JP6054766B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, for example, Patent Document 1 discloses an ignition timing control device for an internal combustion engine including an exhaust gas recirculation device (EGR device). In this conventional control device, in order to prevent the occurrence of knocking at the time of return from the fuel cut in the EGR region where the recirculated exhaust gas (EGR gas) is introduced into the intake passage, the cylinder is set at the time of return from the fuel cut. The ignition timing is calculated based on the response of the intake EGR gas amount or the cylinder intake EGR rate.

JP 2007-32530 A JP 2010-127134 A Japanese Patent Laid-Open No. 11-107824 JP 2008-45428 A

  The technique described in Patent Document 1 is premised on a configuration in which fuel cut is performed uniformly for all cylinders of an internal combustion engine. On the other hand, during operation accompanied by the introduction of EGR gas, for example, when a sudden preignition (abnormal combustion) occurs in an internal combustion engine with a supercharger, it is applied to some cylinders of the internal combustion engine. Only a fuel cut may be performed. If some of the cylinders that perform such fuel cut include an EGR take-out cylinder that takes out EGR gas, the component of the EGR gas supplied to each cylinder by executing the fuel cut for that cylinder Change occurs. More specifically, since fresh air passes through the combustion chamber of the cylinder that is executing the fuel cut, the EGR rate of the gas supplied to each cylinder decreases. In such a case, if no consideration is given to the ignition timing of the cylinder that is not executing the fuel cut, there is a concern that abnormal combustion such as knocking may occur due to a decrease in the EGR rate. The

  The present invention has been made to solve the above-described problems, and suppresses the occurrence of abnormal combustion when a fuel cut is performed on some cylinders during execution of exhaust gas recirculation control. An object of the present invention is to provide a control device for an internal combustion engine that can perform the above-described operation.

A first invention is a control device for an internal combustion engine,
A control device for an internal combustion engine having a plurality of cylinders,
An exhaust gas recirculation device for supplying a part of exhaust gas from at least one of the plurality of cylinders as a recirculation exhaust gas to the intake passage of the internal combustion engine;
Fuel cut control means for performing a fuel cut on one or a plurality of some of the plurality of cylinders when a predetermined fuel cut execution condition is satisfied;
Cylinders other than the partial cylinders when a fuel cut is performed on the partial cylinders during execution of exhaust gas recirculation control for supplying recirculated exhaust gas to the intake passage by the exhaust gas recirculation device A fuel cut point ignition timing control means for performing an ignition delay that is retarded compared to a value when the fuel cut is not performed,
Equipped with a,
The fuel cut time ignition timing control means, it and performs the ignition retard after a predetermined time from the start of the fuel cut with respect to the partial-cylinder has elapsed.

The second invention is the first invention, wherein
The fuel cut point ignition timing control means increases the amount of the ignition delay as the number of cylinders that perform the fuel cut for the partial cylinders increases.

A third aspect of the present invention is the first or second inventions in Oite,
The fuel cut point ignition timing control means changes the amount of the ignition delay based on the number of execution cycles of the fuel cut for the partial cylinders.

Moreover, 4th invention is set in any one of 1st- 3rd invention,
Injection increase execution means for increasing the fuel injection during a predetermined time after return from the fuel cut return time for the partial cylinder;
A post-return ignition timing control means for retarding the ignition timing by an amount proportional to the amount of increase in the fuel injection during a predetermined time after the return;
Is further provided.

The fifth invention is the fourth invention, wherein
The injection increase execution means increases the fuel injection largely as the number of cylinders that perform the fuel cut for the partial cylinders increases.

The sixth invention is the fourth or fifth invention, wherein
The injection increase execution means changes the amount of increase in the fuel injection based on the number of execution cycles of the fuel cut for the partial cylinders.

Moreover, 7th invention in any one of 4th - 6th invention,
In a case where the partial cylinder where the fuel cut is performed is constituted by a cylinder other than the recirculation exhaust gas take-out cylinder, the fuel injection increase by the injection increase execution means and the ignition by the post-return ignition timing control means It is further characterized by further comprising post-return control prohibiting means for prohibiting the timing delay.

Moreover, 8th invention in any one of 4th - 7th invention,
When the exhaust temperature exceeds a predetermined value upon return from the fuel cut, the amount of increase in the fuel injection by the injection increase execution means and the retard amount of the ignition timing by the post-return ignition timing control means are limited to be small. And a post-return control limiting means.

Moreover, 9th invention in any one of 1st- 8th invention,
A fuel cut control prohibiting means for prohibiting the ignition delay by the fuel cut timing control means when the partial cylinder to which the fuel cut is performed is constituted by a cylinder other than the recirculated exhaust gas extraction cylinder; It is further provided with the feature.

The tenth aspect of the invention is any one of the first to ninth aspects of the invention.
The fuel cut execution condition is satisfied during high load operation.

Further, an eleventh aspect of the invention is any one of the first to tenth aspects of the invention,
The fuel cut execution condition is established when abnormal combustion is detected.

According to the first aspect of the present invention, the occurrence of abnormal combustion such as knocking in cylinders other than some cylinders due to a decrease in the exhaust gas recirculation rate due to the fuel cut to some cylinders is suppressed. Can do. Further, according to the present invention, the ignition timing can be corrected at an appropriate timing in consideration of the recirculation delay of the recirculated exhaust gas.

As the number of cylinders that perform fuel cuts increases, the amount of fresh air contained in the recirculated exhaust gas increases. According to the second aspect of the invention, the amount of the ignition delay can be appropriately set in consideration of the number of cylinders in which fuel cut is performed.

The number of fuel cut execution cycles affects the amount of fresh air contained in the recirculated exhaust gas. According to the third aspect of the invention, the ignition retard amount can be appropriately set in consideration of the number of fuel cut execution cycles.

According to the fourth aspect , by increasing the fuel injection during a predetermined time after the return, the lean air-fuel ratio of the exhaust gas due to the recirculation delay of the recirculated exhaust gas can be suppressed. Further, by increasing the fuel injection amount and retarding the ignition timing, it is possible to suppress an increase in torque associated with the increase in fuel injection amount. Thus, according to the present invention, during the period in which the recirculation exhaust gas recirculation delay remains after returning from the fuel cut, while improving drivability (suppressing torque fluctuation), the exhaust emission is reduced. Deterioration can be suppressed.

As the number of cylinders that perform fuel cut increases, the air-fuel ratio of the exhaust gas during the predetermined time after the return becomes leaner. According to the fifth aspect of the present invention, the amount of increase in the fuel injection can be appropriately set in consideration of the number of cylinders in which fuel cut is performed.

The number of fuel cut execution cycles affects the lean degree of exhaust gas during a predetermined time after the return. According to the sixth aspect of the present invention, the amount of increase in the fuel injection can be appropriately set in consideration of the number of fuel cut execution cycles.

According to the seventh aspect of the present invention, the increase in the fuel injection and the retard of the ignition timing are performed in vain in a situation where the fuel cut for some cylinders does not affect the component of the recirculated exhaust gas. Can be prevented.

According to the eighth aspect of the present invention, it is possible to prevent the exhaust system parts from being overheated due to the excessive increase in the exhaust gas temperature accompanying the increase of the fuel injection and the delay of the ignition timing.

According to the ninth aspect of the present invention, it is possible to prevent the ignition delay from being performed in vain in a situation where the fuel cut for some cylinders does not affect the component of the recirculated exhaust gas.

According to the tenth aspect of the present invention, abnormal combustion such as knocking can be prevented when fuel cut is performed on some cylinders during high load operation where abnormal combustion such as knocking is likely to occur.

According to the eleventh aspect of the present invention, abnormal combustion such as knocking is prevented in a situation where abnormal combustion such as knocking is likely to occur due to a decrease in the exhaust gas recirculation rate due to the fuel cut to some cylinders. Can do.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure showing an example of generation | occurrence | production of the preignition in a low rotation high load area | region. It is a time chart for demonstrating the continuous prevention control of pre-ignition performed in Embodiment 1 of this invention. 6 is a time chart showing the operation of various parameters of the internal combustion engine when executing pre-ignition continuous prevention control. 6 is a time chart showing characteristic control operations that are executed in association with execution of pre-ignition continuous firing prevention control in Embodiment 1 of the present invention. It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 2 of this invention.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. Here, the internal combustion engine 10 is an inline 4-cylinder gasoline engine as an example, and the explosion order is assumed to be # 1 → # 3 → # 4 → # 2. As shown in FIG. 1, the internal combustion engine 10 includes an intake passage 12 for taking air into the cylinder and an exhaust passage 14 through which exhaust gas discharged from the cylinder flows.

  In the vicinity of the inlet of the intake passage 12, an air flow meter 16 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 12 is provided. A compressor 18 a of the turbocharger 18 is disposed downstream of the air flow meter 16. The turbocharger 18 includes a turbine 18b that is integrally connected to the compressor 18a and that is operated by exhaust gas exhaust energy. The compressor 18a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 18b.

  An intercooler 20 for cooling the air compressed by the compressor 18a is arranged in the intake passage 12 on the downstream side of the compressor 18a. Further, an electronically controlled throttle valve 22 for adjusting the amount of air flowing through the intake passage 12 is disposed downstream of the intercooler 20. A catalyst (three-way catalyst) 24 for purifying the exhaust gas is disposed in the exhaust passage 14 on the downstream side of the turbine 18b.

  Further, the internal combustion engine 10 shown in FIG. 1 includes an exhaust gas recirculation device (EGR device) 26. The EGR device 26 includes an exhaust gas recirculation passage (EGR passage) 28 that connects the exhaust passage 14 upstream of the turbine 18b and the intake passage 12 upstream of the compressor 18a. In the middle of the EGR passage 28, a recirculation exhaust gas cooler (EGR cooler) 30 and an exhaust gas recirculation valve are arranged in order from the upstream side of the flow of the recirculation exhaust gas (EGR gas) when introduced into the intake passage 12. (EGR valve) 32 is provided. The EGR cooler 30 is provided for cooling the EGR gas flowing through the EGR passage 28, and the EGR valve 32 is provided for adjusting the amount of EGR gas returned to the intake passage 12 through the EGR passage 28. It has been.

  The EGR device 26 controls the recirculation of a part of the exhaust gas flowing through the exhaust passage 14 to the intake passage 12 via the EGR passage 28 when a predetermined execution condition is satisfied in a predetermined operation region of the internal combustion engine 10, so-called Perform external EGR control. More specifically, the EGR device 26 provided for the internal combustion engine 10 having the configuration shown in FIG. 1 supplies a part of the exhaust gas from all cylinders of the internal combustion engine 10 to the intake passage 12 as EGR gas. Is. That is, in the internal combustion engine 10 of the present embodiment, all cylinders # 1 to # 4 correspond to EGR gas take-out cylinders. Note that, according to the configuration of the EGR passage 28, the EGR gas is introduced into the intake passage 12 upstream of the compressor 18a, so that external EGR control can be performed even in the supercharging region.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the air flow meter 16, the operating state of the internal combustion engine 10 such as the crank angle sensor 42 for detecting the engine speed and the in-cylinder pressure sensor 44 for detecting the in-cylinder pressure is input to the input unit of the ECU 40. Various sensors for detection are connected. Further, in addition to the throttle valve 22 and the EGR valve 32 described above, an output portion of the ECU 40 includes a fuel injection valve 46 for injecting fuel into the cylinder or the intake port of the internal combustion engine 10 and an air-fuel mixture. Various actuators for controlling the operation of the internal combustion engine 10 such as a spark plug 48 are connected. The ECU 40 performs predetermined engine control such as ignition control and fuel injection control by operating various actuators based on the outputs of the various sensors described above and predetermined programs.

[Fuel cut control to suppress pre-ignition]
FIG. 2 is a diagram illustrating an example of occurrence of pre-ignition in a low rotation high load region. Note that FIG. 2 continuously captures the in-cylinder pressure waveform within the same cylinder.

  As shown in FIG. 2, when pre-ignition occurs, the peak value of the in-cylinder pressure (maximum in-cylinder pressure Pmax) is significantly higher than during normal combustion. In the example shown in FIG. 2, pre-ignition occurs continuously in a short time in the same cylinder. The pre-ignition shown here has a characteristic that it occurs in a low-rotation and high-load region where supercharging is performed, and terminates after suddenly occurring a plurality of times. The cause of the continuous occurrence (sequential occurrence) of such sudden pre-ignition is that the deposit in the combustion chamber peels off due to the strong knocking that occurs along with the pre-ignition, and the peeled deposit floats in the cylinder and the next cycle. Or it is thought that it is because it remains after that and becomes an ignition source, and the next preignition occurs.

  FIG. 3 is a time chart for explaining the pre-ignition repetitive prevention control executed in the first embodiment of the present invention. In the chart shown in FIG. 3, an example is given of a case where the pre-ignition is repeated a predetermined number of times or more in a short time in the # 1 cylinder. The pre-ignition can be detected based on, for example, whether or not the in-cylinder pressure detected using the in-cylinder pressure sensor 44 is higher than a predetermined value (maximum in-cylinder pressure Pmax during normal combustion).

  Here, as control for suppressing pre-ignition (abnormal combustion), control for partially pressing pre-ignition is taken up. In the pre-ignition repetitive prevention control, as shown in FIG. 3A, fuel cut is performed only for some cylinders (# 1 cylinder) in which pre-ignition repetitive occurrence has occurred (fuel injection by the fuel injection valve 46 is stopped). As shown in FIG. 3B, fuel injection is continued as usual for the other cylinders (# 2 to # 4 cylinders). As described above, the pre-ignition continuous firing is considered to be caused by the deposit floating in the cylinder as an ignition source. For this reason, the fuel cut for some cylinders in this case is continued for a predetermined number of cycles required until the peeled deposit is scavenged from the combustion chamber to the exhaust passage 14, and then the return from the fuel cut ( (Resumption of fuel injection) is executed.

[Problems related to prevention of repeated pre-ignition during execution of external EGR control]
In the internal combustion engine 10 of this embodiment, even in the supercharging region, external EGR control is performed using the EGR device 26 in a predetermined operating region set in advance. As a result, when pre-ignition continuous firing is detected during execution of external EGR control, pre-ignition continuous firing prevention control may be executed.

  In the internal combustion engine 10 of the present embodiment, all cylinders # 1 to # 4 correspond to EGR gas extraction cylinders. For this reason, if a fuel cut is performed on some cylinders in order to prevent pre-ignition during the external EGR control, fresh air passes through the combustion chamber in the cylinder where the fuel cut is performed. A part of the gas is contained in the EGR gas supplied to each cylinder. As a result, the EGR gas component changes. More specifically, the EGR rate of the gas supplied to each cylinder decreases.

  In such a case, if no consideration is given to the ignition timing of the cylinders that are not executing the fuel cut (for example, if the ignition timing remains constant), the EGR rate is reduced. There is a concern that abnormal combustion such as knocking may occur. When the EGR gas is introduced into the cylinder, the cylinder gas temperature at the time of combustion can be lowered, which has an effect of suppressing knocking. For this reason, in the ignition timing control, the ignition timing may be set to the advance side in anticipation of the knocking suppression effect due to the introduction of EGR gas. Therefore, particularly when such an ignition timing is set, knocking is likely to occur because the EGR rate becomes lower than the expected value due to the fuel cut.

  FIG. 4 is a time chart showing the operation of various parameters of the internal combustion engine 10 when the pre-ignition continuous firing prevention control is executed. FIG. 4 is directed to the case where pre-ignition fire is detected in the # 1 cylinder as an example. In this case, as shown in FIGS. 4 (A) and 4 (B), fuel cut is executed over the predetermined number of cycles only for the # 1 cylinder.

  There is a delay (EGR) in the change in the EGR rate of the in-cylinder gas accompanying the execution of the fuel cut for some cylinders (here, the # 1 cylinder) and the change in the EGR rate of the in-cylinder gas accompanying the return from the fuel cut. There is a gas reflux delay). For this reason, when the fuel cut is executed only for some cylinders, as shown in FIG. 4D, the gas component is changed after a predetermined EGR delay time Δte1 has elapsed from the start of the fuel cut. The changed EGR gas (including fresh air that has passed through the # 1 cylinder) is introduced into the cylinder, and the EGR rate of the cylinder gas decreases. The EGR rate continues to decrease while the fuel cut continues.

  Also, when the return from the fuel cut (resumption of fuel injection to the # 1 cylinder) is executed, EGR gas containing fresh air is introduced into the cylinder until the EGR delay time Δte2 elapses. Therefore, as shown in FIG. 4D, the EGR rate also decreases in the EGR delay time Δte2 after returning from the fuel cut due to the EGR gas recirculation delay, and after the EGR delay time Δte2 has elapsed. EGR gas at the expected EGR rate is introduced into the cylinder. Therefore, as a period during which knocking is likely to occur due to a change in the component of the EGR gas, as shown in FIG. 4C, the fuel cut implementation period after the elapse of the EGR delay time Δte1, and immediately after the return from the fuel cut. This corresponds to the EGR delay time Δte2.

  Further, when the fuel cut is performed on some cylinders, as shown in FIG. 4E, the air-fuel ratio of the exhaust gas becomes lean, so that the purification performance (emission performance) of the catalyst 24 that is a three-way catalyst deteriorates. . In this regard, in the present embodiment, leaning of the air-fuel ratio itself is allowed, and priority is given to preventing the pre-ignition from occurring repeatedly. However, as described above, fuel injection is performed in all cylinders after the return of the fuel cut, but the EGR rate of the in-cylinder gas decreases due to the return delay of the EGR gas even in the EGR delay time Δte2 after the return. . As a result, the air-fuel ratio of the exhaust gas continues to be leaner than when the fuel cut is not performed.

[Characteristic Control in Embodiment 1]
FIG. 5 is a time chart showing the characteristic control operation that is executed accompanying the execution of the pre-ignition continuous firing prevention control in the first embodiment of the present invention.

(Ignition timing control during fuel cut)
In the present embodiment, when fuel cut is executed for some cylinders in order to prevent repeated pre-ignition during execution of external EGR control during high load operation, as shown in FIG. The ignition timing of the cylinders (# 2 to # 4 cylinders) that have not been subjected to fuel cut during the fuel cut execution period after elapse of the EGR delay time Δte1 is compared with a value when the fuel cut is not performed. The amount of correction is delayed by the amount of correction ΔSA1. In this case, the retard of the ignition timing is continuously executed during the period of the fuel cut.

  The EGR delay time Δte1 can be estimated using, for example, the following method. That is, the EGR delay time Δte1 can be calculated based on parameters such as the passage volume of the EGR introduction path (part of the exhaust passage 14, part of the EGR passage 28, and part of the intake passage 12) and the engine speed. it can. The passage volume is a known value. Moreover, since the flow rate of EGR gas per unit time increases as the engine speed increases, the EGR delay time Δte1 is estimated as a shorter time as the engine speed increases.

  The EGR rate of the in-cylinder gas when the fuel cut is performed on some cylinders can be estimated using, for example, the following method. In other words, the base value of the EGR rate is set in advance as a map or the like with the relationship between the operating state of the internal combustion engine 10 (engine load (intake air amount) and engine speed). After that, the EGR rate after elapse of the EGR delay time Δte1 is calculated as a value lower than the obtained base value by an EGR rate deviation amount ΔEGR. The EGR rate deviation amount ΔEGR is preferably set as a value according to the degree of fuel cut.

  More specifically, the amount of fresh air contained in the EGR gas increases as the number of cylinders that perform fuel cut increases. For this reason, it is preferable to set the EGR rate deviation amount ΔEGR to be larger as the number of cylinders that perform fuel cut increases. Further, the exhaust gas discharged from the cylinder where the fuel cut is performed immediately after the start of the fuel cut is a mixed gas of EGR gas and fresh air when fuel injection is performed on all the cylinders. Until the EGR delay time Δte1 elapses, the mixed gas having the above components is discharged from the cylinder where the fuel cut is performed. After that, when EGR gas containing fresh air is supplied to each cylinder, the ratio of fresh air in the gas discharged from the cylinder where the fuel cut is performed gradually increases with time. Along with this, the proportion of fresh air in the EGR gas that recirculates thereafter increases with time. In this way, strictly speaking, the EGR rate during execution of fuel cut changes according to the number of fuel cut execution cycles. For this reason, when the number of execution cycles of fuel cut can be grasped in advance as in the case of performing pre-ignition repetitive prevention control of the present embodiment, by changing the EGR rate deviation amount ΔEGR based on the number of execution cycles, The EGR rate having a value corresponding to the number of execution cycles may be estimated.

  The ignition timing correction amount ΔSA1 is determined in accordance with the estimated value of the EGR rate so as to increase as the estimated EGR rate decreases. Therefore, the ignition timing correction amount ΔSA1 is also changed according to the degree of fuel cut (the number of cylinders that perform fuel cut and the number of execution cycles). More specifically, the correction amount ΔSA1 is increased as the number of cylinders that perform fuel cut increases. Further, the correction amount ΔSA1 is changed according to the number of fuel cut execution cycles.

(Fuel injection control and ignition timing control after return from fuel cut)
Further, in the present embodiment, in the EGR delay time Δte2 after returning from the fuel cut, the lean air-fuel ratio (A / F deviation amount ΔA / F) due to the recirculation delay of the EGR gas is eliminated. Therefore (in order to control the air-fuel ratio to the stoichiometric air-fuel ratio (stoichiometric)), as shown in FIGS. 5A and 5B, the fuel injection is increased for all the cylinders. More specifically, in order to return the air-fuel ratio to the original target value (stoichiometric), the difference (A / F deviation amount ΔA / F) between the target A / F value and the current A / F estimated value is empty. The fuel injection is increased by an amount for making the fuel ratio rich. As a result, as shown in FIG. 5F, the air-fuel ratio is controlled to a target value.

  The EGR delay time Δte2 after returning from the fuel cut can be estimated using the same method as the EGR delay time Δte1. The estimated A / F value can be calculated using the following method, for example. That is, the base value of the estimated A / F value is calculated based on the intake air amount measured by the air flow meter 16 and the engine speed. And it is suitable to correct | amend the base value of the obtained A / F estimated value by the correction amount of the magnitude | size according to the grade of implementation of a fuel cut.

  More specifically, the air-fuel ratio of the exhaust gas becomes leaner as the number of cylinders that perform fuel cut increases. For this reason, it is preferable to correct the estimated A / F value to a leaner value with respect to the base value as the number of cylinders that perform fuel cut increases. Further, as described above with respect to the EGR rate, strictly speaking, the lean degree of the air-fuel ratio of the exhaust gas at the time of return from the fuel cut can be changed according to the number of execution cycles of the fuel cut. Therefore, the estimated A / F value corresponding to the number of execution cycles may be calculated by correcting the base value of the estimated A / F value based on the number of execution cycles.

  The magnitude of the increase in fuel injection is determined according to the difference (A / F deviation amount ΔA / F) between the estimated A / F value and the target A / F value calculated as described above. Therefore, the increase in fuel injection is also changed according to the degree of fuel cut (the number of cylinders that perform fuel cut and the number of execution cycles). More specifically, as the number of cylinders that perform fuel cut increases, the A / F deviation amount ΔA / F increases, so the fuel injection increases greatly. Further, the amount of increase in fuel injection is changed according to the number of fuel cut execution cycles.

  On the other hand, since the EGR rate of the in-cylinder gas is low (that is, the amount of fresh air is large), the amount of air passing through the intake valve relative to the amount of air passing through the air flow meter 16 (in-cylinder air amount) Will increase. For this reason, if no consideration is given, as indicated by a broken line in FIG. 5D, the torque becomes excessive by the amount of torque deviation ΔTQ, and drivability deteriorates. Therefore, as shown in FIG. 5C, the ignition timing of all the cylinders is retarded using the correction amount ΔSA2 for eliminating the generation of the torque deviation amount ΔTQ accompanying the increase in fuel injection. More specifically, the correction amount ΔSA2 is calculated as a value proportional to the amount of increase in fuel injection. As a result, the ignition timing is further retarded after the return from the fuel cut with respect to the ignition delay during the fuel cut.

(Measures for rising exhaust temperature)
FIG. 5G schematically shows changes in the exhaust temperature. As shown in FIG. 5G, the exhaust temperature (estimated value) decreases as the fuel cut is performed because fresh air from the partial cylinder flows into the exhaust passage 14 by the fuel cut to the partial cylinder. To do. Thereafter, the exhaust gas temperature rises by retarding the ignition timing during the fuel cut period. Further, the exhaust gas temperature further rises by executing the increase in fuel injection and the retard of the ignition timing after returning from the fuel cut.

  Therefore, in the present embodiment, when the estimated value of the exhaust temperature exceeds a predetermined value (allowable criteria shown in FIG. 5G) when returning from the fuel cut to some cylinders, the exhaust temperature falls below the above allowable criteria. In order to be within the limits, the amount of increase in fuel injection performed during the EGR delay time Δte2 after return and the retard amount of ignition timing are limited to be small. The estimated value of the exhaust temperature is obtained by, for example, using a base value calculated based on the intake air amount and the fuel injection amount, a correction amount based on the amount of increase in fuel injection, and a correction amount based on the retard amount of ignition timing. It can acquire by correcting using.

(Effect by control in Embodiment 1)
As described above, in the present embodiment, when a fuel cut is performed on some cylinders in order to prevent repeated pre-ignition during execution of external EGR control during high load operation, the fuel cut is performed. The ignition timing of the cylinder that has not been performed is retarded by a predetermined correction amount ΔSA1 compared to the value when the fuel cut is not performed. Thereby, it is possible to suppress the occurrence of knocking due to the decrease in the EGR rate accompanying the fuel cut for some cylinders.

  In addition, the above-described retard of the ignition timing is executed during execution of the fuel cut after elapse of the EGR delay time Δte1. As a result, the ignition timing can be corrected at an appropriate timing considering the recirculation delay of the EGR gas. Further, since the ignition timing correction amount ΔSA1 is determined according to the number of cylinders and the number of execution cycles of the fuel cut, the ignition timing can be retarded by an appropriate amount corresponding to the degree of fuel cut execution. .

  Further, in the present embodiment, in the EGR delay time Δte2 after returning from the fuel cut for some cylinders, an increase in fuel injection for eliminating the lean air-fuel ratio of the exhaust gas caused by the EGR gas recirculation delay And retarding the ignition timing by an amount proportional to the amount of increase in the fuel injection. As a result, it is possible to suppress the deterioration of exhaust emission while improving drivability (while suppressing torque fluctuation) during the period in which the recirculation delay of EGR gas remains after returning from the fuel cut. In addition, since the amount of fuel injection increase is determined according to the number of cylinders and the number of execution cycles of fuel cut, it is possible to increase the amount of fuel injection by an appropriate amount according to the degree of fuel cut execution. become.

  Furthermore, in this embodiment, when the estimated value of the exhaust temperature exceeds a predetermined value at the time of return from the fuel cut for some cylinders, the amount of increase in fuel injection and ignition performed during the EGR delay time Δte2 after the return The amount of retarded timing is limited to a small amount. As a result, it is possible to prevent the exhaust system parts from being overheated due to the excessive increase in the exhaust gas temperature accompanying the increase in the fuel injection and the delay of the ignition timing.

In the above-described first embodiment, when the ECU 40 detects the pre-ignition continuous firing, the “fuel cut control means” according to the first aspect of the present invention is executed by performing fuel cut on the cylinder that has detected the continuous firing. The ECU 40 retards the ignition timing of the cylinders that are not performing the fuel cut while executing the fuel cut for some cylinders by the correction amount ΔSA1. "Time control means" is realized.
In the first embodiment described above, the EGR delay time Δte1 corresponds to the “predetermined time” in the first invention.
In the first embodiment described above, the EGR delay time Δte2 corresponds to the “predetermined time after return” in the fourth aspect of the invention. Further, the ECU 40 increases the fuel injection in order to eliminate the A / F deviation amount ΔA / F during the EGR delay time Δte2, thereby realizing the “injection increase execution means” in the fourth aspect of the invention. The “post-return ignition timing control means” according to the fourth aspect of the present invention is realized by retarding the ignition timing by the correction amount SA2 corresponding to the increase in fuel injection during the EGR delay time Δte2.
In the first embodiment described above, the ECU 40 increases the amount of fuel injection and retards the ignition timing so that the exhaust temperature falls below a predetermined allowable criterion when the estimated value of the exhaust temperature exceeds a predetermined value. By limiting the amount to be small, the “post-return control limiting means” according to the eighth aspect of the present invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.

[System Configuration of Embodiment 2]
FIG. 6 is a diagram for explaining a system configuration of the internal combustion engine 50 according to the second embodiment of the present invention. In FIG. 6, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  As shown in FIG. 6, the exhaust passage 52 provided in the internal combustion engine 50 of the present embodiment includes an independent path for each predetermined cylinder group. More specifically, the exhaust passage 52 includes a first exhaust passage 52 a through which exhaust gas discharged from the first cylinder group (# 2 and # 3 cylinders) of the internal combustion engine 50 flows, and the remaining second exhaust passage of the internal combustion engine 10. A second exhaust passage 52b through which exhaust gas discharged from the cylinder group (# 1 and # 4 cylinders) flows, and a single post-merging exhaust passage 52c after joining the first exhaust passage 52a and the second exhaust passage 52b, It has.

  As shown in FIG. 6, the turbine 54b of the turbocharger 54 is installed at a junction between the first exhaust passage 52a and the second exhaust passage 52b. As described above, the turbocharger 54 includes the first cylinder group (# 2 and # 3) and the second cylinder group (# 1 and # 4) via the first exhaust passage 52a and the second exhaust passage 52b. ) Are turbochargers that receive the supply of exhaust gas independently of each other, that is, so-called twin scroll turbochargers.

  Further, in the internal combustion engine 50, as shown in FIG. 6, the EGR passage 56 is not an all-cylinder, but an intake passage using a part of the exhaust gas discharged from the first cylinder group (# 2 and # 3) as EGR gas. 12 is configured as a passage to be supplied to 12. That is, in the internal combustion engine 50 of the present embodiment, only the first cylinder group (# 2 and # 3) corresponds to the EGR gas extraction cylinder.

[Characteristic control in the second embodiment]
In the present embodiment, the preignition repetitive prevention control by the fuel cut for some cylinders is performed when the preignition repetitive is detected during the execution of the external EGR control during the high load operation. Is the same.

  In the internal combustion engine 50 having the above-described configuration, when fuel cut is performed on one or both cylinders of the first cylinder group (# 2 and # 3) corresponding to the EGE gas take-out cylinder, The component will be affected by the fuel cut. However, if a fuel cut is performed on one or both cylinders of the second cylinder group (# 1 and # 4) corresponding to cylinders other than the EGR gas take-out cylinder, the component of the EGR gas is the fuel cut. Not affected.

  Therefore, in the present embodiment, when the EGE gas take-out cylinder is included in a part of the cylinders that perform the fuel cut, the ignition timing delay during execution of the fuel cut in the first embodiment described above and the fuel cut In the case where the increase in the fuel injection after the return and the retard of the ignition timing are executed, and on the other hand, when some of the cylinders that perform the fuel cut are constituted by cylinders other than the EGE gas take-out cylinder, the above-described first embodiment The retarding of the ignition timing during the execution of the fuel cut and the increase of the fuel injection after the return from the fuel cut and the retarding of the ignition timing are prohibited.

  As described above, in the present embodiment, the ignition timing control and the fuel injection control of the above-described first embodiment are performed based on the determination result of whether or not the partial cylinder that performs the fuel cut is the EGR gas extraction cylinder. The presence or absence of implementation is determined. Thereby, when the one part cylinder which performs fuel cut is comprised by cylinders other than an EGR gas extraction cylinder, it is possible to prevent the ignition timing from being retarded and the fuel injection from being increased.

  By the way, in Embodiment 2 mentioned above, the internal combustion engine 50 provided with the exhaust passage 52 which has an independent path | route for every predetermined cylinder group is mentioned as an example, and the EGR gas extraction cylinder is not a part of all cylinders of an internal combustion engine. The control for the configuration of cylinders has been described. The configuration in which the EGR gas take-out cylinder is a part of the cylinders of the internal combustion engine is not limited to the configuration provided in the internal combustion engine 50. For example, in the V-type internal combustion engine, only the cylinders belonging to one bank are used for EGR. The structure which takes out gas is mentioned. For this reason, you may apply control of this embodiment with respect to such a structure.

In the second embodiment described above, the ECU 40 prohibits the ignition timing from being retarded during the fuel cut when a part of the cylinder that performs the fuel cut is constituted by a cylinder other than the EGE gas take-out cylinder. Thus, the “fuel cut control prohibiting means” according to the ninth aspect of the present invention is realized. In the above case, the ECU 40 prohibits the increase in fuel injection and the retard of the ignition timing after returning from the fuel cut. The “post-return control prohibiting means” in the seventh invention is realized.

  In the first and second embodiments described above, the internal combustion engine 10 including the turbocharger 18 and the like has been described as an example of the internal combustion engine that is the subject of the present invention. However, the internal combustion engine that is the subject of the present invention is not limited to the above, and may be, for example, an internal combustion engine that includes a turbocharger other than a turbocharger, or a naturally aspirated internal combustion engine. It may be.

  By the way, in the first and second embodiments described above, a predetermined fuel cut execution condition is established when the occurrence of (continuous) pre-ignition (abnormal combustion) is detected, and fuel cut is executed for some cylinders. An example was given. However, in the present invention, the execution condition when performing fuel cut for some cylinders is not limited to when abnormal combustion is detected as described above, for example, when performing vehicle traction control using fuel cut for some cylinders. There may be.

10, 50 Internal combustion engine 12 Intake passage 14, 52 Exhaust passage 16 Air flow meter 18, 54 Turbocharger 18a Turbocharger compressor 18b, 54b Turbocharger turbine 20 Intercooler 22 Throttle valve 24 Catalyst 26 Exhaust gas re- Circulation device (EGR device)
28, 56 Exhaust gas recirculation passage (EGR passage)
30 Recirculation exhaust gas cooler (EGR cooler)
32 Exhaust gas recirculation valve (EGR valve)
40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Cylinder pressure sensor 46 Fuel injection valve 48 Spark plug 52a First exhaust passage 52b Second exhaust passage 52c Exhaust passage after joining

Claims (11)

A control device for an internal combustion engine having a plurality of cylinders,
An exhaust gas recirculation device for supplying a part of exhaust gas from at least one of the plurality of cylinders as a recirculation exhaust gas to the intake passage of the internal combustion engine;
Fuel cut control means for performing a fuel cut on one or a plurality of some of the plurality of cylinders when a predetermined fuel cut execution condition is satisfied;
Cylinders other than the partial cylinders when a fuel cut is performed on the partial cylinders during execution of exhaust gas recirculation control for supplying recirculated exhaust gas to the intake passage by the exhaust gas recirculation device A fuel cut point ignition timing control means for performing an ignition delay that is retarded compared to a value when the fuel cut is not performed,
Equipped with a,
The fuel cut time ignition timing control means, the control apparatus for an internal combustion engine it and performs the ignition retard after a predetermined time from the start of the fuel cut with respect to the partial-cylinder has elapsed. 2. The internal combustion engine according to claim 1 , wherein the fuel cut timing control means increases the amount of ignition delay as the number of cylinders that perform the fuel cut for the partial cylinders increases. Control device. 3. The internal combustion engine according to claim 1, wherein the fuel cut point ignition timing control unit changes the amount of the ignition delay based on the number of cycles of the fuel cut for the partial cylinders. Control device. Injection increase execution means for increasing the fuel injection during a predetermined time after return from the fuel cut return time for the partial cylinder;
A post-return ignition timing control means for retarding the ignition timing by an amount proportional to the amount of increase in the fuel injection during a predetermined time after the return;
The control device for an internal combustion engine according to any one of claims 1 to 3 , further comprising: 5. The control apparatus for an internal combustion engine according to claim 4 , wherein the injection increase execution means increases the fuel injection largely as the number of cylinders that perform the fuel cut for the partial cylinders increases. The injection increase execution means, control of the internal combustion engine according to claim 4 or 5, characterized in that changing the size of the increase of the fuel injection based on the embodiment the number of cycles of the fuel cut with respect to the partial-cylinder apparatus. In a case where the partial cylinder where the fuel cut is performed is constituted by a cylinder other than the recirculation exhaust gas take-out cylinder, the fuel injection increase by the injection increase execution means and the ignition by the post-return ignition timing control means The control device for an internal combustion engine according to any one of claims 4 to 6 , further comprising post-return control prohibiting means for prohibiting timing delay. When the exhaust temperature exceeds a predetermined value upon return from the fuel cut, the amount of increase in the fuel injection by the injection increase execution means and the retard amount of the ignition timing by the post-return ignition timing control means are limited to be small. The control device for an internal combustion engine according to any one of claims 4 to 7 , further comprising post-return control limiting means. A fuel cut control prohibiting means for prohibiting the ignition delay by the fuel cut timing control means when the partial cylinder to which the fuel cut is performed is constituted by a cylinder other than the recirculated exhaust gas extraction cylinder; The control device for an internal combustion engine according to any one of claims 1 to 8 , further comprising: The control apparatus for an internal combustion engine according to any one of claims 1 to 9 , wherein the fuel cut execution condition is satisfied during a high load operation. The control apparatus for an internal combustion engine according to any one of claims 1 to 10 , wherein the fuel cut execution condition is satisfied when abnormal combustion is detected.

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