JP5614320B2 - Control device for internal combustion engine - Google Patents

Description

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

  In an internal combustion engine, a phenomenon called preignition may occur in which the air-fuel mixture in the cylinder ignites before normal ignition timing. If combustion starts due to pre-ignition and the air-fuel mixture in the cylinder burns earlier than the normal timing, an abnormally high in-cylinder pressure may be generated and the engine may be damaged. There is also a problem that knocking is induced by pre-ignition and noise is generated.

  As a technique for avoiding such adverse effects of preignition, Patent Document 1 discloses a pre-processing method by comparing the in-cylinder pressure predicted by the physical model with the in-cylinder pressure measured by the in-cylinder pressure sensor. When ignition is detected and pre-ignition is detected, by re-injecting fuel from the in-cylinder injector in the detected cycle, the pre-ignition flame is extinguished or attenuated, and the in-cylinder pressure rises abnormally. Techniques that attempt to avoid this are disclosed.

JP 2010-71284 A JP-A-11-36956 JP 2002-339788 A

  The amount of fuel injected from the injector per hour (hereinafter referred to as “injection rate”) varies depending on the differential pressure between the fuel pressure and the pressure of the space into which the fuel is injected. Since normal fuel injection by the in-cylinder injector is performed in the intake stroke, the pressure in the cylinder during injection is constant, and the differential pressure between the fuel pressure and in-cylinder pressure is also constant, so the injection rate is also constant. is there. Therefore, since the fuel injection amount is proportional to the net injection time, the injection amount can be accurately controlled by controlling the injection time.

  On the other hand, additional fuel injection from the in-cylinder injector during combustion (hereinafter referred to as “in-combustion additional injection”) as in the case of performing fuel injection to avoid an abnormal increase in in-cylinder pressure due to pre-ignition. When performing the above, the injection rate is determined by the differential pressure between the fuel pressure and the in-cylinder pressure. The in-cylinder pressure during combustion changes rapidly during short-time combustion. Therefore, in the case of additional injection during combustion, the injection rate changes rapidly during short-time injection. For this reason, the injection amount of the additional injection during combustion is not proportional to the injection time. Moreover, since the magnitude and waveform of the in-cylinder pressure during combustion vary depending on the engine operating state, it is difficult to predict. In particular, the combustion when pre-ignition occurs is abnormal combustion, is controlled by chance, and varies, so it is extremely difficult to accurately predict the magnitude and waveform of the in-cylinder pressure during combustion. For this reason, when performing additional injection during combustion, it is difficult to accurately control the injection amount, and the actual injection amount cannot be specified. As a result, the following problems are caused.

  When the injection amount of the additional injection during combustion is less than the target amount, it is not possible to sufficiently achieve its original purpose, for example, avoiding an abnormal increase in in-cylinder pressure due to pre-ignition. Conversely, if the amount of additional injection during combustion is greater than the target amount, not only is the fuel wasted, but a large amount of unburned fuel flows into the exhaust purification catalyst, and the unburned fuel Combustion with the exhaust purification catalyst may cause an abnormal increase in the temperature of the exhaust purification catalyst and damage. In any case, since the air-fuel ratio of the exhaust gas deviates from the target value, the exhaust purification performance is deteriorated.

  The present invention has been made to solve the above-described problems, and is a control device for an internal combustion engine that can accurately control the injection amount when additional fuel injection is performed from an in-cylinder injector during combustion. The purpose is to provide.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An injector that injects fuel directly into the cylinder;
In-cylinder pressure detecting means for detecting in-cylinder pressure in real time during combustion in the cylinder;
Based on the in-cylinder pressure detected by the in-cylinder pressure detecting means during the additional injection during combustion when performing additional injection during combustion in which additional fuel is injected from the injector into the cylinder during combustion, Effective injection pressure calculating means for calculating in real time an effective injection pressure that is the difference between the fuel pressure of the injector and the in-cylinder pressure;
An additional injection end timing control means for controlling the timing of ending the additional injection during combustion based on the effective injection pressure calculated by the effective injection pressure calculating means when the additional injection during combustion is performed;
It is characterized by providing.

The second invention is the first invention, wherein
The additional injection end timing control means calculates the amount of fuel injected up to the present time in real time by integrating the injection amount per time determined by the effective injection pressure calculated by the effective injection pressure calculation means, The additional injection during combustion is terminated when the fuel amount injected up to the calculated current time reaches a target amount.

The third invention is the first or second invention, wherein
The internal combustion engine has at least one cylinder group consisting of a plurality of cylinders sharing an exhaust purification catalyst provided in an exhaust passage,
A calorific value calculating means for calculating a calorific value of combustion in one cycle based on the in-cylinder pressure detected by the in-cylinder pressure detecting means;
When the additional injection during combustion is performed in one cylinder belonging to the cylinder group, based on the total fuel injection amount of the one cylinder and the heat generation amount calculated by the heat generation amount calculation means, Unburned fuel calculating means for calculating an amount of unburned fuel discharged without burning from the cylinder or a calorific value corresponding to the amount;
Next, the fuel injection amount of the next combustion cylinder whose combustion order is the next cylinder of the one cylinder in the cylinder group to which the one cylinder belongs is corrected based on the value calculated by the unburned fuel calculation means. Combustion cylinder correction means;
It is characterized by providing.

Moreover, 4th invention is set in 3rd invention,
The next combustion cylinder correction means includes:
Catalyst temperature estimating means for estimating the temperature of the exhaust purification catalyst based on the value calculated by the unburned fuel calculating means;
An increase correction means for increasing the fuel injection amount of the next combustion cylinder when the catalyst temperature estimated by the catalyst temperature estimation means is higher than a predetermined temperature;
It is characterized by including.

The fifth invention is the third invention, wherein
The next combustion cylinder correction means includes:
Catalyst temperature estimating means for estimating the temperature of the exhaust purification catalyst based on the value calculated by the unburned fuel calculating means;
A decrease correction means for correcting a decrease in the fuel injection amount of the next combustion cylinder when the catalyst temperature estimated by the catalyst temperature estimation means is lower than a predetermined temperature;
It is characterized by including.

According to a sixth invention, in any one of the first to fifth inventions,
Pre-ignition detection means for detecting pre-ignition is provided,
When the preignition is detected, the additional injection during combustion is performed during combustion in the same cycle as the detected preignition.

According to a seventh invention, in any one of the first to sixth inventions,
An arithmetic device for performing arithmetic processing of the effective injection pressure calculating means;
Effective injection pressure predicting means for predicting the effective injection pressure when performing the additional injection during combustion based on the operating state of the internal combustion engine;
When performing the additional injection during combustion, if the calculation load of the arithmetic unit exceeds a predetermined reference value, the effective injection is replaced with the control by the effective injection pressure calculating means and the additional injection end timing control means. Additional injection time determining means for determining the duration of the additional injection during combustion based on the effective injection pressure predicted by the pressure predicting means;
It is characterized by providing.

  According to the first aspect of the present invention, when performing the additional injection during combustion in which additional fuel is injected into the burning cylinder, the injection amount can be accurately controlled. Therefore, the original purpose of performing the additional injection during combustion can be surely achieved, and fuel can be saved without injecting more fuel than necessary. Further, since the injection amount of the additional injection during combustion can be accurately specified, the deviation of the exhaust air-fuel ratio can be reliably suppressed, and the reduction in the purification ability of the exhaust purification catalyst can be avoided reliably.

  According to the second aspect, the injection amount of the additional injection during combustion can be accurately controlled to the target amount.

  According to the third aspect of the present invention, when additional injection is performed during combustion, the amount of unburned fuel discharged from the cylinder or the calorific value corresponding to the amount can be accurately calculated. The fuel injection amount of the next combustion cylinder to be corrected can be corrected based on the calculated value. Thereby, the bad effect accompanying implementation of additional injection during combustion can be controlled.

  According to the fourth aspect of the invention, it is possible to reliably suppress the deterioration of the exhaust purification catalyst accompanying the execution of the additional injection during combustion.

  According to the fifth aspect of the present invention, it is possible to reliably suppress a decrease in exhaust purification capacity due to an exhaust air / fuel ratio shift accompanying the execution of additional injection during combustion.

  According to the sixth aspect of the invention, it is possible to reliably suppress an abnormal increase in in-cylinder pressure when preignition occurs.

  According to the seventh invention, when the calculation load of the calculation device is large, it is possible to prevent the calculation load from becoming too large by reducing the control load of the additional injection during combustion.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the relationship between a crank angle and the value of PV ( ^kappa ). It is a graph which shows the relationship between the cylinder pressure in a compression stroke and an expansion stroke of an internal combustion engine, and a crank angle. It is a figure for demonstrating the injection quantity control of the additional injection during combustion in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system according to the first embodiment of the present invention includes a spark ignition type internal combustion engine 10. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. In FIG. 1, only one cylinder is representatively depicted.

  Each cylinder of the internal combustion engine 10 is provided with a piston 12, an intake valve 14, an exhaust valve 16, a spark plug 18, and an injector 20 that injects fuel directly into the cylinder (combustion chamber). In addition, an intake passage 22 and an exhaust passage 24 are connected to each cylinder.

  The internal combustion engine 10 has a turbocharger 26 that is a supercharger. The turbocharger 26 has a compressor 26a and a turbine 26b. The compressor 26 a is arranged in the middle of the intake passage 22, and the turbine 26 b is arranged in the middle of the exhaust passage 24.

  An air cleaner 28 and an air flow meter 30 for detecting the amount of intake air are installed in the intake passage 22 upstream of the compressor 26a. An intercooler 32 and a throttle valve 34 are provided in the intake passage 22 on the downstream side of the compressor 26a.

  In the vicinity of the turbine 26b, a bypass passage 38 communicating the upstream exhaust passage 24 and the downstream exhaust passage 24 of the turbine 26b, and a bypass valve 40 (a waste gate valve) capable of opening and closing the bypass passage 38 are provided. And are installed. When the bypass valve 40 is opened, a part of the exhaust gas flows through the bypass passage 38 without passing through the turbine 26b. An exhaust purification catalyst 42 for purifying exhaust gas is installed in the exhaust passage 24 downstream of the turbine 26b. The exhaust purification catalyst 42 can obtain a high purification rate when the air-fuel ratio of the inflowing exhaust gas is in the vicinity of the stoichiometric air-fuel ratio.

  The system of this embodiment includes a crank angle sensor 44 that detects the rotation angle of the crankshaft of the internal combustion engine 10, an in-cylinder pressure sensor 46 that detects in-cylinder pressure, and a fuel pump 48 that supplies high-pressure fuel to the injector 20. And an ECU (Electronic Control Unit) 50 for controlling the operating state of the internal combustion engine 10. The ECU 50 is electrically connected to the various sensors and actuators described above.

  The ECU 50 controls the operation of the internal combustion engine 10 by driving each actuator based on information detected by each sensor. For example, the fuel injection amount is calculated based on the engine speed detected by the crank angle sensor 44 and the intake air amount detected by the air flow meter 30, and the fuel injection timing, ignition timing, etc. are determined based on the crank angle. Later, the injector 20 and the spark plug 18 are driven. In the internal combustion engine 10 of the present embodiment, the main fuel injection (normal fuel injection) from the injector 20 is performed in the intake stroke. Alternatively, it may be performed from the intake stroke to the first half of the compression stroke. This fuel injection forms an air-fuel mixture in the cylinder, and this air-fuel mixture is ignited by the spark plug 18 and burned.

  The fuel pressure of the injector 20, that is, the pressure of fuel injected from the injector 20 (hereinafter simply referred to as “fuel pressure”) is adjusted to a predetermined pressure by the fuel pump 48 or a pressure regulating valve provided in the fuel path to the injector 20. Pressed. The fuel pump 48 may be provided with a fuel pressure switching mechanism so that the fuel pressure setting can be changed by a command from the ECU 50 to the fuel pump 48. Alternatively, a fuel pressure sensor that detects the fuel pressure may be provided. In these cases, the ECU 50 can acquire the value of the fuel pressure based on information on a predetermined fuel pressure stored in advance, a command to the fuel pump 48, or a detection result of the fuel pressure sensor.

  Preignition means that the air-fuel mixture in the cylinder ignites before the normal ignition timing. In the case of the internal combustion engine 10 of this embodiment, the air-fuel mixture in the cylinder before ignition by the spark plug 18 is performed. Says to ignite. The whole principle of pre-ignition is not always clear, but as an example, the deposit (carbon) deposited on the wall of the combustion chamber is peeled off, and the peeled piece becomes a fire type and pre-ignition occurs. It is thought that there is. Preignition may have a tendency to occur easily in a specific operation region (for example, a low rotation high load region).

  If combustion starts due to preignition and the air-fuel mixture burns earlier than originally intended, the in-cylinder pressure will rise abnormally, and the internal combustion engine 10 may be damaged. There is also a problem that knocking is induced by pre-ignition and noise is generated.

The ECU 50 according to the present embodiment executes an operation capable of detecting the occurrence of pre-ignition in real time (hereinafter referred to as “pre-ignition detection operation”) based on the in-cylinder pressure detected by the in-cylinder pressure sensor 46. Can do. Hereinafter, the pre-ignition detection operation in this embodiment will be described. The ECU 50 can calculate PV ^κ as a calorific value index value, where P is the in-cylinder pressure detected by the in-cylinder pressure sensor 46, V is the in-cylinder volume, and κ is the specific heat ratio of the in-cylinder gas. . Note that the value of the in-cylinder volume V is a function of the crank angle θ and is stored in the ECU 50 in advance. The value of the specific heat ratio κ is also stored in the ECU 50 in advance. The value of PV ^κ correlates with the amount of heat generated in the cylinder.

In the pre-ignition detection operation, the ECU 50 repeatedly calculates the value of PV ^κ for each unit crank angle or for each unit time from the middle of the compression stroke. FIG. 2 is a diagram showing the relationship between the crank angle and the value of PV ^κ . The case of normal combustion is indicated by a solid line, and the case where preignition occurs is indicated by a one-dot chain line. In FIG. 2 and subsequent figures, the preignition is abbreviated as “playgue”.

In the case of normal combustion, the air-fuel mixture in the cylinder is ignited at the ignition timing, and combustion is started by the propagation of the flame, and combustion heat is generated. For this reason, as shown in FIG. 2, the value of PV ^κ rises after the ignition timing. On the other hand, when preignition occurs, combustion starts at an earlier timing than in the case of normal combustion, so the value of PV ^κ rises earlier than in the case of normal combustion. In view of this, the ECU 50 determines that pre-ignition has occurred when it is detected that the timing at which the value of PV ^κ exceeds the predetermined threshold is earlier than in the case of normal combustion.

The calorific value index value such as PV ^κ described above is maintained substantially constant before pre-ignition occurs, and increases rapidly from the moment when pre-ignition occurs. Therefore, by performing the preignition detection operation based on such a calorific value index value, the occurrence of preignition can be accurately detected at an early stage (at the start of burning).

In the present invention, the value used as the calorific value index value in the pre-ignition detection operation is not limited to PV ^κ . For example, d (PV ^κ ) / dθ, which is a value obtained by differentiating PV ^κ with respect to the crank angle θ, may be used as the calorific value index value. In this case, the ECU 50 can calculate d (PV ^κ ) / dθ by dividing the change amount of PV ^{κ by} the change amount of the crank angle θ. Then, the ECU 50 repeatedly calculates the value of d (PV ^κ ) / dθ every unit crank angle or every unit time. When it is detected that the calculated timing at which the value of d (PV ^κ ) / dθ exceeds a predetermined threshold is earlier than in the case of normal combustion, it is determined that preignition has occurred.

  FIG. 3 is a graph showing the relationship between the in-cylinder pressure and the crank angle in the compression stroke and the expansion stroke of the internal combustion engine 10. The in-cylinder pressure shown by the solid line in FIG. 3 is the in-cylinder pressure when preignition occurs and combustion starts, and combustion (abnormal combustion) occurs earlier than normal combustion. The cause of pre-ignition includes accidental events such as deposit peeling as described above. For this reason, there is a variation in the timing at which pre-ignition occurs, and there is also a variation in how the flame spreads. Therefore, the magnitude and waveform of the in-cylinder pressure in the case of abnormal combustion due to preignition indicated by a solid line in FIG. 3 are examples, and actually include variations.

  On the other hand, the in-cylinder pressure indicated by the broken line in FIG. 3 is the in-cylinder pressure in the case of normal combustion, that is, when combustion starts by ignition at the spark plug 18. The in-cylinder pressure of normal combustion shown in FIG. 3 is when the ignition timing is after the compression top dead center. In this case, the in-cylinder pressure increases due to compression in the compression stroke, and after the compression top dead center has passed and the in-cylinder pressure has started to decrease, combustion starts and the in-cylinder pressure rises again.

  As can be seen from FIG. 3, when the combustion starts by preignition and the air-fuel mixture burns earlier than originally intended, the in-cylinder pressure rises abnormally higher than in the case of normal combustion. May increase beyond the design guarantee in-cylinder pressure of the internal combustion engine 10. In this case, the internal combustion engine 10 may be damaged. In order to prevent damage to the internal combustion engine 10 with certainty, it is desirable to avoid the in-cylinder pressure exceeding the design-guaranteed in-cylinder pressure as much as possible in one cycle. Therefore, when the occurrence of pre-ignition is detected in real time, it is ideal to avoid an abnormal increase in in-cylinder pressure in the same cycle as the detected cycle. In order to realize this ideal, when preignition is detected, the combustion may be suppressed before the combustion spreads and the in-cylinder pressure rapidly increases. That is, if the spread of the flame caused by preignition can be suppressed, an abnormal increase in in-cylinder pressure can be avoided. In order to suppress the spread of the preignition flame, it is effective to inject fuel from the injector 20 (hereinafter referred to as “additional injection during combustion”). By performing additional injection during combustion and making the surroundings of the flame in a state where the fuel is too rich to burn, the spread of the flame can be suppressed. The in-cylinder pressure indicated by the alternate long and short dash line in FIG. 3 is the in-cylinder pressure when additional injection during combustion is performed when preignition occurs. In this manner, an abnormal increase in the in-cylinder pressure can be suppressed as compared with the case where the additional injection during combustion is not performed (solid line). For this reason, damage to the internal combustion engine 10 can be avoided.

  The amount of fuel injected per hour from the injector 20 (hereinafter referred to as “injection rate”) varies depending on the differential pressure between the fuel pressure and the in-cylinder pressure. The fuel pressure is controlled by the ECU 50 and the fuel pump 48, and is kept constant at a predetermined pressure. As shown in FIG. 3, since normal fuel injection is performed in the intake stroke, the in-cylinder pressure during injection is constant, and the differential pressure between the fuel pressure and in-cylinder pressure is also constant, so the injection rate is also high. It is constant. Therefore, since the fuel injection amount is proportional to the net injection time, the injection amount can be accurately controlled by controlling the injection time.

  On the other hand, the in-cylinder pressure during combustion changes abruptly during short-time combustion. Therefore, in the case of additional injection during combustion, the injection rate determined by the differential pressure between the fuel pressure and the in-cylinder pressure (hereinafter referred to as “effective injection pressure”) also changes abruptly during short-time injection. For this reason, the injection amount of the additional injection during combustion is not proportional to the injection time. Moreover, since the magnitude and waveform of the in-cylinder pressure during combustion vary depending on the engine operating state, it is difficult to predict. Particularly, since the magnitude and waveform of the in-cylinder pressure when pre-ignition occurs vary as described above, it is extremely difficult to accurately predict the magnitude and waveform of the in-cylinder pressure during combustion.

  In view of the above-described matters, in the present embodiment, when performing additional injection during combustion, the following control is performed in order to accurately control the injection amount. FIG. 4 is a diagram for explaining a method of controlling the injection amount of the additional injection during combustion in the present embodiment. Among the three graphs in FIG. 4, the upper graph is a graph obtained by extracting the in-cylinder pressure and the fuel pressure when additional injection during combustion is performed from the graph of FIG. 3. The middle graph is a graph showing the pressure obtained by subtracting the in-cylinder pressure from the fuel pressure in the upper graph. That is, the middle graph corresponds to the effective injection pressure. The lower graph is a graph of the injection rate. The injection rate is determined by the effective injection pressure. The higher the effective injection pressure, the higher the injection rate. Therefore, the waveform of the injection rate graph is substantially similar to the waveform of the effective injection pressure graph. By integrating this injection rate graph from the start of injection to the end of injection, an accurate injection amount can be obtained. That is, an accurate injection amount can be obtained by calculating the area of the hatched portion in the figure.

  In the present embodiment, the injection amount of the additional injection during combustion is controlled based on the above principle. That is, when performing the additional injection during combustion, the ECU 50 detects the in-cylinder pressure in real time by the in-cylinder pressure sensor 46, and calculates the effective injection pressure in real time by subtracting the in-cylinder pressure from the fuel pressure. The ECU 50 stores in advance a map that defines the relationship between the effective injection pressure and the injection rate, and the injection rate can be calculated in real time from the effective injection pressure. The ECU 50 calculates the amount of fuel injected up to the current time in real time by integrating the injection rate from the start of additional injection during combustion. When the amount of fuel injected up to the current time reaches the target amount, the additional injection during combustion is terminated. According to the above process, the injection amount of the additional injection during combustion can be accurately controlled to the target amount.

  FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. This routine is repeatedly executed every predetermined crank angle or every predetermined time. However, this routine may be executed in a period during which preignition may occur in one cycle, and there may be a period in which this routine is not executed in one cycle. Further, this routine may be executed only in an operation region where pre-ignition may occur, and may not be executed in other operation regions.

  According to the routine shown in FIG. 5, it is first determined whether or not the occurrence of pre-ignition is detected in the above-described pre-ignition detection operation (step 100). If pre-ignition is not detected, normal control is continued (step 102). In normal control, since it is not necessary to perform additional injection during combustion, additional injection during combustion is not performed.

  On the other hand, if it is determined in step 100 that preignition has been detected, it is determined that additional injection during combustion should be executed (step 104). In this case, an injection command is immediately issued to the injector 20 (step 106), and additional injection during combustion is started. During execution of the additional injection during combustion, the in-cylinder pressure is detected by the in-cylinder pressure sensor 46 at every predetermined short time or every predetermined small crank angle, and effective by subtracting the in-cylinder pressure from the fuel pressure. By calculating the injection pressure and further integrating the injection rate determined by the effective injection pressure, the amount of fuel injected from the start of injection to the current time (hereinafter referred to as “integrated injection amount”) is calculated in real time. . Then, it is determined whether or not the integrated injection amount has reached the target injection amount (step 108). This target injection amount is an amount that is set in advance as an amount necessary and sufficient to prevent the flame generated by preignition from burning and spreading to avoid an abnormal increase in the in-cylinder pressure.

  If it is determined in step 108 that the integrated injection amount has not yet reached the target injection amount, the process returns to step 106 to continue the additional injection during combustion. On the other hand, if it is determined that the integrated injection amount has reached the target injection amount, the additional injection during combustion is terminated (step 110).

  According to the control described above, it is possible to accurately control so that the injection amount of the additional injection during combustion becomes the target injection amount. As a result, the amount of additional injection during combustion does not become insufficient relative to the target injection amount, so that the flame generated by preignition is reliably suppressed from spreading and the abnormal increase in in-cylinder pressure is suppressed. Thus, the internal combustion engine 10 can be reliably protected. In addition, since the injection amount of the additional injection during combustion does not become excessive with respect to the target injection amount, fuel waste can be prevented. Further, since the injection amount of the additional injection during combustion can be accurately specified, the control can be accurately performed in controlling the air-fuel ratio (exhaust air-fuel ratio) flowing into the exhaust purification catalyst 42. For this reason, it is possible to avoid the deterioration of the exhaust purification performance due to the deviation of the exhaust air-fuel ratio.

  Although the first embodiment of the present invention has been described above, the present invention is not limited to the embodiment. For example, the preignition detection operation in the present invention is not limited to detecting preignition based on the calorific value index value, and the preignition is detected based on the value of the in-cylinder pressure itself detected by the in-cylinder pressure sensor 46. What detects may be what detects pre-ignition by detecting the ionic current which flows between the electrodes of a spark plug.

  In the present embodiment, the case where the present invention is applied to a spark ignition internal combustion engine has been described. However, the present invention is not limited to a spark ignition internal combustion engine, such as a premixed compression ignition internal combustion engine, a premixed compression ignition, The present invention can also be applied to an internal combustion engine that uses spark ignition together.

  Further, the present invention is not limited to the case where the additional injection during combustion is performed for the purpose of suppressing the abnormal increase in the in-cylinder pressure due to the preignition, and is similarly applicable to the case where the additional injection during combustion is performed for other purposes. It is.

  In the first embodiment described above, the in-cylinder pressure sensor 46 corresponds to the “in-cylinder pressure detecting means” in the first invention. Further, when the ECU 50 executes the processing of the above steps 108 and 110, the “executed injection pressure calculating means” and the “additional injection end timing control means” in the first invention execute the processing of the above step 100. Thus, the “preignition detection means” according to the sixth aspect of the present invention is realized.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 6. The description will focus on the differences from the above-described embodiment, and the description of the same matters will be simplified or omitted. To do. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine shown in FIG. 6 instead of the routine shown in FIG. 5 described above, using the hardware configuration shown in FIG.

  In the control of the injection amount of the additional injection during combustion explained in the first embodiment, the in-cylinder pressure sensor 46 detects the in-cylinder pressure, calculates the effective injection pressure, and integrates the injection rate determined by the effective injection pressure. It is necessary to repeatedly execute the process of calculating the injection amount in the ECU 50 in a short time. For this reason, for example, when the engine rotational speed is high, the calculation load on the ECU 50 may be excessively high. Therefore, in this embodiment, when the calculation load of the ECU 50 becomes too high, instead of controlling the injection amount of the additional combustion injection as described in the first embodiment, the injection amount of the additional combustion injection is fed. Control was made forward.

  FIG. 6 is a flowchart of a routine executed by the ECU 50 in the present embodiment. Hereinafter, in FIG. 6, the same steps as those of the routine shown in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 6, when preignition is detected in step 100 and it is determined in step 104 that the additional injection during combustion should be executed, the calculation load of the ECU 50 is set to a predetermined reference. It is determined whether the value is equal to or less than the value (step 105). In this step 105, for example, the calculation load in the previous calculation process of the ECU 50 is compared with the reference value. If the calculation load of the ECU 50 is equal to or less than the reference value, the injection of the additional combustion injection described in the first embodiment is performed. It is determined that quantity control is feasible. Therefore, when the calculation load of the ECU 50 is equal to or less than the reference value in step 105, the processing after step 106 is executed, and the injection amount of the additional injection during combustion is controlled as in the first embodiment.

  On the other hand, when the calculation load of the ECU 50 exceeds the reference value in step 105, it is determined that the calculation load of the ECU 50 should be reduced. Therefore, in this case, the following processing is executed to control the injection amount of the additional injection during combustion in a feedforward manner. The ECU 50 stores in advance a map for predicting the effective injection pressure when the additional injection during combustion is performed based on the operating state of the internal combustion engine 10 (engine speed, engine load, air-fuel ratio, EGR rate, etc.). ing. This map is created on the basis of the results of experiments examining the relationship between the effective injection pressure when the additional injection during combustion is performed and the operating state of the internal combustion engine 10. In step 112, the effective injection pressure is predicted based on this map, and the injection time required to inject the target injection amount is calculated based on the predicted effective injection pressure. Then, additional injection is performed during combustion (step 114). In this step 114, after the additional injection during combustion is continued for the injection time calculated in step 112, the additional injection during combustion is terminated.

  According to the control of the second embodiment described above, the same effect as that of the first embodiment can be obtained, and it is possible to reliably avoid the calculation load of the ECU 50 from becoming too high when the engine speed is high. it can.

  In the second embodiment described above, the ECU 50 corresponds to the “arithmetic apparatus” in the seventh aspect of the invention. Further, the “effective injection pressure predicting means” and the “additional injection time determining means” according to the seventh aspect of the present invention are realized by the ECU 50 executing the processing of steps 105, 112, and 114 described above.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 7. The description will focus on the differences from the above-described embodiments, and the description of the same matters will be simplified or omitted. To do. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine shown in FIG. 7 instead of the routine shown in FIG. 5 described above, using the hardware configuration shown in FIG.

  However, in the present embodiment, it is assumed that the internal combustion engine 10 has at least one cylinder group including a plurality of cylinders sharing the same exhaust purification catalyst 42. For example, in an in-line engine, there is usually one exhaust system, and all cylinders share the same exhaust purification catalyst 42. In this case, the internal combustion engine 10 has one set of cylinder groups that share the exhaust purification catalyst 42. On the other hand, in the case of the V-type engine, the cylinder group of one bank and the cylinder group of the other bank each have the exhaust purification catalyst 42 separately. In this case, the internal combustion engine 10 has two sets of cylinder groups that share the exhaust purification catalyst 42.

  When additional injection is performed during combustion, the fuel may be surplus in the cylinder and oxygen may be insufficient, and a portion of the fuel may be discharged into the exhaust passage 24 without being burned. When this unburned fuel flows into the exhaust purification catalyst 42 and burns, the temperature of the exhaust purification catalyst 42 becomes abnormally high, and the exhaust purification catalyst 42 may be deteriorated. Further, the inflow of unburned fuel may cause the air-fuel ratio in the exhaust purification catalyst 42 to become rich and reduce the exhaust purification capability. In the present embodiment, in addition to the control similar to that in the first embodiment, control for suppressing these influences is performed.

  FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment. Hereinafter, in FIG. 7, the same steps as those of the routine shown in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 7, when preignition is detected in step 100 and it is determined in step 104 that additional injection during combustion should be executed, steps 106 to 110 are performed as in the first embodiment. These processes are executed, and additional injection is performed during combustion.

When the additional injection during combustion is performed, next, the total calorific value Q _total of combustion in the current cycle of the cylinder in which the additional injection during combustion is performed is calculated (step 116). According to thermodynamics, assuming that the heat generation amount is Q, the in-cylinder pressure is P, the in-cylinder volume is V, the crank angle is θ, and the specific heat ratio of the in-cylinder gas is κ, the heat generation rate dQ / dθ is given by Can be calculated.

The ECU 50 calculates the heat generation rate dQ / dθ expressed by the above equation (1) for each predetermined crank angle based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 46, and the calculated heat generation. An integrated value obtained by integrating the rate dQ / dθ until the end of combustion is calculated. The integrated value corresponds to the calorific value Q _total calculated in step 116.

Subsequently, the amount of unburned fuel F _m [g] discharged from the cylinder where the additional injection during combustion is performed to the exhaust passage 24 in this cycle and the calorific value Q _{m of the} unburned fuel are as follows. In this way, it is calculated (step 118). The calorific value Q _m of the unburned fuel is calculated by the following equation based on Q _total calculated in step 116 above.
Q _m = F × q _F −Q _total (2)

In the above equation (2), F [g] is the total fuel injection amount of the current cycle of the cylinder in which the additional injection during combustion is performed. The value of the total fuel injection amount F can be obtained by adding the injection amount of normal injection and the injection amount of additional injection during combustion. q _F [J / g] is a lower calorific value that is a physical property value of the fuel. The value of the lower heating value q _F is stored in the ECU 50 in advance. The value of F × q _F corresponds to the heat generation amount when all the fuel injection amounts F are burned. Therefore, it can be considered that the difference between the value of F × q _F and the actual calorific value Q _total of the current cycle corresponds to the calorific value of unburned fuel. Therefore, the above equation (2) can be obtained calorific value Q _m unburned fuel has.

The amount F _m of unburned fuel can be determined by dividing the calorific value Q _m unburned fuel having at the lower heating value q _F. That is, it is calculated by the following formula.
F _m = Q _m / q _F (3)

In the present embodiment, it is calculated when carrying out the additional combustion injection, as described above, the amount F _m and its calorific value Q _m of the unburned fuel added during fuel injection is discharged from the performed cylinder Can do. Subsequently, a process for calculating the estimated temperature of the exhaust purification catalyst 42 and comparing the estimated temperature with a predetermined temperature is performed as follows (step 120). The ECU 50 stores in advance a catalyst temperature map for calculating the temperature (floor temperature) of the exhaust purification catalyst 42 based on the operating state of the internal combustion engine 10 (engine speed, engine load, etc.). Based on the map, the temperature of the exhaust purification catalyst 42 can be calculated. The temperature of the exhaust purification catalyst 42 calculated based on this catalyst temperature map is the temperature when the additional injection during combustion is not performed. When additional injection is performed during combustion, unburned fuel is burned by the exhaust purification catalyst 42 to raise the temperature of the exhaust purification catalyst 42. Accordingly, the temperature of the exhaust purification catalyst 42 becomes higher as the amount F _m of unburned fuel is large. The ECU 50 stores a temperature increase range map created by examining in advance the relationship between the amount F _{m of} unburned fuel or the calorific value Q _m thereof and the temperature increase range of the exhaust purification catalyst 42 due to combustion of unburned fuel. ing. And this temperature rise map, based on the value of the quantity F _m or the calorific value Q _m of unburned fuel calculated in step 118, the temperature rise ΔT of the exhaust purification catalyst 42 by burning of unburned fuel Calculated. Then, the estimated temperature of the exhaust purification catalyst 42 is calculated by adding the temperature increase width ΔT to the temperature calculated based on the catalyst temperature map, and the estimated catalyst temperature is compared with a predetermined temperature. The predetermined temperature is a temperature set in advance to determine whether or not the exhaust purification catalyst 42 is deteriorated.

  When the estimated catalyst temperature is equal to or lower than the predetermined temperature in step 120, it can be considered that the temperature of the exhaust purification catalyst 42 has not reached the temperature at which the exhaust purification catalyst 42 is deteriorated. In this case, there is a process for reducing the fuel injection amount of a cylinder (hereinafter referred to as “next combustion cylinder”) that burns next to the cylinder group to which the cylinder that has undergone additional injection during combustion belongs. It is executed (step 122). Usually, the fuel injection amount is controlled so that the air-fuel ratio (A / F) becomes the stoichiometric air-fuel ratio. For this reason, the fuel injection amount is corrected to decrease in step 122, so that the air-fuel ratio of the next combustion cylinder becomes leaner than the stoichiometric air-fuel ratio. On the other hand, the cylinder in which the additional injection during combustion is performed discharges the rich air-fuel ratio exhaust gas containing unburned fuel. According to the processing of step 122, the rich air-fuel ratio exhaust gas discharged from the cylinder where the additional injection during combustion is mixed with the lean air-fuel ratio exhaust gas discharged from the next combustion cylinder, so that the exhaust gas is exhausted. The air-fuel ratio of the exhaust gas flowing into the purification catalyst 42 can be adjusted to the vicinity of the theoretical air-fuel ratio. For this reason, it is possible to avoid a decrease in the purification capability of the exhaust purification catalyst 42 and to reduce emissions.

  On the other hand, when the estimated catalyst temperature exceeds the predetermined temperature in step 120, it is considered that the temperature increase of the exhaust purification catalyst 42 should be suppressed in order to suppress the deterioration of the exhaust purification catalyst 42. it can. In this case, a process for increasing the fuel injection amount of the next combustion cylinder is executed (step 124). As a result, the air-fuel ratio of the next combustion cylinder becomes richer than the stoichiometric air-fuel ratio. According to the processing of step 124, the increase in the fuel injection amount of the next combustion cylinder increases the latent heat that is lost when the injected fuel vaporizes, so the temperature of the exhaust gas that exits from the next combustion cylinder decreases. To do. For this reason, the temperature rise of the exhaust purification catalyst 42 can be suppressed, and the exhaust purification catalyst 42 can be reliably prevented from being deteriorated or damaged.

  In the third embodiment described above, the ECU 50 executes the process of step 116, so that the “heat generation amount calculation means” in the third invention executes the process of step 118, thereby executing the third step. When the “unburned fuel calculating means” in the invention executes the processing of steps 120, 122, and 124, the “next combustion cylinder correcting means” in the third invention executes the processing of step 120. The “catalyst temperature estimating means” in the fourth and fifth inventions executes the process of step 124, and the “increase correction means” in the fourth invention executes the process of step 122. The “reduction amount correction means” in the fifth aspect of the invention is realized.

10 Internal combustion engine 12 Piston 14 Intake valve 16 Exhaust valve 18 Spark plug 20 Injector 22 Intake passage 24 Exhaust passage 26 Turbocharger 34 Throttle valve 42 Exhaust purification catalyst 46 In-cylinder pressure sensor 50 ECU

Claims (6)

In a control device for an internal combustion engine having at least one set of a cylinder group consisting of a plurality of cylinders sharing an exhaust purification catalyst provided in an exhaust passage,
An injector that injects fuel directly into the cylinder;
In-cylinder pressure detecting means for detecting in-cylinder pressure in real time during combustion in the cylinder;
Based on the in-cylinder pressure detected by the in-cylinder pressure detecting means during the additional injection during combustion when performing additional injection during combustion in which additional fuel is injected from the injector into the cylinder during combustion, Effective injection pressure calculating means for calculating in real time an effective injection pressure that is the difference between the fuel pressure of the injector and the in-cylinder pressure;
An additional injection end timing control means for controlling the timing of ending the additional injection during combustion based on the effective injection pressure calculated by the effective injection pressure calculating means when the additional injection during combustion is performed;
A calorific value calculating means for calculating a calorific value of combustion in one cycle based on the in-cylinder pressure detected by the in-cylinder pressure detecting means;
When the additional injection during combustion is performed in one cylinder belonging to the cylinder group, based on the total fuel injection amount of the one cylinder and the heat generation amount calculated by the heat generation amount calculation means, Unburned fuel calculating means for calculating an amount of unburned fuel discharged without burning from the cylinder or a calorific value corresponding to the amount;
Next, the fuel injection amount of the next combustion cylinder whose combustion order is the next cylinder of the one cylinder in the cylinder group to which the one cylinder belongs is corrected based on the value calculated by the unburned fuel calculation means. Combustion cylinder correction means;
A control device for an internal combustion engine, comprising:   The additional injection end timing control means calculates the amount of fuel injected up to the present time in real time by integrating the injection amount per time determined by the effective injection pressure calculated by the effective injection pressure calculation means, 2. The control apparatus for an internal combustion engine according to claim 1, wherein the additional injection during combustion is terminated when the calculated fuel amount injected up to the present time reaches a target amount. The next combustion cylinder correction means includes:
Catalyst temperature estimating means for estimating the temperature of the exhaust purification catalyst based on the value calculated by the unburned fuel calculating means;
An increase correction means for increasing the fuel injection amount of the next combustion cylinder when the catalyst temperature estimated by the catalyst temperature estimation means is higher than a predetermined temperature;
Control apparatus for an internal combustion engine according to claim 1, characterized in that it comprises a. The next combustion cylinder correction means includes:
Catalyst temperature estimating means for estimating the temperature of the exhaust purification catalyst based on the value calculated by the unburned fuel calculating means;
A decrease correction means for correcting a decrease in the fuel injection amount of the next combustion cylinder when the catalyst temperature estimated by the catalyst temperature estimation means is lower than a predetermined temperature;
Control apparatus for an internal combustion engine according to claim 1, characterized in that it comprises a. Pre-ignition detection means for detecting pre-ignition is provided,
When said pre-ignition is detected, the said detected pre-ignition internal combustion engine according to any one of claims 1 to 4 characterized in that said performing in additional injection combustion during the combustion of the same cycle Control device. An arithmetic device for performing arithmetic processing of the effective injection pressure calculating means;
Effective injection pressure predicting means for predicting the effective injection pressure when performing the additional injection during combustion based on the operating state of the internal combustion engine;
When performing the additional injection during combustion, if the calculation load of the arithmetic unit exceeds a predetermined reference value, the effective injection is replaced with the control by the effective injection pressure calculating means and the additional injection end timing control means. Additional injection time determining means for determining the duration of the additional injection during combustion based on the effective injection pressure predicted by the pressure predicting means;
The control device for an internal combustion engine according to any one of claims 1 to 5 , further comprising:

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