JP4432915B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

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

  It has a first fuel injection valve that injects fuel directly into the cylinder and a second fuel injection valve that injects fuel into the intake port, and supplies fuel into the cylinder using these two fuel injection valves An internal combustion engine that performs homogeneous combustion is known. In such an internal combustion engine, generally, the combustion air-fuel ratio is leaner than the stoichiometric air-fuel ratio on the low load side, and is the stoichiometric air-fuel ratio on the high load side. Also, on the low load side, the fuel injection ratio of the second fuel injection valve is made larger than the fuel injection ratio of the first fuel injection valve with the intention of increasing the homogeneity of the homogeneous mixture, and on the high load side, The fuel injection ratio of the first fuel injection valve is made larger than the fuel injection ratio of the second fuel injection valve with the intention of lowering the in-cylinder temperature and increasing the charging efficiency.

  Further, when the combustion air-fuel ratio is the stoichiometric air-fuel ratio, the combustion temperature rises and the in-cylinder temperature is increased. Therefore, deposits are easily generated in the nozzle holes of the first fuel injection valve that opens in the cylinder. Thereby, making the fuel injection ratio of the first fuel injection valve larger than the fuel injection ratio of the second fuel injection valve reduces the temperature of the injection hole of the first fuel injection valve and suppresses deposit accumulation in the injection hole. Is advantageous.

  Incidentally, in order to accurately control the amount of fuel supplied into the cylinder, it is necessary to correct the fuel injection amount from each fuel injection valve. In the case of the above-described internal combustion engine, fuel is always injected from the two fuel injection valves. Therefore, it is difficult to set a different fuel injection correction coefficient for each fuel injection valve, which is detected by an air-fuel ratio sensor. The amount of fuel actually supplied into the cylinder is calculated from the air-fuel ratio of the exhaust gas, and the same fuel injection correction coefficient for the two fuel injection valves is learned based on the excess and deficiency with respect to the required amount of fuel supplied.

  The fuel injection correction coefficient learned in this way is effective only for the fuel injection ratios of the first fuel injection valve and the second fuel injection valve at the time of learning and, strictly speaking, the required fuel supply amount at the time of learning. is there. Thus, it has been proposed to learn a correction coefficient for each operation region having a different fuel injection ratio (see, for example, Patent Document 1).

JP 3-185242 JP-A-2005-315124

In general, an air-fuel ratio sensor can detect an accurate air-fuel ratio in the vicinity of the theoretical air-fuel ratio, and can learn a fuel injection correction coefficient for the fuel injection ratio at this time when the stoichiometric air-fuel ratio is homogeneously combusted. . However, the air-fuel ratio sensor cannot accurately detect an air-fuel ratio leaner than about 18 as in the homogeneous combustion of the lean air-fuel ratio in which the amount of NO _x produced is suppressed. It is not possible to learn an accurate fuel injection correction coefficient for the current fuel injection ratio.

As a result, during homogeneous combustion with a lean air-fuel ratio, the fuel injection amount cannot be accurately corrected, and more fuel than necessary is supplied into the cylinder, resulting in an increase in the amount of NO _x generated, or more than necessary. There may be a case where only a small amount of fuel is supplied into the cylinder and the required torque cannot be generated.

  Accordingly, an object of the present invention includes a first fuel injection valve that injects fuel into a cylinder and a second fuel injection valve that injects fuel into an intake port, and the first fuel injection valve, the second fuel injection valve, Both are used to supply fuel into the cylinder, the combustion air-fuel ratio is close to the stoichiometric air-fuel ratio, and the first fuel injection ratio of the first fuel injection valve and the second fuel injection valve is the first fuel injection ratio. And internal combustion engine fuel that is switched between the second combustion mode in which the combustion air-fuel ratio is lean from the vicinity of the theoretical air-fuel ratio and the fuel injection ratio of the first fuel injection valve and the second fuel injection valve is the second fuel injection ratio. In the injection control device, the fuel injection correction coefficient at the time of the second combustion can be learned.

According to a first aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine comprising a first fuel injection valve for injecting fuel into a cylinder and a second fuel injection valve for injecting fuel into an intake port. The fuel is supplied into the cylinder using both the one fuel injection valve and the second fuel injection valve, the combustion air-fuel ratio is made close to the theoretical air-fuel ratio, and the first fuel injection valve and the second fuel injection valve First combustion in which the fuel injection ratio is the first fuel injection ratio, the combustion air-fuel ratio is lean from the vicinity of the theoretical air-fuel ratio, and the fuel injection ratio of the first fuel injection valve and the second fuel injection valve is the second fuel injection In a fuel injection control device for an internal combustion engine that switches between second combustion as a ratio and performs fuel injection correction of the first fuel injection valve and the second fuel injection valve with respect to the second fuel injection ratio in the second combustion The coefficient is the operating range of the second combustion When Oite engine temperature is below the set temperature, the fuel injection rate to implement the combustion was near stoichiometric air-fuel ratio of the combustion air-fuel ratio by said second fuel injection ratio, learning region based on the amount of fuel supplied to the cylinder It is learned every time.

  According to a second aspect of the present invention, there is provided the fuel injection control device for an internal combustion engine according to the first aspect, wherein a fuel injection correction coefficient in the second combustion is set for each learning region. When not learned, when the engine temperature is higher than the set temperature, the first combustion is performed with the fuel injection ratio as the first fuel injection ratio in the operation region of the second combustion.

According to the fuel injection control device for an internal combustion engine according to claim 1 of the present invention, at the time of the second combustion in which the air-fuel ratio cannot be accurately detected by the air-fuel ratio sensor, the second fuel injection ratio in the second combustion. Since the fuel injection correction coefficients of the first fuel injection valve and the second fuel injection valve cannot be learned with respect to the As a second fuel injection ratio, combustion is performed with the combustion air-fuel ratio in the vicinity of the theoretical air-fuel ratio so that the air-fuel ratio can be accurately detected by the air-fuel ratio sensor, and a learning region based on the fuel supply amount into the cylinder Every time, the fuel injection correction coefficient of the first fuel injection valve and the second fuel injection valve with respect to the second fuel injection ratio in the second combustion is learned. At this time, the combustion temperature of combustion with the combustion air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio becomes relatively high, but if the engine temperature is equal to or lower than the set temperature, the in-cylinder temperature is not increased so much, and the fuel injection ratio is Even if the second fuel injection ratio suitable for the second combustion is set to be small and the fuel injection ratio of the first fuel injection valve is small, no deposit is deposited in the injection hole of the first fuel injection valve.

According to the fuel injection control device for an internal combustion engine according to claim 2 of the present invention, in the fuel injection control device for internal combustion engine according to claim 1, the fuel injection correction coefficient in the second combustion is determined for each learning region. When not learned, when the engine temperature is higher than the set temperature, the first combustion is performed with the fuel injection ratio as the first fuel injection ratio in the operation region of the second combustion. If the engine temperature is higher than the set temperature, in order to learn a fuel injection correction coefficient in the second combustion, the fuel injection ratio to a second fuel injection ratio of the combustion air-fuel ratio to the stoichiometric air-fuel ratio near the operating region of the second combustion Since the in-cylinder temperature is increased and deposits are likely to accumulate in the nozzle holes of the first fuel injection valve when performing the combustion, the learning of the fuel injection correction coefficient in the second combustion is abandoned at this time, The first combustion is performed with the fuel injection ratio as the first fuel injection ratio, and deposit accumulation in the nozzle hole of the first fuel injection valve is suppressed, and the second combustion in which accurate correction of the fuel injection amount is not performed. Implemented to prevent exhaust emissions from deteriorating.

  FIG. 1 is a schematic view showing an internal combustion engine to which a fuel injection control device according to the present invention is attached. In the figure, 1 is an engine body, and 2 is a surge tank common to each cylinder. An intake manifold 3 communicates the surge tank 2 and each cylinder, and 4 is an intake passage on the upstream side of the surge tank 2. A throttle valve 5 is disposed in the intake passage 4 immediately upstream of the surge tank 2. An air flow meter 6 for measuring the intake air amount is disposed upstream of the throttle valve 5 in the intake passage 4, and an air cleaner 7 is disposed in the most upstream part.

An exhaust manifold 8 communicates with each cylinder. An upstream NO _x storage reduction catalyst device 10 and a downstream three-way catalyst device 11 are arranged in series in an exhaust passage 9 downstream of the exhaust manifold 8. An air-fuel ratio sensor 12 capable of detecting the air-fuel ratio of the exhaust gas is disposed upstream of the NO _x storage reduction catalyst device 10, and the air-fuel ratio of the exhaust gas is rich on the downstream side of the three-way catalyst device 11. An oxygen sensor 13 that can detect whether the sensor is lean or lean is disposed. Based on the output of the oxygen sensor 13, the deviation of the output of the air-fuel ratio sensor 12 to the rich side or the lean side is corrected. 14 is a first fuel injection valve for directly injecting fuel into each cylinder, and 15 is a second fuel injection valve for injecting fuel into the intake port of each cylinder.

The internal combustion engine injects fuel during the intake stroke by the first fuel injection valve 14 and during the intake stroke (intake synchronization) by the second fuel injection valve 15 or during the exhaust stroke before the intake stroke (intake asynchronous). The fuel is injected, and a homogeneous mixture is formed in the cylinder by the fuel injected from these two fuel injection valves 14 and 15 to perform homogeneous combustion. However, in the high load region where the engine load is equal to or higher than the set load, the air-fuel ratio of the homogeneous mixture is the stoichiometric air-fuel ratio (or a rich air-fuel ratio slightly richer than the stoichiometric air-fuel ratio) and the engine load is less than the set load. In the side region, the air-fuel ratio of the homogeneous mixture is leaner than the stoichiometric air-fuel ratio, so that fuel consumption is suppressed. The lean air-fuel ratio is selected to be 18 or more so that the NO _x generation amount is suppressed. Hereinafter, the combustion at the stoichiometric air-fuel ratio will be described as the first combustion, and the combustion at the lean air-fuel ratio will be described as the second combustion.

  The fuel directly injected into the cylinder from the first fuel injection valve 14 is advantageous in increasing the intake charging efficiency in order to sufficiently reduce the temperature in the cylinder when vaporizing in the cylinder. On the other hand, since the fuel injected from the second fuel injection valve 15 is supplied into the cylinder together with the intake air, it is advantageous for homogenizing the fuel in the cylinder. Accordingly, in the first combustion that requires high engine output, the amount of fuel injected from the second fuel injection valve 15 is reduced with respect to each required amount of supplied fuel, and the first fuel injection valve correspondingly. It is preferable to increase the amount of fuel injected from 14, and the fuel injection ratio of the first fuel injection valve 14 and the second fuel injection valve 15 is set to 7: 3, for example. In the second combustion, which does not require a very high engine output and it is necessary to stabilize the combustion by increasing the homogeneity of the homogeneous mixture, the first fuel injection is performed for each required amount of supplied fuel. It is preferable to reduce the amount of fuel injected from the valve 14 and increase the amount of fuel injected from the second fuel injection valve 15 correspondingly, and the fuel of the first fuel injection valve 14 and the second fuel injection valve 15 The injection ratio is set as 3: 7, for example.

  Even in the first combustion, homogeneity is necessary, and 30% of the supplied fuel amount is injected by the second fuel injection valve 15. On the other hand, in the second combustion, it is conceivable that all the supplied fuel amount is injected by the second fuel injection valve 15, but when the fuel injection of the first fuel injection valve 14 is stopped, the second fuel injection valve 14 opens into the cylinder. Deposits may accumulate in the nozzle hole of one fuel injection valve 14 and the nozzle hole may be clogged. Thereby, in the second combustion, 30% of the supplied fuel amount is injected by the first fuel injection valve 14.

  In the second combustion where the combustion air-fuel ratio is lean, the combustion temperature does not increase so much and the in-cylinder temperature does not increase so much, so about 30% of the supplied fuel amount is injected by the first fuel injection valve 14. Thus, deposit accumulation in the nozzle hole of the first fuel injection valve 14 can be suppressed. However, in the first combustion in which the combustion air-fuel ratio is the stoichiometric air-fuel ratio, the combustion temperature is high, and about 70% of the supplied fuel amount must be injected by the first fuel injection valve 14 in order to sufficiently increase the in-cylinder temperature. In this case, deposit accumulation on the injection hole of the first fuel injection valve 14 cannot be suppressed.

  Incidentally, in order to accurately control the amount of fuel supplied into the cylinder, it is necessary to correct the fuel injection amounts from the first fuel injection valve 14 and the second fuel injection valve 15. When fuel is always injected from two fuel injection valves as in this internal combustion engine, the respective fuel injection amounts actually injected from the first fuel injection valve 14 and the second fuel injection valve must be grasped. It is difficult. Accordingly, it is difficult to set a different fuel injection correction coefficient for each fuel injection valve, and the amount of fuel supplied from the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 12 to the actual cylinder (the first fuel injection valve 14). And the total fuel injection amount injected from the second fuel injection valve 15), and based on the excess or deficiency of the supplied fuel amount with respect to the required supply fuel amount, the first fuel injection valve 14 and the second fuel injection valve 15 are calculated. The same fuel injection correction coefficient is learned.

The fuel injection correction coefficient learned in this way is only for the fuel injection ratios of the first fuel injection valve 14 and the second fuel injection valve 15 at the time of learning and, strictly speaking, the necessary fuel supply amount at the time of learning. It is valid. For example, when the required fuel supply amount is 20 mm ³ and the fuel injection ratio of the first fuel injection valve 14 and the second fuel injection valve 15 is 7: 3, the first fuel injection valve 14 supplies 14 mm ³ of fuel. The second fuel injection valve 15 is required to inject 6 mm ³ of fuel. Further, if the fuel injection ratio of the first fuel injection valve 14 and the second fuel injection valve 15 is 3: 7, the first fuel injection valve 14 is required to inject 6 mm ³ of fuel, and the second fuel injection The valve 15 is required to inject 14 mm ³ of fuel.

  In such a case, the first fuel injection valve 14 can only inject 80% of the fuel to the demand, and the second fuel injection valve 15 injects 90% of the fuel to the demand. If it can only be done, the fuel injection correction coefficient calculated when the fuel injection ratio is 7: 3 is 20 / (14 * 0.8 + 6 * 0.9) = 1.20, and the fuel injection ratio The fuel injection correction coefficient calculated when is 3: 7 is 20 / (6 * 0.8 + 14 * 0.9) = 1.15. Of course, when calculating these fuel injection correction coefficients, the value in () is the actual amount of fuel supplied based on the actual air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 12. As described above, when the fuel injection ratios are different, the common fuel injection correction coefficient of the first fuel injection valve 14 and the second fuel injection valve 15 is obviously different, and even if the required supply fuel amount changes, the fuel The injection correction coefficient has a different value.

  Thereby, it is conceivable to learn the fuel injection correction coefficient for each required supply fuel amount in the first combustion and the second combustion with different fuel injection ratios. It is not possible to accurately detect the lean air-fuel ratio, that is, it is impossible to grasp the actual amount of fuel supplied at this time, and as it is, it is not possible to learn the fuel injection correction coefficient during the second combustion. Can not.

  The fuel injection control device can learn the fuel injection correction coefficient k2n at the time of the second combustion according to the flowchart shown in FIG. First, in step 101, it is determined whether or not the requested engine load L is equal to or greater than a set load L '. When this determination is affirmative, it is the first combustion operation region of the stoichiometric air-fuel ratio, and in step 111, the air-fuel ratio is set to the basic supply fuel amount Qb necessary for the stoichiometric air-fuel ratio operation based on the engine load, the engine speed, and the like. The supplied fuel amount Q is calculated by multiplying the feedback correction coefficient f of the sensor 12 and the first fuel injection correction coefficient k1n. Next, in step 112, the first fuel injection valve 14 and the second fuel injection valve 15 are used to supply the supply fuel amount Q into the cylinder based on the first fuel injection ratio (for example, 7: 3) of the first combustion. Each fuel injection amount is set, and the first combustion is performed. That is, the fuel injection amounts of the first fuel injection valve 14 and the second fuel injection valve 15 for injecting the basic supply fuel amount Qb at the first fuel injection ratio are corrected by the same first fuel injection correction coefficient k1n. Will be. Here, the required supply fuel amount to be supplied into the cylinder is the basic supply fuel amount Qb.

  As shown in FIG. 3, the first fuel injection correction coefficient k1n is set, for example, for each of the three divided areas in the range of the basic supply fuel amount Qb for the first combustion. In the first combustion, feedback for further correcting the basic supply fuel amount Qb corrected by the first fuel injection correction coefficient k1n so that the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 12 becomes the stoichiometric air-fuel ratio. A correction coefficient f is calculated. The first fuel injection correction coefficient k1n is updated so that the calculated feedback correction coefficient f is set to 1 during operation in each region.

  On the other hand, if the requested engine load L is less than the set load L ′, it is an operating region in the second combustion with a lean air-fuel ratio, the determination in step 101 is negative and the routine proceeds to step 102. In step 102, it is determined whether or not a flag F that is reset to 0 when the engine is stopped is 1. Initially, the flag F is 0, the determination in step 102 is denied, and the process proceeds to step 103. In step 103, it is determined whether or not the engine temperature T represented by the cooling water temperature or the like is equal to or lower than a set temperature T '. When this determination is affirmative, such as immediately after the engine is started, the routine proceeds to step 106, where the basic supply fuel amount Qb necessary for the theoretical air-fuel ratio operation based on the engine load, the engine speed, and the like is the same as the supply fuel amount Q. Is done.

Currently, it is an operation region in the second combustion in which the required engine load L is less than the set load L ′, but when the flag F is 0, that is, when the engine is started, the combustion air-fuel ratio is made the lean air-fuel ratio. No reduction correction of the basic supply fuel amount Qb is performed. Next, in step 107, the first fuel injection valve 14 and the second fuel injection valve 15 are supplied in order to supply the supplied fuel amount Q into the cylinder based on the second fuel injection ratio (for example, 3: 7) of the second combustion. the set each of the fuel injection quantity, combustion of the stoichiometric air-fuel ratio is performed.

Then, the process proceeds to step 108, in combustion at this time, based on the air-fuel ratio of the exhaust gas near the stoichiometric air-fuel ratio detected by the air-fuel ratio sensor 12, and calculates the actual supply fuel quantity Q ', basic fuel supply quantity The ratio Q / Q ′ between the actual fuel supply amount Q ′ and the actual fuel supply amount Q ′ is learned as the second fuel injection correction coefficient k2n. As shown in FIG. 3, the second fuel injection correction coefficient k2n needs to be learned, for example, for each of the five divided areas in the range of the basic supply fuel amount Qb for the second combustion.

  In step 109, it is determined whether or not all of the five second fuel injection correction coefficients k2n have been learned. When this determination is negative, the flag F remains 0. Accordingly, Step 105 to Step 107 are repeated in the operation region of the second combustion, during which the basic supply fuel amount Q changes due to changes in the engine load and the engine speed, and the second fuel injection in another region. The correction coefficient k2n is learned, and finally all the second fuel injection correction coefficients k2n in each region are learned. At this time, the determination at step 109 is affirmed and the flag F is set to 1 at step 110.

  As a result, the determination in step 102 is affirmed in the operation region in the second combustion, and in step 104, the basic supply fuel amount Qb necessary for the theoretical air-fuel ratio operation based on the engine load, the engine speed, and the like. Further, the supply fuel amount Q is calculated by multiplying the reduction correction coefficient a (a positive value smaller than 1) for making the combustion air-fuel ratio a lean air-fuel ratio and the second fuel injection correction coefficient k2n. Next, in step 105, the first fuel injection valve 14 and the second fuel injection valve 15 are supplied in order to supply the supplied fuel amount Q into the cylinder based on the second fuel injection ratio (for example, 3: 7) of the second combustion. The respective fuel injection amounts are set, and the second combustion is performed. That is, the respective fuel injection amounts of the first fuel injection valve 14 and the second fuel injection valve 15 for injecting the basic fuel supply amount Qb · a corrected for reduction for the second combustion at the second fuel injection ratio are as follows. The second fuel injection correction coefficient k2n is corrected without feedback correction based on the output of the air-fuel ratio sensor 12. Here, the required supply fuel amount to be supplied into the cylinder is the basic supply fuel amount Qb · a corrected for reduction, and the second fuel injection correction coefficient k2n is the basic fuel supply amount Qb · a after correction for reduction. The second fuel injection correction coefficient in the region corresponding to is selected.

In while learning a second fuel injection correction coefficient k2n (while the flag F is 0), in the operating region of the second combustion, combustion amount supplied fuel can be detected by the air-fuel ratio sensor 12 is performed, The combustion temperature is higher than in the second combustion. At this time, since the fuel injection ratio is the second fuel injection ratio, the fuel injection ratio of the first fuel injection valve 14 is reduced. However, even if the combustion temperature increases, the engine temperature T is lower than the set temperature T ′, so that the in-cylinder temperature is not increased so much, and deposits accumulate in the nozzle holes of the first fuel injection valve 14. Absent.

On the other hand, when the engine temperature T is higher than the set temperature T ′, if the stoichiometric air-fuel ratio combustion is performed at the second fuel injection rate, the in-cylinder temperature is sufficiently increased, and deposits are formed in the injection holes of the first fuel injection valve 14. May accumulate. Thereby, even if the flag F is 0, when the engine temperature T is higher than the set temperature T ′, the determination in step 103 is denied, and the first combustion at the first fuel injection ratio in steps 111 and 112 is performed. It is supposed to be implemented.

  In the first fuel injection ratio, even if the fuel injection ratio of the first fuel injection valve 14 is large and the in-cylinder temperature increases, the nozzle hole of the first fuel injection valve 14 is sufficiently cooled by a relatively large amount of injected fuel. Therefore, deposit accumulation on the nozzle holes can be suppressed. In this first combustion, since the fuel injection amount is corrected by the feedback correction coefficient f calculated based on the output of the air-fuel ratio sensor 12, it is possible to realize a good first combustion at the stoichiometric air-fuel ratio. it can. At this time, if necessary, the first fuel injection correction coefficient k1n with respect to the amount of fuel supplied in the operation region of the second combustion can be calculated based on the calculated feedback correction coefficient f.

By the way, the exhaust gas during the first combustion at the stoichiometric air-fuel ratio is well purified by the three-way catalyst device 11. On the other hand, NO _{X in} the exhaust gas at the time of the second combustion with the lean air-fuel ratio is stored by the NO _X storage reduction catalyst device 10. However, the NO _X storage reduction catalyst device 10 cannot store NO _X indefinitely, and a regeneration process for reducing and purifying the stored NO _X before the NO _X storage amount reaches the maximum storable amount is necessary. It becomes. Such regeneration processing is realized by making the air-fuel ratio of the exhaust gas rich, and for this purpose, rich spike is performed in which the combustion air-fuel ratio is the desired rich air-fuel ratio.

The air-fuel ratio sensor 12 cannot accurately detect a rich air-fuel ratio such as a rich spike, so that feedback correction based on the output of the air-fuel ratio sensor 12 is performed on the fuel injection amount at the time of the rich spike. Can not. The rich spike is performed when the estimated stored NO _X amount of the NO _X storage reduction catalyst device 10 reaches a set amount, often during the second combustion of the lean air-fuel ratio. Thus, when the rich spike is performed, in step 104, in order to enrich the combustion air-fuel ratio, the basic supply fuel amount Qb is multiplied by the increase correction coefficient b (a value greater than 1) instead of the decrease correction coefficient a. In addition, the supplied fuel amount Q may be calculated by multiplying by the second fuel injection correction coefficient k2n.

  The rich spike is for supplying the supplied fuel amount Q into the cylinder based on the second fuel injection ratio (for example, 3: 7) of the second combustion in the operation region of the second combustion. 14 and the second fuel injection valve 15 are set, and combustion at a rich air-fuel ratio is performed. That is, the fuel injection of each of the first fuel injection valve 14 and the second fuel injection valve 15 for injecting the basic fuel supply amount Qb · b that has been increased and corrected for the rich air-fuel ratio combustion at the second fuel injection ratio. The amount is corrected by the second fuel injection correction coefficient k2n without being feedback-corrected based on the output of the air-fuel ratio sensor 12. Here, the required amount of fuel to be supplied into the cylinder is the basic supply fuel amount Qb · b that has been corrected for increase, and the second fuel injection correction coefficient k2n is the basic fuel supply amount Qb · b that has been corrected for increase. The second fuel injection correction coefficient in the region corresponding to is selected. Thus, the second fuel injection correction coefficient k2n learned in step 108 can be used not only during the second combustion at the lean air-fuel ratio but also during the rich spike.

  In the present embodiment, the second combustion is not performed in the second combustion operation region until the second fuel injection correction coefficient k2n of all the learning regions is learned. In the learning region in which the coefficient is learned, the second combustion at the second fuel injection ratio may be performed using the learned second fuel injection correction coefficient.

  In the present embodiment, the learning region of the fuel injection correction coefficient based on the required supply fuel amount is divided into three in the first combustion operation region and five in the second combustion operation region. It is not limited. Strictly speaking, since the common fuel injection correction coefficient for the first fuel injection valve 14 and the second fuel injection valve 15 has a different value for each required amount of supplied fuel, each operation region is further subdivided into a learning region. Each fuel injection correction coefficient can be made more accurate by setting the required fuel supply amount range to be smaller.

In the present embodiment, since the fuel injection ratio at the time of rich spike is the same as the second fuel injection ratio at the time of second combustion, the fuel injection amount at the time of rich spike is corrected with respect to the second fuel injection ratio. The second fuel injection correction coefficient k2n is used. Of course, if the fuel injection ratios of the first fuel injection valve and the second fuel injection valve during the rich spike are different from the second fuel injection ratio, the second fuel injection correction coefficient k2n should be used during the rich spike. The fuel injection amount of the first fuel injection valve and the second fuel injection valve is set according to the fuel injection ratio at the time of the rich spike in the range of the supplied fuel amount at the time of the rich spike, and the combustion of the stoichiometric air-fuel ratio is performed. By performing the above, the fuel injection correction coefficient at the time of rich spike may be learned for each learning region based on the required supply fuel amount.

It is the schematic which shows the internal combustion engine to which the fuel-injection control apparatus by this invention is attached. It is a flowchart which shows the fuel-injection control implemented by the fuel-injection control apparatus by this invention. It is a map of the learning area | region used in the flowchart of FIG.

Explanation of symbols

1 Engine Body 14 First Fuel Injection Valve 15 Second Fuel Injection Valve

Claims (2)

A first fuel injection valve for injecting fuel into the cylinder and a second fuel injection valve for injecting fuel into the intake port, and using both the first fuel injection valve and the second fuel injection valve Fuel is supplied into the cylinder, the combustion air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio, the first combustion injection ratio of the first fuel injection valve and the second fuel injection valve is the first fuel injection ratio, Fuel injection control for an internal combustion engine, which is performed by switching between the second combustion with the fuel ratio being lean from the vicinity of the stoichiometric air-fuel ratio and the fuel injection ratio of the first fuel injection valve and the second fuel injection valve being the second fuel injection ratio In the apparatus, the fuel injection correction coefficient of the first fuel injection valve and the second fuel injection valve with respect to the second fuel injection ratio in the second combustion is such that the engine temperature is equal to or lower than a set temperature in the operation region of the second combustion. Sometimes the fuel injection rate is The combustion air-fuel ratio and the fuel injection rate by implementing combustion with the stoichiometric air-fuel ratio near the fuel injection control apparatus for an internal combustion engine, characterized in that it is learned for each learning region based on the amount of fuel supplied to the cylinder.   When the fuel injection correction coefficient in the second combustion is not learned for each learning region and the engine temperature is higher than a set temperature, the fuel injection ratio in the second combustion operation region is set as the first fuel injection proportion. The fuel injection control device for an internal combustion engine according to claim 1, wherein the first combustion is performed.

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