JP2012002101A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine that can prevent the variation of an EGR rate between cylinders regarding the internal combustion engine.SOLUTION: The internal combustion engine having a plurality of cylinders includes an intake passage that is connected with a plurality of cylinders and an external EGR passage that connects an exhaust passage with the intake passage. Moreover, a capacity of each path from a connection position of the intake passage and the external EGR passage to the plurality of cylinders is predetermined to be a capacity that can introduce a gas in the connection position in the cylinders in intake process of each cylinder.

Description

  The present invention relates to an internal combustion engine, and more particularly, to an internal combustion engine provided with an external EGR (Exhaust Gas Recirculation) device.

  2. Description of the Related Art Conventionally, as disclosed in, for example, Patent Document 3, an internal combustion engine having an external EGR passage that connects an exhaust passage and an intake passage and introduces part of the exhaust gas into the intake passage as EGR gas is known. . Patent Document 1 discloses control for shifting the phases of intake pulsation and exhaust pulsation.

JP 2008-267198 A JP 11-44228 A JP 2009-41488 A JP-A-8-210203 JP 2009-185617 A JP 2001-227348 A

  FIG. 8 is a diagram showing an intake image of gas sucked during the intake stroke of each cylinder in the configuration of Patent Document 3. In the configuration of FIG. 8, the external EGR passage and the intake passage are connected in the vicinity of the fourth cylinder (# 4), and EGR gas is introduced into the intake passage from this connection position. The gas (region a) near this connection position is sucked into the fourth cylinder. On the other hand, the gas (region b) in the downstream region from the connection position is sucked into the first cylinder (# 1). Here, the EGR rate of the gas in the regions a and b is different in the transition, and is different because the mixing distance between the fresh air and the EGR gas cannot be sufficiently secured from the viewpoint of the mountability. Therefore, the EGR rate varies among the cylinders, and there is a concern that the emission may deteriorate.

  Further, the intake pulsation and the exhaust pulsation change depending on the engine speed. In addition, the ease of gas entry into the cylinder varies depending on the phase difference between the intake pulsation and the exhaust pulsation. For this reason, in the control of Patent Document 1, the EGR rate between the cylinders varies depending on the engine speed. If the EGR rate varies, a certain cylinder introduces more EGR gas than the target value, and there is a concern about emission deterioration. Therefore, it becomes necessary to limit the amount of EGR.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine that can suppress variations in the EGR rate between cylinders.

In order to achieve the above object, a first invention is an internal combustion engine,
An intake passage connected to a plurality of cylinders;
An external EGR passage connecting the exhaust passage and the intake passage,
The volume of each path from the connection position of the intake passage and the external EGR passage to the plurality of cylinders is a volume capable of introducing the gas at the connection position into the cylinder during the intake stroke of each cylinder. Features.

A second invention is an internal combustion engine for achieving the above object,
An intake passage connected to a plurality of cylinders;
An external EGR passage connecting the exhaust passage and the intake passage and introducing EGR gas into the intake passage;
Exhaust pulsation calculating means for calculating the phase of exhaust pulsation when introducing EGR gas from a model that defines the relationship between engine parameters including engine speed and the phase of exhaust pulsation;
Phase difference determination means for determining whether or not the phase difference between the exhaust pulsation calculated by the exhaust pulsation calculation means and the intake pulsation is equal to or greater than a specified value;
Pulsation control means for controlling the valve timing of the exhaust valves of the plurality of cylinders so as to reduce the phase difference in accordance with the engine speed when the phase difference is equal to or greater than the specified value. It is characterized by.

The third invention is the second invention, wherein
The volume of each path from the connection position of the intake passage and the external EGR passage to the plurality of cylinders is a volume capable of introducing the gas at the connection position into the cylinder during the intake stroke of each cylinder. Features.

Moreover, 4th invention is 2nd or 3rd invention,
A light load determination means for determining whether or not the operating state is a light load;
The pulsation control means is configured to reduce the phase difference when the operation state is a light load and the phase difference is equal to or greater than the specified value. The valve timing of the exhaust valve is controlled.

The fifth invention is the second or third invention, wherein
A high load high rotation determination means for determining whether or not the operation state is high load high rotation,
The pulsation control means is configured to reduce the phase difference when the operation state is a high load and high rotation and the phase difference is equal to or greater than the specified value. The valve timing of the exhaust valve of the cylinder is controlled.

  According to the first invention, the volume of each path from the connection position between the intake passage and the external EGR passage to the plurality of cylinders is determined, and the volume at which the gas at the connection position can be introduced into the cylinder in the intake stroke of each cylinder. And For this reason, according to the present invention, in the intake stroke of each cylinder, at least the gas at the connection position can be introduced into the cylinder, and variations in the EGR rate between the cylinders can be suppressed.

  According to the second invention, the valve timings of the exhaust valves of a plurality of cylinders can be controlled according to the engine speed so as to reduce the phase difference. For this reason, according to the present invention, variation in the EGR rate among the cylinders can be suppressed, and the target value of the EGR rate can be sufficiently increased. As a result, deterioration of NOx and fuel consumption can be suppressed.

  According to the third invention, the volume of each path from the connection position between the intake passage and the external EGR passage to the plurality of cylinders is determined, and the volume at which the gas at the connection position can be introduced into the cylinder in the intake stroke of each cylinder. And In addition, the phase difference is reduced. For this reason, according to this invention, the dispersion | variation in the EGR rate between cylinders can be suppressed more suitably.

  According to the fourth aspect of the invention, the phase difference can be reduced when the operating state is a light load and the phase difference between the exhaust pulsation and the intake pulsation is equal to or greater than a specified value. In light loads, correction control by a throttle valve or the like is included and adaptation is difficult. According to the present invention, variation in EGR rate between cylinders is suppressed without being affected by such correction control. Can do. As a result, the target value of the EGR rate can be sufficiently increased, and the deterioration of NOx can be suitably suppressed even at a light load.

  According to the fifth aspect of the invention, the phase difference can be reduced when the operating state is high load and high rotation and when the phase difference between the exhaust pulsation and the intake pulsation is equal to or greater than the specified value. For this reason, according to this invention, the dispersion | variation in the EGR rate between cylinders can be suppressed. By suppressing the variation in the EGR rate, it is possible to suppress the deterioration of smoke. As a result, it is possible to suitably introduce a large amount of EGR gas required at high load and high rotation, and to suitably suppress the deterioration of NOx.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a schematic block diagram for demonstrating the structure of the intake passage downstream part A in Embodiment 1 of this invention. It is a figure for demonstrating the outline | summary of Embodiment 2 of this invention. It is a flowchart of the control routine which ECU50 performs in Embodiment 2 of this invention. It is a flowchart of the control routine which ECU50 performs in Embodiment 3 of this invention. It is a figure showing the operation mode in the system of Embodiment 4 of this invention. It is a flowchart of the control routine which ECU50 performs in Embodiment 4 of this invention. It is a figure showing the inhalation image of the gas inhaled during the intake stroke of each cylinder in the conventional structure.

  Hereinafter, embodiments of the present invention will be described in detail 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.
[System Configuration of Embodiment 1]
FIG. 1 is a schematic configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 is a diesel engine system having a characteristic intake passage downstream portion A. First, configurations other than the intake passage downstream portion A will be described. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. The engine 10 shown in FIG. 1 is an in-line four-cylinder type, but in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto. Each cylinder of the engine 10 is provided with an injector (not shown) that injects high-pressure fuel into the cylinder. Further, an intake passage 12 and an exhaust passage 14 are connected to each cylinder.

  An air cleaner 16 is attached near the inlet of the intake passage 12. An air flow meter 18 that outputs a signal GA corresponding to the flow rate of fresh air sucked into the intake passage 12 is attached in the vicinity of the downstream side of the air cleaner 16.

  A supercharger 20 is provided downstream of the air flow meter 18. The supercharger 20 includes a compressor 20a and a turbine 20b. The compressor 20a and the turbine 20b are integrally connected by a connecting shaft. The compressor 20a is rotationally driven by the exhaust energy of the exhaust gas input to the turbine 20b.

  An intercooler 22 for cooling the fresh air compressed by the compressor 20a is provided downstream of the compressor 20a. An intake passage downstream portion A described later is provided downstream of the intercooler 22. An intake valve 24 that opens and closes the inside of the cylinder and the intake passage 12 is provided for each cylinder at the downstream end of the intake passage 12.

  An exhaust valve 26 that opens and closes between the cylinder and the exhaust passage 14 is provided at the upstream end of the exhaust passage 14. An exhaust manifold 28 is provided in the exhaust passage 14 downstream of the exhaust valve 26. The exhaust passage 14 joins downstream of the exhaust manifold 28. A turbine 20b is provided in the exhaust passage 14 after merging. Further, a catalyst (not shown) for purifying exhaust gas is disposed downstream of the turbine 20b. As the catalyst, for example, a NOx storage reduction catalyst is used.

  One end of an external EGR passage 30 toward the intake passage 12 is connected to the exhaust manifold 28. An EGR cooler 32 is provided in the middle of the external EGR passage 30. The external EGR passage 30 downstream of the EGR cooler 32 is connected to the intake passage downstream portion A.

  Further, the system of the present embodiment is provided with a variable valve mechanism 34 that can change the opening timing and closing timing of the exhaust valve 26 in each cylinder.

  The system of this embodiment includes an ECU (Electronic Control Unit) 50. In addition to the air flow meter 18 described above, various sensors such as a crank angle sensor 36 that outputs a signal CA according to the rotation angle of the crankshaft and a supercharging pressure sensor 40 described later are connected to the input portion of the ECU 50. In addition to the injector and the variable valve mechanism 34 described above, various actuators such as a throttle valve 38 and an EGR valve 44 described later are connected to the output unit of the ECU 50. The ECU 50 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors.

  For example, the ECU 50 sets a target torque according to the accelerator opening, etc., and sets a target value for the fuel injection amount and the EGR rate in consideration of suitable drivability and emission performance. Then, the ECU 50 causes the injector to inject fuel according to the target value of the fuel injection amount. Further, the ECU 50 controls the opening degree of the EGR valve 44 according to the target value of the EGR rate (the throttle valve 38 is used together according to the operating state).

[Characteristic Configuration in Embodiment 1]
Next, a characteristic configuration of the intake passage downstream portion A will be described with reference to FIG. FIG. 2 is a schematic configuration diagram for illustrating the configuration of the intake passage downstream portion A in the first embodiment of the present invention.

  The intake passage downstream portion A is provided downstream of the intercooler 22. An electronically controlled throttle valve 38 is provided in the intake passage 12 downstream of the intercooler 22. In the vicinity of the throttle valve 38, a supercharging pressure sensor 40 for measuring the pressure of air supercharged by the compressor 20a is attached. The intake passage 12 downstream of the throttle valve 38 is provided with a surge tank and a manifold (hereinafter simply referred to as an intake manifold 42). The intake manifold 42 is branched and connected to each cylinder.

  Further, an EGR valve 44 that controls the flow rate of the external EGR gas is provided in the external EGR passage 30 downstream of the EGR cooler 32. The downstream end of the external EGR passage 30 is connected to the upstream side of the intake manifold 42 (the collecting portion before branching to each cylinder). At the connection position of the intake manifold 42 and the external EGR passage 30, fresh air and EGR gas merge. Hereinafter, this connection position is referred to as “fresh air-EGR gas merge position 60”.

  In the present embodiment, the volume of each piping path from the fresh air-EGR gas merge position 60 to each cylinder (# 1 to # 4) is at the fresh air-EGR gas merge position 60 in the intake stroke of each cylinder. It is designed based on the volume in the cylinder so that the gas is introduced into the cylinder.

  As described above, according to the configuration of the present embodiment shown in FIGS. 1 and 2, the gas at the fresh air-EGR gas merging position 60 can be introduced into the cylinder during the intake stroke of each cylinder. Therefore, according to the system of the present embodiment, it is possible to suppress variations in EGR rate between cylinders.

  By the way, in the system of the first embodiment described above, the path length from the fresh air-EGR gas merging position 60 to the intake port of each cylinder may be made equal. This point is the same in the following embodiments. According to such a configuration, variation in the EGR rate between the cylinders can be further suppressed.

  In the first embodiment described above, the intake air passage 12 is the “intake air passage” in the first invention, the external EGR passage 30 is the “external EGR passage” in the first invention, and the fresh air-EGR gas. The merge position 60 corresponds to the “connection position” in the first invention.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 4 described later in the configuration shown in FIGS. 1 and 2.

[Characteristic Control in Embodiment 2]
FIG. 3 is a diagram for explaining the outline of the second embodiment of the present invention. In the system configuration described above, exhaust pulsation occurs in the exhaust gas flowing through the exhaust passage 14 due to the opening / closing operation of the exhaust valve 26. Therefore, exhaust pulsation also occurs in the EGR gas recirculated from the exhaust passage 14 to the intake passage 12. Similarly, intake pulsation also occurs in the air flowing through the intake passage due to the opening / closing operation of the intake valve 24. When the engine speed changes, the valve opening / closing operation changes, and the phase and cycle of intake pulsation and exhaust pulsation also change.

  Therefore, as indicated by a broken line 70 in FIG. 3B, the phase difference between the intake pulsation and the exhaust pulsation changes depending on the engine speed. If the phase difference changes, the ease of gas entering the cylinder also changes. As a result, as shown by a broken line 72 in FIG. 3A, the EGR rate between the cylinders varies greatly depending on the engine speed.

  If there is a variation in the EGR rate between the cylinders, more EGR gas than the target value is introduced in a certain cylinder, and there is a concern about emission deterioration. Therefore, there is a problem that the target value of the EGR rate cannot be sufficiently increased.

  Therefore, in the system of this embodiment, as indicated by a solid line 74 in FIG. 3B, the valve timing of the exhaust valve 26 is advanced according to the engine speed so that the intake pulsation and the exhaust pulsation are synchronized. -It was decided to correct the retarded angle (FIG. 3C). As a result, as shown by the solid line 76 in FIG. 3A, the variation in the EGR rate between the cylinders is suppressed.

(Control routine)
FIG. 4 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. In the routine shown in FIG. 4, first, the engine speed NE and the valve timing of the exhaust valve 26 are acquired (step 100). Specifically, the engine speed NE is calculated from the signal CA of the crank angle sensor 36. Further, the ECU 50 stores valve timing reference data of the exhaust valve 26 corresponding to the operating state in advance, and the valve timing corresponding to the operating state is acquired.

  Next, the path length of the external EGR is acquired (step 110). Specifically, the ECU 50 stores a path length from the exhaust valve 26 to the fresh air-EGR gas merge position 60 in advance, and acquires this path length.

  Further, the temperature and pressure of the EGR gas in the external EGR passage 30 are calculated (step 120). Specifically, the EGR gas temperature is calculated from a known model. The EGR gas pressure is calculated from a known model using the EGR gas amount as a parameter. This EGR gas amount is calculated based on the EGR rate and the intake air amount. This intake air amount is calculated from the signal GA of the air flow meter 18. Note that a sensor may be attached to the external EGR passage 30 to detect the EGR gas temperature and the EGR gas pressure.

  Subsequently, the phase / cycle of the exhaust pulsation is calculated (step 130). The ECU 50 uses the engine speed NE, exhaust valve timing, external EGR path length, EGR gas temperature, and EGR gas pressure acquired in Steps 100 to 120 as input parameters, and the phase of exhaust pulsation when EGR gas is introduced. -A model whose output is a cycle is stored. Based on this model, the phase of the exhaust pulsation at the fresh air-EGR gas merge position 60 is calculated.

  Then, the phase difference between the intake pulsation and the exhaust pulsation is calculated (step 140). This intake pulsation correlates with the timing and cycle of air flowing into the cylinder. The ECU 50 stores in advance a map in which the phase of the intake pulsation at the fresh air-EGR gas merge position 60 is determined based on the engine speed NE, the valve timing of the intake valve 24, and the like. Using this map, the phase difference between the intake pulsation and the exhaust pulsation at the fresh air-EGR gas merge position 60 can be calculated.

  Next, it is determined whether or not the phase difference between the intake pulsation and the exhaust pulsation is within the target range (step 150). If it is determined that the phase difference is within the target range, the routine is terminated.

  On the other hand, if it is determined that the phase difference is outside the target range, the correction amount of the valve timing of the exhaust valve 26 is then calculated (step 160). Specifically, the ECU 50 determines the relationship between the engine speed NE and the advance angle correction amount / retard angle correction amount of the exhaust valve 26 so that the exhaust air pulsation at the fresh air-EGR gas merge position 60 is synchronized with the intake air pulsation. A relationship map as shown in FIG. 3C is stored. The advance angle correction amount / retard angle correction amount are, for example, correction amounts for the opening timing of the exhaust valve. From this relationship map, the exhaust valve timing correction amount corresponding to the engine speed NE is calculated.

  Subsequently, the valve timing of the exhaust valve 26 is corrected by the variable valve mechanism 34 based on the exhaust valve timing correction amount calculated in step 160 (step 170).

  As described above, according to the routine shown in FIG. 4, the valve timing of the exhaust valve 26 can be corrected according to the engine speed NE. By this correction, the intake pulsation and the exhaust pulsation can be synchronized. For this reason, according to the system of the present embodiment, it is possible to suppress variations in the EGR rate between the cylinders at any engine speed. Therefore, the target value of the EGR rate can be sufficiently increased, and deterioration of NOx and fuel consumption can be suppressed.

  Further, in the system of the present embodiment, as shown in FIG. 2, the volume of the intake manifold 42 is set so that the gas at the fresh air-EGR gas merging position 60 is introduced into the cylinder in the intake stroke of each cylinder. It is small. In addition, the phases of intake pulsation and exhaust pulsation are synchronized. Therefore, according to the system of the present embodiment, the gas at the fresh air-EGR gas merging position 60 can be suitably introduced into the cylinder without variation in the EGR rate between the cylinders.

  Incidentally, in the system of the second embodiment described above, the configuration shown in FIG. 2 is used as the intake manifold 42. The configuration shown in FIG. 2 is preferable, but the configuration shown in FIG. 8 may be used. This point is the same in the following embodiments.

In the second embodiment described above, the intake air passage 12 is the “intake passage” in the second invention, and the external EGR passage 30 is the “external EGR passage” in the second invention. The merge position 60 corresponds to the “connection position” in the third aspect of the invention.
In addition, here, the ECU 50 executes the process of step 130, so that the “exhaust pulsation calculating means” in the second aspect of the invention executes the process of step 150, so that “ The “phase difference determining means” executes the processing of steps 160 to 170 described above, thereby realizing the “pulsation control means” in the second invention.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 5 described later in the configuration shown in FIGS. 1 and 2. It is assumed that an exhaust temperature sensor (not shown) for detecting the exhaust temperature T4 in the exhaust manifold 28 is connected to the input portion of the ECU 50.

[Characteristic Control in Embodiment 3]

  In the system of the second embodiment described above, the valve timing of the exhaust valve 26 is corrected to synchronize the intake pulsation and the exhaust pulsation. However, the following cases may be considered in which it is not always desirable to correct the valve timing.

  In the first case, when the pressure difference between the exhaust manifold 28 and the intake manifold 42 when the exhaust valve 26 is opened is larger than a certain threshold value, there is a concern about deterioration of pump loss. As a second case, when the temperature of the exhaust manifold 28 is higher than a certain threshold value, the efficiency of the EGR cooler 32 is lowered, and there is a concern about the deterioration of smoke. As a third case, when the temperature of the exhaust manifold 28 falls below a certain threshold, the bed temperature of the catalyst is lowered and the exhaust gas purification rate is lowered. Therefore, there is a concern about deterioration of exhaust emissions such as HC and CO.

  Therefore, in the system of the present embodiment, as a first process, when the pressure difference between the exhaust manifold 28 and the intake manifold 42 when the exhaust valve 26 is opened is equal to or greater than the threshold value α, the opening timing of the exhaust valve 26 is set. The amount of correction to be advanced (advance angle correction amount) was limited. Further, as the second processing, when the temperature of the exhaust manifold 28 is equal to or higher than the threshold value β, the advance correction amount is limited. Further, as a third process, when the temperature of the exhaust manifold 28 is equal to or lower than the threshold γ, the correction amount (retarding correction amount) for retarding the opening timing of the exhaust valve 26 is limited.

(Control routine)
FIG. 5 is a flowchart of a control routine executed by the ECU 50 in order to realize the first to third processes described above. This routine is the same as the routine shown in FIG. 4 except that the processing of steps 200 to 260 is added between step 160 and step 170. In FIG. 5, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 5, the pressure difference between the exhaust pressure P4 in the exhaust manifold 28 and the supercharging pressure Pb in the intake manifold 42 when the exhaust valve 26 is opened after the processing of step 160 is greater than or equal to the threshold value α. It is determined whether or not there is (step 200). Specifically, the exhaust pressure P4 is calculated from a known model. The supercharging pressure Pb is detected from the supercharging pressure sensor 40. Further, the threshold value α is a value obtained by experimentally determining the upper limit value of the allowable pump loss. If it is determined that the pressure difference is greater than or equal to the threshold value α, an advance angle limit flag that limits the advance angle correction amount is set to ON (step 210).

  Thereafter, in step 260, the exhaust valve timing correction amount is determined. Specifically, when the advance angle limit flag is ON and the exhaust valve timing correction amount calculated in step 160 is the advance angle correction amount, the advance correction of the exhaust valve opening timing is limited. Specifically, when the advance angle correction amount is equal to or greater than a predetermined upper limit value, this upper limit value is set as the advance angle correction amount. The upper limit value may be 0, and in this case, advance angle correction is prohibited.

  On the other hand, if it is determined in step 200 that the pressure difference is smaller than the threshold value α, whether or not the exhaust temperature T4 in the exhaust manifold 28 when the exhaust valve 26 is opened is equal to or higher than the threshold value β. Is determined (step 220). The exhaust temperature T4 is detected from an exhaust temperature sensor attached to the exhaust manifold 28. Further, the threshold value β is a value obtained by experiment or the like, which defines an upper limit value of the temperature at which smoke deterioration does not occur. If it is determined that the exhaust gas temperature T4 is equal to or higher than the threshold value β, an advance angle limit flag that limits the advance angle correction amount is set to ON (step 230).

  Thereafter, in step 260, the exhaust valve timing correction amount is determined. Specifically, as described above, when the advance angle limit flag is ON and the exhaust valve timing correction amount calculated in step 160 is the advance angle correction amount, the advance angle correction of the exhaust valve opening timing is limited. Is done.

  On the other hand, if it is determined in step 220 that the exhaust gas temperature T4 is lower than the threshold value β, it is next determined whether or not the exhaust gas temperature T4 is less than or equal to the threshold value γ (step 240). The threshold value γ is a value determined by experiment or the like as the lower limit value of the exhaust gas temperature necessary for the catalyst to maintain a suitable purification performance. When it is determined that the exhaust gas temperature T4 is equal to or lower than the threshold value γ, a retard limit flag that limits the retard correction amount is turned on (step 250).

  Thereafter, in step 260, the exhaust valve timing correction amount is determined. Specifically, when the retard limit flag is ON and the exhaust valve timing correction amount calculated in step 160 is the retard correction amount, the retard correction of the exhaust valve opening timing is limited. Specifically, when the retardation correction amount is equal to or greater than a prescribed upper limit value, this upper limit value is set as the advance correction amount. Note that the upper limit value may be 0, and in this case, retardation correction is prohibited.

  On the other hand, if it is determined in step 240 that the exhaust gas temperature T4 is higher than the threshold value γ, both the advance angle limit flag and the retard angle limit flag are turned OFF. Thereafter, in step 260, the exhaust valve timing correction amount is determined. Specifically, when both the advance angle limit flag and the retard angle limit flag are OFF, the exhaust valve timing correction amount calculated in step 160 is determined as the final correction amount.

  Subsequently, the valve timing of the exhaust valve 26 is corrected by the variable valve mechanism 34 based on the exhaust valve timing correction amount determined in step 260 (step 170).

  As described above, according to the routine shown in FIG. 5, even when the phase difference between the intake pulsation and the exhaust pulsation is outside the target range, the exhaust valve timing correction amount can be limited according to the operating state. it can. By limiting the exhaust valve timing correction amount, deterioration of pump loss, deterioration of smoke, and reduction of the purification rate of the catalyst can be suppressed. Therefore, deterioration of fuel consumption and exhaust emission can be suppressed.

  In addition, according to the routine shown in FIG. 5, when the pump loss and the exhaust manifold temperature are within the allowable ranges, the intake pulsation and the exhaust pulsation can be synchronized. Therefore, according to the system of the present embodiment, it is possible to appropriately suppress the variation in the EGR amount between the cylinders while suppressing the deterioration of the fuel consumption and the exhaust emission according to the driving situation.

  By the way, in the system of the third embodiment described above, the first process (steps 200 to 210), the second process (steps 220 to 230), and the third process (steps 240 to 250) are used in combination. However, it is not limited to this. For example, any one of the first to third processes or a plurality of processes may be used in combination. This point is the same in the following embodiments.

In the third embodiment described above, the intake passage 12 is the “intake passage” in the first or second invention, and the external EGR passage 30 is the “external EGR passage” in the first or second invention. The fresh air-EGR gas merge position 60 corresponds to the “connection position” in the first or third aspect of the invention.
In addition, here, the ECU 50 executes the process of step 130, so that the “exhaust pulsation calculating means” in the second aspect of the invention executes the process of step 150, so that “ The “phase difference determining means” executes the processing of steps 160 to 170 described above, thereby realizing the “pulsation control means” in the second invention.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 7 described later in the configuration shown in FIGS. 1 and 2.

[Characteristic Control in Embodiment 3]

  In the light load operation state, the in-cylinder temperature is low, so that HC in the exhaust gas tends to increase. For this reason, the amount of EGR at a light load is limited by HC restrictions. Therefore, in order to reduce NOx at light loads, it is necessary to improve the EGR amount distributed between the cylinders, that is, the variation in the EGR rate between the cylinders. By the way, in a light load operation state, it is mainly used in UDC (Urban Cycle) and is in a cold condition, so that the EGR amount and the electronically controlled throttle valve 38 are corrected. And since the dispersion | variation in the EGR rate between cylinders changes with this correction | amendment, it is difficult to adapt to this correction | amendment.

  Further, in a high-load operation state, the air-fuel ratio becomes closer to that in the normal state, so that mixing of fuel and fresh air is insufficient, and there is a concern that smoke may deteriorate. Furthermore, since the combustion temperature is high and the amount of NOx generated increases, a large amount of EGR is required to reduce NOx. However, if the EGR rate between the cylinders varies, smoke deterioration occurs, so that it becomes necessary to limit the EGR amount.

  Therefore, in the system of the present embodiment, when the operation state is light load or high load, the intake pulsation and the exhaust pulsation are synchronized, and the EGR rate between the cylinders is not affected by the correction of the throttle valve 38 or the like. It was decided to suppress the variation of.

(Control routine)
FIG. 7 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. This routine is the same as the routine shown in FIG. 4 except that the processing of steps 300 to 310 is added as the preprocessing of step 100. In FIG. 7, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 7, it is first determined whether or not the operation mode is a light load (step 300). FIG. 6 is a diagram illustrating an operation mode of the present system. When it is a cold condition (for example, a water temperature of 80 ° C. or less) and the load is as shown in the region (A) of FIG. 6, it is determined that the light load mode is set. When it is determined that the light load mode is set, the processing after step 100 is started.

  On the other hand, if it is determined that the mode is not the light load mode, it is next determined whether or not the mode is a high load operation mode (step 310). For example, when the load is high and the rotation is high as shown in the region B of FIG. 6, it is determined that the mode is the high load mode. If it is determined that the mode is the high load mode, the processing after step 100 is started. On the other hand, when it is determined that neither the light load mode nor the high load mode is set, the processing of this routine is terminated.

  As described above, according to the routine shown in FIG. 7, the phases of the intake pulsation and the exhaust pulsation can be synchronized in the light load mode. Therefore, even when the EGR amount and the throttle valve 38 are corrected and controlled under the cold condition, the variation in the EGR rate between the cylinders can be suppressed without being influenced by the correction control. By suppressing the variation in the EGR rate, the target value of the EGR rate can be sufficiently increased, and the deterioration of NOx can be suitably suppressed even at a light load.

  Further, according to the routine shown in FIG. 7, in the high load mode, it is possible to synchronize the phases of the intake pulsation and the exhaust pulsation to suppress the variation in the EGR rate between the cylinders. By suppressing the variation in the EGR rate, it is possible to suppress the deterioration of smoke. Therefore, it is possible to suitably introduce a large amount of EGR gas required at a high load and high rotation, and to appropriately suppress the deterioration of NOx.

  By the way, in the system of the above-described fourth embodiment, the determination of the light load mode (step 300) and the determination of the high load mode (step 310) are used together, but the present invention is not limited to this. . Only one of the mode determination processes may be used.

  Further, in the system of the fourth embodiment described above, the processes of steps 200 to 260 described above may be added between the processes of step 160 and step 170.

  In the above-described fourth embodiment, the ECU 50 executes the process of step 300, so that the “light load determination means” in the fourth invention executes the process of step 310. The “high-load high-rotation determination means” according to the fifth aspect of the invention implements the “pulsation control means” according to the fourth or fifth aspect of the invention by executing the processing of steps 160 to 170 described above.

A Intake passage downstream portion NE Engine speed P4 Exhaust pressure Pb Supercharging pressure T4 Exhaust temperature 10 Engine 12 Intake passage 14 Exhaust passage 18 Air flow meters 20, 20a, 20b Supercharger, compressor, turbine 22 Intercooler 24 Intake valve 26 Exhaust Valve 28 Exhaust manifold 30 External EGR passage 32 EGR cooler 34 Variable valve mechanism 36 Crank angle sensor 38 Throttle valve 40 Supercharging pressure sensor 42 Intake manifold 44 EGR valve 50 ECU
60 Shin-EGR gas merge position

Claims (5)

An intake passage connected to a plurality of cylinders;
An external EGR passage connecting the exhaust passage and the intake passage,
The volume of each path from the connection position of the intake passage and the external EGR passage to the plurality of cylinders is a volume capable of introducing the gas at the connection position into the cylinder in the intake stroke of each cylinder;
An internal combustion engine characterized by the above. An intake passage connected to a plurality of cylinders;
An external EGR passage connecting the exhaust passage and the intake passage and introducing EGR gas into the intake passage;
Exhaust pulsation calculating means for calculating the phase of exhaust pulsation when introducing EGR gas from a model that defines the relationship between engine parameters including engine speed and the phase of exhaust pulsation;
Phase difference determination means for determining whether or not the phase difference between the exhaust pulsation calculated by the exhaust pulsation calculation means and the intake pulsation is equal to or greater than a specified value;
Pulsation control means for controlling the valve timings of the exhaust valves of the plurality of cylinders according to the engine speed so as to reduce the phase difference when the phase difference is equal to or greater than the specified value;
An internal combustion engine comprising:   The volume of each path from the connection position of the intake passage and the external EGR passage to the plurality of cylinders is a volume capable of introducing the gas at the connection position into the cylinder during the intake stroke of each cylinder. 3. The internal combustion engine according to claim 2, wherein A light load determination means for determining whether or not the operating state is a light load;
The pulsation control means is configured to reduce the phase difference when the operation state is a light load and the phase difference is equal to or greater than the specified value. Controlling the valve timing of the exhaust valve,
The internal combustion engine according to claim 2 or 3, characterized in that. A high load high rotation determination means for determining whether or not the operation state is high load high rotation,
The pulsation control means is configured to reduce the phase difference when the operation state is a high load and high rotation and the phase difference is equal to or greater than the specified value. Controlling the valve timing of the exhaust valve of the cylinder,
The internal combustion engine according to claim 2 or 3, characterized in that.

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