JP2007315230A - Apparatus for recirculating exhaust gas of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of further appropriately supplying EGR gas in an apparatus for recirculating the exhaust gas of an internal combustion engine. <P>SOLUTION: The apparatus for recirculating the exhaust gas of the internal combustion engine comprises a super charger having a turbine in an exhaust passage and a compressor in an intake passage, an EGR passage for connecting the exhaust passage on the downstream side than the turbine to the intake passage on the upstream side than the compressor, and an inside EGR quantity changing means for changing the inside EGR quantity of the internal combustion engine. The ratio of the outside EGR quantity to be introduced into cylinders by flowing the exhaust gas of the internal combustion engine into the EGR passage to the inside EGR quantity to be remained in the cylinders is changed according to the load to be applied to the internal combustion engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  Low-temperature and low-pressure EGR gas (hereinafter referred to as low-pressure EGR) can be supplied by a low-pressure EGR passage that connects an exhaust passage downstream of the turbine of the turbocharger and an intake passage upstream of the compressor. Further, high-temperature and high-pressure EGR gas (hereinafter referred to as high-pressure EGR) can be supplied by a high-pressure EGR passage that connects an exhaust passage upstream of the turbine of the turbocharger and an intake passage downstream of the compressor.

  However, in the low pressure EGR, the temperature of the EGR gas is lowered by the exhaust gas passing through the turbine or the intercooler. For this reason, if low pressure EGR is performed at low load, the temperature of the intake manifold will decrease too much, leading to a decrease in combustion temperature, which may increase the amount of HC emissions.

And, by performing low pressure EGR in the operation state from high load to medium load, and performing high pressure EGR in the operation state from low load to idling, it realizes premixed compression ignition in the operation state except the high load operation state There is known an exhaust gas recirculation device for an internal combustion engine (see, for example, Patent Document 1).
JP 2002-21625 A Japanese Patent Laid-Open No. 5-71428 JP 2004-162552 A Japanese Patent No. 3046707 Japanese Patent Laid-Open No. 9-296740

For example, in an internal combustion engine with a low compression ratio aimed at reducing NOx and increasing output, the combustion temperature is low, so it is difficult to suppress a decrease in combustion temperature even if high pressure EGR is performed at a low load. Further, in the high pressure EGR, the exhaust gas flows into the intake passage from the upstream side of the turbine, so that the energy supplied to the turbine is reduced. This may lead to a decrease in supercharging pressure and a decrease in intake air amount.

  Further, in the prior art that performs internal EGR, the nozzles of the variable capacity turbocharger are excessively closed. If it does so, since the pressure of exhaust_gas | exhaustion upstream from a turbine will rise, pump loss will increase and a fuel consumption will deteriorate. Further, since the temperature of the internal EGR is not lowered by the EGR cooler, there is a possibility that the combustion chamber temperature is excessively raised and the amount of NOx emission increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a technique capable of supplying EGR gas more appropriately in an exhaust gas recirculation apparatus for an internal combustion engine.

In order to achieve the above object, an exhaust gas recirculation apparatus for an internal combustion engine according to the present invention employs the following means. That is, the exhaust gas recirculation device for an internal combustion engine according to the present invention is:
A turbocharger equipped with a turbine in the exhaust passage and a compressor in the intake passage;
An EGR passage connecting an exhaust passage downstream of the turbine and an intake passage upstream of the compressor;
Internal EGR amount changing means for changing the internal EGR amount of the internal combustion engine;
With
The ratio of the external EGR amount introduced into the cylinder by flowing exhaust gas from the internal combustion engine through the EGR passage and the internal EGR amount remaining in the cylinder is changed in accordance with the load of the internal combustion engine. And

  The external EGR is performed by introducing the burned gas discharged from the internal combustion engine into the exhaust passage into the cylinder by flowing in the order of the EGR passage and the intake passage. Since the EGR passage connects the exhaust passage downstream of the turbine and the intake passage through which the intake air before being compressed by the compressor flows, even in the case where the supercharging pressure is high, the EGR passage is closer to the exhaust passage side. Also, the pressure on the intake passage side can be lowered. Therefore, the EGR gas can be circulated even when the supercharging pressure is high.

  On the other hand, the internal EGR is burned gas remaining in the cylinder without passing through the EGR passage. For example, the amount of burned gas blown back into the intake passage is re-inhaled into the cylinder, the burned gas discharged into the exhaust passage is backflowed into the cylinder, or the amount of burned gas discharged from the cylinder. The internal EGR is performed by reducing the amount of burnt gas remaining in the cylinder. This internal EGR can be performed, for example, by a variable valve mechanism changing the opening / closing characteristics of the exhaust valve. This variable valve mechanism adjusts the opening timing, closing timing, lift amount, and operating angle of the exhaust valve to adjust the amount of fresh air, EGR amount, and residual gas amount (internal EGR amount), pump loss, etc. are adjusted to change the operating state of the internal combustion engine. For example, if the closing timing of the exhaust valve is made earlier than the exhaust top dead center, the amount of burned gas that blows back to the intake passage increases, and this burned gas is sucked into the cylinder in the intake stroke. Therefore, the burnt gas remaining in the cylinder increases. Further, if the closing timing of the exhaust valve is made later than the exhaust top dead center, the burnt gas once discharged into the exhaust passage flows back into the cylinder in the intake stroke. Therefore, the burnt gas remaining in the cylinder increases. In this way, the internal EGR amount can be increased.

And since the temperature of internal EGR gas is higher than the temperature of external EGR gas, the temperature in a cylinder can be raised by increasing the ratio of internal EGR gas in a cylinder. However, as the load on the internal combustion engine increases, the temperature rise in the cylinder due to the internal EGR increases, so that the combustion temperature may increase excessively and the NOx emissions may increase. In that respect, since the temperature of the external EGR gas is lower than the temperature of the internal EGR gas, the temperature in the cylinder can be lowered by increasing the ratio of the external EGR gas in the cylinder. Therefore, an excessive decrease in the combustion temperature can be suppressed by increasing the ratio of the internal EGR and decreasing the ratio of the external EGR as the low-load operation in which the combustion temperature is lowered. Thereby, the discharge amount of HC can be reduced. Further, by increasing the internal EGR rate and increasing the external EGR rate for higher load operation where the combustion temperature becomes higher, it is possible to suppress an excessive increase in the combustion temperature. Thereby, NOx emission can be suppressed. further,
By performing the internal EGR, a decrease in the amount of exhaust gas passing through the turbine can be suppressed, so that a decrease in engine output can be suppressed.

  In the present invention, when the temperature in the cylinder is raised, the ratio of the internal EGR is made higher than before the temperature is raised, and when the temperature in the cylinder is lowered, the ratio of the external EGR is made higher than before the temperature is lowered. The temperature in the cylinder can be adjusted.

That is, since the temperature differs between the external EGR gas and the internal EGR gas, the temperature of the EGR gas as a whole can be adjusted by changing the ratio of the external EGR amount and the internal EGR amount in the cylinder. Thereby, the temperature in a cylinder can be adjusted to desired temperature. For example, when the temperature in the cylinder is to be lowered, the ratio of the external EGR gas having a low temperature is increased, and when the temperature in the cylinder is to be increased, the ratio of the internal EGR gas having a high temperature is decreased.

  In the present invention, the ratio of the external EGR can be made higher during high load operation of the internal combustion engine than during low load operation.

When the load is high, the temperature in the cylinder becomes high. At this time, by increasing the ratio of the external EGR, the temperature of the entire EGR gas can be lowered. Therefore, generation of NOx due to an excessive increase in the combustion temperature Can be suppressed. In the predetermined load range, the ratio of the external EGR may be increased as the load increases.

  In the present invention, the ratio of the external EGR can be set to zero during low load operation of the internal combustion engine.

  Here, at the time of low load operation, the combustion temperature may be excessively lowered, so that there is almost no need to lower the combustion temperature by the external EGR. On the other hand, by setting the ratio of external EGR to 0 during low-load operation, the temperature of the entire EGR gas can be increased, and HC emissions can be further reduced. Therefore, external EGR may be prohibited when the combustion temperature is lower than a predetermined temperature. In other words, the “low load” here means, for example, a low load in the vicinity of an idle or idle, a load that may discharge HC when external EGR is performed, or a discharge amount of HC may exceed an allowable value. It can be a certain load.

  In the present invention, the supercharger is a variable displacement turbocharger, and the nozzle of the variable displacement turbocharger can be opened when the proportion of the external EGR is increased compared to when the proportion is not increased.

  Even when the amount of exhaust is small, such as when the internal combustion engine is operating at a low load, by rotating the nozzle of the variable displacement turbocharger in the closing direction, the exhaust flow rate is increased and the rotational speed of the exhaust turbine The rotational force can be increased. However, when the nozzle is rotated in the closing direction, the back pressure increases. Thereby, the ratio of internal EGR gas becomes high and the ratio of external EGR gas becomes low. In addition, the pump loss increases as the back pressure increases.

  Here, for example, the ratio of the internal EGR gas can also be increased by changing the opening / closing timing of the exhaust valve by a variable valve mechanism. When the ratio of the internal EGR gas is increased by the variable valve mechanism, the back pressure can be reduced compared with the case where the nozzle is rotated in the closing direction, so that the pump loss is reduced. be able to. Furthermore, since the nozzle can be rotated in the opening direction by an amount corresponding to an increase in the ratio of the internal EGR gas, the pump loss can be further reduced.

According to the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the EGR gas can be supplied more appropriately by changing the ratio between the internal EGR amount and the external EGR amount according to the load of the internal combustion engine. As a result, NOx and HC emissions can be reduced. Further, the engine output can be improved by increasing the supercharging pressure.

  Hereinafter, specific embodiments of an exhaust gas recirculation device for an internal combustion engine according to the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the exhaust gas recirculation apparatus for an internal combustion engine according to this embodiment is applied, its intake / exhaust system, and a supercharger. An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2. The internal combustion engine 1 is a low compression ratio internal combustion engine having a compression ratio of, for example, 14 to 15.8.

  An intake pipe 3 and an exhaust pipe 4 are connected to the internal combustion engine 1. In the middle of the intake pipe 3, a compressor housing 5a of a turbocharger 5 that operates using exhaust energy as a drive source is provided. The intake pipe 3 upstream of the compressor housing 5a is provided with an intake throttle 6 for adjusting the flow rate of the intake air flowing through the intake pipe 3. The intake throttle 6 is opened and closed by an electric actuator. The intake pipe 3 upstream of the intake throttle 6 is provided with an air flow meter 7 that outputs a signal corresponding to the flow rate of intake air flowing through the intake pipe 3. The air flow meter 7 measures the intake air amount of the internal combustion engine 1.

  On the other hand, a turbine housing 5 b of the turbocharger 5 is provided in the middle of the exhaust pipe 4. An exhaust purification catalyst 8 is provided in the exhaust pipe 4 downstream of the turbine housing 5b.

  The internal combustion engine 1 is provided with an EGR device 30 that recirculates a part of the exhaust gas flowing through the exhaust pipe 4 to the intake pipe 3. The EGR device 30 includes an EGR passage 31, an EGR valve 32, and an EGR cooler 33. The EGR passage 31 connects the exhaust pipe 4 downstream of the turbine housing 5b and the intake pipe 3 upstream of the compressor housing 5a. Exhaust gas is recirculated through the EGR passage 31. In this embodiment, the exhaust gas recirculated through the EGR passage 31 is referred to as external EGR gas. Further, the EGR valve 32 adjusts the amount of the external EGR gas flowing through the EGR passage 31 by adjusting the passage sectional area of the EGR passage 31. Further, the EGR cooler 33 reduces the temperature of the external EGR gas that passes through the EGR cooler 33.

  In the present embodiment, a variable capacity turbocharger is adopted as the turbocharger 5. FIG. 2 is a cross-sectional view showing the configuration of the variable capacity turbocharger. 2A shows the case where the nozzle vane 51 is open, and FIG. 2B shows the case where the nozzle vane 51 is closed.

  As shown in the figure, the variable displacement turbocharger is configured to include a plurality of nozzle vanes 51 around an exhaust turbine 5c provided in a turbine housing 5b. The nozzle vane 51 is opened and closed by an actuator 52. When the nozzle vane 51 is rotated to the closing side, the gap between the adjacent nozzle vanes 51 is narrowed, and the flow path between the nozzle vanes 51 is closed. On the other hand, when the nozzle vane 51 is rotated to the opening side, the gap between the adjacent nozzle vanes 51 is widened, and the flow path between the nozzle vanes 51 is opened.

  In the variable displacement turbocharger configured as described above, the direction of the flow path between the nozzle vanes 51 and the gap between the nozzle vanes 51 are changed by adjusting the rotation direction and the rotation amount of the nozzle vanes 51 by the actuator 52. It becomes possible. That is, by controlling the rotation direction and the rotation amount of the nozzle vane 51, the direction, flow rate, and amount of the exhaust blown to the exhaust turbine 5c are adjusted.

Further, the internal combustion engine 1 according to this embodiment includes a variable valve mechanism 60. Each cylinder 2 is provided with two exhaust valves 61, and each exhaust valve 61 is opened and closed by an exhaust side cam 62. The exhaust side cam 62 is attached to an exhaust side camshaft 63, and an exhaust side pulley 64 is provided at the end of the exhaust side camshaft 63. Furthermore, a variable rotation phase mechanism (hereinafter referred to as “exhaust side VVT”) 65 that can change the relative rotation phase between the exhaust side camshaft 63 and the exhaust side pulley 64 is provided. The exhaust side VVT 65 controls the relative rotation phase between the exhaust side camshaft 63 and the exhaust side pulley 64 in accordance with a command from the ECU 10.

  The rotation of the exhaust camshaft 63 is driven by the driving force of the crankshaft. Then, the exhaust camshaft 63 is rotationally driven by the driving force of the crankshaft, and the exhaust cam 62 is further rotated, so that the exhaust valve 61 is opened and closed. In this embodiment, the open / close timing of the exhaust valve 61 is advanced or retarded from the exhaust top dead center by the variable valve mechanism 60 to change the amount of burned gas in the cylinder 2. In the present embodiment, the burned gas remaining in the cylinder 2 in this way is referred to as internal EGR gas.

  The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver. Further, the ECU 10 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 11 by the driver, an accelerator opening sensor 12 that can detect the engine load, a crank position sensor 13 that detects the engine speed, Various sensors are connected via electric wiring, and output signals of these various sensors are input to the ECU 10. On the other hand, the intake throttle 6, the EGR valve 32, the actuator 52, and the VVT 65 are connected to the ECU 10 through electric wiring, and these devices are controlled by the ECU 10.

  In this embodiment, the internal EGR amount and the external EGR amount are adjusted by the ECU 10. The amount of internal EGR can be adjusted by controlling the VVT 65. The earlier the exhaust valve 61 closes than the exhaust top dead center, the greater the amount of burnt gas that remains in the cylinder 2 without being discharged into the exhaust pipe 4. After that, the burned gas flows backward to the intake pipe 3 by opening the intake valve, but the burned gas that has flowed back flows again into the cylinder 2 in the immediately following intake stroke. That is, the earlier the exhaust valve 61 closes than the exhaust top dead center, the more the internal EGR amount can be increased. Further, as the exhaust valve 61 closes later than the exhaust top dead center, the amount of burnt gas that flows back into the cylinder 2 from the exhaust pipe 4 during the intake stroke increases. That is, the internal EGR amount can be increased as the exhaust valve 61 closes later than the exhaust top dead center. In this embodiment, the variable valve mechanism 60 corresponds to the internal EGR amount changing means in the present invention.

  On the other hand, the amount of external EGR can be adjusted by controlling the intake throttle 6. By reducing the valve opening amount of the intake throttle 6, the pressure in the intake pipe 3 downstream of the intake throttle 6 can be reduced. As a result, the pressure difference between the exhaust pipe 4 and the intake pipe 3 increases, so that more exhaust flows through the EGR passage 31 and the amount of external EGR increases. At this time, the EGR valve 32 is fully opened. Thus, the external EGR amount can be adjusted by adjusting the opening of the intake throttle 6. Instead of the intake throttle 6, an exhaust throttle can be provided in the exhaust pipe 4 downstream of the location where the EGR passage 31 is connected to the exhaust pipe 4, and the external EGR amount can be adjusted by opening and closing the exhaust throttle. . In this case, as the opening of the exhaust throttle is reduced, the pressure in the exhaust pipe 4 is increased and the amount of external EGR is increased. Further, the amount of external EGR can be adjusted by adjusting the opening degree of the EGR valve 32. In this case, the external EGR amount increases as the opening degree of the EGR valve 32 is increased.

Since the internal EGR gas has a higher temperature than the external EGR gas, the temperature in the cylinder 2 can be increased as the amount of the internal EGR gas is increased. Further, since the temperature of the external EGR gas is lowered by passing through the EGR passage 31 and the EGR cooler 33, the temperature in the cylinder 2 can be lowered as the amount of the external EGR gas is increased. Moreover, the temperature in the cylinder 2 can be adjusted to a desired temperature by adjusting the ratio of the internal EGR gas and the external EGR gas. Thereby, the excessive raise of combustion temperature can also be suppressed. If the external EGR amount is increased or decreased according to the increase or decrease of the internal EGR amount, the total amount of EGR gas can be prevented from changing. Further, since the ratio of the internal EGR gas can be increased by the variable valve mechanism 60, it is not necessary to close the nozzle vane 51 excessively, and the nozzle vane 51 can be opened. Thereby, pump loss can be reduced. Further, since the EGR passage 31 is connected downstream of the turbine housing 5b, the amount of exhaust gas passing through the turbine housing 5b is increased as compared with the EGR device connected upstream of the turbine housing 5b. Can do. Thereby, since the rotation speed of the exhaust turbine 5c can be made higher, the supercharging pressure can be further increased, so that the engine output can be improved.

In this way, even in a low compression ratio internal combustion engine having a low combustion temperature, the temperature in the cylinder 2 can be increased to reduce the amount of HC emission. In addition, since the temperature in the cylinder 2 can be prevented from rising excessively, the amount of NOx emission can be reduced. Furthermore, since the supercharging pressure can be increased even when the engine load is low, sufficient oxygen can be introduced into the cylinder 2, and the amount of unburned HC discharged can be further reduced. .

  In this embodiment, when the engine load is low, the ratio of the internal EGR gas is larger than that of the external EGR gas, and when the engine load is high, the ratio of the external EGR gas is larger than that of the internal EGR gas. The other hardware is the same as that of the first embodiment, and a description thereof will be omitted.

  FIG. 3 is a diagram showing the relationship between the engine speed and the engine load, and the distribution of EGR types. FIG. 4 is a graph showing the relationship between the engine load and the distribution of EGR types at the engine speed indicated by A in FIG. In FIG. 3, the “external EGR region” is a region in which the ratio of the external EGR gas to the total EGR gas in the cylinder 2 is as high as possible. Since it is difficult to completely remove the burned gas remaining in the cylinder 2, the ratio of the internal EGR is not strictly zero, but for simplicity, the ratio of the internal EGR is shown in FIGS. 0. In the “internal EGR combined use area”, the ratio of internal EGR is increased. In FIG. 4, the horizontal axis represents the engine load, and the vertical axis represents the ratio of the internal EGR and the external EGR to the total EGR amount.

  As shown in FIG. 3, in the case of a low load, it becomes an “internal EGR combined use region”. That is, in the case of a low load, the internal EGR is used together because the exhaust gas temperature is low. On the other hand, in the case of medium / high load, it becomes an “external EGR region”. That is, in the case of medium and high loads, since the exhaust gas temperature is high, only the external EGR is supplied so that the temperature in the cylinder 2 does not rise excessively. Further, as shown in FIG. 4, the ratio of external EGR is set to 0 in the case of an extremely low load. That is, when the engine load is zero, only the internal EGR is supplied into the cylinder 2. And when engine load becomes a little large, external EGR is used together. As the engine load increases, the ratio of external EGR gas gradually increases. Further, when the load becomes medium load or higher, only the external EGR is supplied into the cylinder 2.

In this embodiment, the target value of the internal EGR amount is determined from the operating state of the internal combustion engine 1, and the VVT 65 is controlled so that the actual internal EGR amount becomes the target value. Specifically, the relationship between the engine speed, the engine load, and the control value of the VVT 65 is obtained in advance through experiments or the like and mapped, and the engine speed and the engine load are substituted into the map to obtain the control value of the VVT 65. . At this time, considering the cooling water temperature of the internal combustion engine 1, the outside air temperature, or the amount of HC discharged, VVT
A control value of 65 may be obtained. The ECU 10 controls the VVT 65 based on the control value of the VVT 65 to adjust the internal EGR amount. On the other hand, the target value of the total EGR amount in the cylinder 2 is determined from the operating state of the internal combustion engine 1, and the intake throttle 6 is controlled so as to be the target value of the total EGR amount. At this time, the control value of the intake throttle 6 may be obtained in consideration of the coolant temperature of the internal combustion engine 1, the outside air temperature, or the amount of HC discharged. For example, the opening degree of the intake throttle 6 is adjusted based on the intake air amount obtained by the air flow meter 7. Here, since the intake air amount detected by the air flow meter 7 is reduced by the total EGR amount in the cylinder 2, the total EGR amount in the cylinder 2 can be indirectly obtained based on the intake air amount. . Specifically, the relationship between the engine speed, the engine load, the intake air amount, and the opening degree of the intake throttle 6 is obtained in advance by experiments or the like, and is mapped to the map. The opening of the intake throttle 6 can be obtained by substituting the amount. As described above, in this embodiment, the internal EGR is open-loop controlled, and the external EGR is feedback-controlled based on the intake air amount.

In the exhaust gas recirculation device for an internal combustion engine configured as described above, when the internal combustion engine 1 is operated at a low load, the temperature in the cylinder 2 can be increased by increasing the proportion of the internal EGR gas. . Thereby, since combustion temperature becomes high, discharge | emission of unburned HC can be suppressed. On the other hand, when the internal combustion engine 1 is operated at a high load, the combustion temperature can be lowered by increasing the proportion of the external EGR gas or by supplying only the external EGR gas, so that NOx emission is suppressed. can do. Moreover, since it is not necessary to perform the high pressure EGR as in the prior art by performing the internal EGR, the nozzle vane 51 can be opened more than in the prior art. Thereby, since pump loss can be reduced, fuel consumption can be improved. Further, since the EGR temperature in the cylinder can be gradually changed by gradually changing the ratio between the internal EGR gas and the external EGR gas, it is possible to suppress a sudden change in the temperature of the EGR gas and the combustion temperature in the cylinder 2. Is done. Thereby, the temperature control in the cylinder 2 can be easily performed.

  Further, in the case of idling and a low load near the idling, the EGR temperature drop in the cylinder 2 can be suppressed by setting the ratio of the external EGR to 0. Therefore, even in a low compression ratio internal combustion engine A decrease in combustion temperature in the cylinder 2 can be suppressed. Thereby, the discharge amount of unburned HC can be reduced.

1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas recirculation device for an internal combustion engine according to an embodiment is applied, an intake / exhaust system thereof, and a supercharger. FIG. It is sectional drawing which shows the structure of a variable capacity | capacitance type turbocharger. 2A shows a case where the nozzle vane is open, and FIG. 2B shows a case where the nozzle vane is closed. It is the figure which showed the relationship between an engine speed and an engine load, and distribution of the type of EGR. FIG. 4 is a diagram showing the relationship between engine load and EGR type distribution at the engine speed indicated by A in FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake pipe 4 Exhaust pipe 5 Turbocharger 5a Compressor housing 5b Turbine housing 5c Exhaust turbine 6 Intake throttle 7 Air flow meter 8 Exhaust purification catalyst 10 ECU
11 Accelerator pedal 12 Accelerator opening sensor 13 Crank position sensor 30 EGR device 31 EGR passage 32 EGR valve 33 EGR cooler 51 Nozzle vane 52 Actuator 60 Variable valve mechanism 61 Exhaust valve 62 Exhaust side cam 63 Exhaust side camshaft 64 Exhaust side pulley 65 Variable rotation phase mechanism (exhaust side VVT)

Claims (5)

A turbocharger equipped with a turbine in the exhaust passage and a compressor in the intake passage;
An EGR passage connecting an exhaust passage downstream of the turbine and an intake passage upstream of the compressor;
Internal EGR amount changing means for changing the internal EGR amount of the internal combustion engine;
With
The ratio of the external EGR amount introduced into the cylinder by flowing exhaust gas from the internal combustion engine through the EGR passage and the internal EGR amount remaining in the cylinder is changed in accordance with the load of the internal combustion engine. An exhaust gas recirculation device for an internal combustion engine.   When the temperature in the cylinder is raised, the ratio of the internal EGR is made higher than before the temperature is raised, and when the temperature in the cylinder is lowered, the percentage of the external EGR is made higher than before the temperature is lowered. The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, wherein:   The exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, wherein the ratio of the external EGR is made higher during high load operation of the internal combustion engine than during low load operation.   The exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2, wherein the ratio of the external EGR is set to 0 when the internal combustion engine is operated at a low load.   The supercharger is a variable displacement turbocharger, and when the ratio of the external EGR is increased, the nozzle of the variable displacement turbocharger is opened as compared with a case where the ratio is not increased. 5. An exhaust gas recirculation device for an internal combustion engine according to any one of 4 above.

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