JP2005036790A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of suppressing the deterioration of exhaust emission resulting from the response delay of an exhaust sensor when automatic start or the return of fuel cut is performed in the fuel injection control device for setting a fuel injection amount so that an actual air-fuel ratio in starting an engine or returning the fuel cut becomes richer than a theoretical air-fuel ratio in the internal combustion engine in which the automatic stop and automatic start of the engine are performed and in the internal combustion engine in which the fuel cut and the return of the fuel cut are performed. <P>SOLUTION: This fuel injection control device is formed to perform air-fuel ratio feedback control when the detection signal of the exhaust sensor after automatic stop is determined to be rich. Also, the detection signal of the exhaust sensor after automatic start is determined not to be rich in the device, it is determined whether a specified time TA is passed from the automatic start or not. When the specified time TA is not passed, the start of the air-fuel ratio feedback control is prohibited and when the specified time TA is passed, the air-fuel ratio feedback control is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  As is well known, in-vehicle internal combustion engines usually purify harmful components (HC, CO, NOx, etc.) contained in the exhaust by a catalyst provided in the exhaust passage. This purification action is most efficient when the air-fuel mixture is burned at the stoichiometric air-fuel ratio. Therefore, when setting the fuel injection amount for the internal combustion engine, the fuel injection amount correction, that is, the air-fuel ratio feedback control, is performed to maximize the exhaust gas purification performance by the catalyst by matching the actual air-fuel ratio of the air-fuel mixture with the stoichiometric air-fuel ratio. Is executed. In this air-fuel ratio feedback control, the exhaust gas oxygen concentration is detected by an exhaust sensor provided in the exhaust passage, and the actual air-fuel ratio (hereinafter referred to as the actual air-fuel ratio) of the air-fuel mixture used for combustion is determined from this oxygen concentration. It is determined whether the air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.

  Then, a fuel injection amount correction coefficient for performing feedback correction of the fuel injection amount is set based on the determination result, and the actual air-fuel ratio is calculated by correcting the fuel injection amount to increase or decrease based on the correction coefficient. The deviation from the theoretical air-fuel ratio is compensated so as to match these.

Such air-fuel ratio feedback control is performed on the premise that an output corresponding to the oxygen concentration of the exhaust is obtained from the exhaust sensor.
Here, the exhaust sensor has a characteristic that an output corresponding to the oxygen concentration of the exhaust gas cannot be obtained unless a predetermined activation temperature is reached. Therefore, in the device described in Patent Document 1, the activation state of the exhaust sensor after the engine is started is determined, and after confirming that the exhaust sensor is in the activated state, the air-fuel ratio feedback control is started. ing.
JP-A-5-71394 JP 2002-327640 A

  By the way, in recent years, by stopping the internal combustion engine when the engine is in an idling state and restarting the engine after a predetermined time has elapsed from the time of starting the vehicle or starting, the so-called automatic stop / automatic start of the engine is performed. There are known vehicles that suppress fuel consumption and the like. Here, the engine stop time at the time of the automatic stop is a normal internal combustion engine in which the engine is not automatically stopped or automatically started (for example, the engine is started or stopped only when the driver operates an ignition switch or the like). Shorter than the engine stop time of the internal combustion engine. Therefore, the temperature drop of the exhaust sensor during the automatic stop is small, and when the automatic start is performed, the exhaust sensor tends to be activated quickly. Further, when the engine stop time is extremely short, the exhaust sensor may be maintained in an activated state even during the automatic stop.

  On the other hand, it is known that, in a vehicle-mounted internal combustion engine, if the fuel injection amount is temporarily increased at the time of starting, the startability of the engine can be improved or the exhaust emission at the time of starting the engine can be improved ( For example, see Patent Document 2). A fuel injection control device that performs such an increase at start-up is provided, and the device described in Patent Document 1, that is, the exhaust sensor is in an activated state in the internal combustion engine that performs automatic stop / automatic start of the engine described above. When a device that starts air-fuel ratio feedback control under the above conditions is applied, the following problems may occur.

  That is, since the exhaust sensor is exposed to the atmosphere when the engine is stopped, the detection result of the sensor becomes lean. When the engine is started, the actual air-fuel ratio becomes rich due to the increase at the time of starting, and the detection result of the exhaust sensor should also become rich. However, if a response lag occurs between the detection result of the exhaust sensor and the change in the actual air-fuel ratio, the detection result of the exhaust sensor becomes the result even though the actual air-fuel ratio changes from lean to rich due to the increase at the start. It will be lean for a while after the start-up amount. At this time, in the case of the above-described normal internal combustion engine, the exhaust sensor is activated after a certain amount of time has elapsed since the start of the engine. Therefore, when the air-fuel ratio feedback control is started, the exhaust sensor caused by this response delay In many cases, the difference between the detection result and the actual air-fuel ratio is small.

  On the other hand, when an automatic start is performed in an internal combustion engine that performs automatic stop / automatic start of the engine, the exhaust sensor tends to be activated quickly. The air-fuel ratio feedback control is started before the difference between the detection result and the actual air-fuel ratio becomes small. Therefore, in this case, the fuel injection amount is further increased to enrich the air-fuel ratio based on the lean detection of the exhaust sensor. As a result, the actual air-fuel ratio becomes rich even though it is rich, which may lead to deterioration of exhaust purification performance.

  In addition, when fuel is decelerated or when the engine rotational speed is excessively increased, the same phenomenon as the case where the engine is automatically stopped / started as described above may occur. is there. That is, the fuel injection amount is temporarily increased in order to quickly recover combustion in the internal combustion engine even when the fuel cut is restored. Further, since the exhaust sensor is exposed to the atmosphere during fuel cut, the detection result of the sensor becomes lean. Then, when the fuel cut is restored, the exhaust sensor tends to be activated quickly. Therefore, the air-fuel ratio feedback control is started before the difference between the detection result of the exhaust sensor due to the response delay described above and the actual air-fuel ratio becomes small. Therefore, also in this case, the fuel injection amount is further increased to enrich the air-fuel ratio based on the lean detection of the exhaust sensor. Therefore, even when the fuel cut is restored, the actual air-fuel ratio becomes rich even though it is rich, and there is a risk of deteriorating the exhaust purification performance.

  The present invention has been made in view of such circumstances, and is premised on an internal combustion engine that automatically stops and starts the engine, and an internal combustion engine that performs fuel cut and return of fuel cut. The purpose of the fuel injection control device is to set the fuel injection amount so that the actual air-fuel ratio at the time of engine start or return from fuel cut becomes richer than the stoichiometric air-fuel ratio. It is an object of the present invention to provide a fuel injection control device for an internal combustion engine that can suppress deterioration of exhaust emission due to a response delay of an exhaust sensor at the time.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, there is provided a start-time increase means for increasing and correcting the fuel injection amount so that the actual air-fuel ratio at the time of engine start becomes richer than the stoichiometric air-fuel ratio, and an exhaust gas provided in the exhaust passage of the internal combustion engine. The fuel injection amount correction coefficient for making the actual air fuel ratio coincide with the target air fuel ratio is calculated based on the detection signal of the exhaust sensor that detects the oxygen concentration of the fuel, and the fuel injection amount feedback correction is performed based on the fuel injection amount correction coefficient In the fuel injection control device for an internal combustion engine that automatically stops and starts the engine under a predetermined condition, the detection result of the exhaust sensor is activated after the exhaust sensor is activated. The gist of the present invention is to provide a limiting means for limiting the correction amount of the feedback correction based on the above.

  In this configuration, in an internal combustion engine that automatically stops and starts the engine, the actual air-fuel ratio at the start of the engine is richer than the stoichiometric air-fuel ratio in order to improve its startability and exhaust emission at the time of engine start. It is trying to become. Here, in the internal combustion engine in which the engine start and the engine stop are automatically performed, and the exhaust sensor tends to be activated quickly at the time of the automatic start, the air-fuel ratio feedback control can also be performed quickly. it can. However, when the response delay as described above occurs in the exhaust sensor, the detection signal may be lean even if the actual air-fuel ratio is rich. In such a case, if the feedback correction is executed immediately after the exhaust sensor is activated, the actual air-fuel ratio becomes excessively rich, and the exhaust emission may deteriorate. Therefore, in the above configuration, the correction amount of the feedback correction is limited based on the detection result of the exhaust sensor after the exhaust sensor is activated. Accordingly, feedback correction based on an erroneous detection signal due to the response delay of the exhaust sensor is limited, and deterioration of exhaust emission due to the response delay of the exhaust sensor when automatic start is executed is suppressed. Will be able to.

  As the execution condition of the restriction by the restriction means, as in the invention described in claim 2, the restriction means is provided that the change in the actual air-fuel ratio due to the fuel increase of the start-time increase means is not detected by the exhaust sensor. It is possible to adopt a configuration in which the above restriction is executed. According to this configuration, when the detection signal of the exhaust sensor is not a detection signal corresponding to the fuel increase, the feedback correction is limited. Therefore, the detection of the exhaust sensor that does not reflect the actual air-fuel ratio. Feedback correction based on the signal is limited. Accordingly, it is possible to suppress the deterioration of exhaust emission due to the response delay of the exhaust sensor when the automatic start is executed.

  According to a third aspect of the present invention, the restriction means adopts a configuration in which the restriction is performed on the condition that the air-fuel ratio detected by the exhaust sensor is leaner than a predetermined air-fuel ratio. By doing so, it becomes possible to suitably determine that a response delay has occurred in the exhaust sensor, and thus it becomes possible to suitably perform the limitation of the feedback correction.

  As the predetermined air-fuel ratio, a stoichiometric air-fuel ratio can be set as in the fourth aspect of the invention. When the actual air-fuel ratio at the time of starting the engine is made richer than the stoichiometric air-fuel ratio by the starting-time increasing means, and the air-fuel ratio detected by the exhaust sensor is leaner than the stoichiometric air-fuel ratio, the exhaust sensor It can be considered that there is a response delay. Therefore, according to the above configuration, it is possible to clearly determine that a response delay has occurred in the exhaust sensor.

  According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fourth aspects, the restriction by the restriction means is prohibited when a predetermined period has elapsed since the automatic start. The gist is to further include means.

  The limiting means limits the correction amount of the feedback correction based on the detection result of the exhaust sensor after the exhaust sensor is activated. Therefore, for example, when the response delay of the exhaust sensor is excessively large, the start of the feedback correction is excessively delayed, which may cause deterioration of exhaust emission. Here, even when the fuel injection amount is corrected to be increased so that the actual air-fuel ratio at the start of the engine is richer than the stoichiometric air-fuel ratio, even when there is a response delay in the exhaust sensor, The detection signal changes from the lean side to the rich side. That is, the detection signal of the exhaust sensor approaches the actual air-fuel ratio after a predetermined period has elapsed. Therefore, in the above configuration, when the predetermined period has elapsed since the automatic start, the restriction by the restriction means is prohibited, that is, the feedback correction is executed. Therefore, feedback correction can be started at a time when the difference between the detection signal of the exhaust sensor and the actual air-fuel ratio is considered to be small. Therefore, when the feedback correction is limited based on the detection result of the exhaust sensor in consideration of the response delay of the exhaust sensor, it is possible to suppress the deterioration of exhaust emission due to the delay of the start of the feedback correction. The predetermined period can be set to a period until the change in the actual air-fuel ratio due to the fuel increase of the starting increase means is reflected in the detection signal of the exhaust sensor.

  According to a sixth aspect of the present invention, in the fuel injection control apparatus for an internal combustion engine according to any one of the first to fifth aspects, the start-time increasing means is an air-fuel ratio detected by the exhaust sensor after the automatic start. The gist of the present invention is to start the decrease of the increase value in the increase correction from when the value changes to the richer side than the stoichiometric air-fuel ratio.

  The automatic start of the engine described above is often a warm start, and at this time, a decrease in fuel density, generation of vapor, and the like are likely to occur. For this reason, there is a possibility that the actual air-fuel ratio does not immediately become rich even if the increase at the start is performed at the time of engine start. Therefore, in the above configuration, the decrease in the increase value in the increase correction is started when the air-fuel ratio detected by the exhaust sensor changes to the richer side than the stoichiometric air-fuel ratio. Therefore, when the air-fuel ratio detected by the exhaust sensor is leaner than the stoichiometric air-fuel ratio, the above reduction is not started, so that the actual air-fuel ratio at the time of engine start can be reliably enriched. Further, when the air-fuel ratio detected by the exhaust sensor becomes richer than the stoichiometric air-fuel ratio, the above decrease is started. Therefore, the increase at the start is continued even though the actual air-fuel ratio is rich, and the actual air-fuel ratio is increased. It is also possible to suppress the occurrence of defects such as excessively rich.

  According to a seventh aspect of the present invention, in the fuel injection control apparatus according to the sixth aspect, the air-fuel ratio detected by the exhaust sensor when the start-up increase means has a predetermined increase period after the automatic start. The gist is to forcibly start the decrease of the increase value regardless of the value of.

  When the exhaust sensor has a response delay in the configuration according to claim 6, it is delayed that the air-fuel ratio detected by the exhaust sensor shifts to a richer side than the stoichiometric air-fuel ratio. There is a possibility that the starting amount is excessively continued after the start is delayed. In this regard, in the above configuration, when the predetermined increase period has elapsed since the automatic start, the decrease in the increase value is forcibly started regardless of the value of the air-fuel ratio detected by the exhaust sensor. Therefore, it is possible to suppress the occurrence of a problem that the actual air-fuel ratio becomes excessively rich due to the response delay of the exhaust sensor. Also, when the predetermined increase period elapses, the increase value is forcibly started to decrease, so that even if there is a response delay in the air-fuel ratio detected by the exhaust sensor, Thus, the deviation from the air-fuel ratio of the air-fuel mixture used for combustion can be reduced, and the air-fuel ratio feedback control started thereafter can be performed more stably.

  By setting a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor as the predetermined increase period, the actual air-fuel ratio can be shifted from rich to lean side at an early stage. Thus, the difference between the air-fuel ratio detected by the exhaust sensor and the air-fuel ratio of the air-fuel mixture used for actual combustion can be reduced early.

  The invention according to claim 8 is provided in a return-time increase means for increasing and correcting the fuel injection amount so that the actual air-fuel ratio at the time of fuel cut return is richer than the stoichiometric air-fuel ratio, and provided in the exhaust passage of the internal combustion engine. A fuel injection amount correction coefficient for making the actual air-fuel ratio coincide with the target air-fuel ratio is calculated based on the detection signal of the exhaust sensor that detects the oxygen concentration of the exhaust gas, and the fuel injection amount is fed back based on the fuel injection amount correction coefficient. An air-fuel ratio feedback control means for performing correction, and in a fuel injection control device for an internal combustion engine that performs fuel cut and return of fuel cut under a predetermined condition, a detection result of the exhaust sensor after activation of the exhaust sensor The gist of the present invention is to provide a limiting means for limiting the correction amount of the feedback correction based on the above.

  In this configuration, in an internal combustion engine that performs fuel cut, the actual air-fuel ratio at the time of fuel cut return becomes richer than the stoichiometric air-fuel ratio in order to quickly recover combustion in the internal combustion engine at the time of fuel cut return. I have to. Here, in the internal combustion engine in which the fuel cut and the return of the fuel cut are performed, the exhaust sensor tends to be activated quickly when the fuel cut is restored, so that the air-fuel ratio feedback control can also be executed quickly. . However, when the response delay as described above occurs in the exhaust sensor, the detection signal may be lean even if the actual air-fuel ratio is rich. In such a case, if the feedback correction is executed immediately after the exhaust sensor is activated, the actual air-fuel ratio becomes excessively rich, and the exhaust emission may deteriorate. Therefore, in the above configuration, the correction amount of the feedback correction is limited based on the detection result of the exhaust sensor after the exhaust sensor is activated. Accordingly, feedback correction based on an erroneous detection signal caused by the response delay of the exhaust sensor is limited, and exhaust emission deterioration caused by the response delay of the exhaust sensor when the fuel cut is restored is reduced. It becomes possible to suppress.

  As an execution condition of the restriction by the restricting means, as in the invention according to claim 9, the restricting means is provided that the change in the actual air-fuel ratio due to the fuel increase of the return increasing means is not detected by the exhaust sensor. It is possible to adopt a configuration in which the above restriction is executed. According to this configuration, when the detection signal of the exhaust sensor is not a detection signal corresponding to the fuel increase, the feedback correction is limited. Therefore, the detection of the exhaust sensor that does not reflect the actual air-fuel ratio. Feedback correction based on the signal is limited. Accordingly, it is possible to suppress the deterioration of exhaust emission due to the response delay of the exhaust sensor when the fuel cut is restored.

  Further, according to a tenth aspect of the present invention, the restriction means adopts a configuration in which the restriction is executed on condition that the air-fuel ratio detected by the exhaust sensor is leaner than a predetermined air-fuel ratio. By doing so, it becomes possible to suitably determine that a response delay has occurred in the exhaust sensor, and thus it becomes possible to suitably perform the limitation of the feedback correction.

  As the predetermined air-fuel ratio, the stoichiometric air-fuel ratio can be set as in the invention described in claim 11. When the actual air-fuel ratio at the time of fuel cut return is made richer than the stoichiometric air-fuel ratio by the above-mentioned return-increasing means, and the air-fuel ratio detected by the exhaust sensor is leaner than the stoichiometric air-fuel ratio, It can be considered that there is a response delay in the sensor. Therefore, according to the above configuration, it is possible to clearly determine that a response delay has occurred in the exhaust sensor.

  A twelfth aspect of the invention is the internal combustion engine fuel injection control apparatus according to any of the sixth to eleventh aspects, wherein the restriction by the restricting means is prohibited when a predetermined period has elapsed since the fuel cut recovery. The gist is to further include means.

  The limiting means limits the correction amount of the feedback correction based on the detection result of the exhaust sensor after the exhaust sensor is activated. Therefore, for example, when the response delay of the exhaust sensor is excessively large, the start of the feedback correction is excessively delayed, which may cause deterioration of exhaust emission. Here, even when the fuel injection amount is increased and corrected so that the actual air-fuel ratio at the time of fuel cut recovery becomes richer than the stoichiometric air-fuel ratio, even when there is a response delay in the exhaust sensor, the exhaust sensor Will eventually change from the lean side to the rich side. That is, the detection signal of the exhaust sensor approaches the actual air-fuel ratio after a predetermined period has elapsed. Therefore, in the above configuration, when the predetermined period has elapsed since the fuel cut return, the restriction by the restriction means is prohibited, that is, the feedback correction is executed. Therefore, feedback correction can be started at a time when the difference between the detection signal of the exhaust sensor and the actual air-fuel ratio is considered to be small. Therefore, when the feedback correction is limited based on the detection result of the exhaust sensor in consideration of the response delay of the exhaust sensor, it is possible to suppress the deterioration of exhaust emission due to the delay of the start of the feedback correction. The predetermined period can be set to a period until the change in the actual air-fuel ratio due to the fuel increase by the return-time increasing means is reflected in the detection signal of the exhaust sensor.

  A thirteenth aspect of the present invention is the internal combustion engine fuel injection control apparatus according to any of the sixth to twelfth aspects, wherein the return-time increasing means is an air-fuel ratio detected by the exhaust sensor after returning from the fuel cut. The gist of the present invention is to start the decrease of the increase value in the increase correction from when the value changes to the richer side than the stoichiometric air-fuel ratio.

  When the fuel cut is restored as described above, the internal combustion engine is often in a warm state, and at this time, a decrease in fuel density, generation of vapor or the like is likely to occur. Therefore, there is a possibility that the actual air-fuel ratio does not immediately become rich even if the return increase is performed as described above at the time of fuel cut recovery. Therefore, in the above configuration, the decrease in the increase value in the increase correction is started when the air-fuel ratio detected by the exhaust sensor changes to the richer side than the stoichiometric air-fuel ratio. Therefore, when the air-fuel ratio detected by the exhaust sensor is leaner than the stoichiometric air-fuel ratio, the reduction is not started, so that the actual air-fuel ratio at the time of fuel cut return can be reliably enriched. Further, when the air-fuel ratio detected by the exhaust sensor becomes richer than the stoichiometric air-fuel ratio, the above-described decrease starts, so that the increase at the time of return continues even though the actual air-fuel ratio is rich. It is also possible to suppress the occurrence of defects such as excessively rich.

  According to a fourteenth aspect of the present invention, in the fuel injection control apparatus according to the thirteenth aspect, the return-time increase means is an empty space detected by the exhaust sensor when a predetermined increase period elapses after the fuel cut return time. The gist is to forcibly start the decrease of the increase value regardless of the value of the fuel ratio.

  When the response of the exhaust sensor is delayed in the configuration according to claim 13, the air-fuel ratio detected by the exhaust sensor is delayed from being shifted to the richer side than the stoichiometric air-fuel ratio. There is a possibility that the increase at the time of return is continued excessively after the start is delayed. In this regard, in the above configuration, when the predetermined increase period has elapsed since the fuel cut return, the decrease in the increase value is forcibly started regardless of the value of the air-fuel ratio detected by the exhaust sensor. Therefore, it is possible to suppress the occurrence of a problem that the actual air-fuel ratio becomes excessively rich due to the response delay of the exhaust sensor. Also, when the predetermined increase period elapses, the increase value is forcibly started to decrease, so that even if there is a response delay in the air-fuel ratio detected by the exhaust sensor, Thus, the deviation from the air-fuel ratio of the air-fuel mixture used for combustion can be reduced, and the air-fuel ratio feedback control started thereafter can be performed more stably.

  By setting a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor as the predetermined increase period, the actual air-fuel ratio can be shifted from rich to lean side at an early stage. Thus, the difference between the air-fuel ratio detected by the exhaust sensor and the air-fuel ratio of the air-fuel mixture used for actual combustion can be reduced early.

  According to a fifteenth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the sixth, seventh, thirteen, and fourteenth aspects, the internal combustion engine includes a plurality of exhaust systems, and is provided in each exhaust system. The gist of the present invention is to start reducing the increase value with respect to the fuel injection amount of the cylinder connected to the exhaust system provided with the exhaust sensor based on the detection result of the exhaust sensor.

  For example, in an internal combustion engine having a plurality of exhaust systems such as a V-type internal combustion engine, the exhaust sensor is often provided for each exhaust system, and the exhaust flow mode, the response delay of the exhaust sensor, and the like are different for each exhaust system. There may be. Therefore, in the above-described configuration, the increase start of the increase value in the increase correction of the fuel injection amount is executed independently for each exhaust system. Therefore, even in an internal combustion engine having a plurality of exhaust systems, the effect of the invention according to any one of claims 6, 7, 13, and 14 can be suitably obtained.

  According to a sixteenth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fifteenth aspects, the internal combustion engine includes a plurality of exhaust systems, and the limiting means is provided for each exhaust system. The gist of the invention is to limit the correction amount of the feedback correction with respect to the fuel injection amount of the cylinder connected to the exhaust system provided with the exhaust sensor based on the detection result of the provided exhaust sensor.

  As described above, in an internal combustion engine having a plurality of exhaust systems, the exhaust sensor is often provided for each exhaust system, and the exhaust flow mode and the response delay of the exhaust sensor are different for each exhaust system. There is. Therefore, in the above configuration, the limitation to the feedback correction performed by the limiting unit is executed independently for each exhaust system. Therefore, even an internal combustion engine having a plurality of exhaust systems can suppress deterioration of exhaust emissions.

  As a limitation on the correction amount of the feedback correction by the limiting unit, as in the invention according to claim 17, the configuration in which the limiting unit prohibits the feedback correction, or in accordance with the invention according to claim 18. The air-fuel ratio feedback control means sets an upper limit guard value for the fuel injection amount correction coefficient and limits the fuel injection correction coefficient to a value smaller than the upper limit guard value. According to a configuration in which the upper limit guard value is set to a smaller value, or according to the invention of claim 19, the limiting means changes the fuel injection amount correction coefficient so that the fuel injection amount decreases at the time of the limitation. A configuration such as can be adopted. According to these configurations, the amount of feedback correction can be reliably limited.

(First embodiment)
Hereinafter, a first embodiment of a fuel injection control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS.

FIG. 1 schematically shows an internal combustion engine to which the fuel injection device according to the present embodiment is applied and its peripheral configuration.
As shown in FIG. 1, an intake passage 11 and an exhaust passage 13 are connected to the first cylinder # 1 to the fourth cylinder # 4 of the internal combustion engine 10, respectively. The intake passage 11 is provided with a throttle valve 26 that is opened and closed by a motor or the like. The intake air metered by the throttle valve 26 is introduced into the cylinders # 1 to # 4 as the intake valve is opened. The fuel directly injected from the fuel injection valve 20 into the combustion chambers of the cylinders # 1 to # 4 is mixed with the introduced intake air, ignited by the spark plug, burned, and then the exhaust valve is opened. As a result, the gas is discharged into the exhaust passage 13.

  A catalyst 16 having an exhaust purification function is provided in the exhaust passage 13, and harmful components contained in the exhaust are purified by the catalyst 16. The catalyst 16 is composed of two catalyst devices such as a three-way catalyst device and a NOx occlusion reduction catalyst device (in FIG. 1, these catalyst devices are collectively shown as one). The three-way catalyst device has a function of mainly purifying hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas through its redox action. In contrast, the NOx occlusion reduction catalyst device occludes NOx in the exhaust when combustion is performed under a lean air-fuel ratio, while the NOx occluded is stored in the rich air-fuel ratio or the stoichiometric air-fuel ratio. It has the function of reducing and purifying the HC and CO contained in the exhaust when combustion is performed.

  The fuel injection valve 20 is an in-cylinder injection type that directly injects fuel into the combustion chambers of the cylinders # 1 to # 4, and high-pressure fuel is supplied from the delivery pipe 24. The delivery pipe 24 is connected in turn to a feed pump and a fuel tank via a high-pressure pump, and fuel pressurized by the high-pressure pump is supplied.

  On the other hand, the crankshaft 17 that is the engine output shaft in the internal combustion engine 10 is connected to the drive wheels of the vehicle through the automatic transmission 30. The crankshaft 17 is connected to a starter 45, which is an electric motor for starting the engine, as required.

  Further, the crankshaft 17 is drivingly connected to a belt transmission mechanism 19 via an electromagnetic clutch 15. The belt transmission mechanism 19 is provided with an auxiliary machine such as a compressor for an air conditioner and a water pump, and a generator motor 40 that functions as either a generator or an electric motor depending on the situation. The electromagnetic clutch 15 is configured such that the drive connection between the belt transmission mechanism 19 and the crankshaft 17 can be connected and disconnected as necessary.

  The starter 45 and the generator motor 40 are electrically connected to the battery 18. The battery 18 supplies electric power to the starter 45 and the generator motor 40 to cause them to function as an electric motor. The battery 18 is charged with electric power generated when the generator motor 40 functions as a generator.

  Further, the internal combustion engine 10 and the like are provided with various sensors for detecting the engine operating state and the like. For example, an intake air amount sensor 66 for detecting the intake air amount is provided in a portion upstream of the throttle valve 26 in the intake passage 11. An engine rotation speed sensor 61 that detects the rotation speed (engine rotation speed) is provided in the vicinity of the crankshaft 17. An accelerator sensor 65 is provided in the vicinity of the accelerator pedal to detect the operation amount (depression amount). Further, a water temperature sensor 63 for detecting the coolant temperature THW of the engine, a vehicle speed sensor 62 for detecting the vehicle speed, a battery sensor 64 for detecting the charge amount of the battery 18 and the like are also provided.

  Further, an exhaust sensor 67 for detecting the oxygen concentration of exhaust gas, in other words, for detecting the actual air-fuel ratio, is provided in a portion of the exhaust passage 13 upstream of the catalyst 16. The exhaust sensor 67 is a so-called limiting current type oxygen concentration sensor, and its detection signal changes according to the actual air-fuel ratio.

  FIG. 2 is a graph showing the output characteristics of the exhaust sensor 67. As shown in the figure, the exhaust sensor 67 has a detection signal (output current value, usually referred to as “limit current value”) corresponding to the richness or leanness in both the rich region and the lean region. It has an output characteristic that changes continuously (linearly). Therefore, based on the detection signal of the exhaust sensor 67, the difference between the actual air-fuel ratio and the stoichiometric air-fuel ratio, in other words, the richness or the leanness can be detected.

  In addition, a heater is built in the exhaust sensor 67. In the exhaust sensor 67, the heater is energized to generate heat, and the temperature of the detection part of the exhaust sensor 67 is increased, thereby enabling early activation thereof.

  Various controls relating to the traveling of the vehicle are performed by the control device 50. The control device 50 includes a CPU for executing the various controls, a memory for storing information necessary for the control, an input port for inputting a signal from the outside, an output port for outputting a command signal to the outside, and the like. Configured. Detection signals from the various sensors 61 to 67 are input to the input port of the control device 50. On the other hand, the output port of the control device 50 is connected to a drive circuit such as a motor for driving the ignition plug of the internal combustion engine 10, the fuel injection valve 20 and the throttle valve 26, and a hydraulic control circuit of the automatic transmission 30. Through these drive controls, the control device 50 controls the switching of the combustion mode of the internal combustion engine 10, that is, the compression stroke injection mode in which combustion is performed under a lean air-fuel ratio and the intake stroke injection in which combustion is performed under a stoichiometric air-fuel ratio. Various controls such as mode switching control, air-fuel ratio control, or shift control of the automatic transmission 30 are performed. The output port is also connected to a control circuit for the starter 45, the generator motor 40, a drive circuit for the electromagnetic clutch 15, and the like. The operations of the starter 45, the generator motor 40, and the electromagnetic clutch 15 are also controlled by the control device 50. ing.

  In this vehicle, the control device 50 performs idle stop control, that is, intermittent operation, in which the operation of the internal combustion engine 10 is automatically stopped and restarted according to the traveling state. Next, an outline of the idle stop control in this vehicle will be described with reference to FIG.

  When the ignition switch is operated from the “OFF” position to the “ON” position by the driver and the control device 50 is activated, the control device 50 changes its control mode to “mode 0” indicating a normal engine stop state. Set. When the driver operates the ignition switch to the “STA” position when the “mode 0” is set, the starter 45 is drivingly connected to the crankshaft 17 and the output of the starter 45 starts the internal combustion engine 10. Is called. When the startup is successfully completed, the control mode of the control device 50 is shifted to “mode 1” indicating a normal engine operating state.

  When “mode 1” is set, the belt transmission mechanism 19 is drivingly connected to the crankshaft 17 by the electromagnetic clutch 15, and the accessories are driven by the output of the internal combustion engine 10. The generator motor 40 also receives the output of the internal combustion engine 10 through the belt transmission mechanism 19. The generator motor 40 at this time functions as a generator, and the generated power is charged in the battery 18.

  When the ignition switch is operated to the “OFF” position by the driver during the setting of “mode 1”, the control device 50 executes normal engine stop processing to stop the internal combustion engine 10 and control mode thereof. Is shifted to the “mode 0”.

On the other hand, when the idle stop execution condition is satisfied during the setting of “mode 1”, the control mode of the control device 50 is shifted to “mode 2” in which engine stop processing for automatically stopping the internal combustion engine 10 is executed. In the present embodiment, as the idle stop execution condition, for example, the establishment of the idle stop execution condition is determined when all of the following conditions (a1) to (a6) are satisfied.
(A1) The accelerator operation amount is “0”.
(A2) The vehicle speed is equal to or lower than a predetermined speed.
(A3) The brake pedal is depressed.
(A4) The cooling water temperature is equal to or higher than a predetermined temperature Ta.
(A5) The hydraulic oil temperature of the automatic transmission 30 is equal to or higher than a predetermined temperature.
(A6) The amount of charge of the battery 18 is equal to or greater than a predetermined value.

  When the control mode is shifted to “mode 2” in this way, the control device 50 stops the fuel supply and stops the internal combustion engine 10. When it is confirmed that the internal combustion engine 10 is completely stopped, the control mode of the control device 50 is shifted to “mode 3” indicating an engine stop state due to idle stop.

  When “mode 3” is set, the drive connection between the crankshaft 17 and the belt transmission mechanism 19 by the electromagnetic clutch 15 is released. At the same time, the generator motor 40 is operated as an electric motor, and the auxiliary machine is driven by the output. Thereby, the driving of the auxiliary machine is maintained even when the internal combustion engine 10 is stopped due to the idle stop.

When the engine restart execution condition is satisfied during the setting of “mode 3”, the control mode of the control device 50 is shifted to “mode 4” in which restart processing for restarting the internal combustion engine 10 is executed. In the present embodiment, as the restart execution condition, for example, the establishment of the engine restart execution condition is determined when any of the following conditions (b1) to (b3) is satisfied.
(B1) The brake pedal was released.
(B2) The accelerator operation amount is not “0”.
(B3) The amount of charge of the battery 18 has fallen below a predetermined value.

  When the control mode is shifted to “mode 4” in this way, the crankshaft 17 is reconnected to the belt transmission mechanism 19 by the electromagnetic clutch 15. At the same time, the generator motor 40 is operated as an electric motor, and the internal combustion engine 10 is restarted by the output. When the restart of the internal combustion engine 10 is completed successfully, the control mode of the control device 50 is shifted to the “mode 1”.

As described above, in this embodiment, so-called eco-run operation is performed to reduce the fuel consumption and the emission amount of harmful components contained in the exhaust gas.
On the other hand, during the operation of the internal combustion engine 10, the emission amount of harmful components contained in the exhaust gas is reduced as follows. That is, so-called air-fuel ratio feedback control is performed in which the air-fuel ratio is controlled to the target air-fuel ratio by feedback correcting the fuel injection amount injected from the fuel injection valve 20 based on the detection signal of the exhaust sensor 67. Yes. The target air-fuel ratio is normally set to the stoichiometric air-fuel ratio in order to bring out the exhaust purification action of the catalyst 16. Incidentally, since this air-fuel ratio feedback control is a control conventionally performed, a detailed description thereof is omitted, but the outline is as follows.

  In a series of processes related to feedback correction of the air-fuel ratio feedback control, first, a fuel injection amount correction coefficient, that is, a feedback correction coefficient, is determined based on a detection result of the exhaust sensor 67, that is, a deviation ΔRAF between the actual air-fuel ratio and the target air-fuel ratio. FAF is calculated through the following arithmetic expression (1). The feedback correction coefficient FAF has an upper limit guard value FAFMAX and a lower limit guard value FAFMIN determined in advance with the reference value “0” as the center, and falls within a range between the upper limit guard value FAFMAX and the lower limit guard value FAFMIN. As such, the amount of change is regulated.

FAF ← KP ・ (ΔRAF) (1)
KP: Correction coefficient (proportional gain)

Incidentally, the feedback correction coefficient FAF is corrected so that the basic fuel injection amount obtained from the engine operating state and the target air-fuel ratio becomes an appropriate value for matching the actual air-fuel ratio with the target air-fuel ratio. Here, the feedback correction coefficient FAF is added to the basic fuel injection amount QBASE to perform correction related to the fuel injection amount.

  When the actual air-fuel ratio is leaner than the target air-fuel ratio, the second term on the right side of the above equation (1) is a positive value, so the feedback correction coefficient FAF is a positive value corresponding to the lean degree. Is set. Therefore, in this case, the fuel injection amount increase correction is performed based on the feedback correction coefficient FAF.

  On the other hand, when the actual air-fuel ratio is richer than the target air-fuel ratio, the second term on the right side of the above equation (1) is a negative value, so the feedback correction coefficient FAF is a negative value corresponding to the rich degree. Is set. Therefore, in this case, the fuel injection amount reduction correction is performed based on the feedback correction coefficient FAF.

  Thus, based on the deviation ΔRAF between the actual air-fuel ratio and the target air-fuel ratio, the feedback correction coefficient FAF is calculated to a size corresponding to the deviation ΔRAF, so that the deviation between the actual air-fuel ratio and the target air-fuel ratio at that time is calculated. The fuel injection amount is appropriately set so as to cancel out, and the fuel injection amount is feedback-corrected. Note that a series of processes relating to the feedback correction constitutes the air-fuel ratio feedback control means.

  Further, in the present embodiment, at the time of engine start, a predetermined increase correction amount is temporarily added to the basic fuel injection amount, so that the actual air-fuel ratio for a while after the engine start is made richer than the theoretical air-fuel ratio. The starting amount is increased. By executing the start-up increase process, the startability of the internal combustion engine 10 is improved. Further, the following effects are obtained by executing the start-up amount increasing process. That is, when the engine is stopped, the catalyst 16 is in a state of capturing oxygen, so that the NOx purification function at the time of starting the engine may be deteriorated. Therefore, the fuel injection amount is set so that the actual air-fuel ratio becomes richer than the stoichiometric air-fuel ratio when the engine is started, that is, the oxygen trapped by the catalyst 16 is reduced by performing the increase at the time of starting, so that the engine is started. The reduction of the NOx purification function of the catalyst 16 is suppressed. The start-up increase process constitutes the start-up increase means.

  Here, the exhaust sensor 67 may have a response delay as described above. In this case, if the start timing of the air-fuel ratio feedback control is not set to an optimum one, the actual air-fuel ratio will be excessive as described above. There is a possibility that the exhaust gas is enriched and the exhaust emission at the time of automatic start deteriorates. Therefore, in the present embodiment, the limiting process for limiting the correction amount of the feedback correction is executed based on the detection signal of the exhaust sensor 67 from the time of automatic start until the elapse of a predetermined period. More specifically, the change in the actual air-fuel ratio due to the increase in fuel at the start is not detected by the exhaust sensor 67, that is, on the condition that the air-fuel ratio detected by the exhaust sensor 67 is leaner than the predetermined air-fuel ratio. The correction amount of the feedback correction is limited. In the present embodiment, the stoichiometric air-fuel ratio is set as the predetermined air-fuel ratio, so that it is possible to clearly determine that the exhaust sensor 67 has a response delay.

  On the other hand, the above-described automatic start of the internal combustion engine 10 is often a warm start, and at this time, a decrease in fuel density, generation of vapor, etc. are likely to occur. For this reason, there is a possibility that the actual air-fuel ratio does not immediately become rich even if the increase at the start is performed at the time of engine start. Therefore, in the present embodiment, the decrease in the increase value in the increase correction by the start-up increase process is started when the air-fuel ratio detected by the exhaust sensor 67 changes to the richer side than the stoichiometric air-fuel ratio. However, when there is a response delay in the exhaust sensor 67, it is delayed that the air-fuel ratio detected by the exhaust sensor shifts to a richer side than the stoichiometric air-fuel ratio. There is a risk that the starting amount will be excessively continued with a delay in the start of the engine. Therefore, in the present embodiment, as the above-described reduction process, the reduction of the increase value is forcibly started regardless of the value of the air-fuel ratio detected by the exhaust sensor 67 when a predetermined increase period has elapsed since the automatic start. I have to.

Hereinafter, the execution determination process of the air-fuel ratio feedback control having the restriction process and the start-up increase attenuation execution determination process having the reduction process will be described.
First, the execution determination process of air-fuel ratio feedback control will be described with reference to FIG. FIG. 4 shows a processing procedure for execution determination processing of air-fuel ratio feedback control (hereinafter referred to as FB control). This execution determination process is repeatedly executed every predetermined time after the automatic start by the control device 50.

  When this process is started, it is first determined whether or not the coolant temperature THW is equal to or higher than a predetermined value (S100). The predetermined value is set in advance to determine whether the current automatic start is a cold start or a warm start. If the coolant temperature THW is less than the predetermined value (NO in S100), it is determined that the current automatic start is a cold start (S160), and the start of the FB control is prohibited (S160), and this process ends. Then, after the predetermined time has elapsed, the determination process in S100 is executed again.

  On the other hand, when the coolant temperature THW is equal to or higher than the predetermined value (YES in S100), it is determined whether the exhaust sensor 67 is activated next, assuming that the current automatic start is a warm start (S110). ). The activation determination of the exhaust sensor 67 can be performed, for example, by detecting the internal resistance value of the heater and estimating the temperature of the exhaust sensor 67 based on the detection result, or based on the energization time of the heater. If it is determined that the exhaust sensor 67 is not activated (NO in S110), the start of the FB control is prohibited (S160), and this process is terminated. Then, after a predetermined time elapses, the processing procedure after S100 is executed again.

  On the other hand, when it is determined that the exhaust sensor 67 is activated (YES in S110), it is determined whether the internal combustion engine 10 is currently started (S120). This start determination can be made based on the engine speed NE, for example. If it is determined that the internal combustion engine 10 has not been started (NO in S120), the start of FB control is prohibited (S160), and this process is terminated. Then, after a predetermined time elapses, the processing procedure after S100 is executed again.

  On the other hand, when it is determined that the internal combustion engine 10 has been started (YES in S120), it is determined whether or not the current detection result of the exhaust sensor 67 is richer than the stoichiometric air-fuel ratio (S130). . The process of S130 constitutes the limiting means. Here, the current actual air-fuel ratio is made rich by the above-described start-up increase process. Therefore, if there is no response delay in the exhaust sensor 67, the detection result should be rich. Therefore, if it is determined in S130 that the current detection result of the exhaust sensor 67 is rich (YES in S130), it can be determined that there is no response delay in the exhaust sensor 67. Therefore, even if the air-fuel ratio feedback control is started, the actual air-fuel ratio is not likely to be excessively enriched, so the start of the FB control is permitted and executed (S140).

  On the other hand, if there is a response delay in the exhaust sensor 67, the detection result may indicate the actual air-fuel ratio before engine startup, that is, lean. Accordingly, if it is determined in S130 that the current detection result of the exhaust sensor 67 is not rich (NO in S130), it can be determined that a response delay has occurred in the exhaust sensor 67.

  Here, when the detection signal of the exhaust sensor 67 indicates lean despite the increase at the start time being executed, the following problem may occur only by the process of prohibiting the FB control. For example, when the response delay is excessively large, the start of the feedback correction is excessively delayed, and exhaust emission may be deteriorated. Here, even when the fuel injection amount is increased and corrected so that the actual air-fuel ratio at the time of engine start becomes richer than the stoichiometric air-fuel ratio, even if there is a response delay in the exhaust sensor 67, the exhaust sensor The detection signal 67 changes from lean to rich. That is, the detection signal of the exhaust sensor 67 approaches the actual air-fuel ratio after a predetermined period has elapsed since the automatic start. Therefore, in this process, when the predetermined period TA has elapsed from the time of automatic start, the restriction of the feedback correction is prohibited, that is, the feedback correction is executed. Therefore, feedback correction can be started at a time when the difference between the detection signal of the exhaust sensor 67 and the actual air-fuel ratio is considered to be small. Therefore, when the feedback correction is limited based on the detection result of the exhaust sensor 67 in consideration of the response delay of the exhaust sensor 67, the deterioration of the exhaust emission due to the delay of the start of the feedback correction can be suppressed.

  Accordingly, if a negative determination is made in S130, it is next determined whether or not a predetermined period TA has elapsed since the automatic start (S150). The predetermined period TA is a period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67, that is, the response delay time of the exhaust sensor 67 is set. The response delay time is determined to be an optimum value at the time of starting the engine through a prior experiment or the like. If it is determined that the predetermined period TA has not elapsed since the automatic start (NO in S150), it can be determined that the current detection signal of the exhaust sensor 67 does not reflect the actual air-fuel ratio. The start of the FB control is prohibited (S160), and the present process is terminated. Then, after a predetermined time elapses, the processing procedure after S100 is executed again.

  On the other hand, if it is determined that the predetermined period TA has elapsed since the automatic start (YES in S150), the response delay time has elapsed, so the detection signal of the current exhaust sensor 67 is the actual air-fuel ratio. It can be determined that this is reflected. At this time, even if the influence of the response delay remains on the detection signal and the actual air-fuel ratio is not accurately reflected, the predetermined signal TA has elapsed from the time of automatic start. It can be estimated that the value is close to the air-fuel ratio. For this reason, even if the air-fuel ratio feedback control is started, the actual air-fuel ratio is not likely to be excessively enriched. Therefore, the start of the FB control is permitted and executed (S140), and this process is terminated. Note that the process of S150 constitutes the prohibition means.

  As described above, in the execution determination process, it is determined not only whether to start air-fuel ratio feedback control based on the activation state of the exhaust sensor 67, but also from the time of automatic start until a predetermined period elapses. Based on the detection signal of the exhaust sensor 67, it is determined whether to start air-fuel ratio feedback control. As a result, even when there is a response delay in the exhaust sensor 67, the air-fuel ratio feedback control can be started at an optimum timing, thereby suppressing the deterioration of exhaust emission during automatic start. It becomes like this.

  Next, the above-described start-up amount attenuation execution determination process will be described with reference to FIG. FIG. 5 shows a processing procedure for the start-up amount attenuation execution determination process. This attenuation execution determination process is also repeatedly executed every predetermined time after the automatic start by the control device 50.

  When this process is started, it is first determined whether or not the exhaust sensor 67 is activated (S200). The activation determination of the exhaust sensor 67 is the same as the determination mode in S110 described above.

  If it is determined that the exhaust sensor 67 has not been activated (NO in S200), the start of attenuation of the increase correction amount is prohibited (S250), and this process ends. Then, after a predetermined time elapses, the processing procedure after S200 is executed again.

  On the other hand, when it is determined that the exhaust sensor 67 is activated (YES in S200), it is determined whether the internal combustion engine 10 is currently started (S210). This start determination can be made based on the engine speed NE, for example. If it is determined that the internal combustion engine 10 has not been started (NO in S210), the start of attenuation of the increase correction amount is prohibited (S250), and this process is terminated. Then, after a predetermined time elapses, the processing procedure after S200 is executed again.

  On the other hand, when it is determined that the internal combustion engine 10 has been started (YES in S210), it is determined whether or not the detection result of the exhaust sensor 67 is richer than the stoichiometric air-fuel ratio (S220). If it is determined that the detection result is rich (YES in S220), the increase correction amount is attenuated (S230), and the process ends.

  On the other hand, if it is determined that the detection result of the exhaust sensor is not rich (NO in S220), it is determined whether or not a predetermined increase period TB has elapsed since the automatic start (S240). The increase period TB is set to a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67, that is, a period shorter than the response delay time of the exhaust sensor 67. If it is determined that the increase period TB has not elapsed since the automatic start (NO in S240), the start of attenuation of the increase correction amount is prohibited (S250), and this process is terminated. Then, after a predetermined time elapses, the processing procedure after S200 is executed again.

  On the other hand, if it is determined that the increase period TB has elapsed since the automatic start (YES in S240), the increase correction amount is forcibly attenuated regardless of the air-fuel ratio value detected by the exhaust sensor 67. Is executed (S230), and the process is terminated.

  Thus, in the attenuation execution determination process, the decrease in the increase value in the increase correction by the start-up increase process is started after the air-fuel ratio detected by the exhaust sensor 67 has changed to a richer side than the theoretical air-fuel ratio. ing. By executing such a reduction process, the above reduction is not started when the air-fuel ratio detected by the exhaust sensor 67 is leaner than the stoichiometric air-fuel ratio, so that the actual air-fuel ratio at the time of engine startup is reliably enriched. Can be made. In addition, when the air-fuel ratio detected by the exhaust sensor 67 becomes richer than the stoichiometric air-fuel ratio, the above-described decrease starts, so that the increase at the start is continued even though the actual air-fuel ratio is rich. It is also possible to suppress the occurrence of a problem such that the air-fuel ratio becomes excessively rich.

  However, when the reduction process is performed based on the detection result of the exhaust sensor 67 and the exhaust sensor 67 has a response delay, the air-fuel ratio detected by the exhaust sensor is richer than the stoichiometric air-fuel ratio. Since there is a delay in shifting to, the start of weight reduction is delayed, and there is a risk that the amount of increase at the start will be excessively continued. Therefore, in the attenuation execution determination process, as the decrease process, the decrease in the increase value is forcibly started regardless of the value of the air-fuel ratio detected by the exhaust sensor 67 when the increase period TB has elapsed since the automatic start. I am doing so. Therefore, even when the detection signal of the exhaust sensor 67 does not indicate rich due to the response delay of the exhaust sensor 67, the fuel injection amount starts to decrease, and the actual air-fuel ratio is excessive due to the response delay of the exhaust sensor 67. It is possible to suppress the occurrence of defects such as being rich.

  Further, the following effect can be obtained by forcibly starting the decrease of the increase value when the increase period TB has elapsed since the automatic start. As described above, when there is a response delay in the exhaust sensor 67, the detection signal from the automatic start shows lean for a while even when the increase at the start is executed. Here, when the above reduction is forcibly started, the actual air-fuel ratio is shifted in the lean direction at an early stage, so that the difference between the actual air-fuel ratio and the detection result of the exhaust sensor 67 becomes early. That is, even when there is a response delay in the air-fuel ratio detected by the exhaust sensor 67, the difference between this air-fuel ratio and the air-fuel ratio of the air-fuel mixture that is actually used for combustion becomes small. The air-fuel ratio feedback control can be performed more stably.

  In particular, in the above-described embodiment, a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67 (response delay time of the exhaust sensor 67) is set as the increase period TB. . Therefore, compared with the case where the response delay time of the exhaust sensor 67 is set as the increase period TB, the actual air-fuel ratio can be shifted from rich to lean side at an early stage, and thus the air-fuel ratio detected by the exhaust sensor, The deviation from the air-fuel ratio of the air-fuel mixture used for actual combustion can be reduced early.

  Next, in the case where a response delay has occurred in the exhaust sensor 67, one aspect of the change in the actual air-fuel ratio when the execution determination process of the air-fuel ratio feedback control and the start-up increase attenuation execution determination process are executed is performed. Will be described with reference to FIG.

  FIG. 6 shows changes in the output of the exhaust sensor 67, that is, the detection result of the sensor, the actual air-fuel ratio, the feedback correction amount of the fuel injection amount, and the increase correction amount by the start-up increase process after each automatic start. An embodiment is shown. In addition, the change aspect shown with the continuous line in FIG. 6 has shown the change aspect in this embodiment. The change mode indicated by the alternate long and short dash line indicates a change mode in the case where the air-fuel ratio feedback control is started with the activation detection of the exhaust sensor and the attenuation of the increase correction amount is started with the rich detection by the exhaust sensor. This engine start is an automatic start after a temporary engine stop by the idle stop control, and is a warm start. Further, before the time t1, the operation of the internal combustion engine 10 is stopped, and the actual air-fuel ratio is lean.

First, the change mode of each parameter indicated by the alternate long and short dash line will be described.
When the automatic start is executed at time t1, the increase correction amount is added to the basic fuel injection amount by the start time increase process, and the actual air-fuel ratio starts to change from lean to rich. When it is determined that the exhaust sensor 67 is activated (time t2), air-fuel ratio feedback control is started. At this time, the actual air-fuel ratio is rich, but the detection result of the exhaust sensor shows lean due to the response delay. Therefore, the feedback correction amount set by the air-fuel ratio feedback control is set to the increase side, and the actual air-fuel ratio is excessively enriched. When the detection result of the exhaust sensor 67 shows rich (time t4), the increase correction amount starts to be attenuated, and the increase correction amount is gradually decreased.

  As described above, when the air-fuel ratio feedback control is started with the activation detection of the exhaust sensor 67 and the attenuation of the increase correction amount is started with the rich detection by the exhaust sensor 67, the actual air-fuel ratio is excessively enriched. End up. Further, since the correction direction of the feedback correction amount does not correspond to the actual air-fuel ratio, the actual air-fuel ratio fluctuates for a while even after the air-fuel ratio feedback control is started. Then, since the attenuation of the increase correction amount does not start until the exhaust sensor 67 in which the response delay has occurred performs rich detection, unnecessary fuel increase is continued, and the actual air-fuel ratio that has already been enriched is further enriched. It will also end up.

Next, how each parameter is changed in the present embodiment indicated by a solid line will be described.
When the automatic start is executed at time t1, the increase correction amount is added to the basic fuel injection amount by the start time increase process, and the actual air-fuel ratio starts to change from lean to rich. Then, it is determined that the exhaust sensor 67 is activated (time t2), and when the increase period TB has elapsed from the time of automatic start (time t1) (time t3), the increase correction amount starts to be attenuated. The correction amount is gradually reduced. As a result, compared with the case indicated by the one-dot chain line, the actual air-fuel ratio changes from rich to lean, that is, toward the stoichiometric air-fuel ratio earlier, and the actual air-fuel ratio is excessively enriched. The occurrence of problems such as When a predetermined period TA elapses from the time of automatic start (time t1) (time t5), air-fuel ratio feedback control is started and control is performed so that the actual air-fuel ratio becomes the target air-fuel ratio. Since the deviation between the actual air-fuel ratio and the detection result of the exhaust sensor 67 has decreased after the predetermined period TA has elapsed, the occurrence of problems such as excessive enrichment of the actual air-fuel ratio is suppressed. The actual air-fuel ratio after the start of air-fuel ratio feedback control is also stabilized near the stoichiometric air-fuel ratio.

As described above, according to the fuel injection control device for an internal combustion engine according to the present embodiment, the following effects can be obtained.
(1) After the exhaust sensor 67 is activated, the correction amount of the feedback correction is limited based on the detection result of the exhaust sensor 67. Therefore, feedback correction based on an erroneous detection signal due to the response delay of the exhaust sensor 67 is limited, and exhaust emission deterioration due to the response delay of the exhaust sensor 67 when the automatic start is executed is reduced. It becomes possible to suppress.

  (2) The above restriction is executed on condition that the exhaust sensor 67 does not detect a change in the actual air-fuel ratio due to the increase in fuel at the start. Accordingly, when the detection signal of the exhaust sensor 67 is not a detection signal corresponding to the increase in fuel, feedback correction is limited, and therefore, based on the detection signal of the exhaust sensor 67 that does not reflect the actual air-fuel ratio. Feedback correction is limited. Accordingly, it is possible to suppress the deterioration of the exhaust emission due to the response delay of the exhaust sensor 67 when the automatic start is executed.

  (3) As a more specific aspect of the above condition, the amount of feedback correction is limited on the condition that the air-fuel ratio detected by the exhaust sensor 67 is leaner than a predetermined air-fuel ratio. For this reason, since it is possible to suitably determine that a response delay has occurred in the exhaust sensor 67, it is possible to suitably execute the limitation of the feedback correction.

  (4) When the actual air-fuel ratio at the time of starting the engine is made richer than the stoichiometric air-fuel ratio by the increase at the time of starting, when the air-fuel ratio detected by the exhaust sensor 67 is leaner than the stoichiometric air-fuel ratio, It can be considered that there is a response delay in the exhaust sensor 67. Therefore, the stoichiometric air-fuel ratio is set as the predetermined air-fuel ratio. Therefore, it is possible to clearly determine that the exhaust sensor 67 has a response delay.

  (5) A response delay time of the exhaust sensor 67 is set as a predetermined period TA until a change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67, and the predetermined period TA has elapsed since the automatic start. Sometimes, the limitation of the feedback correction is prohibited. Therefore, feedback correction can be started at a time when the difference between the detection signal of the exhaust sensor 67 and the actual air-fuel ratio is considered to be small. Therefore, when the feedback correction is limited based on the detection result of the exhaust sensor 67 in consideration of the response delay of the exhaust sensor 67, the deterioration of the exhaust emission due to the delay of the start of the feedback correction can be suppressed. become.

  (6) As a specific aspect of the restriction process, feedback correction is prohibited. Therefore, erroneous feedback correction based on the detection signal of the exhaust sensor 67 that does not reflect the actual air-fuel ratio is prohibited. Therefore, it is possible to suppress the deterioration of the actual air-fuel ratio due to the response delay of the exhaust sensor 67 at the time of automatic start, thereby suppressing the deterioration of the exhaust emission.

  (7) A so-called start-up increase is performed to increase the fuel injection amount when starting the engine. Therefore, it is possible to improve the startability of the internal combustion engine 10 as described above, exhaust emission at the time of engine start, and the like. On the other hand, when such an increase at start-up is performed, if there is a response delay in the exhaust sensor 67, the exhaust emission may be easily deteriorated. However, in the above-described embodiment, the above-described restriction process is executed in the internal combustion engine that performs the increase at the time of starting. Therefore, it is possible to improve the startability of the internal combustion engine 10 and the exhaust emission at the time of starting the engine, and to suppress the deterioration of the exhaust emission due to the response delay of the exhaust sensor 67.

  (8) After the internal combustion engine 10 is automatically started, the decrease in the increase value in the increase correction by the increase process at the start is started after the air-fuel ratio detected by the exhaust sensor 67 changes to the richer side than the theoretical air-fuel ratio. I have to. Therefore, the actual air-fuel ratio at the time of engine start can be reliably enriched. It is also possible to suppress the occurrence of a problem that the increase at the start is continued despite the actual air-fuel ratio being rich and the actual air-fuel ratio becomes excessively rich.

  (9) When the above-described reduction process is performed based on the detection result of the exhaust sensor 67 and when the increase period TB has elapsed since the automatic start of the internal combustion engine 10, the value of the air-fuel ratio detected by the exhaust sensor 67 is concerned. First, the decrease of the increase value in the increase correction by the increase process at the start is forcibly started. Therefore, it is possible to suppress the occurrence of a problem that the actual air-fuel ratio becomes excessively rich due to the response delay of the exhaust sensor 67. Further, the air-fuel ratio feedback control started thereafter can be performed more stably.

  Incidentally, a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67 is set as the increase period TB. Therefore, the actual air-fuel ratio can be shifted from rich to lean side at an early stage, so that the difference between the air-fuel ratio detected by the exhaust sensor 67 and the air-fuel ratio of the air-fuel mixture provided for actual combustion is reduced early. Become.

(10) In the internal combustion engine 10 mounted on the vehicle that performs the eco-run operation, the number of engine start tends to be increased as compared with a normal internal combustion engine that is started only by the operation of the driver. Therefore, the exhaust emission deterioration at the time of starting the engine as described above may become more serious. In this regard, in the above embodiment, the fuel injection control device according to this embodiment is applied as the fuel injection control device of the internal combustion engine 10 that performs such an eco-run operation. For this reason, it is possible to more effectively suppress the deterioration of exhaust emission.
(Second Embodiment)
Next, a second embodiment that embodies the fuel injection control device for an internal combustion engine according to the present invention will be described with reference to FIGS.

  In the first embodiment, in order to suppress the deterioration of exhaust emission at the time of automatic stop / automatic start of the internal combustion engine 10, the restriction process and the weight reduction process as described above are executed at the time of the automatic start.

  On the other hand, when the vehicle is decelerated or when the engine speed is excessively increased, the same phenomenon occurs as when the internal combustion engine 10 is automatically stopped and started as described above. There is a fear.

  That is, when the fuel cut is restored, the fuel injection amount is temporarily increased in order to quickly recover the combustion in the internal combustion engine 10 or improve the exhaust emission. The fuel injection amount increasing process at the time of returning from the fuel cut is performed through a return-time increasing process similar to the start-up increasing process. The return increase process constitutes the return increase means. Here, since the fuel injection is interrupted during the fuel cut, the exhaust sensor 67 is exposed to the atmosphere, and the detection result of the sensor becomes lean. Then, when the fuel cut is restored, the exhaust sensor 67 tends to be activated quickly. Accordingly, the air-fuel ratio feedback control is started before the difference between the detection result of the exhaust sensor 67 and the actual air-fuel ratio due to the response delay described above becomes small. Therefore, in this case as well, the fuel injection amount is further increased to enrich the air-fuel ratio based on the lean detection of the exhaust sensor 67. Therefore, even when the fuel cut is restored, the actual air-fuel ratio becomes rich even though it is rich, and there is a risk of deteriorating the exhaust purification performance.

Therefore, in the present embodiment, the restriction process as described above is executed even when the fuel cut is restored.
Further, the internal combustion engine 10 is often in a warm state at the time of fuel cut recovery, and at this time, a decrease in fuel density, generation of vapor, etc. are likely to occur. Therefore, there is a possibility that the actual air-fuel ratio does not immediately become rich even if the increase at the start is performed at the time of fuel cut recovery. Therefore, in this embodiment as well, in the same way as in the first embodiment, the increase value in the increase correction by the return increase process from the time when the air-fuel ratio detected by the exhaust sensor 67 changes to the richer side than the stoichiometric air-fuel ratio. I'm trying to start weight loss. However, when there is a response delay in the exhaust sensor 67, it is delayed that the air-fuel ratio detected by the exhaust sensor shifts to a richer side than the stoichiometric air-fuel ratio. There is a risk that the starting amount will be excessively continued with a delay in the start of the engine. Therefore, in this embodiment as well, as in the first embodiment, the above-described reduction processing is further performed regardless of the value of the air-fuel ratio detected by the exhaust sensor 67 when a predetermined increase period has elapsed since the fuel cut return. The decrease of the increase value is forcibly started.

  In the limiting process in the present embodiment, it is assumed that the automatic start in the execution determination process of the air-fuel ratio feedback control shown in FIG. 4 is in a state where the combustion of the air-fuel mixture is restarted by the return of the fuel cut. Part of the processing procedure shown in FIG. 4 is changed to the processing procedure shown in FIG. That is, the process of step S150 in FIG. 4 is changed to the process of step S300 shown in FIG. The processing procedure shown in FIG. 7 is executed when the fuel cut is restored. In the following, the execution determination process in the present embodiment will be described focusing on differences from the execution determination process in the first embodiment.

  That is, if it is determined in S120 that combustion in the internal combustion engine 10 has been resumed (YES in S120), whether or not the current detection result of the exhaust sensor 67 is richer than the stoichiometric air-fuel ratio. Is determined (S130). If it is determined that the current detection result of the exhaust sensor 67 is rich (YES in S130), the start of FB control is permitted and executed (S140).

  On the other hand, if it is determined that the current detection result of the exhaust sensor 67 is not rich (NO in S130), it is determined whether or not a predetermined period TC has elapsed since the fuel cut recovery (after the F / C recovery). (S300). This predetermined period TC is a period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67, that is, the response delay time of the exhaust sensor 67 is set. It should be noted that the response delay time is determined to be an optimum value at the time of return from fuel cut through a prior experiment or the like, and in this embodiment, the same value as the predetermined period TA is set. By the way, since the exhaust flow rate is different between automatic stop / automatic start and fuel cut / fuel cut return, a value different from the predetermined period TA is set for the predetermined period TC in consideration of such differences. It may be.

  If it is determined that the predetermined period TC has not elapsed since the fuel cut return (NO in S300), it can be determined that the current detection signal of the exhaust sensor 67 does not reflect the actual air-fuel ratio. Therefore, the start of the FB control is prohibited (S160), and this process is terminated. Then, after a predetermined time elapses, the processing procedure after S100 is executed again.

  On the other hand, if it is determined that the predetermined period TA has elapsed since the fuel cut return (YES in S300), the response delay time has elapsed, so the detection signal of the current exhaust sensor 67 is actually empty. It can be determined that the fuel ratio is reflected. Also, at this time, even if the effect of response delay remains in the detection signal and the actual air-fuel ratio is not accurately reflected, since the predetermined period TA has elapsed since the fuel cut return, the detection signal is It can be estimated that the value is close to the actual air-fuel ratio. For this reason, even if the air-fuel ratio feedback control is started, the actual air-fuel ratio is not likely to be excessively enriched. Therefore, the start of the FB control is permitted and executed (S140), and this process is terminated.

  As described above, even in the execution determination process in the second embodiment, not only is it determined whether to start the air-fuel ratio feedback control based on the activation state of the exhaust sensor 67, but there is also a predetermined period from when the fuel cut is restored. Whether or not to start the air-fuel ratio feedback control is determined based on the detection signal of the exhaust sensor 67 until the time elapses. As a result, even when there is a response delay in the exhaust sensor 67, the air-fuel ratio feedback control can be started at an optimal timing, thereby suppressing the deterioration of exhaust emission when the fuel cut is restored. become able to.

  On the other hand, the reduction process in the present embodiment is also the state in which the combustion of the air-fuel mixture has been resumed by the return of the fuel cut in the automatic start in the start-up increase attenuation execution determination process shown in FIG. A part of the processing procedure shown in FIG. 5 is changed to the processing procedure shown in FIG. That is, the process of step S240 in FIG. 5 is changed to the process of step S400 shown in FIG. The processing procedure shown in FIG. 8 is executed when the fuel cut is restored. Hereinafter, the attenuation execution determination process in the present embodiment will be described with a focus on differences from the attenuation execution determination process in the first embodiment.

  That is, in the process of S220, when it is determined that the detection result of the exhaust sensor 67 is richer than the theoretical air-fuel ratio (YES in S220), the increase correction amount is attenuated (S230). Is terminated.

  On the other hand, if it is determined that the detection result of the exhaust sensor is not rich (NO in S220), it is determined whether or not a predetermined increase period TD has elapsed since the fuel cut return (S400). The increase period TD is set to a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67, that is, a period shorter than the response delay time of the exhaust sensor 67. The increase period TD in the present embodiment is set to the same value as the increase period TB. Incidentally, since the flow rate of the exhaust gas is different between the automatic stop / automatic start and the fuel cut / recovery of the fuel cut, a value different from the increase period TB is set in the increase period TD in consideration of such a difference. It may be.

  If it is determined that the increase period TD has not elapsed since the return of fuel cut (NO in S400), the start of attenuation of the increase correction amount is prohibited (S250), and the process ends. Then, after a predetermined time elapses, the processing procedure after S200 is executed again.

  On the other hand, if it is determined that the increase period TD has elapsed since the fuel cut return (YES in S400), the increase correction amount is forcibly set regardless of the value of the air-fuel ratio detected by the exhaust sensor 67. Attenuation is executed (S230), and this process is terminated.

  As described above, also in the attenuation execution determination process according to the second embodiment, the decrease in the increase value in the increase correction by the return increase process from the time when the air-fuel ratio detected by the exhaust sensor 67 changes to the richer side than the stoichiometric air-fuel ratio. Like to start. Therefore, it is possible to reliably enrich the actual air-fuel ratio when returning from fuel cut. Further, when the air-fuel ratio detected by the exhaust sensor 67 becomes richer than the stoichiometric air-fuel ratio, the above-described reduction starts, so that the increase at the time of return is continued even though the actual air-fuel ratio is rich. It is also possible to suppress the occurrence of a problem such that the air-fuel ratio becomes excessively rich.

  Further, in the attenuation execution determination process, as the decrease process, the decrease in the increase value is forcibly started regardless of the value of the air-fuel ratio detected by the exhaust sensor 67 when the increase period TD has elapsed since the fuel cut recovery. I have to. Therefore, even when the detection signal of the exhaust sensor 67 does not indicate rich due to the response delay of the exhaust sensor 67, the fuel injection amount starts to decrease, and the actual air-fuel ratio is excessive due to the response delay of the exhaust sensor 67. It is possible to suppress the occurrence of defects such as being rich.

  Further, when the increase period TD elapses from the time when the fuel cut is restored, the following effect as described above can be obtained by forcibly starting the decrease of the increase value. That is, even when there is a response delay in the air-fuel ratio detected by the exhaust sensor 67, the difference between this air-fuel ratio and the air-fuel ratio of the air-fuel mixture provided for actual combustion becomes small and is started after that. The air-fuel ratio feedback control can be performed more stably.

  In this embodiment as well, as in the first embodiment, the increase period TD is longer than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67 (response delay time of the exhaust sensor 67). A short period is set. Therefore, the difference between the air-fuel ratio detected by the exhaust sensor and the air-fuel ratio of the air-fuel mixture used for actual combustion can be reduced early.

As described above, according to the fuel injection control device for an internal combustion engine according to the present embodiment, the same effect as that of the first embodiment can be obtained even when the fuel cut is restored.
(Third embodiment)
Next, a third embodiment of the internal combustion engine fuel injection control device according to the present invention will be described with reference to FIG.

  In an internal combustion engine having a plurality of exhaust systems such as a V-type internal combustion engine, the exhaust sensor 67 is often provided for each exhaust system, and the exhaust flow mode, the response delay of the exhaust sensor 67, and the like are different for each exhaust system. May be different. Therefore, in the present embodiment, based on the detection result of the exhaust sensor provided in each exhaust system, the correction amount of the air-fuel ratio feedback correction with respect to the fuel injection amount of the cylinder connected to the exhaust system provided with the exhaust sensor Try to limit.

  For the same reason, based on the detection result of the exhaust sensor provided in each exhaust system, attenuation of the increase correction amount with respect to the fuel injection amount of the cylinder connected to the exhaust system having the exhaust sensor is started. I have to.

  FIG. 9 schematically shows an internal combustion engine 70 to which the fuel injection device according to the present embodiment is applied and its peripheral configuration, and is provided with a V-type internal combustion engine and an exhaust system for each bank. Except for this point, the configuration is basically the same as that of the internal combustion engine 10 in each of the above embodiments.

  The internal combustion engine 70 includes a first bank 71R and a second bank 71L, and a first exhaust passage 72R is connected to the first bank 71R. More specifically, the first exhaust passage 72R is connected to an exhaust port of a cylinder provided in the first bank 71R. In the middle of the first exhaust passage 72R, a first exhaust sensor 67R and a first catalyst 16R are provided.

  A second exhaust passage 72L is connected to the second bank 71L. More specifically, the second exhaust passage 72L is connected to an exhaust port of a cylinder provided in the second bank 71L. A second exhaust sensor 67L and a second catalyst 16L are provided in the middle of the second exhaust passage 72L.

  Detection signals from the first and second exhaust sensors are input to the control device 75. The control device 75 is the same device as the control device 50 described above. Then, the control device 75 controls the fuel injection amount of the cylinder of the first bank 71R based on the detection signal of the first exhaust sensor 67R. Similarly, the control device 75 controls the fuel injection amount of the cylinder of the second bank 71L based on the detection signal of the second exhaust sensor 67L.

The control device 75 executes the air-fuel ratio feedback control execution determination process as described above for each bank.
That is, in the execution determination process at the time of automatic start shown in FIG. 4 and the execution determination process at the time of fuel cut return shown in FIG. 7, the process of S110 and the process of S130 are the first exhaust sensor 67R. It is executed based on the detection result. In S140, the start of FB control is permitted and executed with respect to the fuel injection amount in the cylinder of the first bank 71R. In S160, the start of the FB control is prohibited with respect to the fuel injection amount in the cylinder of the first bank 71R.

The control device 75 also executes the attenuation execution determination process as described above for each bank.
That is, in the execution of the attenuation execution determination process at the time of the automatic start shown in FIG. 5 and the execution of the attenuation execution determination process at the time of the fuel cut recovery shown in FIG. 8, the process of S200 and the process of S220 are the first exhaust. It is executed based on the detection result of the sensor 67R. In S230, the increase correction amount is attenuated with respect to the fuel injection amount in the cylinders of the first bank 71R. In S250, the start of attenuation of the increase correction amount with respect to the fuel injection amount in the cylinder of the first bank 71R is prohibited.

  The air-fuel ratio feedback control execution determination process and the attenuation execution determination process in the second bank 71L are also performed in the same manner as each process in the first bank 71R. That is, based on the detection result of the second exhaust sensor 67L, the FB control is performed or prohibited in the second bank 71L. Further, based on the detection result of the second exhaust sensor 67L, execution of attenuation of the increase correction amount in the second bank 71L or prohibition of start of attenuation of the increase correction amount is prohibited.

  As described above, in this embodiment, the execution determination process for the air-fuel ratio feedback control is executed independently for each exhaust system. Therefore, even an internal combustion engine having a plurality of exhaust systems can suppress deterioration of exhaust emissions.

  The attenuation execution determination process is executed independently for each exhaust system. Therefore, even in an internal combustion engine having a plurality of exhaust systems, the effects obtained by executing the attenuation execution determination process, that is, the effects described in (8) and (9) in the first embodiment are suitably obtained. Will be able to.

In addition, each said embodiment can also be changed and implemented as follows.
In each of the above embodiments, the stoichiometric air-fuel ratio is set as the predetermined air-fuel ratio. However, the predetermined air-fuel ratio is appropriately changed as long as the air-fuel ratio can detect the response delay of the exhaust sensor 67. can do.

  In the above embodiments, the feedback correction limiting mode prohibits air-fuel ratio feedback control. In addition to this, even if a limiting mode as described in (a) or (b) below is adopted, the above-mentioned feedback correction can be reliably limited, so that the actual sky at the time of engine start or fuel cut return An excessive enrichment of the fuel ratio can be suppressed.

  (A) In the air-fuel ratio feedback control, the upper limit guard value FAFMAX is set for the feedback correction coefficient FAF, and the feedback correction coefficient FAF is limited to a value smaller than the upper limit guard value FAFMAX. Set the value FAFMAX to a smaller value.

(B) The feedback correction coefficient FAF is changed so that the fuel injection amount is reduced at the time of the restriction. For example, the correction coefficient (proportional gain) KP is changed to a smaller value.
In the first embodiment, the start-time increasing process is executed in order to make the actual air-fuel ratio at the start of the engine richer than the stoichiometric air-fuel ratio. In the second embodiment, the return increasing process is executed to make the actual air-fuel ratio at the time of fuel-cut return richer than the stoichiometric air-fuel ratio. In addition to this, for example, in air-fuel ratio feedback control, the target air-fuel ratio at engine start or fuel cut return is set to be richer than the stoichiometric air-fuel ratio. The present invention can be similarly applied to any fuel injection control device that corrects the fuel injection amount to be richer than the stoichiometric air-fuel ratio.

  The exhaust sensor in each of the above embodiments is a so-called limiting current type oxygen concentration sensor that can detect the richness or the leanness of the actual air-fuel ratio. In addition, the present invention can be similarly applied to a so-called concentration cell type oxygen concentration sensor that can detect only whether the actual air-fuel ratio is rich or lean.

  In the first embodiment, as the increase period TB, a period shorter than the period until the change in the actual air-fuel ratio is reflected in the detection signal of the exhaust sensor 67 is set, but other periods are appropriately set. It can also be set. Similarly, the increase period TD in the second embodiment can be set as appropriate in other periods.

  In the third embodiment, the case where the present invention is applied to the fuel injection control device for a V-type internal combustion engine having two exhaust systems has been described. However, this is an internal combustion engine having a plurality of other exhaust systems. Can be applied similarly.

  In each of the above embodiments, the case where the present invention is applied to the fuel injection control device for an internal combustion engine of a vehicle that performs eco-run operation has been described. In addition, the present invention can be similarly applied to a fuel injection control device for an internal combustion engine mounted on a so-called hybrid vehicle including an internal combustion engine and an electric motor as a drive source of the vehicle.

  In the second and third embodiments, the air-fuel ratio feedback control execution determination process and the attenuation execution determination process at the time of fuel cut return are performed when the vehicle that does not perform the eco-run operation, that is, the engine is automatically stopped and automatically started. It can also be implemented with no internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the 1st Embodiment about the internal combustion engine to which the fuel-injection control apparatus concerning this invention was applied, and its periphery structure. The graph which shows the output characteristic of an exhaust sensor. The control mode figure of idle stop control in the same embodiment. The flowchart which shows the procedure about the execution determination process of the air fuel ratio feedback control by the embodiment. The flowchart which shows the procedure about attenuation | damping execution determination processing of the increase amount at the start by the embodiment. The timing chart explaining the effect | action by the embodiment. The flowchart which shows the procedure about the execution determination processing of the air fuel ratio feedback control by 2nd Embodiment. The flowchart which shows the procedure about attenuation | damping execution determination processing of the increase at the time of return by the embodiment. Schematic which shows the internal combustion engine in 3rd Embodiment, and its periphery structure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 70 ... Internal combustion engine, 11 ... Intake passage, 13 ... Exhaust passage, 15 ... Electromagnetic clutch, 16 ... Catalyst, 16R ... First catalyst, 16L ... Second catalyst, 17 ... Crankshaft 17 ... Battery, 19 ... Belt transmission Mechanism: 20 ... Fuel injection valve, 24 ... Delivery pipe, 26 ... Throttle valve, 30 ... Automatic transmission, 40 ... Generator motor, 45 ... Starter, 50, 75 ... Control device, 61 ... Engine speed sensor, 62 ... Vehicle speed Sensor: 63 ... Water temperature sensor, 64 ... Battery sensor, 65 ... Accelerator sensor, 66 ... Intake air amount sensor, 67 ... Exhaust sensor, 67R ... First exhaust sensor, 67L ... Second exhaust sensor, 71R ... First bank, 71L ... second bank, 72R ... first exhaust passage, 72L ... second exhaust passage.

Claims (19)

An increase unit at the time of start-up that corrects the fuel injection amount so that the actual air-fuel ratio at the time of engine start becomes richer than the stoichiometric air-fuel ratio, and an exhaust sensor that detects the oxygen concentration of exhaust gas provided in the exhaust passage of the internal combustion engine Air-fuel ratio feedback control means for calculating a fuel injection amount correction coefficient for making the actual air-fuel ratio coincide with the target air-fuel ratio based on the detection signal, and performing feedback correction of the fuel injection amount based on the fuel injection amount correction coefficient; A fuel injection control device for an internal combustion engine that automatically stops and automatically starts the engine under a predetermined condition.
A fuel injection control device for an internal combustion engine, comprising: limiting means for limiting a correction amount of the feedback correction based on a detection result of the exhaust sensor after the exhaust sensor is activated. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the limiting unit executes the limitation on the condition that a change in an actual air-fuel ratio due to the fuel increase of the start-up increasing unit is not detected by the exhaust sensor. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the restriction unit executes the restriction on a condition that an air-fuel ratio detected by the exhaust sensor is leaner than a predetermined air-fuel ratio. The fuel injection control device for an internal combustion engine according to claim 3, wherein the predetermined air-fuel ratio is a stoichiometric air-fuel ratio. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
A fuel injection control device for an internal combustion engine, further comprising prohibiting means for prohibiting restriction by the restricting means when a predetermined period has elapsed since the automatic start. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5,
The starting increase means starts reducing the increase value in the increase correction when the air-fuel ratio detected by the exhaust sensor changes to a richer side than the stoichiometric air-fuel ratio after the automatic start. A fuel injection control device for an internal combustion engine. 7. The start-up increase means forcibly starts decreasing the increase value regardless of the air-fuel ratio value detected by the exhaust sensor when a predetermined increase period has elapsed since the automatic start. Fuel injection control device for internal combustion engine. A return increase means for increasing the fuel injection amount so that the actual air-fuel ratio at the time of fuel cut return becomes richer than the stoichiometric air-fuel ratio, and an exhaust sensor provided in the exhaust passage of the internal combustion engine for detecting the oxygen concentration of the exhaust gas An air-fuel ratio feedback control means for calculating a fuel injection amount correction coefficient for making the actual air-fuel ratio coincide with the target air-fuel ratio on the basis of the detection signal and performing feedback correction of the fuel injection amount based on the fuel injection amount correction coefficient In a fuel injection control device for an internal combustion engine that performs fuel cut and return of fuel cut under a predetermined condition,
A fuel injection control device for an internal combustion engine, comprising: limiting means for limiting a correction amount of the feedback correction based on a detection result of the exhaust sensor after the exhaust sensor is activated. The fuel injection control device for an internal combustion engine according to claim 8, wherein the limiting means executes the restriction on condition that a change in the actual air-fuel ratio due to the fuel increase of the return increasing means is not detected by the exhaust sensor. 10. The fuel injection control device for an internal combustion engine according to claim 8, wherein the limiting means executes the limiting on condition that an air-fuel ratio detected by the exhaust sensor is leaner than a predetermined air-fuel ratio. The fuel injection control device for an internal combustion engine according to claim 10, wherein the predetermined air-fuel ratio is a stoichiometric air-fuel ratio. The fuel injection control device for an internal combustion engine according to any one of claims 6 to 11,
A fuel injection control device for an internal combustion engine, further comprising: prohibiting means for prohibiting restriction by the restricting means when a predetermined period has elapsed since the time of fuel cut recovery. The fuel injection control device for an internal combustion engine according to any one of claims 6 to 12,
The return increasing means starts decreasing the increase value in the increase correction when the air-fuel ratio detected by the exhaust sensor changes to a richer side than the stoichiometric air-fuel ratio after returning from the fuel cut. A fuel injection control device for an internal combustion engine. The return-time increase means forcibly starts decreasing the increase value regardless of the value of the air-fuel ratio detected by the exhaust sensor when a predetermined increase period has elapsed since the fuel cut return. A fuel injection control device for an internal combustion engine as described. The internal combustion engine includes a plurality of exhaust systems, and the increase relative to the fuel injection amount of a cylinder connected to the exhaust system provided with the exhaust sensor based on a detection result of the exhaust sensor provided in each exhaust system. The fuel injection control device for an internal combustion engine according to any one of claims 6, 7, 13, and 14. The internal combustion engine includes a plurality of exhaust systems, and the limiting means is a fuel for a cylinder connected to the exhaust system provided with the exhaust sensor based on a detection result of the exhaust sensor provided in each exhaust system. The fuel injection control device for an internal combustion engine according to claim 1, wherein a correction amount of the feedback correction with respect to an injection amount is limited. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 16, wherein the limiting means prohibits the feedback correction. The air-fuel ratio feedback control means sets an upper limit guard value for the fuel injection amount correction coefficient, and limits the fuel injection correction coefficient to a value smaller than the upper limit guard value,
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 16, wherein the restriction means sets the upper limit guard value to a smaller value at the time of the restriction. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 16, wherein the restriction means changes the fuel injection amount correction coefficient so that the fuel injection amount is reduced at the time of the restriction.

Images