JP2013130121A - Exhaust gas recirculation system for spark-ignition-type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation system capable of an appropriate quantity of EGR reliably and accurately even in a high load region in such a case that internal EGR takes place in a spark-ignition-type internal combustion engine which controls an intake air flow by a throttle.SOLUTION: A gasoline engine system 2 includes an exhaust valve 20b, a first EGR valve 20a, an exhaust pipe 24, an EGR passage 50, an exhaust valve mechanism 28, a second EGR valve 52, and an ECU 90. The EGR passage 50 has one end communicating with an exhaust port 22a and the another end communicating with the exhaust pipe 24. The exhaust valve mechanism 28 has an internal EGR drive mode for opening the exhaust valve 20b in an exhaust process and opening the first EGR valve 20a in an intake process. The second EGR valve 52 is provided between the one end and the another end of the EGR passage 50. The ECU 90 for a valve capable of varying an opening makes an opening of the second EGR valve 52 the larger, the higher the engine load becomes during internal EGR driving mode.

Description

  The present invention relates to an exhaust gas recirculation device for a spark ignition type internal combustion engine.

  Conventionally, various internal combustion engines equipped with an exhaust gas recirculation device that performs exhaust gas recirculation (EGR) are known. In particular, in recent years, a technique for performing so-called mass EGR in which a large amount of EGR gas is recirculated in a spark ignition internal combustion engine (hereinafter, also referred to as “gasoline engine” in particular) is known from the viewpoint of reducing pumping loss. .

  In this regard, Japanese Patent Laid-Open No. 6-10774 (hereinafter also referred to as “Patent Document 1”) discloses an exhaust gas recirculation device for a spark ignition type internal combustion engine. The exhaust gas recirculation device of this publication is provided with exhaust valves at a plurality of exhaust ports, some exhaust valves are used as EGR valves, and the remaining exhaust valves are used as normal exhaust valves. The exhaust ports communicate with each other via a merging portion on the exhaust gas downstream side. By opening the exhaust valve used as the EGR valve during the intake stroke, the exhaust gas from one exhaust port flows to the other exhaust port that has been opened via the junction. That is, the exhaust gas is again taken into the cylinder from the exhaust port on the EGR valve side. This mechanism can be said to belong to a so-called internal EGR type exhaust gas recirculation device. Hereinafter, the exhaust port that opens the exhaust valve in the exhaust stroke is referred to as “exhaust valve side exhaust port”, and the exhaust port that opens the exhaust valve in the intake stroke is referred to as “EGR side exhaust port”.

  According to the internal EGR system according to Patent Document 1, one of the two exhaust valves is opened during the intake stroke, whereby the exhaust gas is sucked from the exhaust port as the piston descends during the intake stroke. This method does not depend on the intake side pressure in the EGR gas introduction part of the intake passage unlike the so-called external EGR method. Therefore, there is an advantage that EGR can be reliably performed from a low load range to a high load range, and EGR can be reliably performed even in a supercharge range of a supercharged internal combustion engine.

JP-A-6-10774 JP 2004-293341 A

  The technique according to Patent Document 1 is not intended for a general gasoline engine with a throttle. There is a point that is not enough to apply the internal EGR system to a general gasoline engine that controls the intake air amount with a throttle. This point will be described below.

  In the technique according to Patent Document 1, optimization of the EGR amount in consideration of a general gasoline engine with a throttle has not been studied. Patent Document 1 discloses a technique for adjusting the EGR amount by providing a valve (regulating valve) in the exhaust passage on the “EGR valve side exhaust port” side, but the control of the regulating valve is special. The exhaust gas recirculation device according to Patent Document 1 controls the opening degree of the regulating valve 11 to be larger as the load becomes smaller at low load (see Paragraph 0024 of Patent Document 1). The reason for adopting such control is mainly due to the special configuration (special hardware and control) of the internal combustion engine of Patent Document 1.

  The technology according to Patent Document 1 is directed to a gasoline engine, but the gasoline engine has a special hardware configuration such as not having a throttle (see paragraph 0021 of Patent Document 1). Whether or not the control of the adjustment valve of Patent Document 1 has effectiveness is largely due to a special hardware configuration assumed in Patent Document 1. The premise of the gasoline engine according to Patent Document 1 and a general gasoline engine having a mechanism for adjusting the intake air amount with a throttle are greatly different in terms of intake air amount control with the throttle.

  The present invention has been made in order to solve the above-described problems. When internal EGR is performed on a spark ignition type internal combustion engine in which intake air amount control is performed by a throttle, an appropriate amount of EGR is loaded at a high load. An object of the present invention is to provide an exhaust gas recirculation device that can be reliably and accurately carried out even in a region.

In order to achieve the above object, a first invention is an exhaust gas recirculation device for a spark ignition type internal combustion engine,
An exhaust valve provided in a first exhaust port communicating with a combustion chamber of a spark ignition type internal combustion engine with a throttle, and opening and closing the first exhaust port;
A first valve provided in a second exhaust port communicating with the combustion chamber and opening and closing the second exhaust port;
An exhaust pipe communicating with the first exhaust port;
An EGR passage having one end communicating with the second exhaust port and the other end communicating with the exhaust pipe;
A valve gear having a drive mode for opening the exhaust valve in an exhaust stroke of the internal combustion engine and opening the first valve in an intake stroke of the internal combustion engine;
A second valve that is provided between the one end and the other end in the EGR passage and is capable of changing an opening;
A controller that increases the opening of the second valve as the load of the internal combustion engine increases during the drive mode;
It is characterized by providing.

According to a second invention, in the first invention,
The spark ignition internal combustion engine is a supercharged internal combustion engine including a supercharger,
An intake valve provided in an intake port communicating with the combustion chamber;
An intake side variable valve operating device that drives the intake valve, and the phase of the intake valve is variable;
In the spark ignition type internal combustion engine, the intake air pressure is reduced so that the valve overlap amount between the first valve and the intake valve is reduced in a positive pressure region where the intake pressure is higher than the exhaust pressure. An intake valve controller that retards the phase of the valve;
With
The controller opens the opening of the second valve in the positive pressure region to be larger than the opening of the second valve in the negative pressure region where the intake pressure of the spark ignition internal combustion engine is lower than the exhaust pressure. It includes a setting unit for setting the time.

According to a third invention, in the first or second invention,
The EGR passage further includes an EGR cooler provided between the second valve and the other end.

  According to the first invention, the amount of EGR gas can be increased according to the load, and an appropriate amount of EGR gas can be accurately and reliably recirculated to the combustion chamber even in a high load region. Thus, there is provided an exhaust gas recirculation device that can carry out a large amount of EGR in a spark ignition type internal combustion engine with a throttle over a wide range of operation including a high load range with an appropriate amount.

  According to the second invention, it is possible to secure the EGR gas introduction amount by opening the first valve even in the supercharging region where the intake pressure is higher than the exhaust pressure.

  According to the third aspect of the invention, it is possible to circulate a low temperature and appropriate amount of exhaust gas as EGR gas to the combustion chamber even in a high load operation region. While satisfying the requirements of both misfire suppression and knocking suppression, EGR in the high load operation region can be realized by the internal EGR method.

It is a figure which shows the structure of the exhaust gas recirculation apparatus of the spark ignition type internal combustion engine concerning embodiment of this invention. It is a figure for demonstrating operation | movement of the exhaust gas recirculation apparatus of the spark ignition internal combustion engine concerning embodiment of this invention. It is a figure for demonstrating operation | movement of the exhaust gas recirculation apparatus of the spark ignition internal combustion engine concerning embodiment of this invention. It is a figure for demonstrating operation | movement of the exhaust gas recirculation apparatus of the spark ignition internal combustion engine concerning embodiment of this invention. It is a figure for demonstrating operation | movement of the exhaust gas recirculation apparatus of the spark ignition internal combustion engine concerning embodiment of this invention. 4 is a flowchart of a routine executed by the ECU in the exhaust gas recirculation apparatus for the spark ignition type internal combustion engine according to the embodiment of the present invention.

[Configuration of the embodiment]
FIG. 1 is a diagram showing a configuration of an exhaust gas recirculation device for a spark ignition type internal combustion engine according to an embodiment of the present invention. FIG. 1 schematically shows a gasoline engine system 2 to which an exhaust gas recirculation apparatus according to the present embodiment is applied. The gasoline engine system 2 is a spark ignition internal combustion engine that includes a throttle 34 and uses gasoline as fuel.

  The gasoline engine system 2 includes a cylinder 10 having a piston therein. A combustion chamber including an upper surface of the piston and an inner surface of the cylinder head is formed in the cylinder 10. The cylinder 10 is provided with a spark plug 12 and an in-cylinder fuel injection valve 14.

  An intake port 18a and an intake port 18b communicate with the cylinder 10. The intake port 18a and the intake port 18b are provided with an intake valve 16a and an intake valve 16b that open and close the respective intake ports. An exhaust port 22 a and an exhaust port 22 b communicate with the combustion chamber of the cylinder 10. The exhaust port 22a is provided with a first EGR valve 20a responsible for opening and closing thereof, and the exhaust port 22b is provided with an exhaust valve 20b responsible for opening and closing thereof. These four valves provided in the cylinder 10 are all general poppet valves. In the following description, for convenience, the intake valves 16a and 16b, the first EGR valve 20a, and the exhaust valve 20b are also collectively referred to as “intake and exhaust valve groups 16a, 16b, 20a, and 20b”.

  The gasoline engine system 2 is actually an in-line four-cylinder gasoline engine mounted on a vehicle, but FIG. 1 shows only one cylinder 10 for convenience. The gasoline engine system 2 has an inline 4-cylinder cylinder block (not shown). The cylinder block includes a configuration around the cylinder 10 (ignition plug, in-cylinder fuel injection valve, intake valve, intake port, first EGR valve, exhaust gas). 4 sets of valves and exhaust ports) are incorporated. The illustration of the intake manifold connected to each intake port of the four cylinders 10 and the exhaust manifold connected to each exhaust port of the four cylinders 10 is omitted.

  The intake ports 18 a and 18 b communicate with the surge tank 30. The surge tank 30 communicates with the intake pipe 32. The intake pipe 32 includes a throttle 34, an intercooler 36, and an air flow meter 38, and communicates with an air cleaner 40 upstream.

  The exhaust port 22 b communicates with the exhaust pipe 24. A start catalyst 42 and a main catalyst 44 are sequentially provided in the exhaust pipe 24 toward the downstream side of the exhaust gas. An air-fuel ratio sensor 46 is provided upstream of the start catalyst 42 in the exhaust pipe 24. A sub oxygen sensor 48 is provided between the start catalyst 42 and the main catalyst 44 in the exhaust pipe 24.

  The gasoline engine system 2 includes an EGR passage 50. One end of the EGR passage 50 communicates with the exhaust port 22a. The other end of the EGR passage 50 communicates with a portion between the start catalyst 42 and the main catalyst 44 in the exhaust pipe 24.

The EGR passage 50 is provided with a second EGR valve 52 and an EGR cooler 54. The second EGR valve 52 is a valve that is provided between the one end and the other end in the EGR passage 50 and whose opening degree can be changed.
If the amount of EGR gas introduced is not appropriate, problems such as misfire occur, and there is a demand for an appropriate amount of EGR. Therefore, in order to accurately adjust the EGR amount, a second EGR valve 52 is provided as an adjustment valve on the exhaust port 22a side. By adjusting the flow rate of the EGR gas with the second EGR valve 52 together with the opening of the first EGR valve 20a during the intake stroke, the adjustment accuracy of the EGR amount can be increased.
The second EGR valve 52 is preferably a butterfly valve. According to the butterfly valve, the opening degree adjustment (flow rate adjustment) can be carried out continuously and accurately, the flow path resistance is small, and it is suitable for introducing a large amount of EGR.

  The EGR cooler 54 is provided between the second EGR valve 52 and the merging portion 24a in the EGR passage 50. According to the gasoline engine system 2, the exhaust gas whose temperature has decreased via the turbine 64 and the start catalyst 42 can be guided from the joining portion 24 a to the EGR passage 50 and further cooled by the EGR cooler 54. By introducing the sufficiently cooled EGR gas in this way, a large amount of EGR gas can be introduced while avoiding knocking.

  The gasoline engine system 2 includes an intake valve operating device 26 and an exhaust valve operating device 28. The intake valve device 26 is a device that drives the intake valves 16a and 16b, and the phases of the intake valves 16a and 16b are variable. The exhaust valve device 28 is a device for driving the first EGR valve 20a and the exhaust valve 20b, and is also a variable valve device having a variable phase. In particular, the exhaust valve device 28 is configured so that the phase of the first EGR valve 20a can be changed independently of the intake valves 16a and 16b and the exhaust valve 20b. Various technical literatures are already known for variable valve actuating devices in which the phase of the valve is variable, and are not new matters, so detailed description thereof will be omitted.

The exhaust valve device 28 has a drive mode in which the exhaust valve 20b is opened during the exhaust stroke of the cylinder 10 and the first EGR valve 20a is opened during the intake stroke of the cylinder 10 (after intake TDC). Hereinafter, this drive mode is also referred to as “internal EGR drive mode”.
According to the internal EGR drive mode, the internal EGR can be performed on the same principle as that of the exhaust gas recirculation apparatus described in Patent Document 1. That is, a poppet valve is provided in each of the exhaust ports 22a and 22b, one is used as a normal exhaust valve (exhaust valve 20b), and the other is used as an EGR valve (first EGR valve 20a). The exhaust ports 22a and 22b communicate with each other via a merging portion 24a on the exhaust gas downstream side. By opening the first EGR valve 20a during the intake stroke, the exhaust gas from the exhaust port 22b flows to the exhaust port 22a via the junction 24a. The exhaust port 22b corresponds to an “exhaust valve side exhaust port”, and the exhaust port 22a corresponds to an “EGR side exhaust port”. According to the internal EGR drive mode, unlike the external EGR system, there is an advantage that the EGR can be reliably performed from the low load range to the high load range without being influenced by the intake side pressure in the EGR gas introduction portion of the intake passage. is there.

  The gasoline engine system 2 is a supercharged internal combustion engine provided with a supercharger. In the present embodiment, the turbocharger is a turbocharger 60. The turbocharger 60 includes a compressor 62 and a turbine 64. The compressor 62 is provided in the intake pipe 32, and its position is upstream of the intercooler 36 in the intake pipe 32 and downstream of the air cleaner 40 (downstream of the air flow meter 38). The turbine 64 is provided upstream of the start catalyst 42 in the exhaust pipe 24 (downstream of the exhaust port 22b). Instead of the turbocharger 60, a supercharger may be used as a supercharger.

  The system of the present embodiment includes a sensor system including various sensors for grasping the engine operating state of the gasoline engine system 2 and an ECU (Electronic Control Unit) 90 for engine control. First, the sensor system will be described. The crank angle sensor outputs a signal synchronized with the rotation of the crankshaft, and the air flow meter 38 detects the intake air amount. The water temperature sensor detects the temperature of the engine cooling water (engine water temperature) as an example of the engine temperature that reflects the temperature state of the engine, and the intake air temperature sensor detects the intake air temperature. In addition to this, the sensor system includes various sensors necessary for engine control (such as a throttle sensor for detecting the opening of the throttle 34).

  The ECU 90 is configured by an arithmetic processing device including a storage circuit including, for example, a ROM, a RAM, a nonvolatile memory, and the like. Each sensor of the sensor system is connected to the input side of the ECU 90, and various actuators including the throttle 34, the spark plug 12, the in-cylinder fuel injection valve 14, and the like are connected to the output side of the ECU 90. In addition, the ECU 90 has a function of storing various data that change according to the crank angle as time series data together with the crank angle. This time-series data includes the output value of each sensor and various indexes, parameters, and the like calculated based on the output value.

  The ECU 90 controls the operating state by driving each actuator while detecting the operation information of the engine by the sensor system. Specifically, the engine speed (engine speed) and the crank angle are detected based on the output of a crank angle sensor (not shown), and the intake air amount is calculated based on the output of the air flow meter 38. An intake pressure sensor or an intake air temperature sensor may be used. Further, the engine load (load factor) is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and the ignition timing are determined based on the crank angle, and when these timings arrive, the spark plug 12 and the in-cylinder fuel injection valve 14 are driven. Thereby, the air-fuel mixture is combusted in the cylinder 10 and the engine can be operated.

  The ECU 90 is connected to the second EGR valve 52, and specifically, is connected to an opening adjusting actuator (motor) of the second EGR valve 52. The opening degree of the second EGR valve 52 is adjusted according to a control signal from the ECU 90. The ECU 90 is also connected to the intake valve device 26 and the exhaust valve device 28. The ECU 90 drives the intake / exhaust valve groups 16a, 16b, 20a, 20b in accordance with a control program for controlling the variable valve operating device stored in the ROM. The “internal EGR drive mode” is also stored in advance as part of this control program.

[Operation of the embodiment]
2 to 5 are diagrams for explaining the operation of the exhaust gas recirculation device for the spark ignition type internal combustion engine according to the embodiment of the present invention. Among these, FIG. 2, FIG. 4 and FIG. 5 are diagrams showing the valve phase timings according to the operating state. Specifically, FIG. 2 is a diagram showing each valve phase timing when the EGR is introduced after the engine is warmed up. FIG. 4 is a diagram showing valve phase timings when EGR is introduced in the high load operation region. FIG. 5 is a diagram showing valve phase timings when EGR is introduced in the WOT (Wide open throttle) region. On the other hand, FIG. 3 is a diagram showing the opening degree of the second EGR valve 52 and the opening timings of the intake valves 16a and 16b with respect to the engine load.

(Low, medium load range after warm-up)
In the present embodiment, when the engine load is in the low to medium load range with the engine warmed up, the intake / exhaust valve groups 16a, 16b, 20a and 20b are driven with the valve opening characteristics shown in FIG. To do. The valve opening characteristics shown in FIG. 2 are those in the “internal EGR drive mode”. The exhaust valve 20b is opened during the exhaust stroke of the cylinder 10, and the first EGR valve 20a is opened during the intake stroke of the cylinder 10 (after the intake TDC). An open control action has been implemented. In FIG. 2, the hatched area (the overlapping area of the intake valve characteristic and the first EGR valve characteristic) is the valve overlap section. The area of this region corresponds to the valve overlap amount between the intake valves 16a and 16b and the first EGR valve 20a.

In FIG. 2, the opening degree of the second EGR valve 52 is described as 50%, but in the present embodiment, the control of the second EGR valve 52 is opening degree control according to the engine load.
In the gasoline engine system 2, as with a general spark ignition internal combustion engine with a throttle, as the load increases, the throttle 34 opens and the intake air amount increases. As shown in FIG. 3, the ECU 90 increases the opening degree of the second EGR valve 52 as the engine load increases during the internal EGR drive mode. Thereby, the amount of EGR can be increased in accordance with the increase in load (intake air amount increase). In the present embodiment, the relationship between the opening degree and the load is a linear proportional relationship. In the present embodiment, control for making the opening degree and the load proportional is executed when the engine load is within a predetermined low and medium load range. The process is executed in a region indicated as “negative pressure region” in FIG. The negative pressure region means a load region where the pressure in the intake passage (pressure in the intake pipe 32) is negative.

  According to the above control, the internal EGR can be performed by opening the first EGR valve 20a in the intake stroke, and the EGR can be reliably performed over a wide range of operation including the high load range. Furthermore, by adding an EGR amount adjustment function by the second EGR valve 52 to the first EGR valve 20a, the EGR amount can be adjusted with high accuracy. Furthermore, by increasing the opening of the second EGR valve 52 in accordance with the load increase, the EGR gas can be increased in accordance with the load, and an appropriate amount of EGR can be performed. Therefore, the amount of EGR gas can be increased according to the load, and an appropriate amount of EGR gas can be accurately and reliably recirculated to the combustion chamber over a wide range of operation including the high load region. Thus, an exhaust gas recirculation device suitable for mass EGR in a general spark ignition internal combustion engine with a throttle is provided.

(High load operating range / supercharging range)
In the present embodiment, when the engine load belongs to a high load region (supercharging region), the intake / exhaust valve groups 16a, 16b, 20a, 20b are driven with the valve opening characteristics shown in FIG. The valve opening characteristics shown in FIG. 4 are those in the “internal EGR drive mode”, but the phases of the intake valves 16a and 16b are different from the valve opening characteristics shown in FIG. In the valve opening characteristics shown in FIG. 4, the phases of the intake valves 16a and 16b are retarded, and the valve overlap amount is reduced. In the present embodiment, the ECU 90 performs the valve opening characteristic control of FIG. 4 in the “positive pressure region” of FIG. This positive pressure region is an operating region where the intake pressure is higher than the exhaust pressure. The ECU 90 controls the intake valve device 26 to retard the phase of the intake valves 16a and 16b so as to reduce the valve overlap amount between the first EGR valve 20a and the intake valves 16a and 16b. Note that, as shown by the broken line in “intake valve opening timing” in FIG. 3, in this embodiment, the valve opening timing is proportionally shifted to the retard side as the engine load increases.

  Further, the ECU 90 switches the opening degree of the second EGR valve 52 in the positive pressure region to fully open at a predetermined load (threshold value) as shown in FIG. In FIG. 4 as well, “second EGR valve opening%” is described as 100%. Note that the second EGR valve 52 does not necessarily have to be fully opened stepwise in a predetermined high load region, and may be made to be fully opened stepwise or continuously in multiple stages, such as 80% → 90% → 100%. . What is necessary is just to set the opening degree larger than the opening degree of the 2nd EGR valve 52 in a negative pressure area.

  In the positive pressure region, the intake pressure is higher than the exhaust pressure. If the overlap amount is large, the EGR gas suction of the first EGR valve 20a is hindered by the high pressure intake air (fresh air). Therefore, in this embodiment, the overlap amount is reduced to avoid this. Also, by increasing the second EGR valve 52, a large amount of EGR gas commensurate with a large amount of fresh air in the positive pressure region can be secured.

(WOT area)
In the present embodiment, when the engine load belongs to the WOT region, the intake / exhaust valve groups 16a, 16b, 20a, and 20b are driven with the valve opening characteristics shown in FIG. The valve opening characteristic shown in FIG. 5 is no longer the “internal EGR drive mode”, but a drive mode in which the first EGR valve 20a functions as an exhaust valve. That is, the first EGR valve 20a is opened during the exhaust stroke (between BDC and TDC). The second EGR valve 52 is also fully opened (opening degree 100%). As a result, the exhaust gas flows into the EGR passage 50 through the exhaust port 22a in the exhaust stroke, and the exhaust gas flows through the second EGR valve 52 to the exhaust pipe 24. As a result, exhaust pump loss can be reduced.

(Cooling of EGR gas)
According to the present embodiment, by introducing the EGR gas sufficiently cooled through the turbine 64, the start catalyst 42, and the EGR cooler 54, a large amount of EGR can be performed while avoiding knocking. Therefore, an appropriate amount of exhaust gas at a low temperature can be circulated in the combustion chamber as EGR gas even in the high load operation region. This makes it possible to perform EGR while avoiding both misfire and knocking.

Regarding this advantageous effect, the relationship with the prior art will be described below.
Patent Document 2 discloses an internal EGR type exhaust gas recirculation device based on a diesel engine. Diesel engines make NOx reduction one of the main purposes of EGR, while spark-ignition internal combustion engines with throttles make fuel efficiency improvement by reducing pumping loss one of the main purposes of EGR. Both cannot be identified. Both Patent Document 1 and Patent Document 2 have a common point that the purpose is to recirculate high-temperature EGR gas. Both of them achieve the common purpose by the internal EGR method. However, the situation is different when considering a large amount of EGR in a spark ignition type internal combustion engine. This is because introduction of a large amount of high-temperature EGR gas may induce knocking, and knocking cannot be neglected in a spark ignition internal combustion engine.
The exhaust gas recirculation device according to the prior art document does not have a large amount of EGR in a spark ignition type internal combustion engine in mind. On the other hand, the exhaust gas recirculation device according to the present embodiment is a device that can realize EGR in the high load operation region by the internal EGR method while satisfying both the misfire suppression and knocking suppression requirements. A large amount of EGR in a spark-ignition internal combustion engine with a throttle can be realized.

[Specific processing of the embodiment]
FIG. 6 is a flowchart of a routine executed by the ECU 90 in the exhaust gas recirculation apparatus for the spark ignition type internal combustion engine according to the embodiment of the present invention. This routine is repeatedly executed at a predetermined cycle during the engine operation of the gasoline engine system 2.

  In the routine of FIG. 6, first, the ECU 90 executes a process of determining whether or not the engine is warmed up in the gasoline engine system 2 (step S100). If there is no warm-up, the current routine ends.

  If the result of step S100 is YES, the ECU 90 next executes a process of determining whether or not the engine load belongs to a high load range (step S102). In this step, a comparison process for comparing the current engine load with a predetermined load value (“threshold” in FIG. 3) is executed. If the engine load is equal to or greater than the threshold, the result of step S102 is YES, and if the engine load is less than the threshold, the result of step S102 is NO.

If the result of step S102 is NO, the ECU 90 executes the process of step S104. The process of step S104 is a control process that realizes the operation described in “low and medium load range after warm-up” in the description of the operation according to the above-described embodiment. That is, the following substep A1 and substep A2 are executed.
In substep A1, the ECU 90 sets the exhaust valve device 28 to the above-described internal EGR drive mode. As a result, the intake / exhaust valve groups 16a, 16b, 20a, 20b are driven with the valve opening characteristics shown in FIG.
In sub-step A2, the ECU 90 controls the second EGR valve 52 so that the opening degree is proportionally increased as the engine load increases. As a premise, in the present embodiment, the ECU 90 stores a “second EGR valve opening characteristic map”. The “second EGR valve opening characteristic map” is a map that defines the relationship between the engine load and the second EGR valve opening shown in FIG. 3, and is created in advance and stored in the ROM of the ECU 90. In step S104, the ECU 90 acquires the current target opening of the second EGR valve 52 according to the “second EGR valve opening characteristic map” based on the current engine load. A control signal is sent to the actuator of the second EGR valve 52 so as to realize this target opening.
Thereafter, the current routine ends.

  If the result of step S102 is YES, the ECU 90 next executes a process of determining whether or not it corresponds to the WOT region (step S106). The determination as to whether it falls within the WOT region may be performed by detection based on the output of the throttle sensor, for example.

  If the result of step S106 is NO, the ECU 90 executes the process of step S108. The process of step S108 is a control process for realizing the operation described in the “high load operation region / supercharging region” in the description of the operation according to the above-described embodiment. At this time, supercharging by the turbocharger 60 is performed, and the supercharging pressure is high. Since the result of step S102 is YES, the engine load is equal to or greater than the threshold value, and the intake pressure is in a positive pressure range higher than the exhaust pressure. In step S108, the following sub-step B1 and sub-step B2 are executed.

In sub-step B1, the ECU 90 sets the exhaust valve device 28 to the internal EGR drive mode described above. Further, the ECU 90 controls the intake valve operating device 26 so that the opening timing (phase) of the intake valves 16a and 16b is proportionally retarded according to the engine load. As a premise, in the present embodiment, the ECU 90 stores an “intake valve opening characteristic map”. The “intake valve opening characteristic map” is a map that defines the relationship between the engine load and the intake valve opening timing shown in FIG. 3 and is created in advance and stored in the ROM of the ECU 90. In step S108, the ECU 90 acquires the current valve opening timing of the intake valves 16a, 16b according to the “intake valve opening characteristic map” based on the current engine load. The valve opening timing here is the amount of retardation from the reference characteristic shown in FIG. The ECU 90 sends a control signal to the intake valve device 26 so that the phase is retarded by this retard amount. As a result, the intake / exhaust valve groups 16a, 16b, 20a, 20b are driven with the valve opening characteristics shown in FIG.
On the other hand, in sub-step B2, the second EGR valve 52 is set to fully open (opening degree 100%). Thereafter, the current routine ends.

  If the result of step S106 is YES, the ECU 90 executes the process of step S110. The process of step S110 is a control process for realizing the operation described in the “WOT region” in the description of the operation according to the above-described embodiment. The ECU 90 controls the phase of the first EGR valve 20a by a predetermined amount so that the first EGR valve 20a opens during the exhaust stroke so that the intake / exhaust valve groups 16a, 16b, 20a, 20b follow the valve opening characteristics shown in FIG. As a result, the first EGR valve 20a functions as an exhaust valve. Further, the second EGR valve 52 is fully opened. Thereafter, the current routine ends.

According to the specific processing described above, the amount of EGR gas can be increased according to the engine load (see FIG. 3), and an appropriate amount of EGR gas can be accurately and reliably recirculated to the combustion chamber even in a high load region. it can. As a result, in the gasoline engine system 2 having the throttle 34, an exhaust gas recirculation device that can carry out a large amount of EGR in an appropriate amount and reliably over a wide range of operation including a high load range (see FIG. 3) is provided. Is done.
Further, according to the above specific processing, the amount of EGR gas introduced by opening the first EGR valve 20a can be reduced even in the positive pressure region by adjusting the valve overlap amount and increasing the opening degree of the second EGR valve 52 (fully opened). It can be secured sufficiently.
Further, according to the present embodiment, the cooled EGR gas can be obtained by passing through the turbine 64, the start catalyst 42, and the EGR cooler 54. Even in a high load operation region, an appropriate amount of exhaust gas at a low temperature can be circulated as EGR gas to the combustion chamber. While satisfying the requirements of both misfire suppression and knocking suppression, EGR in the high load operation region can be realized by the internal EGR method.

2 Gasoline engine system, 10 cylinders, 11 regulating valve, 12 spark plug, 14 cylinder fuel injection valve, 16a intake valve, 16b intake valve, 18a intake port, 20a first EGR valve, 20b exhaust valve, 22a exhaust port, 22b exhaust Port, 24 Exhaust pipe, 24a Merging section, 26 Inlet valve operating device, 28 Exhaust valve operating device, 30 Surge tank, 32 Intake pipe, 34 Throttle, 36 Intercooler, 38 Air flow meter, 40 Air cleaner, 42 Start catalyst, 44 Main Catalyst, 46 Air-fuel ratio sensor, 48 Sub oxygen sensor, 50 EGR passage, 52 Second EGR valve, 54 EGR cooler, 60 Turbocharger, 62 Compressor, 64 Turbine

Claims (3)

An exhaust valve provided in a first exhaust port communicating with a combustion chamber of a spark ignition type internal combustion engine with a throttle, and opening and closing the first exhaust port;
A first valve provided in a second exhaust port communicating with the combustion chamber and opening and closing the second exhaust port;
An exhaust pipe communicating with the first exhaust port;
An EGR passage having one end communicating with the second exhaust port and the other end communicating with the exhaust pipe;
A valve gear having a drive mode for opening the exhaust valve in an exhaust stroke of the internal combustion engine and opening the first valve in an intake stroke of the internal combustion engine;
A second valve that is provided between the one end and the other end in the EGR passage and is capable of changing an opening;
A controller that increases the opening of the second valve as the load of the internal combustion engine increases during the drive mode;
An exhaust gas recirculation apparatus for a spark ignition type internal combustion engine. The spark ignition internal combustion engine is a supercharged internal combustion engine including a supercharger,
An intake valve provided in an intake port communicating with the combustion chamber;
An intake side variable valve operating device that drives the intake valve, and the phase of the intake valve is variable;
In the spark ignition type internal combustion engine, the intake air pressure is reduced so that the valve overlap amount between the first valve and the intake valve is reduced in a positive pressure region where the intake pressure is higher than the exhaust pressure. An intake valve controller that retards the phase of the valve;
With
The controller opens the opening of the second valve in the positive pressure region to be larger than the opening of the second valve in the negative pressure region where the intake pressure of the spark ignition internal combustion engine is lower than the exhaust pressure. The exhaust gas recirculation device for a spark ignition type internal combustion engine according to claim 1, further comprising a setting unit that sets the temperature.   The exhaust gas recirculation device for a spark ignition type internal combustion engine according to claim 2, further comprising an EGR cooler provided between the second valve and the other end in the EGR passage.

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