at a constant time when the internal combustion engine 1 is idling.

  2A and 2B are explanatory diagrams of the electronic throttle valve. The throttle valve 16 shown in FIG. 1 has a structure in which an accelerator pedal and a butterfly valve 16b are mechanically connected, and the butterfly valve 16b is directly opened and closed by the accelerator pedal. The electronic throttle valve 16 'converts the accelerator opening into an electric signal by the accelerator opening sensor 42, and opens and closes the butterfly valve 16b by the actuator 16a while applying feedback by the throttle opening sensor 16s based on the electric signal. It is something to be made. When ISC is executed by the electronic throttle valve 16 ′, the opening speed of the butterfly valve 16b is adjusted based on the idling control signal from the engine ECU 30 to thereby determine the engine speed NE of the internal combustion engine 1 when the internal combustion engine 1 is idling. Control to be constant.

  The air flow sensor 43 measures the mass flow rate of the air A from which dust and dust have been removed by the air cleaner 19. Then, after passing through the throttle valve 16, it is introduced into the intake pipe 4 i, where an amount of fuel F corresponding to the mass flow rate is injected from the port injection valve 2. The air A and the fuel F mix with each other through the intake pipe 4i and become an air-fuel mixture that flows into the combustion chamber 1b from the intake port 11i. This air-fuel mixture is ignited and burned by a spark plug 7 which is a spark ignition means, and the pressure of the combustion gas causes the piston 5 to reciprocate. The reciprocating motion of the piston 5 is transmitted to the crankshaft 6 via the connecting rod 9, where it is converted into rotational motion and taken out as the output of the internal combustion engine 1. The air-fuel mixture after combustion becomes exhaust gas Ex and is discharged from the exhaust port 11e to the exhaust manifold 4e. The exhaust gas Ex is purified by the catalyst 12 and then discharged from the exhaust gas port 8eo through the exhaust gas passage 8e. The exhaust manifold 4e is a part of the exhaust gas passage and refers to a part that guides the exhaust gas from the exhaust gas valve 10e to a pre-catalyst, a turbocharger, and other devices.

  If the temperature of the catalyst 12 increases excessively, the purification performance of the exhaust gas Ex deteriorates. For this reason, when the temperature of the catalyst 12 exceeds a predetermined temperature, a warning is issued or the temperature of the exhaust gas Ex discharged from the internal combustion engine 1 is lowered. For use in this control, the catalyst 12 is provided with a thermometer 12t for temperature measurement.

  The exhaust gas Ex of the internal combustion engine 1 is recirculated to the intake side (for example, the intake passage 8i and the internal combustion engine 1 side from the throttle valve 16), thereby reducing the combustion speed of the internal combustion engine 1 and reducing NOx. This is called EGR (Exhaust Gas Recirculation) and is generally performed when the load on the internal combustion engine 1 is high to some extent. In the internal combustion engine 1 of the first embodiment, the exhaust gas passage 8e on the downstream side of the catalyst 12, that is, on the catalyst outlet 12o side, and the intake passage 8i are connected by the exhaust gas recirculation passage 15 to execute EGR. An exhaust gas recirculation valve (hereinafter referred to as an EGR valve) 14 is provided in the middle of the exhaust gas recirculation passage 15. Then, the EGR valve 14 is opened in a condition for executing EGR, and in other conditions, the EGR valve 14 is kept closed. Further, an exhaust gas cooler (hereinafter referred to as EGR cooler) 13 is provided in the middle of the exhaust gas recirculation passage 15, and after cooling the exhaust gas Ex, it is recirculated to the intake side of the internal combustion engine 1. Thereby, the combustion temperature of the internal combustion engine 1 can be further reduced, and the generation of NOx can be further suppressed. And since the temperature of exhaust gas Ex can be lowered | hung, deterioration of the catalyst 12 can also be suppressed.

  The operating state of the internal combustion engine 1 is controlled by an engine ECU (Electronic Control Unit) 30. The engine ECU 30 acquires outputs from a crank angle sensor 41 that detects the rotation angle of the crankshaft 6, an airflow sensor 43 that measures the intake air amount, and other various sensors. Based on the information acquired from these various sensors and the information acquired from the accelerator opening sensor 42, the operating state of the internal combustion engine 1 is controlled.

  FIG. 3 is an explanatory diagram illustrating the operation control apparatus for the internal combustion engine according to the first embodiment. The operation control method for the internal combustion engine according to the first embodiment can be realized by the operation control apparatus 20 for the internal combustion engine according to the first embodiment. The operation control device 20 for the internal combustion engine is built into the engine ECU 30. In addition, separately from engine ECU30, the operation control apparatus 20 of the internal combustion engine which concerns on this Example may be prepared, and this may be connected to engine ECU30. In realizing the operation control method for the internal combustion engine according to this embodiment, the control function of the internal combustion engine 1 provided in the engine ECU 30 may be configured so that the operation control device 20 for the internal combustion engine can be used.

  The operation control device 20 for the internal combustion engine includes a fuel cut condition determination unit 21, an EGR amount calculation unit 22, an EGR control unit 23, and a fuel cut control unit 25. These are the parts that execute the operation control method for the internal combustion engine according to this embodiment. Here, the EGR amount calculation unit 22 corresponds to the “exhaust gas recirculation amount calculation unit” in the claims, and the EGR control unit 23 corresponds to the “exhaust gas recirculation control unit” in the claims.

  The fuel cut condition determination unit 21, the EGR amount calculation unit 22, the EGR control unit 23, and the fuel cut control unit 25 are connected via an input / output port (I / O) 39 of the engine ECU 30. Thereby, the fuel cut condition determination unit 21, the EGR amount calculation unit 22, the EGR control unit 23, and the fuel cut control unit 25 are configured to exchange data in both directions. Note that data may be transmitted and received in one direction as required in the apparatus configuration (the same applies hereinafter).

  The operation control device 20 of the internal combustion engine, the processing unit 30p of the engine ECU 30, and the storage unit 30m are connected via an input / output port (I / O) 39 provided in the engine ECU 30, and mutual data is transmitted between them. Can be exchanged. As a result, the operation control device 20 of the internal combustion engine acquires the load of the internal combustion engine 1, the engine speed, and other operation control data of the internal combustion engine included in the engine ECU 30, and controls the operation control device 20 of the internal combustion engine of the engine ECU 30. It is possible to interrupt the operation control routine of the internal combustion engine.

  The input / output port (I / O) 39 is connected to an accelerator opening sensor 42, a thermometer 12t, and other sensors for acquiring information related to the operation of the internal combustion engine 1. Thereby, the engine ECU 30 and the operation control device 20 of the internal combustion engine can acquire information necessary for operation control of the internal combustion engine 1. The input / output port (I / O) 39 is connected to the EGR valve 14, the ISC valve 17, and other control targets of the internal combustion engine 1, and the EGR control unit 23 included in the operation control device 20 of the internal combustion engine, These operations are controlled by a control signal from the processing unit 30p of the engine ECU 30.

  The storage unit 30m stores a computer program including a processing procedure of the operation control method of the internal combustion engine according to this embodiment, a data map of a fuel injection amount used for operation control of the internal combustion engine 1, and the like. Here, the storage unit 30m can be configured by a volatile memory such as a RAM (Random Access Memory), a nonvolatile memory such as a flash memory, or a combination thereof. Further, the operation control device 20 of the internal combustion engine and the processing unit 30p of the engine ECU 30 can be configured by a memory and a CPU.

  The computer program can realize the processing procedure of the operation control method of the internal combustion engine according to this embodiment by combining with the computer program already recorded in the fuel cut condition determination unit 21, the EGR amount calculation unit 22, and the like. There may be. The internal combustion engine operation control device 20 uses functions of a fuel cut condition determination unit 21, an EGR amount calculation unit 22, an EGR control unit 23, and a fuel cut control unit 25 using dedicated hardware instead of the computer program. It may be realized. Next, a procedure for realizing the operation control method for the internal combustion engine according to this embodiment using the operation control device 20 for the internal combustion engine will be described. In this description, please refer to FIGS.

  FIG. 4 is a flowchart illustrating a procedure of the operation control method for the internal combustion engine according to the first embodiment. When the internal combustion engine operation control method according to the first embodiment is executed, the fuel cut condition determination unit 21 included in the internal combustion engine operation control device 20 determines whether or not a condition for stopping fuel injection is satisfied ( Step S101). When stopping fuel injection, the oxygen concentration tends to be high and a high temperature lean state is likely to occur. For this reason, the catalyst 12 is likely to deteriorate when the fuel injection is stopped. Therefore, at least when the fuel injection is stopped, the operation control method for the internal combustion engine according to the first embodiment is executed.

  Note that the exhaust gas temperature increases as the load on the internal combustion engine 1 increases. Therefore, when stopping the fuel injection in a region where the load of the internal combustion engine 1 is high, it is preferable to execute the operation control method for the internal combustion engine according to the first embodiment, because deterioration of the catalyst 12 can be effectively suppressed. Examples of such cases include a case where the accelerator is closed and decelerated during high-speed traveling, and a case where the accelerator is returned while climbing up with a large accelerator opening. Alternatively, there is deceleration from the WOT (Wide Open Throttle) area. When the fuel injection to the internal combustion engine 1 is stopped in such a state, the exhaust gas of the internal combustion engine 1 becomes a high temperature lean. When the exhaust gas that has become lean at high temperature is introduced into the catalyst 12, the deterioration of the catalyst 12 proceeds quickly. For this reason, the operation control method for the internal combustion engine according to the first embodiment suppresses the lean exhaust gas from becoming high temperature. When the internal combustion engine 1 is in a high load operation and the fuel injection stop condition is not satisfied (step S101; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 0. In response to the fuel cut flag F1 becoming 0, the fuel cut control unit 25 does not stop the fuel injection.

  If the condition for stopping fuel injection is satisfied (step S101; Yes), the fuel cut condition determination unit 21 determines whether or not the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S102). This is because when the catalyst temperature θc is low, the deterioration of the catalyst 12 hardly progresses even when lean exhaust gas is introduced into the catalyst 12. When the catalyst temperature θc is lower than the predetermined temperature θb (step S102; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1. The fuel cut control unit 25 stops the fuel injection to the internal combustion engine 1 when the fuel cut flag F1 becomes 1 (step S105). Thereby, control can be simplified. Note that the EGR control according to the first embodiment may be executed even when the catalyst temperature θc is lower than the predetermined temperature θb.

  When the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S102; Yes), the amount of exhaust gas recirculated by the EGR amount calculation unit (exhaust gas recirculation amount calculation unit) 22 from the intake side of the internal combustion engine 1 to the combustion chamber 1b is determined. Determination (step S103) and the opening degree of the EGR valve 14 are determined. The amount of exhaust gas to be recirculated can be determined based on the load of the internal combustion engine 1 so far, the catalyst temperature θc, and the like. In the first embodiment, the throttle valve 16 is completely closed to execute EGR and the ISC valve 17 is closed. At this time, the amount of exhaust gas may be determined so as to recirculate an amount of exhaust gas corresponding to the amount of air that flows in through the ISC valve 17 when the throttle valve 16 is closed. That is, an amount of exhaust gas approximately equal to the amount of intake air when the internal combustion engine 1 is idling is recirculated. In this way, the engine brake performance can be maintained. When the electronic throttle valve 16 ′ (see FIGS. 12 and 13) is used, an amount of exhaust gas corresponding to the air flowing through the intake passage 8i is recirculated when the butterfly valve 16b is stopped at the ISC position.

  Furthermore, if the amount of exhaust gas is determined so that an amount of exhaust gas smaller than the amount corresponding to the air flowing in from the ISC valve 17 is recirculated, the effectiveness of the engine brake can be enhanced. Further, if the amount of exhaust gas is determined so that an amount of exhaust gas larger than the amount corresponding to the air flowing in from the ISC valve 17 is recirculated, the effectiveness of the engine brake can be weakened. Thus, by adjusting the amount of exhaust gas recirculated to the intake side of the internal combustion engine 1, the effectiveness of the engine brake can be varied. It should be noted that a certain amount of exhaust gas may always be recirculated, and in this case, step S103 need not be executed.

  When changing the amount of exhaust gas recirculated to the intake side of the internal combustion engine 1 to change the effectiveness of the engine brake, for example, it may be linked with the collision prevention control. Specifically, when a collision with a preceding vehicle is about to occur, the braking device is automatically activated to reduce the output of the internal combustion engine 1, but at that time, the amount corresponding to the air flowing in from the ISC valve 17 To recirculate a small amount of exhaust gas. This increases the effectiveness of engine braking and avoids rear-end collisions more quickly. Further, for example, when it is determined that the vehicle is going downhill based on information from a car navigation system or the like, an amount of exhaust gas smaller than the amount corresponding to the air flowing in from the ISC valve 17 is recirculated to increase the effectiveness of the engine brake. May be.

  When the amount of exhaust gas to be recirculated to the intake side of the internal combustion engine 1 is obtained (step S103), the EGR control unit (exhaust gas recirculation control unit) 23 opens the EGR valve 14 to recirculate the exhaust gas of the internal combustion engine 1 to the intake side. The ISC valve 17 is closed (step S104). When using the electronic throttle valve 16 '(see FIGS. 2-1 and 2-2), the butterfly valve 16b is not stopped at the ISC position, but the intake passage 8i is completely blocked by the butterfly valve 16b. Thereby, the amount of air flowing in from the intake port 11i of the internal combustion engine 1 is set to 0, and the intake of air can be stopped. And only the exhaust gas of the internal combustion engine 1 can be recirculated. That is, the EGR rate can be almost 100%. Here, the EGR rate is the ratio of exhaust gas to the total gas introduced into the cylinder 1s of the internal combustion engine 1.

  Thus, for example, when stopping fuel injection during deceleration or the like, the exhaust gas is recirculated with an EGR rate of approximately 100%, so that the oxygen concentration contained in the exhaust gas flowing to the catalyst 12 can be extremely low. Further, the exhaust gas temperature can be lowered by the reflux of the exhaust gas. Thereby, deterioration of the catalyst 12 can be suppressed by suppressing the exhaust gas from becoming high temperature lean. The EGR cooler 13 can lower the temperature of the exhaust gas to be recirculated. In addition, when the amount of air flowing in from the intake port 11i of the internal combustion engine 1 is set to 0, the combustion chamber 1b has a negative pressure, and so-called oil drop may occur. However, it is possible to suppress the negative pressure in the combustion chamber 1b from becoming too large due to the recirculation of the exhaust gas, and therefore it is possible to suppress the oil drop.

  Further, by stopping the introduction of air, it is possible to recirculate exhaust gas in which leaning is suppressed, that is, the oxygen concentration is extremely low. As a result, deterioration of the catalyst 12 can be suppressed, so that the exhaust gas may be recirculated from the upstream (catalyst inlet 12i side) of the catalyst 12 or may be recirculated from the downstream (catalyst outlet 12o side). As a result, since the degree of freedom in handling the exhaust gas recirculation passage 15 is increased, the degree of freedom in layout when the internal combustion engine 1 is mounted on a vehicle is improved.

  As in the first embodiment, when the exhaust gas Ex discharged from the catalyst 12, that is, from the outlet 12 o of the catalyst 12, is recirculated to the intake side (more specifically, the intake passage 8 i) of the internal combustion engine 1, The purified exhaust gas can be recirculated to the intake side of the internal combustion engine 1. Thereby, since the contamination of the EGR valve 14 can be suppressed, deterioration with time of the EGR valve 14 can also be suppressed. Further, the atmosphere of the catalyst 12 may flow through the exhaust gas passage 8e. However, if the exhaust gas is recirculated from the downstream of the catalyst 12, the air flowing into the catalyst 12 from the exhaust gas passage 8e can be extremely reduced. Thereby, deterioration of the catalyst 12 due to oxygen contained in the atmosphere can be suppressed.

  When the EGR is started and the ISC valve 17 is closed (step S104), the EGR control unit 23 sets the EGR start flag F2 to 1. In response to the EGR start flag F2 becoming 1, the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1. In response to the fuel cut flag F1 being set to 1, the fuel cut control unit 25 stops the fuel injected into the internal combustion engine 1 (step S105). Thereby, the fuel consumption of the internal combustion engine 1 can be reduced. As described above, the fuel cut flag F1 functions as a command used to stop fuel injection to the internal combustion engine 1.

  As described above, according to the first embodiment, when the fuel injection is stopped, the introduction of air into the internal combustion engine is stopped and the exhaust gas is recirculated from the intake side to the combustion chamber. Thereby, since the oxygen concentration of the exhaust gas introduced into the catalyst 12 can be reduced, the leaning of the exhaust gas can be suppressed and deterioration of the catalyst 12 can be suppressed. In addition, since the temperature of the exhaust gas introduced into the catalyst 12 can be lowered by the reflux of the exhaust gas, the exhaust gas can be prevented from being leaned at a high temperature and deterioration of the catalyst 12 can be suppressed. Moreover, since fuel injection to the internal combustion engine is stopped when the exhaust gas is recirculated, fuel consumption can be suppressed. The configuration of the first embodiment can also be applied as appropriate in the following embodiments. Moreover, what has the same structure as Example 1 has the effect | action and effect similar to Example 1. FIG.

  The second embodiment has substantially the same configuration as the first embodiment, but the exhaust gas is introduced into the combustion chamber by predicting the time from the start of EGR until the exhaust gas reaches the intake port of the internal combustion engine. The difference is that fuel injection to the cylinder is stopped immediately before. Since other configurations are the same as those of the first embodiment, the description thereof is omitted and the same components are denoted by the same reference numerals.

FIG. 5 is a conceptual diagram showing piping of the internal combustion engine 1. A method for estimating the time until the exhaust gas Ex reaches the intake port 11i of the internal combustion engine 1 (hereinafter referred to as exhaust gas arrival time) will be described with reference to FIG. If the distance from the EGR valve 14 to the intake port 11i of the internal combustion engine 1 is L, it can be expressed as L = X ₁ + X ₂ . When the arrival time (exhaust gas arrival time) from the outlet 14o of the EGR valve 14 to the intake port 11i of the internal combustion engine 1 is T, the exhaust gas arrival time T is expressed as a function of the L and the intake pipe pressure P. be able to. That is, T = f (L, P). The L is a constant that is uniquely determined when a cylinder is determined. Therefore, the exhaust gas arrival time T = f (P). Here, the intake pipe pressure P can be obtained based on the engine speed NE of the internal combustion engine 1 and the opening degree VO of the EGR valve 14. That is, P = f (NE, VO). In the second embodiment, the exhaust gas arrival time T is estimated based on the start of EGR, that is, when the EGR valve 14 is opened.

  FIG. 6 is an explanatory diagram illustrating an operation control apparatus for an internal combustion engine according to the second embodiment. The internal combustion engine operation control method according to the second embodiment can be realized by the internal combustion engine operation control device 20a according to the second embodiment. The operation control device 20a for the internal combustion engine according to the second embodiment has substantially the same configuration as the operation control device 20 for the internal combustion engine according to the first embodiment, but instead of the EGR amount calculation unit 22 or an EGR amount calculation unit. In addition to 22, the difference is that an exhaust gas arrival time calculation unit 24 is provided.

  The exhaust gas arrival time calculation unit 24 is connected via an input / output port (I / O) 39 of the engine ECU 30a. The other configuration is the same as that of the operation control apparatus 20 for the internal combustion engine, and therefore the contents described in the first embodiment should be referred to as appropriate. The EGR amount calculation unit 22 included in the operation control apparatus 20 for the internal combustion engine according to the first embodiment may be included in the operation control apparatus 20a for the internal combustion engine according to the second embodiment as necessary. Next, a procedure for realizing the operation control method for the internal combustion engine according to the second embodiment using the operation control device 20a for the internal combustion engine will be described. In this description, please refer to FIG. 1 as appropriate.

  FIG. 7 is a flowchart illustrating the procedure of the operation control method for the internal combustion engine according to the second embodiment. When the internal combustion engine operation control method according to the second embodiment is executed, the fuel cut condition determination unit 21 included in the internal combustion engine operation control device 20 determines whether or not a condition for stopping fuel injection is satisfied ( Step S201). When the fuel injection stop condition is not satisfied (step S201; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 0. In response to the fuel cut flag F1 becoming 0, the fuel cut control unit 25 does not stop the fuel injection.

  When the condition for stopping fuel injection is satisfied (step S201; Yes), the fuel cut condition determination unit 21 determines whether or not the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S202). When the catalyst temperature θc is lower than the predetermined temperature θb (step S202; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1. The fuel cut control unit 25 stops the fuel injection to the internal combustion engine 1 when the fuel cut flag F1 becomes 1 (step S212).

  When the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S202; Yes), the EGR control unit 23 opens the EGR valve 14 to recirculate the exhaust gas of the internal combustion engine 1 from the intake side to the combustion chamber 1b, and at the same time, the ISC. The valve 17 is closed (step S203). Thereby, only the exhaust gas of the internal combustion engine 1 can be recirculated by setting the air flowing from the intake port of the internal combustion engine to substantially zero. That is, the EGR rate can be almost 100%. As described in the first embodiment, the operation control device 20a for the internal combustion engine according to the second embodiment is provided with the EGR amount calculation unit 22, and the EGR amount calculation unit 22 is connected to the intake side of the internal combustion engine 1. The amount of exhaust gas to be refluxed may be obtained.

  When EGR is started and the ISC valve 17 is closed (step S203), the EGR control unit 23 determines whether the ISC valve 17 is fully closed and the EGR valve 14 is at the target opening degree (step S204). . When the ISC valve 17 is fully closed and the EGR valve 14 is not at the target opening (step S204; No), the process waits until the ISC valve 17 is fully closed and the EGR valve 14 is at the target opening.

  When the ISC valve 17 is fully closed and the EGR valve 14 reaches the target opening degree (step S204; Yes), the EGR control unit 23 sets the EGR start flag F2 to 1. The exhaust gas arrival time calculation unit 24 determines whether or not the exhaust gas arrival count number Cex has already been set (step S205). If the exhaust gas arrival count number Cex has already been set (step S205; Yes), the process proceeds to subtraction of the exhaust gas arrival count number Cex (after step S209).

  When the exhaust gas arrival count number Cex has not been set (step S205; No), the exhaust gas arrival time calculation unit 24 receives the fact that the EGR start flag F2 is 1 and uses the time when EGR is started as a reference. The exhaust gas arrival time T until the exhaust gas Ex reaches the intake port 11i of the internal combustion engine 1 is calculated. FIGS. 8A, 8B, and 8C are explanatory diagrams illustrating an example of a calculation map used when calculating the time until the exhaust gas reaches the intake port of the internal combustion engine. The calculation map 50 and the like shown in these drawings are stored in the storage unit 30m of the engine ECU 30a. The exhaust gas arrival time calculation unit 24 acquires the engine speed NE of the internal combustion engine 1 and the opening degree VO of the EGR valve 14 from the sensors of the internal combustion engine 1.

  Then, the exhaust gas arrival time calculation unit 24 gives the acquired engine speed NE and the opening degree VO of the EGR valve 14 to the calculation map 50 (FIG. 8-1) stored in the storage unit 30m of the engine ECU 30A. Then, the intake pipe pressure P at that time is acquired. Since the exhaust gas arrival time T is obtained as a function of the intake pipe pressure P, this function T = f (P) is stored in the storage unit 30m, and the exhaust gas arrival time calculation unit 24 uses the function T = f (P). The exhaust gas arrival time T can be obtained by applying the intake pipe pressure P obtained to the above. It should be noted that the exhaust gas arrival time T may be directly obtained from the engine speed NE of the internal combustion engine 1 and the opening degree VO of the EGR valve 14 as in a calculation map 51 shown in FIG. The calculation maps 50 and 51 can be obtained in advance by experiments or calculations. Moreover, you may make it obtain | require exhaust gas arrival time T directly from the intake pipe pressure P like the calculation map 52 shown to FIGS. 8-3. In the second embodiment, the exhaust gas arrival time T is obtained from the calculation map 52.

  In calculating the exhaust gas arrival time T, the exhaust gas arrival time calculation unit 24 acquires the intake pipe pressure P from the intake pipe pressure sensor 44 in response to the EGR start flag F2 being set to 1 (step S206). Then, the exhaust gas arrival time calculation unit 24 gives the acquired intake pipe pressure P and the engine speed NE of the internal combustion engine 1 to the calculation map 52, and acquires the exhaust gas arrival time T at that time (step S207).

FIG. 9A is an explanatory diagram illustrating a distance from an EGR valve to an intake port in an internal combustion engine having a plurality of cylinders. As shown in FIG. 9A, in the internal combustion engine 1 having a plurality of cylinders (four cylinders in this example), the lengths of the intake pipes 4 ₁ to _{4 4} are different for each cylinder 1s _{1 to} 1s ₄ . That is, when the distance from the EGR valve 14 in the first cylinder 1s ₁ to the intake port 11i ₁ and L _1, it can be expressed by _{L 1 = X + Y + Z} 1. Similarly, in the second cylinder 1s ₂ at _{L 2 = X + Y + Z} 2, the third cylinder 1s ₃ in _{L 3 = X + Y + Z} 3, the fourth in-cylinder _{1s 4 L 4 = X + Y} + Z 4. Thus, when the distances from the EGR valve 14 to the intake ports 11i ₁ to 11i ₄ are different among the cylinders, the exhaust gas arrival time T is also different for each cylinder.

FIG. 9-2 is an explanatory diagram showing a case where EGR is executed in an internal combustion engine having a plurality of cylinders. As already described, the internal combustion engine 1 having a plurality of cylinders has different exhaust gas arrival times for each cylinder, that is, for each combustion chamber of each cylinder. Further, the progress of exhaust gas may vary depending on the timing of opening the EGR valve 14 and the position of the piston of each cylinder. For example, in the example shown in FIG. 9B, the exhaust gas has already reached the third intake port 11i ₃ although the exhaust gas has not yet been introduced into the third cylinder 1s ₃ . Therefore, in the next intake stroke of the third cylinder 1s _3, exhaust gas is introduced into the combustion chamber of the third cylinder 1s _3. In this case, fuel injection to the third cylinder 1s ₃ is stopped. Thereby, it is suppressed that air mixes with the exhaust gas recirculated, suppressing misfire by EGR.

The first cylinder 1s ₁ is a cylinder in which exhaust gas is not introduced into the combustion chamber, and is a cylinder into which exhaust gas is introduced after several cycles. In this case, fuel is injected from the port injection valve 2 ₁ (FIG. 9-2) to the first cylinder 1s ₁ (FIG. 9-2), and all the air A remaining in the first intake pipe 4 ₁ is combusted. Let When the internal combustion engine 1 includes an in-cylinder injection valve, fuel is injected from the in-cylinder injection valve 3 ₁ of the first cylinder 1s ₁ . As a result, the exhaust gas is prevented from becoming lean, and deterioration of the catalyst 12 is suppressed. When the exhaust gas having an EGR rate of approximately 100% reaches the first intake port 11i ₁ and the exhaust gas is introduced into the combustion chamber of the first cylinder 1s _{1 in} the next intake stroke, the first The fuel injection to the cylinder 1s ₁ is stopped. Thereby, it is suppressed that air mixes with the exhaust gas recirculated, suppressing misfire by EGR. When the internal combustion engine 1 includes an in-cylinder injection valve, fuel is injected from the in-cylinder injection valve 3 ₁ of the first cylinder 1s ₁ .

On the other hand, the second cylinder 1s ₂ is a cylinder in which exhaust gas has already been introduced into the combustion chamber, and this exhaust gas is exhaust gas immediately after the EGR valve 14 is opened and the ISC valve 17 is closed. For this reason, the exhaust gas introduced into the second cylinder 1s ₂ may contain air. In this case, fuel is injected from the port injection valve 2 ₂ (FIG. 9-2) to the second cylinder 1s ₂ to burn exhaust gas that may contain air. Then, fuel injection to the second cylinder 1s ₂ is stopped from the next intake stroke. As a result, the lean exhaust gas can be suppressed, and the exhaust gas with a very small amount of oxygen can be sent to the catalyst 12 and recirculated to the intake side. Moreover, since it can also suppress that unburned raw gas is discharged | emitted, while improving an emission, deterioration of the catalyst 12 can also be suppressed.

The time when exhaust gas reaches the intake port can be predicted from the exhaust gas arrival time T. Since the crank angle sensor 41 of the internal combustion engine 1 can determine which stroke each cylinder is in, the fuel injection is stopped with respect to the cylinder in which the exhaust gas reaches the intake port and the exhaust gas can be taken into the combustion chamber in the intake stroke. To do. The fuel cut control unit 25 determines from the exhaust gas arrival time T and the signal of the crank angle sensor 41 whether or not it is time to inject fuel after the exhaust gas Ex reaches the intake port 11i ₁ or the like for each cylinder. judge. That is, a value (exhaust gas arrival crank angle) obtained by adding a crank angle corresponding to the obtained exhaust gas arrival time T to the current crank position obtained from a signal from the crank angle sensor 41 or the like is calculated. Then, the fuel injection is stopped from the cylinder in which the fuel injection stop is in time at the obtained exhaust gas reaching crank angle.

  Further, the cylinder in which the exhaust gas reaches the intake port and the exhaust gas can be taken into the combustion chamber during the intake stroke may be determined as follows. The second embodiment determines a cylinder that can take exhaust gas into the combustion chamber by this method. First, the exhaust gas arrival time calculation unit 24 sets the exhaust gas arrival count number Cex (step S208). The exhaust gas arrival count Cex can be obtained by a value (T / Tc) obtained by dividing the exhaust gas arrival time T by the crank movement time Tc. That is, it is a determination parameter for the exhaust gas arrival time when the engine speed of the internal combustion engine 1 is taken into consideration. Here, the crank movement time Tc refers to the time required for the crankshaft 6 to rotate at a predetermined angle. For example, it is the time required for the crank angle to rotate a degrees. Note that the predetermined crank angle a used when setting the crank movement time Tc is set to an appropriate value in consideration of determination accuracy, hardware resolution, and the like.

  When the exhaust gas arrival count number Cex is set (step S208), the fuel cut condition determination unit 21 subtracts the exhaust gas arrival count number Cex. In the second embodiment, the exhaust gas arrival count number Cex is subtracted by 1 (step S209). The subtraction is continued until the exhaust gas arrival count Cex becomes 0 (step S210). When the exhaust gas arrival count Cex becomes 0 (step S210; Yes), the fuel cut condition determination unit 21 sets the fuel cut flag F1 to 1 for the cylinder (step S211). In other words, the fuel cut condition determination unit 21 generates the fuel cut flag F1 = 1 for the cylinder in which the exhaust gas reaches the intake port and the exhaust gas can be taken into the combustion chamber during the intake stroke.

  Here, the fuel injection execution routine for determining the fuel injection timing and executing the fuel injection is facilitated separately. In this fuel injection execution routine, since the cylinder for injecting fuel has been determined, the fuel is injected when the cylinder for injecting fuel comes at the fuel injection timing. When the fuel injection timing of a cylinder for injecting fuel is 0, if the fuel cut flag F1 for that cylinder is 0, fuel is injected for that cylinder and the fuel cut flag F1 for that cylinder is set to 1. If so, fuel injection to that cylinder is stopped.

  The fuel cut control unit 25 refers to the value of the fuel cut flag F1 when executing the control of the fuel injection execution routine. Then, in response to the fact that the fuel cut flag F1 is set to 1, the processing unit 30p performs fuel injection at the time when the combustion chamber of the cylinder, that is, the fuel cut condition determination unit 21 sets the fuel cut flag F1 to 1. Control is performed so as to stop the fuel injection to the combustion chamber of the cylinder in time to stop the operation (step S212). The fuel cut condition determination unit 21 sets the fuel cut flag F1 to 0 for the combustion chamber of the cylinder not in this timing, that is, the combustion chamber of the cylinder where the exhaust gas has not reached the intake port. In response to the fact that the fuel cut flag F1 is 0, the fuel cut control unit 25 injects fuel into the cylinder where the exhaust gas has not reached the intake port, and burns the air in the intake pipe 4i.

  As described above, according to the second embodiment, when the fuel injection is stopped, the exhaust gas is recirculated with the EGR rate being almost 100%. Therefore, the amount of oxygen contained in the recirculated exhaust gas can be extremely reduced. Further, the exhaust gas temperature can be lowered by the reflux of the exhaust gas. Thereby, the high temperature lean of exhaust gas can be suppressed and deterioration of the catalyst 12 can also be suppressed. Furthermore, the time for exhaust gas to reach the intake port is predicted, and fuel injection is stopped immediately before the exhaust gas is introduced into the combustion chamber during the intake stroke. Thereby, while suppressing the misfire by the recirculation | reflux of waste gas, it can suppress that air mixes in the waste gas to recirculate | reflux. As a result, it is possible to more reliably suppress the lean exhaust gas and suppress the deterioration of the catalyst 12.

(Modification)
The modification of the second embodiment has substantially the same configuration as that of the second embodiment, but the exhaust gas arrival time from the start of EGR until the exhaust gas reaches the intake port of the internal combustion engine is predicted. The difference is that the opening time of the EGR valve is determined so that the fuel injection can be stopped after reaching. More specifically, the start time of EGR is determined so that EGR is started earlier by the exhaust gas arrival time than the timing of stopping fuel injection for a certain cylinder. Since other configurations are the same as those of the first embodiment, the description thereof is omitted and the same components are denoted by the same reference numerals. Next, a procedure for realizing an operation control method for an internal combustion engine according to a modification of the second embodiment will be described. The internal combustion engine operation control method according to the modification of the second embodiment can be realized by the internal combustion engine operation control device 20a according to the second embodiment. In the following description, please refer to FIG. 6 as appropriate.

  FIG. 10 is a flowchart illustrating a procedure of an operation control method for an internal combustion engine according to a modification of the second embodiment. Since steps S301 and S302 are the same as steps S201 and S202 of the operation control method for the internal combustion engine according to the second embodiment, the description thereof is omitted. When the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S302; Yes), the exhaust gas arrival time calculating unit 24 calculates the exhaust gas arrival time T until the exhaust gas Ex reaches the intake port 11i of the internal combustion engine 1 (step). S303). Since the calculation method of the exhaust gas arrival time T is the same as the method described in the second embodiment, the description thereof is omitted.

After calculating the exhaust gas arrival time T (step S303), the EGR control unit 23 determines the opening timing of the EGR valve 14 so that the fuel injection can be stopped after the exhaust gas reaches the intake port (step S304). In the internal combustion engine 1 shown in FIG. 9A, since the lengths of the intake pipes 4 ₁ to 4 ₄ are different, the exhaust gas arrival times T _{1 to} T ₄ are also different. The exhaust gas is introduced into the cylinder having the shortest exhaust gas arrival time T first. For this reason, the valve opening timing of the EGR valve 14 is determined in accordance with the cylinder having the shortest exhaust gas arrival time T. For example, the valve opening timing of the EGR valve 14 is determined so that the exhaust gas reaches the intake port of the cylinder immediately before the cylinder having the shortest exhaust gas arrival time T enters the intake stroke. The fuel injection is stopped immediately before the exhaust gas is introduced into the combustion chamber in the intake stroke.

For example, the exhaust gas arrival time of the second cylinder 1s ₂ of the internal combustion engine 1 shown in Figure 9-1 and T _2. Here, among the internal combustion engine 1, the exhaust gas arrival time T ₂ of the second cylinder 1s ₂ is the shortest. At this time, the EGR valve 14 is opened earlier than the timing of stopping the fuel injection to the second cylinder 1s ₂ by the exhaust gas arrival time T ₂ and EGR is started. The EGR control unit 23 determines the valve opening timing of the EGR valve 14 so that the EGR valve 14 is opened at such timing. Thereby, after the intake valve of the second cylinder 1s ₂ is closed (compression stroke, combustion stroke, or exhaust stroke), the exhaust gas to be recirculated to the second intake port 11i ₂ arrives. Then, before the second cylinder 1s ₂ of the intake valve is opened, it is possible to stop the fuel injection for the second cylinder 1s _2. As a result, the combustion chamber of the second cylinder 1s _2, only the exhaust gas is introduced.

Further, the exhaust gas arrival time for the cylinders other than the second cylinder 1s ₂ and the exhaust gas arrival time for the second cylinder is larger than the exhaust gas arrival time for the second cylinder. Therefore, the fuel cut control unit 25 may determine to stop the fuel injection, the termination timing of fuel injection from the fuel is injected until as possible to the combustion air remaining in the intake pipe 4 ₁ Hitoshinai . By controlling in this way, it is possible to suppress misfire due to recirculation of the exhaust gas and to prevent air from being mixed into the exhaust gas to be recirculated. Further, when the fuel injection stop is executed, it is possible to suppress the introduction of the exhaust gas into the combustion chamber.

  When the opening timing of the EGR valve 14 is determined (step S304), the EGR control unit 23 opens the EGR valve 14 to recirculate the exhaust gas of the internal combustion engine 1 to the intake side, and closes the ISC valve 17 (step S305). Thereby, the air flowing in from the intake port of the internal combustion engine is set to 0, and only the exhaust gas of the internal combustion engine 1 can be recirculated. That is, the EGR rate can be almost 100%.

Based on the exhaust gas arrival time T calculated in step S303, the time when the exhaust gas reaches the intake port can be predicted. Since the crank angle sensor 41 of the internal combustion engine 1 can determine which stroke each cylinder is in, the fuel injection is stopped with respect to the cylinder in which the exhaust gas reaches the intake port and the exhaust gas can be taken into the combustion chamber in the intake stroke. To do. The fuel cut control unit 25 determines from the exhaust gas arrival time T and the signal of the crank angle sensor 41 whether or not it is time to inject fuel after the exhaust gas Ex reaches the intake port 11i ₁ or the like for each cylinder. Determination is made (step S306).

  The fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1 for the cylinder at the timing. In response to the fuel cut flag F1 being set to 1, the fuel cut control unit 25 stops fuel injection into the combustion chamber of the cylinder (step S307). The fuel cut flag F1 is set to 0 for the combustion chambers of the cylinders not in this timing, that is, the combustion chambers of the cylinders where the exhaust gas has not reached the intake port. In response to the fact that the fuel cut flag F1 is 0, the fuel cut control unit 25 injects fuel into the cylinder where the exhaust gas has not reached the intake port, and burns the air in the intake pipe 4i.

  As described above, according to the modification of the second embodiment, when the fuel injection is stopped, the exhaust gas is recirculated with the EGR rate being almost 100%, so that the amount of oxygen contained in the exhaust gas to be recirculated can be extremely reduced. Further, the exhaust gas temperature can be lowered by the reflux. Thereby, it is possible to suppress the deterioration of the exhaust gas at a high temperature to suppress the deterioration of the catalyst 12, and it is possible to reduce the fuel consumption by stopping the fuel injection. Further, the time for exhaust gas to reach the intake port is predicted, and fuel injection is stopped immediately before the exhaust gas is introduced into the combustion chamber in the intake stroke. Thereby, while suppressing the misfire by the recirculation | reflux of waste gas, it can suppress that air mixes in the waste gas to recirculate | reflux. Further, since the opening time of the EGR valve 14 is determined using the exhaust gas arrival time T so that the fuel injection can be stopped after the exhaust gas reaches the intake port, when the fuel injection stop is executed, it is already in the combustion chamber. It is possible to suppress the introduction of exhaust gas. The configuration of the second embodiment can be appropriately applied to the following embodiments. Moreover, what has the same structure as Example 2 has an effect | action similar to Example 2, and an effect.

  The third embodiment has substantially the same configuration as the first and second embodiments. However, after the condition for stopping the fuel injection is satisfied, the amount of fuel injected into the internal combustion engine is increased after the air introduction from the intake passage is stopped. The difference is that the exhaust gas is recirculated to the combustion chamber. Since other configurations are the same as those of the first and second embodiments, the description thereof is omitted. The operation control of the internal combustion engine according to the third embodiment can be realized by the operation control device 20 (FIG. 3) of the internal combustion engine according to the first embodiment.

  FIG. 11 is a timing chart illustrating operation control of the internal combustion engine according to the third embodiment. FIGS. 12-1 to 12-5 are flowcharts illustrating the operation control procedure of the internal combustion engine according to the third embodiment. When executing the operation control of the internal combustion engine according to the third embodiment, the fuel cut condition determination unit 21 included in the operation control device 20 of the internal combustion engine determines whether or not the condition for stopping the fuel injection is satisfied (step) S401). When stopping fuel injection, the oxygen concentration tends to be high and a high temperature lean state is likely to occur. For this reason, since the catalyst 12 is likely to deteriorate when the fuel injection is stopped, the operation control method for the internal combustion engine according to the third embodiment is executed at least when the fuel injection is stopped.

  When the fuel injection stop condition is not satisfied (step S401; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 0. In response to the fuel cut flag F1 becoming 0, the fuel cut control unit 25 does not stop the fuel injection and continues normal operation control. At this time, the opening degree of the throttle valve 16 is controlled based on the accelerator opening degree detected by the accelerator opening degree sensor 42 (step S402). Further, the amount of fuel injected into the internal combustion engine 1 is not increased (step S403), and the EGR is controlled to an EGR amount (EGR amount during normal operation) determined from the operating conditions of the internal combustion engine 1 (step S404). Fuel is injected into the engine 1 (step S405), and normal operation of the internal combustion engine 1 is continued. The operation control device 20 for the internal combustion engine continues to monitor the operation state of the internal combustion engine 1.

  If the condition for stopping fuel injection is satisfied (step S401; Yes), the fuel cut condition determination unit 21 determines whether or not the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S406). This is because when the catalyst temperature θc is low, the deterioration of the catalyst 12 hardly progresses even when lean exhaust gas is introduced into the catalyst 12. When the catalyst temperature θc is lower than the predetermined temperature θb (step S406; No), the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1 (step S407). The fuel cut flag F1 = 1 may also be set when the catalyst temperature θc is lower than the predetermined temperature θb. When the catalyst temperature θc is equal to or higher than the predetermined temperature θb (step S406; Yes), the fuel cut condition determination unit 21 resets the delay count number C to 0 (step S408), and shifts to the first control mode. (Step S409).

  FIG. 12-2 shows the first control mode. In the first control mode, after the supply of air to the internal combustion engine 1 is stopped, control is performed so as to shift to the second control mode after the first predetermined period has elapsed. Here, the second control mode is a control mode in which the amount of fuel injected into the internal combustion engine 1 is increased.

  Even when the supply of air to the internal combustion engine 1 is stopped by closing the throttle valve 16 and the ISC valve valve 17, air remains in the intake passage 8 i of the internal combustion engine 1 and the surge tank provided in the intake passage 8 i. Remaining. Therefore, if the fuel injection to the internal combustion engine 1 is stopped immediately after the supply of air to the internal combustion engine 1 is stopped, the catalyst 12 deteriorates due to oxygen in the air remaining in the surge tank or the like. Therefore, after the supply of air to the internal combustion engine 1 is stopped, the amount of fuel injected into the internal combustion engine 1 is increased from that when the condition for stopping the fuel injection is satisfied, thereby remaining in the air remaining in the surge tank or the like. The exhaust gas introduced into the catalyst 12 is made rich (in a state where there is a lot of fuel) while consuming oxygen.

  Here, after the supply of air to the internal combustion engine 1 is stopped, the amount of fuel injected into the internal combustion engine 1 is increased after the first predetermined period T1 (FIG. 11) has elapsed. This is because the throttle valve 16 and the ISC valve 17 are fully closed, so that the measured value of the air amount by the air flow meter 43 becomes smaller than the actual value, and even if the throttle valve 16 and the ISC valve 17 are fully closed, the throttle valve 16 In addition, since air gradually leaks from the gaps of the ISC valve 17 and the like, the fuel is injected in consideration of these, and oxygen is sufficiently consumed. As a result, oxygen contained in the air remaining in the intake passage or the like can be consumed more sufficiently, the exhaust gas introduced into the catalyst can be made rich, and the deterioration of the catalyst can be suppressed.

  In executing the first control mode, the fuel cut condition determination unit 21 determines whether or not the first predetermined period T1 has elapsed after stopping the supply of air to the internal combustion engine 1 (step S410). . The first predetermined time T1 may be a predetermined value adapted in advance by an experiment, or may be a map of the engine speed NE of the internal combustion engine 1. Further, the first predetermined period T1 may be after the supply of air to the internal combustion engine 1 is stopped and until the oxygen concentration sensor 45 disposed downstream of the catalyst 12 detects the exhaust gas lean. In Example 3, when the delay count C reaches a value corresponding to the first predetermined time T1, it is determined that the first predetermined period T1 has been reached. Here, the first predetermined time is a time considering that the oxygen concentration gradually increases due to the air leaking from the gap of the throttle valve 16 or the like.

  When the first predetermined period T1 has not elapsed (step S410; No), the fuel cut condition determination unit 21 adds the delay count number C (step S411). Next, the EGR controller (exhaust gas recirculation controller) 23 closes the throttle valve 16 and the ISC valve 17 to stop the introduction of air into the internal combustion engine 1 (step S412). At this time, the amount of fuel injected into the internal combustion engine 1 is not increased (step S413), and the EGR is controlled to an EGR amount (EGR amount during normal operation) determined from the operating conditions of the internal combustion engine 1 (step S414). Further, the fuel injection to the internal combustion engine 1 is not stopped, and the fuel is injected with the same injection amount as when the fuel injection stop condition is satisfied (step S415).

  Until the first predetermined period T1 elapses after the fuel injection stop condition is satisfied, the internal combustion engine 1 is injected and ignited with the same fuel injection amount as before the fuel injection stop condition is satisfied. . At this time, the ignition timing of the internal combustion engine 1 may be retarded from before the fuel injection stop condition is satisfied (ignition retarded in FIG. 11). As a result, the torque generated by the internal combustion engine 1 can be reduced, so that the engine braking by the internal combustion engine 1 works well and the feeling of deceleration is improved. The fuel cut control unit 25 executes this ignition timing control.

  Here, after the introduction of air into the internal combustion engine 1 is stopped, the EGR amount may be set to 0 (a broken line in the EGR control amount in FIG. 11) until the first predetermined period T1 elapses. After the first predetermined period T1 has elapsed, in the second control mode described later, the amount of fuel injected into the internal combustion engine 1 is increased to burn oxygen contained in the air remaining in the surge tank or the like. . In the combustion chamber 1b of the internal combustion engine 1, the mixed gas of air and exhaust gas remaining in the surge tank or the like is combusted. At this time, if the exhaust gas is recirculated to the intake passage 8i, the negative pressure in the intake passage 8i. As the air pressure increases, the concentration of exhaust gas in the intake passage 8i increases. As a result, the oxygen concentration in the mixed gas becomes low, the mixed gas cannot be burned, and the mixed gas containing oxygen is sent to the catalyst 12.

  For this reason, after the introduction of air into the internal combustion engine 1 is stopped, the EGR amount is set to 0 until the first predetermined period T1 elapses. As a result, an increase in the concentration of exhaust gas in the intake passage 8i can be suppressed, so that a period during which oxygen contained in the air remaining in the intake passage 8i and the surge tank can be burned (a second predetermined period T2 described later) is long. Become. As a result, more oxygen contained in the air remaining in the surge tank or the like can be consumed, so that oxygen contained in the exhaust gas sent to the catalyst 12 can be further reduced, and deterioration of the catalyst 12 can be further suppressed. This control is executed by the EGR control unit 23.

  The steps S411 to S415 are repeated until the first predetermined time T1 has elapsed. When the first predetermined period T1 has elapsed (step S410; Yes), the fuel cut condition determination unit 21 resets the delay count number C to 0 (step S416), and shifts to the second control mode (step S417). ).

  FIG. 12-3 shows the second control mode. The second control mode is a control mode in which the amount of fuel injected into the internal combustion engine 1 is increased after the first predetermined period has elapsed after the supply of air to the internal combustion engine 1 is stopped. By burning the fuel, oxygen in the air remaining in the surge tank and the intake passage 8i is consumed, and the exhaust gas with little oxygen, that is, in a rich state is introduced into the catalyst 12. Thereby, deterioration of the catalyst 12 is suppressed.

  In executing the second control mode, the fuel cut condition determination unit 21 determines whether or not the second predetermined period T2 (FIG. 11) has elapsed (step S418). When the introduction of air into the internal combustion engine 1 is stopped, the negative pressure in the intake passage 8i becomes too large, and this needs to be suppressed. For this reason, the exhaust gas having a predetermined predetermined EGR amount is recirculated to the intake passage 8i (resulting in the combustion chamber 1b) (FIG. 11). The EGR amount at this time is larger than the EGR amount during the normal operation (FIG. 11).

  However, since the exhaust gas hinders the consumption of oxygen in the air remaining in the surge tank and the intake passage 8i due to the combustion of the fuel, a predetermined amount of exhaust gas after the second predetermined period T2 has elapsed. To reflux. Here, the second predetermined time T2 is a time in consideration of preventing excessive exhaust gas from being introduced and obstructing combustion in the internal combustion engine due to an excessive increase in the EGR rate due to negative pressure. is there. The second predetermined time T2 may be a predetermined value adapted in advance by experiment, or may be a map of the engine speed NE of the internal combustion engine 1. The second predetermined period T2 may be a period from when the fuel injection amount is increased until the pressure in the intake passage 8i reaches a predetermined value. Since a certain delay time is required for the time from when the EGR valve 14 is opened until the exhaust gas due to EGR reaches the combustion chamber 1b, the second predetermined period T2 is set shorter than the delay time.

  When the second predetermined period T2 has not elapsed (step S418; No), the fuel cut condition determination unit 21 adds the delay count number C (step S419). Next, the EGR control unit (exhaust gas recirculation control unit) 23 closes the throttle valve 16 and closes the ISC valve 17 to maintain the state where the introduction of air into the internal combustion engine 1 is stopped (step S420). At this time, the fuel cut control unit 25 injects the fuel to be injected into the internal combustion engine 1 in a larger amount than when the fuel injection stop condition is satisfied (step S421). As a result, oxygen in the air remaining in the surge tank and the intake passage 8i is consumed.

  It should be noted that by increasing the amount of fuel injected into the internal combustion engine 1 more than when the condition for stopping fuel injection is satisfied, a period during which oxygen in the air remaining in the surge tank or the intake passage 8i is consumed (that is, the second time Until the predetermined period T2 elapses), the ignition timing of the internal combustion engine 1 may be retarded from before the fuel injection stop condition is satisfied. As a result, the torque generated by the internal combustion engine 1 can be reduced, so that the engine braking by the internal combustion engine 1 works well and the feeling of deceleration is improved. The fuel cut control unit 25 executes this ignition timing control.

  The EGR amount at this time is controlled to an EGR amount (EGR amount during normal operation) determined from the operating conditions of the internal combustion engine 1 (step S422). Note that, as in the first control mode, the EGR amount at this time may be zero. This control is executed by the EGR control unit 23. Further, as described above, the fuel injection to the internal combustion engine 1 is executed with an increased amount than when the condition for stopping the fuel injection is satisfied (step S423). Steps S419 to S423 are repeated until the second predetermined time T2 has elapsed. When the second predetermined period T2 has elapsed (step S418; Yes), the fuel cut condition determination unit 21 resets the delay count number C to 0 (step S424), and shifts to the third control mode (step S425). ).

  FIG. 12-4 shows the third control mode. In the third control mode, the exhaust gas of the EGR amount at the time of fuel stop, which is larger than the EGR amount during the normal operation, is recirculated to the intake passage 8i (as a result, the combustion chamber 1b). This is because if the introduction of air into the internal combustion engine 1 is stopped, the negative pressure in the intake passage 8i becomes too large, and this needs to be suppressed. As a result, it is possible to suppress the oil rising of the internal combustion engine 1 and the like, and the vehicle equipped with the internal combustion engine 1 can obtain an engine brake having an appropriate effect.

  In executing the third control mode, the fuel cut condition determination unit 21 determines whether or not the third predetermined period T3 (FIG. 11) has elapsed (step S426). When the EGR amount is set to the predetermined EGR amount, a large amount of exhaust gas flows into the combustion chamber 1b of the internal combustion engine 1, and as a result, combustion becomes impossible. For this reason, it is preferable to stop the fuel injection from the cylinder where combustion is impossible. By waiting for the third predetermined period T3 when executing the third control mode, the air remaining in the intake passage is combusted in the combustion chamber, and the exhaust gas increases to increase the exhaust gas. Fuel injection can be stopped from the combustion chamber where the remaining air cannot burn.

  Here, a certain amount of response delay time is required for the time from when the EGR valve 14 is opened until the exhaust gas due to EGR reaches the combustion chamber 1b. In the third embodiment, this response delay time is set as a third predetermined time T3. And in the 4th control mode mentioned later, the fuel injection to the internal combustion engine 1 is stopped from the combustion chamber 1b where the exhaust gas by EGR reached after the EGR valve 14 opened. The response delay time can be obtained by the method described in the first embodiment. The third predetermined time T3 may be a predetermined value adapted in advance by experiment, or may be a map of the engine speed NE of the internal combustion engine 1. In addition, the third predetermined period T3 may be a time from when the combustion state is monitored by a combustion pressure sensor, a combustion ion current sensor or the like to start exhaust gas recirculation until the combustion deteriorates.

  When the third predetermined period T3 has not elapsed (step S426; No), the fuel cut condition determination unit 21 adds the delay count number C (step S427). Next, the EGR control unit (exhaust gas recirculation control unit) 23 closes the throttle valve 16 and also closes the ISC valve 17 to maintain a state where the introduction of air into the internal combustion engine 1 is stopped (step S428). At this time, the fuel cut control unit 25 increases the amount of fuel injected into the internal combustion engine 1 more than when the fuel injection stop condition is satisfied (step S429). As a result, oxygen in the air remaining in the surge tank and the intake passage 8i is consumed.

  The EGR amount at this time is set to the EGR amount when fuel injection is stopped (> the EGR amount during normal operation) (step S430). The EGR amount when the fuel injection is stopped is calculated by the EGR amount calculation unit 22, and the EGR control unit 23 drives the EGR valve 14. Further, as described above, the fuel injection to the internal combustion engine 1 is executed with an increased amount than when the condition for stopping the fuel injection is satisfied (step S431). Steps S426 to S431 are repeated until the third predetermined time T3 has elapsed. When the third predetermined period T3 has elapsed (step S426; Yes), the process proceeds to the fourth control mode (step S432).

  When the exhaust gas is recirculated to the combustion chamber 1b of the internal combustion engine 1 with the EGR amount when the fuel is stopped, the amount of fuel injected into the internal combustion engine 1 is increased by increasing the amount of fuel compared to when the fuel injection stop condition is satisfied. Oxygen in the air remaining in the tank and the intake passage 8i is consumed. The ignition timing of the internal combustion engine 1 at this time may be retarded from before the fuel injection stop condition is satisfied. As a result, the torque generated by the internal combustion engine 1 can be reduced, so that the engine braking by the internal combustion engine 1 works well and the feeling of deceleration is improved. The fuel cut control unit 25 executes this ignition timing control.

  FIG. 12-5 illustrates the fourth control mode. In the fourth control mode, the fuel injection to the internal combustion engine 1 is stopped until the return condition from the fuel injection stop is satisfied, that is, until the fuel injection stop is canceled. The preparation for stopping the fuel injection to the internal combustion engine 1 is completed in the first to third control modes. In executing the fourth control mode, the fuel cut condition determination unit 21 determines whether a return condition from the stop of fuel injection (F / C) is satisfied (step S433).

  When the return condition from the stop of the fuel injection is not satisfied (step S433; No), the EGR control unit (exhaust gas recirculation control unit) 23 closes the throttle valve 16 and the ISC valve 17 so that the air to the internal combustion engine 1 is The state where the introduction is stopped is maintained (step S434). At this time, the fuel cut control unit 25 sets the increase in the amount of fuel injected into the internal combustion engine 1 to 0 (step S435). The EGR amount calculation unit 22 calculates the EGR amount and sets it to the EGR amount when fuel injection is stopped (> the EGR amount during normal operation) (step S436).

  In step S406, since the fuel cut condition determination unit 21 sets the fuel cut flag F1 = 1, the fuel cut control unit 25 sets the combustion chamber 1b in which the exhaust gas has reached based on the fuel injection amount (that is, 0) set in step S435. From this, fuel injection is stopped (step S437). The steps S434 to S437 are repeated until the return condition from the stop of fuel injection is satisfied. If the exhaust gas becomes lean while the fuel injection is stopped, the fuel may be injected at that time. As a result, exhaust gas introduced into the catalyst 12 can be made rich, so that deterioration of the catalyst 12 can be suppressed. The fuel injection amount in this case can be determined by the engine speed NE of the internal combustion engine 1.

  When the return condition from the stop of the fuel injection is satisfied (step S433; Yes), the return process from the stop of the fuel injection is executed (step S438), and the series of procedures ends. Thereafter, returning to START, the operating state of the internal combustion engine 1 is monitored. By the above procedure, the amount of oxygen flowing into the catalyst 12 can be reduced as much as possible when the fuel injection to the internal combustion engine 1 is stopped.

  As described above, in the third embodiment, after the condition for stopping the fuel injection is satisfied, after the air introduction from the intake passage is stopped, the amount of fuel injected into the internal combustion engine is increased and the exhaust gas is recirculated to the combustion chamber. Thereby, after the air introduction is stopped, oxygen in the air remaining in the intake system such as the intake passage and the surge tank can be burned, so that the deterioration of the catalyst 12 can be suppressed. The configuration of the third embodiment can be applied as appropriate in the following embodiments. Moreover, what has the same structure as Example 3 has the effect | action and effect similar to Example 3. FIG.

  The fourth embodiment is control when restarting fuel injection after stopping fuel injection to the internal combustion engine. And, at the time of return from the stop of fuel injection, the time for the air introduced into the internal combustion engine to reach the combustion chamber is estimated, and the fuel injection is started from the combustion chamber where the air is expected to be introduced. There is. Here, restarting the fuel injection after stopping the fuel injection to the internal combustion engine is called returning.

  FIG. 13 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the fourth embodiment. FIG. 14 is an explanatory diagram of the operation control of the internal combustion engine according to the fourth embodiment. FIG. 15 is an explanatory diagram illustrating an operation control apparatus for an internal combustion engine according to the fourth embodiment. In the following description, please refer to FIG. 1 as appropriate. First, the control at the time of forced return will be described. Here, the forced return means a return when the accelerator is depressed while the fuel injection to the internal combustion engine 1 is stopped.

  The operation control of the internal combustion engine according to the fourth embodiment can be realized by the operation control device 20b of the internal combustion engine shown in FIG. The internal combustion engine operation control device 20b includes an EGR amount calculation unit 22 (FIG. 3) and an exhaust gas arrival time calculation unit 24 included in the internal combustion engine operation control devices 20 and 20a according to the first and second embodiments. It may be. By providing these, a series of control from the stop of fuel injection to its return can be executed.

  In executing the operation control of the internal combustion engine according to the fourth embodiment, the fuel cut condition determination unit 21 provided in the operation control device 20b of the internal combustion engine determines whether or not the forced return condition is satisfied (step S501). The forced return condition is satisfied, for example, when the accelerator is depressed when acceleration is required while fuel injection is stopped. That is, it is established when the accelerator is depressed more than a predetermined value while fuel injection is stopped. When the accelerator is depressed more than a predetermined value while the fuel injection is stopped, this operation is set as a forced return trigger Tr_r (FIG. 14).

  When the forced return condition is not satisfied (step S501; No), this control is finished. When the forced return condition is satisfied (step S501; Yes), the EGR control unit 23 closes the EGR valve 14 (step S502) and stops the exhaust gas recirculation. The EGR valve 14 is closed after the forced return trigger Tr_r is established. For this reason, the EGR valve 14 is closed with a delay of about ΔTr after the forced return trigger Tr_r is established (FIG. 14), but ΔTr can be made small enough to be regarded as almost zero.

  Thereafter, the fuel injection to the internal combustion engine 1 is resumed. In the fourth embodiment, scavenging of the exhaust gas remaining in the intake passage 8i and the surge tank is promoted, and the response delay feeling of the torque of the internal combustion engine 1 is reduced. For this reason, after the forced return trigger is established, the opening degree of the throttle valve 16 is made larger than the required opening degree of the throttle valve 16 obtained from the accelerator opening degree for a predetermined period T4 (FIG. 14). That is, a larger amount of air than the amount of air determined from the operating conditions of the internal combustion engine 1 is introduced into the combustion chamber of the internal combustion engine. In this operation control, an electronic throttle valve is assumed.

  The introduced air amount control unit 26 acquires the accelerator opening when the forcible return trigger Tr_r is established (step S503). A value obtained by adding a predetermined opening increment ΔOt to the throttle valve opening Ot determined from the accelerator opening is set as a new throttle valve opening Ot_n (= Ot + ΔOt) (step S504). As a result, more air can be introduced into the internal combustion engine 1, so that the exhaust gas remaining in the intake passage 8i and the surge tank can be effectively scavenged.

  Next, the air arrival time calculation unit 27 performs the air arrival time T5 from when the forced return trigger Tr_r is established, that is, from when the accelerator is depressed more than a predetermined value until air is introduced into the combustion chamber 1b. (FIG. 14) is calculated and estimated (step S505). When the internal combustion engine 1 includes a plurality of combustion chambers, the air arrival time T5 is calculated and estimated for each combustion chamber. This is to restart fuel injection from the combustion chamber where air is expected to be introduced. In this way, fuel is not injected into the combustion chamber into which air has not been introduced, so that ignition can be reliably performed from when fuel injection is resumed. The procedure for calculating the air arrival time T5 and the procedure for restarting fuel injection from the combustion chamber where air is expected to be introduced will be described later.

  The fuel cut condition determination unit 21 determines whether or not the air arrival time T5 has elapsed since the forced return trigger Tr_r was established (step S506). When the arrival time T5 has not elapsed (step S506; No), the process waits until the arrival time T5 has elapsed. When the air arrival time T5 has elapsed (step S506; Yes), it can be predicted that air is introduced into any one of the combustion chambers provided in the internal combustion engine. Therefore, the fuel cut control unit 25 starts fuel injection into the combustion chamber where air is expected to be introduced (step S507).

  The introduced air amount control unit 26 maintains the opening of the throttle valve 16 at a new throttle valve opening Ot_n (= Ot + ΔOt) until a predetermined period T4 has elapsed (step S508). As a result, the feeling of delay in response of the torque of the internal combustion engine 1 at the time of return can be reduced, and drivability is improved. Further, since the exhaust gas remaining in the intake passage 8i and the like can be effectively scavenged, when returning from the stop of fuel injection, the occurrence of misfire due to lack of oxygen can be suppressed, and the discharge of unburned matter can be suppressed. In addition, a decrease in drivability due to misfire can be suppressed. Here, ΔOt can be determined in advance by experiment, analysis, or the like in consideration of the specification of the internal combustion engine 1 or the like. When the predetermined period T4 has elapsed (step S508; Yes), the opening of the throttle valve 16 is controlled to an opening determined from the accelerator opening. That is, the opening degree increase ΔOt = 0 (step S509).

  Next, the procedure for calculating the air arrival time T5 and restarting fuel injection from the combustion chamber where air is expected to be introduced will be described. FIG. 16 is a flowchart showing a procedure for calculating the air arrival time and restarting fuel injection. In calculating the air arrival time T5, the air arrival time calculation unit 27 receives the fact that the forced return trigger Tr_r is satisfied, and the air A is burned by the internal combustion engine 1 on the basis of the time when the forced return condition is satisfied. An air arrival time T5 until reaching the intake port 11i provided in the chamber 1b is calculated.

  FIG. 17 is an explanatory diagram showing an example of a calculation map used when calculating the time until the air reaches the intake port of the internal combustion engine. This calculation map 53 is stored in the storage unit 30m of the engine ECU 30b. The air arrival time calculation unit 27 obtains the engine speed NE of the internal combustion engine 1 and the intake pipe pressure P of the intake passage 8i from the sensors of the internal combustion engine 1. Here, the air arrival time T5 is obtained as a function of the intake pipe pressure P.

  Then, the air arrival time calculation unit 27 gives the acquired engine speed NE and the intake pipe pressure P to the calculation map 50 stored in the storage unit 30m of the engine ECU 30b, and calculates the air arrival time T5 at that time. get. Since the air arrival time T5 is obtained as a function of the intake pipe pressure P, this function T = f (P) is stored in the storage unit 30m, and the air arrival time calculation unit 27 stores the function T = f ( The air arrival time T5 may be obtained by giving the obtained intake pipe pressure P to P).

  In calculating the air arrival time T5, the air arrival time calculation unit 27 obtains the intake pipe pressure P from the intake pipe pressure sensor 44 in response to the forced return trigger Tr_r being established (step S601). Then, the air arrival time calculation unit 27 gives the acquired intake pipe pressure P and the engine speed NE of the internal combustion engine 1 to the calculation map 52, and acquires the air arrival time T5 at that time (step S602).

FIG. 18 is an explanatory diagram showing the distance between the throttle valve and the intake port in an internal combustion engine having a plurality of cylinders. As shown in FIG. 18, in the internal combustion engine 1 having a plurality of cylinders (four cylinders in this example), the lengths of the intake pipes 4 ₁ to _{4 4} are different for each cylinder 1s _{1 to} 1s ₄ . That is, when the distance from the first cylinder 1s throttle 16 in ₁ to the intake port 11i ₁ and L _1, it can be expressed by _{L 1 = Xs + Y + Z} 1. Similarly, in the second cylinder 1s ₂ at _{L 2 = Xs + Y + Z} 2, the third cylinder 1s ₃ in _{L 3 = Xs + Y + Z} 3, the fourth in-cylinder _{1s 4 L 4 = Xs + Y} + Z 4. As described above, when the distance from the EGR valve 14 to the intake port 11i ₁ is different among the cylinders, the air arrival time T5 is also different for each combustion chamber provided in each cylinder.

FIG. 19 is an explanatory diagram showing a case where a forced return is executed in an internal combustion engine having a plurality of cylinders. As already explained, in the internal combustion engine 1 having a plurality of cylinders, the air arrival time T5 is different for each combustion chamber of each cylinder. Further, the progress of air may differ depending on the timing of opening the throttle valve 16 and the position of the piston of each cylinder. For example, in the example shown in FIG. 19, the air has not yet been introduced into the third cylinder 1s ₃ , but the air has already reached the third intake port 11i ₃ . Therefore, in the next intake stroke of the third cylinder 1s _3, air is introduced into the combustion chamber of the third cylinder 1s _3. In this case, fuel injection to the third cylinder 1s ₃ is started. As a result, the fuel is surely burned and the exhaust gas containing excess oxygen is prevented from flowing into the catalyst 12.

The first cylinder 1s ₁ is a cylinder in which air is not introduced into the combustion chamber, and is a cylinder into which air is introduced after several cycles. In this case, for the first cylinder 1s _1, without starting the fuel injection, to wait from the first cylinder 1s within ₁ to the exhaust gas is sufficiently scavenged. When the air reaches the first intake port 11i ₁ and the air is introduced into the combustion chamber of the first cylinder 1s _{1 in} the next intake stroke, fuel injection to the first cylinder 1s ₁ is started. . As a result, the fuel is surely burned and the exhaust gas containing excess oxygen is prevented from flowing into the catalyst 12.

The time when air reaches the intake port can be predicted from the air arrival time T5. Since the crank angle sensor 41 of the internal combustion engine 1 can determine which stroke each cylinder is in, the fuel injection is started for the cylinder in which the air reaches the intake port and the air is taken into the combustion chamber in the intake stroke. To do. Based on the air arrival time T5 and the signal from the crank angle sensor 41, the fuel cut control unit 25 determines whether or not it is time to inject fuel after the air A reaches the intake port 11i ₁ or the like for each cylinder. judge. That is, a value (air arrival crank angle) obtained by adding a crank angle corresponding to the obtained air arrival time T5 to the current crank position obtained from a signal from the crank angle sensor 41 or the like is calculated. Then, fuel is injected from the cylinder in time for fuel injection at the determined air arrival crank angle.

  In addition, the cylinder in which air reaches the intake port and can take air into the combustion chamber during the intake stroke may be determined as follows. In the fourth embodiment, a cylinder that can take air into the combustion chamber by this method is determined. First, the air arrival time calculation unit 27 sets the air arrival count number Ca (step S603). The air arrival count number Ca can be obtained by a value (T5 / Tc) obtained by dividing the air arrival time T5 by the crank movement time Tc. That is, it is a parameter for determining the arrival time of air when the engine speed of the internal combustion engine 1 is taken into consideration. The crank movement time Tc is as described in the second embodiment.

  When the air arrival count number Ca is set (step S603), the fuel cut condition determination unit 21 subtracts the air arrival count number Ca. In the fourth embodiment, the air arrival count number Ca is subtracted by 1 (step S604). The subtraction is continued until the air arrival count number Ca becomes 0 (step S605). When the air arrival count number Ca becomes 0 (step S605; Yes), the fuel cut condition determination unit 21 sets the fuel cut flag F1 to 0 for the cylinder (step S606).

  Here, the fuel injection execution routine for determining the fuel injection timing and executing the fuel injection is facilitated separately. In this fuel injection execution routine, since the cylinder for injecting fuel has been determined, the fuel is injected when the cylinder for injecting fuel comes at the fuel injection timing. When the fuel injection timing of a cylinder for injecting fuel reaches the fuel injection timing, if the fuel cut flag F1 for that cylinder is 0, the fuel is injected into that cylinder.

  The fuel cut control unit 25 refers to the value of the fuel cut flag F1 when executing the control of the fuel injection execution routine. Then, the fuel cut control unit 25 receives the fact that the fuel cut flag F1 has become 0, and at the time when the fuel cut flag F1 is set to 0, that is, the cylinder in time for fuel injection. Control is performed so as to inject fuel into the combustion chamber (step S607). The fuel cut flag F1 is maintained at 1 for the combustion chambers of the cylinders that are not in this timing, that is, the combustion chambers of the cylinders in which air has not reached the intake port. In response to the fuel cut flag F1 being 1, the fuel cut control unit 25 maintains the stop of fuel injection to the combustion chambers of the cylinders in which air has not reached the intake port.

  Next, natural recovery will be described. FIG. 20 is a flowchart showing a procedure at the time of natural recovery. FIG. 21 is a timing chart at the time of natural recovery. Here, the natural return refers to a return when the engine speed NE has dropped to a predetermined speed after the fuel injection to the internal combustion engine 1 is stopped. The natural recovery can be realized by the operation control device 20b (see FIG. 15) for the internal combustion engine according to the fourth embodiment.

  At the time of natural return, the fuel cut condition determining unit 21 provided in the operation control device 20b of the internal combustion engine determines whether or not the natural return condition is satisfied (step S701). The natural return condition is satisfied, for example, when the engine speed NE of the internal combustion engine 1 falls below a predetermined predetermined speed while the fuel injection is stopped. When the engine speed NE of the internal combustion engine 1 falls below a predetermined speed while the fuel injection is stopped, this is set as a natural recovery trigger Tr_n (FIG. 21).

  When the natural return condition is satisfied (step S701; Yes), the introduced air amount control unit 26 supplies air corresponding to the idling time of the internal combustion engine 1 to the internal combustion engine 1 (step S702). For example, the ISC valve 17 is opened to an opening corresponding to idling, or in the case of an electronic throttle valve, the butterfly valve is opened to an opening corresponding to idling. Next, the EGR control unit 23 closes the EGR valve 14 and stops the exhaust gas recirculation (step S703). The exhaust gas recirculation may be stopped at the same time when air corresponding to idling of the internal combustion engine 1 is supplied to the internal combustion engine 1 (step S702).

Next, when a predetermined period T6 (= t ₃ −t ₂ : FIG. 21) has elapsed since the EGR valve 14 was closed (step S704; Yes), the fuel cut control unit 25 injects fuel into the internal combustion engine 1. Is started (step S705). If the fuel injection is resumed immediately after the natural return condition is satisfied, the exhaust gas remaining in the intake passage 8i and the surge tank is more than the air, and there is a risk of misfire. However, since the fuel injection is resumed after the EGR valve 14 is closed, that is, after the recirculation of the exhaust gas is stopped, the exhaust gas remaining in the intake passage 8i and the surge tank can be scavenged. As a result, since the fuel injection is resumed after air is introduced into the combustion chamber 1b, ignition can be reliably performed. Here, the predetermined period T6 is set to a time necessary for scavenging the exhaust gas remaining in the intake passage 8i and the surge tank.

  As described above, in the fourth embodiment, when returning from the stop of fuel injection, the time for the air introduced into the internal combustion engine to reach the combustion chamber is estimated, and fuel injection is performed from the combustion chamber where air is expected to be introduced. Start. As a result, air can be introduced from the combustion chamber of the cylinder where the exhaust gas remaining in the intake passage and the surge tank has been scavenged, so that misfire can be suppressed and recovery can be reliably performed.

  As described above, the internal combustion engine and the operation control device for the internal combustion engine according to the present invention are useful for suppressing the deterioration of the catalyst, and particularly suppress the deterioration of the catalyst due to the stop of the fuel injection during the deceleration operation of the internal combustion engine. Suitable for doing.

FIG. 2 is an explanatory diagram showing one cylinder of the internal combustion engine according to the first embodiment. It is explanatory drawing of an electronic throttle valve. It is explanatory drawing of an electronic throttle valve. 1 is an explanatory diagram illustrating an operation control device for an internal combustion engine according to a first embodiment. FIG. 3 is a flowchart illustrating a procedure of an operation control method for an internal combustion engine according to the first embodiment. 1 is a conceptual diagram showing piping of an internal combustion engine 1. FIG. 6 is an explanatory diagram illustrating an operation control device for an internal combustion engine according to a second embodiment. 6 is a flowchart showing a procedure of an operation control method for an internal combustion engine according to a second embodiment. It is explanatory drawing which shows an example of the calculation map used when calculating time until exhaust gas arrives at the intake port of an internal combustion engine. It is explanatory drawing which shows an example of the calculation map used when calculating time until exhaust gas arrives at the intake port of an internal combustion engine. It is explanatory drawing which shows an example of the calculation map used when calculating time until exhaust gas arrives at the intake port of an internal combustion engine. It is explanatory drawing which shows the distance to an EGR valve and an inlet port in an internal combustion engine provided with a some cylinder. It is explanatory drawing which shows the case where EGR is performed in an internal combustion engine provided with a some cylinder. 7 is a flowchart showing a procedure of an operation control method for an internal combustion engine according to a modification of the second embodiment. 7 is a timing chart showing operation control of an internal combustion engine according to a third embodiment. 12 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the third embodiment. 12 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the third embodiment. 12 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the third embodiment. 12 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the third embodiment. 12 is a flowchart illustrating a procedure of operation control of the internal combustion engine according to the third embodiment. 12 is a flowchart showing a procedure of operation control of the internal combustion engine according to the fourth embodiment. FIG. 10 is an explanatory diagram of operation control of an internal combustion engine according to a fourth embodiment. FIG. 9 is an explanatory diagram showing an operation control device for an internal combustion engine according to a fourth embodiment. It is a flowchart which shows the procedure of calculation of air arrival time, and restart of fuel injection. It is explanatory drawing which shows an example of the calculation map used when calculating time until air arrives at the inlet port of an internal combustion engine. It is explanatory drawing which shows the distance to a throttle valve and an inlet port in an internal combustion engine provided with a some cylinder. It is explanatory drawing which shows the case where forced return is performed in an internal combustion engine provided with a some cylinder. It is a flowchart which shows the procedure at the time of a natural return. It is a timing chart at the time of natural return.

Explanation of symbols

1 an internal combustion engine _{1s, 1s 1, 1s 2,} 1s 3, 1s 4 -cylinder _{4i, 4 1, 4 2,} 4 3, 4 4 intake pipe 4e exhaust manifold 8i intake passage 8e exhaust gas channel _{11i, 11i 1, 11i 2,} 11i ₃ , 11i ₄ Intake port 12 Catalyst 13 EGR cooler 14 EGR valve 15 Exhaust gas recirculation passage 16 Throttle valve 16 'Electronic throttle valve 17 ISC valve 20, 20a, 20b Operation control device of internal combustion engine 21 Fuel cut condition determination unit 22 EGR amount calculation Unit 23 EGR control unit 24 exhaust gas arrival time calculation unit 25 fuel cut control unit 26 introduction air amount control unit 27 air arrival time calculation unit 30, 30a, 30b engine ECU
50, 51, 52, 53 calculation map

Claims (27)

An internal combustion engine that burns a mixture of air and fuel in a combustion chamber;
An intake passage that guides air to an intake port provided in the combustion chamber and introduces air into the combustion chamber;
A fuel injection valve for injecting fuel for forming the air-fuel mixture;
A catalyst for purifying exhaust gas after combustion of the air-fuel mixture;
An exhaust gas recirculation passage for recirculating the exhaust gas to the combustion chamber,
When stopping fuel injection from the fuel injection valve, the exhaust gas is recirculated and air introduction into the combustion chamber is stopped, and then the fuel injection is stopped.   The internal combustion engine according to claim 1, wherein the flow rate of the exhaust gas recirculated to the combustion chamber is changed.   2. The internal combustion engine according to claim 1, wherein a flow rate of the exhaust gas recirculated to the combustion chamber is set to be substantially the same as an intake air amount when the internal combustion engine is idling.   The fuel is injected from the fuel injection valve after increasing the amount of fuel more than when the condition for stopping the fuel injection from the fuel injection valve is satisfied after the introduction of air into the combustion chamber is stopped. The internal combustion engine of any one of 1-3.   After stopping the introduction of air into the combustion chamber, after a predetermined first predetermined period has elapsed, the amount of fuel is increased more than when the condition for stopping fuel injection from the fuel injection valve is satisfied, The internal combustion engine according to claim 4, wherein the fuel is injected from the fuel injection valve.   The introduction of air into the combustion chamber is stopped, and the exhaust gas recirculation is stopped until the first predetermined period and a predetermined second predetermined period have elapsed, and then the exhaust gas is recirculated to the combustion chamber. The internal combustion engine according to claim 5.   The internal combustion engine according to claim 6, wherein fuel injection from the fuel injection valve is stopped after a predetermined third predetermined period has elapsed since the start of recirculation of the exhaust gas.   The period from when the introduction of air into the combustion chamber is stopped until the fuel injection from the fuel injection valve is stopped is to retard the ignition timing before stopping the introduction of air into the combustion chamber. The internal combustion engine according to any one of claims 1 to 7, wherein the internal combustion engine is characterized in that:   Estimating the time from when the exhaust gas recirculation is started until the exhaust gas reaches the intake port, the timing at which the exhaust gas reaches the intake port and the exhaust gas can be taken into the combustion chamber, or 9. The internal combustion engine according to claim 1, wherein the fuel injection to the combustion chamber is stopped at any one time after a predetermined time of 3 has elapsed.   Estimating the time from when the exhaust gas starts to recirculate until the exhaust gas reaches the intake port, earlier than the timing of stopping fuel injection, by the time until the exhaust gas reaches the intake port, The internal combustion engine according to any one of claims 1 to 9, wherein the exhaust gas recirculation is started.   The internal combustion engine according to any one of claims 1 to 10, wherein the exhaust gas discharged from the catalyst is recirculated to the combustion chamber. When forcibly returning from the state where fuel injection is stopped to the state where fuel is injected again,
Estimating the time for air to reach the intake port provided in the combustion chamber after starting the introduction of air into the combustion chamber;
The internal combustion engine according to any one of claims 1 to 11, wherein fuel is injected from a combustion chamber in which air reaches the intake port.   13. The air according to claim 12, wherein an amount of air larger than an air amount determined from an operating condition of the internal combustion engine is introduced into the combustion chamber for a predetermined period after the start of air introduction into the combustion chamber. The internal combustion engine described. When returning from the state where fuel injection is stopped to the state where fuel is injected again,
At the same time as starting the introduction of air into the combustion chamber, or after starting the introduction of air into the combustion chamber, stopping the recirculation of the exhaust gas,
The internal combustion engine according to any one of claims 1 to 13, wherein fuel injection from the fuel injection valve is started after a predetermined period of time has elapsed since the recirculation of the exhaust gas was stopped. The air-fuel mixture is used for operation control of an internal combustion engine having a means for recirculating exhaust gas to the combustion chamber while burning the air-fuel mixture in the combustion chamber,
A fuel cut condition determination unit for determining whether or not fuel injection to the internal combustion engine is in a condition;
An exhaust gas recirculation control unit for recirculating the exhaust gas to the combustion chamber and stopping the intake of air from the intake passage when under conditions where fuel injection is stopped;
A fuel cut control unit for stopping fuel injection to the internal combustion engine after executing the recirculation of the exhaust gas and stopping the intake of air from the intake passage;
An operation control device for an internal combustion engine, comprising:   The operation control device for an internal combustion engine according to claim 15, further comprising an exhaust gas recirculation amount calculation unit for obtaining an amount of the exhaust gas to be recirculated to the combustion chamber.   16. The operation control apparatus for an internal combustion engine according to claim 15, wherein an amount of the exhaust gas recirculated to the combustion chamber is substantially the same as an intake air amount when the internal combustion engine is idling. The fuel cut controller
The fuel is injected from the fuel injection valve after increasing the amount of fuel more than when the condition for stopping the fuel injection from the fuel injection valve is satisfied after the introduction of air into the combustion chamber is stopped. The operation control device for an internal combustion engine according to any one of 15 to 17. The fuel cut controller
After stopping the introduction of air into the combustion chamber, after a predetermined first predetermined period has elapsed, the amount of fuel is increased more than when the condition for stopping fuel injection from the fuel injection valve is satisfied, The operation control device for an internal combustion engine according to claim 18, wherein the fuel injection valve injects the fuel from the fuel injection valve. The exhaust gas recirculation controller
The introduction of air into the combustion chamber is stopped, and the exhaust gas recirculation is stopped until the first predetermined period and a predetermined second predetermined period have elapsed, and then the exhaust gas is recirculated to the combustion chamber. The internal combustion engine operation control device according to claim 19. The fuel cut controller
21. The operation control apparatus for an internal combustion engine according to claim 20, wherein the fuel injection from the fuel injection valve is stopped after a predetermined third predetermined period has elapsed since the start of the recirculation of the exhaust gas. The fuel cut controller
16. The ignition timing is retarded from a period before the fuel injection is stopped after the introduction of air into the combustion chamber is stopped until the fuel injection is stopped. The operation control device for an internal combustion engine according to any one of 21. Furthermore, an exhaust gas arrival time calculating unit for estimating a time until the exhaust gas to be recirculated from the time when the exhaust gas recirculation is started to reach the intake port of the combustion chamber is provided,
The fuel cut control unit predicts a combustion chamber where the exhaust gas reaches the intake port from a time until the exhaust gas reaches the intake port, and at a timing when the exhaust gas can be taken into the combustion chamber. The operation control device for an internal combustion engine according to any one of claims 15 to 22, wherein the fuel injection to the combustion chamber is stopped. Furthermore, an exhaust gas arrival time calculating unit that estimates a time from when the exhaust gas starts to recirculate until the exhaust gas reaches the intake port of the combustion chamber,
The exhaust gas recirculation control unit determines the recirculation start timing of the exhaust gas so as to start the recirculation of the exhaust gas earlier than the timing of stopping fuel injection by the time until the exhaust gas reaches the intake port. The operation control device for an internal combustion engine according to any one of claims 15 to 23. Furthermore, when forcibly returning from the state where fuel injection is stopped to the state where fuel is injected again, air introduction into the combustion chamber is started, and then air is supplied to the intake port provided in the combustion chamber. An air arrival time calculation unit that estimates the time required for
25. The fuel cut control unit according to claim 15, wherein the fuel cut control unit injects fuel from a combustion chamber in which air reaches the intake port based on the time estimated by the air arrival time calculation unit. The operation control device for an internal combustion engine according to the item. Furthermore, an introduction air amount control unit for controlling the amount of air introduced into the combustion chamber is provided,
26. The method according to claim 25, wherein an amount of air larger than an air amount determined from operating conditions of the internal combustion engine is introduced into the combustion chamber for a predetermined period after the start of air introduction into the combustion chamber. The internal combustion engine operation control device according to claim. When returning from the state where fuel injection is stopped to the state where fuel is injected again,
The exhaust gas recirculation control unit stops the recirculation of the exhaust gas simultaneously with starting the air introduction into the combustion chamber or after the air introduction into the combustion chamber is started,
27. The fuel cut control unit according to any one of claims 15 to 26, wherein the fuel cut control unit starts fuel injection from the fuel injection valve after a predetermined period has elapsed since the recirculation of the exhaust gas was stopped. An operation control device for an internal combustion engine according to claim 1.

Images