JP2005076502A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the responsiveness of a throttle valve or an EGR control valve when opened. <P>SOLUTION: The internal combustion engine comprises a change-over means for change-over between low temperature combustion and normal combustion, a turbocharger 15 using a turbine 23 provided in an engine exhaust passage for driving an intake gas compressor 16 provided in an engine intake passage. An exhaust gas circulation device has an exhaust gas recirculation passage 61, a recirculated exhaust gas control valve 64 for controlling the amount of recirculated exhaust gas flowing in the exhaust gas recirculation passage, and a recirculated exhaust gas compressor 65 to be driven by the turbine 23 for increasing the pressure of the recirculated exhaust gas in the exhaust gas recirculation passage. The recirculated exhaust gas control valve is provided on the downstream side of the recirculated exhaust gas compressor 65 and the throttle valve 20 in the engine intake passage is arranged on the downstream side of an intercooler 14 provided in the engine intake passage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine.

  2. Description of the Related Art Conventionally, in an internal combustion engine, for example, a diesel engine, an engine exhaust passage and an engine intake passage are connected by an exhaust gas recirculation (hereinafter referred to as EGR) passage in order to suppress the generation of NOx, and the exhaust gas is exhausted through the EGR passage. Gas, that is, EGR gas is recirculated into the engine intake passage. In this case, since the EGR gas has a relatively high specific heat and can absorb a large amount of heat, the EGR gas amount increases, that is, the EGR rate (EGR gas amount / (EGR gas amount + intake air amount)). As the value increases, the combustion temperature in the combustion chamber decreases. As the combustion temperature decreases, the amount of NOx generated decreases, and as the EGR rate increases, the amount of NOx generated decreases.

  Thus, it has been known that the amount of NOx generated can be reduced if the EGR rate is increased. However, when the EGR rate is increased, when the EGR rate exceeds a certain limit, the generation amount of soot, that is, the smoke starts to increase rapidly. With respect to this point, it is conventionally considered that if the EGR rate is further increased, the smoke will increase as much as possible. Therefore, the EGR rate at which the smoke starts to increase rapidly is considered to be the maximum allowable limit of the EGR rate. It has been.

  Therefore, the EGR rate is conventionally determined within a range not exceeding the maximum allowable limit. The maximum allowable limit for this EGR rate is roughly 30 to 50 percent, although it varies considerably depending on the engine type and fuel. Therefore, in the conventional diesel engine, the EGR rate is suppressed to about 30% to 50% at the maximum.

  As described above, since it has been conventionally considered that there is a maximum allowable limit for the EGR rate, the EGR rate is conventionally determined so that the generation amount of NOx and smoke is minimized within a range not exceeding the maximum allowable limit. It was. However, even if the EGR rate is determined in this way so that the amount of NOx and smoke generated becomes as small as possible, there is a limit to the reduction in the amount of NOx and smoke generated. In fact, a considerable amount of NOx and smoke is still generated. This is the current situation.

  However, if the EGR rate is made larger than the maximum allowable limit in the course of research on combustion of diesel engines, smoke increases rapidly as described above, but there is a peak in the amount of smoke generated, and the EGR rate exceeds this peak. If the value is further increased, the smoke starts to decrease abruptly. When the EGR rate is increased to 70% or higher during idling operation, and when the EGR gas is strongly cooled, the smoke is almost reduced when the EGR rate is increased to approximately 55% or higher. Become zero. That is, it has been found that almost no wrinkles occur. At this time, it has been found that the amount of NOx generated is extremely small. After that, the reason why soot is not generated has been studied based on this knowledge, and as a result, a new combustion system capable of simultaneously reducing soot and NOx has been constructed. Although this new combustion system will be described in detail later, it is basically based on stopping the growth of hydrocarbons in the middle of the course until the hydrocarbons grow into soot.

  That is, as a result of repeated experimental research, it has been found that when the temperature of the fuel during combustion in the combustion chamber and the surrounding gas is below a certain temperature, the growth of the hydrocarbon stops before it reaches the soot. And when the temperature of the gas around it exceeds a certain temperature, the hydrocarbon grows up to a soot. In this case, the endothermic effect of the gas around the fuel when the fuel burns greatly affects the temperature of the fuel and the surrounding gas, and the endothermic amount of the gas around the fuel is adjusted according to the amount of heat generated during fuel combustion. As a result, the temperature of the fuel and the surrounding gas can be controlled.

Therefore, if the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature is suppressed below the temperature at which hydrocarbon growth stops halfway, soot will not be generated, and the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature It is possible to suppress the temperature below the temperature at which hydrocarbon growth stops halfway by adjusting the endothermic amount of the gas around the fuel. On the other hand, hydrocarbons that have stopped growing before reaching soot can be easily purified by post-treatment using an oxidation catalyst or the like. This is the basic concept of the new combustion system. (For example, see Patent Document 1 to Patent Document 4.)
JP 2000-008835 A JP-A-5-180089 JP 11-117751 A JP 2002-089375 A

  By the way, as one of EGR passages provided in an internal combustion engine equipped with an exhaust turbocharger, there is a type called a ropeless loop. In this case, an exhaust gas filter is provided downstream of the exhaust turbine of the exhaust turbocharger. Normally, the EGR passage is downstream of the exhaust gas filter, upstream of the intake gas compressor of the exhaust turbocharger, and downstream of the throttle valve. Connected up to. The EGR passage is provided with a recirculation exhaust gas control valve for adjusting the flow rate of the recirculation exhaust gas. In this case, a part of the exhaust gas discharged from the exhaust passage of the internal combustion engine and passing through the exhaust turbine is used as the recirculated exhaust gas. For this reason, in this case, the pressure of the recirculated exhaust gas flowing into the EGR passage via the exhaust turbine is smaller than the pressure of the exhaust gas immediately after being discharged from the exhaust passage. Therefore, such an EGR passage through which low-pressure recirculated exhaust gas flows is called a ropeless loop.

  In an internal combustion engine provided with such an EGR passage as a ropeless loop, for example, when the required engine load is increased for acceleration, the throttle valve is opened to the vicinity of the fully open position, and the recirculated exhaust before and after this is opened. Close the gas control valve. Thereby, new air is supplied into the combustion chamber of the internal combustion engine.

  However, since the intercooler is usually provided downstream of the compressor of the exhaust turbocharger, the new air taken in by opening the throttle valve has passed through both the compressor and intercooler of the exhaust turbocharger. Reach the combustion chamber. That is, in order for new air after opening the throttle valve to reach the combustion chamber, it is necessary to push the recirculated exhaust gas existing in the compressor and the intercooler into the combustion chamber. For this reason, a time lag occurs until new air actually reaches the combustion chamber, and the responsiveness when the throttle valve is opened becomes poor. In particular, when a large amount of recirculated exhaust gas is supplied to the combustion chamber, the problem of time lag is significant.

  According to the first aspect of the invention, the exhaust gas recirculation device that recirculates the exhaust gas discharged from the combustion chamber into the engine intake passage is provided, and the amount of the recirculated exhaust gas supplied to the combustion chamber is reduced. As the amount of soot increases, the amount of soot gradually increases and reaches a peak, and when the amount of recirculated exhaust gas supplied into the combustion chamber is further increased, the fuel in the combustion chamber and its surroundings are combusted. Low temperature combustion where the gas temperature is lower than the soot generation temperature and soot is hardly generated, and the amount of inert gas supplied into the combustion chamber is less than the amount of inert gas at which soot generation peaks In the internal combustion engine comprising switching means for switching between normal combustion and a turbocharger that drives an intake gas compressor provided in the engine intake passage by a turbine provided in the engine exhaust passage. A circulating device, an exhaust gas recirculation passage, a recirculation exhaust gas control valve capable of controlling an amount of recirculation exhaust gas flowing through the exhaust gas recirculation passage, and the recirculation exhaust gas in the exhaust gas recirculation passage; A recirculation exhaust gas compressor for boosting the pressure, the recirculation exhaust gas control valve being provided downstream of the recirculation exhaust gas compressor, and a throttle valve in the engine intake passage being the internal combustion engine An internal combustion engine is provided which is disposed downstream of an intercooler provided in the intake passage and is configured such that an outlet portion of the exhaust gas recirculation passage is connected to an intake passage downstream of the throttle valve.

  That is, according to the first invention, a throttle valve is provided downstream of the intake gas compressor and the intercooler, a recirculation exhaust gas control valve is provided downstream of the recirculation exhaust gas compressor, and an outlet portion of the exhaust gas recirculation passage is provided at the throttle valve. Since it is connected to the downstream intake passage, it is not necessary for the recirculated exhaust gas flowing through the recirculated exhaust gas control valve to pass through the compressor and the intercooler when the recirculated exhaust gas control valve is opened. Therefore, since no recirculated exhaust gas exists in the compressor and the intercooler (no residual gas), new intake air can be rapidly supplied to the combustion chamber during acceleration, and the response of the internal combustion engine can be improved. Also, the response of the internal combustion engine when increasing the amount of recirculated exhaust gas is improved. In particular, in the first invention, since the recirculated exhaust gas is supplied by the recirculated exhaust gas compressor, when it is desired to supply the recirculated exhaust gas into the combustion chamber, this is performed quickly. In addition, since a large amount of recirculated exhaust gas can be supplied even when the engine required load is high, the low temperature combustion region and the rich combustion region can be expanded.

According to the second invention, in the first invention, the recirculation exhaust gas compressor is driven by the turbine of the turbocharger.
That is, according to the second aspect of the invention, the recirculation exhaust gas compressor can be driven without using another drive source by using the turbine of the exhaust turbocharger as the drive source.

According to a third invention, in the first or second invention, the exhaust gas circulation device further comprises a cooling device for cooling the recirculated exhaust gas in the exhaust gas recirculation passage, and the cooling device Is provided between the inlet of the exhaust gas recirculation passage and the recirculation exhaust gas compressor.
That is, according to the third invention, the recirculated exhaust gas is cooled in the cooling device and then flows into the recirculated exhaust gas compressor. Even when the recirculation exhaust gas compressor is formed from a material with low heat resistance compared to the material of the turbine of the exhaust turbocharger, the temperature of the recirculation exhaust gas flowing into the recirculation exhaust gas compressor can be lowered. The recirculated exhaust gas compressor can be prevented from being damaged by heat.

According to a fourth invention, in any one of the first to third inventions, an inlet portion of the exhaust gas recirculation passage is located downstream of a filter provided downstream of the turbine in the engine exhaust passage. Yes.
That is, according to the fourth aspect of the invention, exhaust gas used as recirculated exhaust gas can be cleaned by a filter, for example, a filter carrying an NOx storage reduction catalyst or a filter carrying an oxidation catalyst. When such a filter is provided, the temperature of the exhaust gas after passing through the filter may increase, but the recirculated exhaust gas can be cooled by the cooling unit described in the third aspect of the invention.

According to each invention, since the gas can be rapidly supplied to the combustion chamber, it is possible to achieve a common effect that the response of the internal combustion engine can be improved.
Furthermore, according to the first invention, it is possible to achieve an effect that the low temperature combustion region and the rich combustion region can be expanded.
Furthermore, according to the second aspect of the present invention, it is possible to effectively drive the recirculation exhaust gas compressor using the exhaust gas.
Furthermore, according to the third aspect of the present invention, the recirculation exhaust gas compressor can be prevented from being damaged by heat.
Furthermore, according to the fourth aspect of the invention, it is possible to produce an effect that the exhaust gas used as the recirculation exhaust gas can be purified.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, the same members are denoted by the same reference numerals. In order to facilitate understanding, the scales of these drawings are appropriately changed.
FIG. 1 shows a first embodiment in which the present invention is applied to a four-stroke compression ignition type internal combustion engine. Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to an outlet of a compressor 16 of a supercharger, for example, an exhaust turbocharger 15, via an intake duct 13 and an intercooler 14. Connected. An inlet portion of the compressor 16 is connected to an air cleaner 18 via an air suction pipe 17. A throttle valve 20 driven by a step motor 19 is disposed in the intake duct 13. A mass flow rate detector 21 for detecting the mass flow rate of intake air is disposed in the air suction pipe 17.

  On the other hand, the exhaust port 10 is connected to an inlet portion of an exhaust turbine 23 of an exhaust turbocharger 15 via an exhaust manifold 22, and an outlet portion of the exhaust turbine 23 is connected to a filter 25 carrying a catalyst having an oxidation function via an exhaust pipe 24. Is connected to a catalytic converter 26 containing the. In this embodiment, a filter carrying an NOx storage reduction catalyst is used. An air-fuel ratio sensor 27 is disposed in the exhaust manifold 22. Instead of the filter 25, a honeycomb structure (straight flow type) catalyst having an oxidation function may be used.

  As shown in FIG. 1, an exhaust gas recirculation (hereinafter referred to as EGR) passage 61 extends from the exhaust pipe 28 connected to the outlet of the catalytic converter 26 to the surge tank 12. An EGR gas compressor 65 for increasing the pressure of the EGR gas is provided in the EGR passage 61 through which the recirculated exhaust gas flows. In FIG. 1, the EGR gas compressor 65 is provided coaxially with the compressor 16 of the exhaust turbocharger 15 and the exhaust turbine 23. Therefore, when the exhaust turbine 23 is driven by the exhaust gas, the EGR gas compressor 65 is driven to rotate together with the exhaust turbocharger 15. Further, an EGR control valve 64 driven by a step motor 63 is disposed downstream of the EGR gas compressor 65. In the EGR passage 61, an EGR cooler 62 for cooling the EGR gas flowing in the EGR passage 61 is disposed upstream of the EGR gas compressor 65. In the embodiment shown in FIG. 1, the engine cooling water is guided into the EGR cooler 62, and the EGR gas is cooled by the engine cooling water.

  On the other hand, the fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 34, through a fuel supply pipe 33. Fuel is supplied into the common rail 34 from an electrically controlled fuel pump 35 with variable discharge amount, and the fuel supplied into the common rail 34 is supplied to the fuel injection valve 6 through each fuel supply pipe 33. A fuel pressure sensor 36 for detecting the fuel pressure in the common rail 34 is attached to the common rail 34, and a fuel pump 35 is set so that the fuel pressure in the common rail 34 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 36. The discharge amount is controlled.

  The electronic control unit 40 comprises a digital computer and is connected to each other by a bidirectional bus 41. A ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45 and an output port 46 are connected. It comprises. The output signal of the mass flow detector 21 is input to the input port 45 via the corresponding AD converter 47, and the output signals of the air-fuel ratio sensor 27 and the fuel pressure sensor 36 are also input to the input port via the corresponding AD converter 47. 45. A load sensor 51 that generates an output voltage proportional to the depression amount L of the accelerator pedal 50 is connected to the accelerator pedal 50, and the output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. . The input port 45 is connected to a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, 30 °. On the other hand, the output port 46 is connected to the fuel injection valve 6, the throttle valve control step motor 19, the EGR control valve control step motors 30 and 63, and the fuel pump 35 through corresponding drive circuits 48. FIG. 2 shows the output when the air-fuel ratio A / F (horizontal axis in FIG. 2) is changed by changing the opening degree of the throttle valve 20 and the EGR rate during engine low load operation with the fuel injection timing fixed. The experiment example which shows the change of the change of a torque and the discharge | emission amount of smoke, HC, CO, NOx is represented. As can be seen from FIG. 2, in this experimental example, the EGR rate increases as the air-fuel ratio A / F decreases, and the EGR rate is 65% or more when the air-fuel ratio is less than the theoretical air-fuel ratio (≈14.6).

  As shown in FIG. 2, when the air-fuel ratio A / F is decreased by increasing the EGR rate, the EGR rate becomes around 40%, and the amount of smoke generated when the air-fuel ratio A / F becomes about 30. Start to increase. Next, when the EGR rate is further increased and the air-fuel ratio A / F is decreased, the amount of smoke generated increases rapidly and reaches a peak. Next, when the EGR rate is further increased and the air-fuel ratio A / F is reduced, the smoke suddenly decreases, the EGR rate is increased to 65% or more, and when the air-fuel ratio A / F is near 15.0, the smoke becomes almost zero. . That is, almost no wrinkles occur. At this time, the output torque of the engine slightly decreases, and the amount of NOx generated becomes considerably low. On the other hand, the generation amount of HC and CO starts to increase at this time.

  The following can be said from the experimental results shown in FIG. That is, first, when the air-fuel ratio A / F is 15.0 or less and the amount of smoke generated is almost zero, the amount of NOx generated decreases considerably as shown in FIG. A reduction in the amount of NOx generated means that the combustion temperature in the combustion chamber 5 has decreased. Therefore, it can be said that the combustion temperature in the combustion chamber 5 is low when soot is hardly generated. .

  Secondly, when the amount of smoke generated, that is, the amount of soot is substantially zero, the HC and CO emissions increase as shown in FIG. This means that the hydrocarbons are discharged without growing to the soot. In other words, linear hydrocarbons and aromatic hydrocarbons contained in fuel are thermally decomposed to form soot precursors when the temperature is raised in an oxygen-deficient state, and then from solids mainly composed of carbon atoms. A cocoon is generated. In this case, the actual soot formation process is complicated, and it is not clear what form the soot precursor will take, but in any case hydrocarbons will grow to soot via the soot precursor. Become. Therefore, as described above, when the generation amount of soot becomes almost zero, the emission amount of HC and CO increases as shown in FIG. 2. At this time, HC is a precursor of soot or a hydrocarbon in the previous state. .

  Summarizing these considerations based on the experimental results shown in FIG. 2, when the combustion temperature in the combustion chamber 5 is low, the amount of soot generated becomes almost zero, and at this time, the precursor of soot or the hydrocarbon in the previous state is not present. It is discharged from the combustion chamber 5. As a result of repeated experimental studies in more detail, when the temperature of the fuel in the combustion chamber 5 and the gas surrounding it is below a certain temperature, the soot growth process stops midway, that is, soot It has been found that soot hardly occurs and soot is generated when the temperature of the fuel in the combustion chamber 5 and the surrounding temperature rise above a certain temperature.

  By the way, when the hydrocarbon generation process stops in the state of soot precursor, the temperature of the fuel and its surroundings, that is, the above-mentioned certain temperature changes depending on various factors such as the type of fuel and the compression ratio of the air-fuel ratio. Although it cannot be said how many times, this certain temperature has a deep relationship with the amount of NOx generated, and therefore this certain temperature can be defined to some extent from the amount of NOx generated. That is, as the EGR rate increases, the temperature of the fuel during combustion and the surrounding gas temperature decrease, and the amount of NOx generated decreases. At this time, the amount of NOx generated is 10 p. p. When it becomes around m or less, wrinkles hardly occur. Therefore, at a certain temperature described above, the amount of NOx generated is 10 p. p. It almost corresponds to the temperature at around m or below.

  Once soot is produced, it cannot be purified by post-treatment using a catalyst having an oxidizing function. On the other hand, the soot precursor or the hydrocarbon in the previous state can be easily purified by post-treatment using a catalyst having an oxidation function. Considering the post-treatment with a catalyst having an oxidation function in this way, it is extremely important whether hydrocarbons are discharged from the combustion chamber 5 in the soot precursor or in the previous state or from the combustion chamber 5 in the form of soot. There is a big difference. The new combustion system employed in the present invention allows hydrocarbons to be discharged from the combustion chamber 5 in the form of soot precursors or in a previous state without generating soot in the combustion chamber 5. The core is to oxidize with a catalyst having an oxidation function.

  Now, in order to stop the growth of hydrocarbons before the soot is generated, it is necessary to suppress the temperature of the fuel and the surrounding gas in the combustion chamber 5 to a temperature lower than the temperature at which soot is generated. There is. In this case, in order to suppress the temperature of the fuel and the surrounding gas, it has been found that the endothermic action of the gas around the fuel when the fuel burns has a great influence.

  That is, if there is only air around the fuel, the evaporated fuel immediately reacts with oxygen in the air and burns. In this case, the temperature of the air away from the fuel does not increase so much, and only the temperature around the fuel becomes extremely high locally. That is, at this time, the air away from the fuel hardly performs the endothermic action of the combustion heat of the fuel. In this case, since the combustion temperature becomes extremely high locally, the unburned hydrocarbons that have received this heat of combustion produce soot.

  On the other hand, the situation is slightly different when fuel is present in a mixed gas of a large amount of inert gas and a small amount of air. In this case, the evaporated fuel diffuses around and reacts with oxygen mixed in the inert gas and burns. In this case, since the combustion heat is absorbed by the surrounding inert gas, the combustion temperature does not rise so much. That is, the combustion temperature can be kept low. That is, the presence of the inert gas plays an important role in suppressing the combustion temperature, and the combustion temperature can be kept low by the endothermic action of the inert gas.

In this case, in order to suppress the temperature of the fuel and the surrounding gas to a temperature lower than the temperature at which soot is generated, an amount of inert gas that can absorb a sufficient amount of heat is required. Therefore, as the amount of fuel increases, the amount of inert gas required increases accordingly. In this case, the greater the specific heat of the inert gas, the stronger the endothermic action. Therefore, the inert gas is preferably a gas having a large specific heat. In this respect, since CO ₂ and EGR gas have relatively large specific heat, it can be said that it is preferable to use EGR gas as an inert gas.

  FIG. 3 shows the relationship between the EGR rate and smoke when EGR gas is used as the inert gas and the cooling degree of the EGR gas is changed. That is, in FIG. 3, curve A shows the case where EGR gas is cooled strongly and the EGR gas temperature is maintained at about 90 ° C., and curve B shows the case where EGR gas is cooled by a small cooling device. Curve C shows the case where the EGR gas is not forcibly cooled.

  As shown by curve A in FIG. 3, when the EGR gas is cooled strongly, the amount of soot peaks when the EGR rate is slightly lower than 50%. In this case, the EGR rate is increased to about 55% or more. If you do, almost no wrinkles will occur.

  On the other hand, as shown by the curve B in FIG. 3, when the EGR gas is slightly cooled, the amount of soot peaks when the EGR rate is slightly higher than 50%. In this case, the EGR rate is about 65% or more. If this is done, almost no wrinkles will occur.

  In addition, as shown by the curve C in FIG. 3, when the EGR gas is not forcibly cooled, the amount of soot generated reaches a peak when the EGR rate is around 55%. In this case, the EGR rate is approximately 70%. If the percentage is exceeded, almost no wrinkles occur.

  FIG. 3 shows the amount of smoke generated when the engine load is relatively high. When the engine load is small, the EGR rate at which the amount of soot reaches a peak slightly decreases, and the EGR rate at which soot hardly occurs. The lower limit is also slightly reduced. Thus, the lower limit of the EGR rate at which soot hardly occurs varies depending on the degree of cooling of the EGR gas and the engine load.

  FIG. 4 shows the amount of mixed gas of EGR gas and air required to make the temperature of the fuel and the surrounding gas lower than the temperature at which soot is generated when EGR gas is used as the inert gas. And the ratio of the air in this gas mixture amount, and the ratio of the EGR gas in this gas mixture are shown. In FIG. 4, the vertical axis represents the total intake gas amount sucked into the combustion chamber 5, and the chain line Y represents the total intake gas amount that can be sucked into the combustion chamber 5 when supercharging is not performed. ing. The horizontal axis indicates the required load.

  Referring to FIG. 4, the ratio of air, that is, the amount of air in the mixed gas, indicates the amount of air necessary to completely burn the injected fuel. That is, in the case shown in FIG. 4, the ratio between the air amount and the injected fuel amount is the stoichiometric air-fuel ratio. On the other hand, in FIG. 4, the ratio of EGR gas, that is, the amount of EGR gas in the mixed gas is used to make the temperature of the fuel and its surrounding gas lower than the temperature at which soot is formed when the injected fuel is burned. The minimum EGR gas amount is shown. This EGR gas amount is approximately 55% or more in terms of EGR rate, and is 70% or more in the embodiment shown in FIG. That is, if the total intake gas amount sucked into the combustion chamber 5 is a solid line X in FIG. 4, and the ratio of the air amount and the EGR gas amount in the total intake gas amount X is a ratio as shown in FIG. The temperature of the fuel and the surrounding gas is lower than the temperature at which soot is produced, so that soot is hardly generated. The amount of NOx generated at this time is 10 p. p. Therefore, the amount of NOx generated is extremely small.

  If the amount of fuel injection increases, the amount of heat generated when the fuel burns increases. Therefore, in order to maintain the temperature of the fuel and the surrounding gas at a temperature lower than the temperature at which soot is generated, the amount of heat absorbed by the EGR gas Must be increased. Therefore, as shown in FIG. 4, the EGR gas amount must be increased as the amount of injected fuel increases. That is, the amount of EGR gas needs to increase as the required load increases.

  When the supercharging is not performed, the upper limit of the total intake gas amount X sucked into the combustion chamber 5 is Y. Therefore, in the region where the required load is larger than Lo in FIG. The EGR gas ratio decreases and cannot be maintained at the stoichiometric air-fuel ratio. In other words, when supercharging is not being performed and an attempt is made to maintain the air / fuel ratio at the stoichiometric air / fuel ratio in a region where the required load is greater than Lo, the EGR rate decreases as the required load increases. In regions where the required load is greater than Lo, the temperature of the fuel and the surrounding gas cannot be maintained below the temperature at which soot is produced.

  However, as shown in FIG. 1, when EGR gas is recirculated into the air suction pipe 17 upstream of the supercharger, that is, upstream of the compressor 16 of the exhaust turbocharger 15 through the EGR passage 29, the required load is larger than Lo. The EGR rate in the region can be maintained at 55 percent or higher, for example 70 percent, and thus the fuel and surrounding gas temperatures can be maintained at a temperature lower than the temperature at which soot is produced. That is, if the EGR gas is recirculated so that the EGR rate in the air suction pipe 17 becomes, for example, 70%, the EGR rate of the intake gas boosted by the compressor 16 of the exhaust turbocharger 15 also becomes 70%. The temperature of the fuel and the surrounding gas can be maintained at a temperature lower than the temperature at which soot is generated, up to a limit that can be increased by the compressor 16. Therefore, the operating range of the engine that can cause low temperature combustion can be expanded. When the EGR rate is 55% or more in a region where the required load is larger than Lo, the EGR control valve 31 is fully opened, and the throttle valve 20 is slightly closed.

  As described above, FIG. 4 shows the case where the fuel is burned under the stoichiometric air-fuel ratio. However, even if the air amount is smaller than the air amount shown in FIG. The amount of NOx generated is 10 p. p. m or less, and even if the air amount is larger than the air amount shown in FIG. 4, that is, even if the average value of the air-fuel ratio is 17 to 18, lean generation is prevented. However, the amount of NOx generated is 10 p. p. It can be around m or less.

  That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but the combustion temperature is suppressed to a low temperature, so that the excess fuel does not grow to soot, and so no soot is generated. At this time, only a very small amount of NOx is generated. On the other hand, when the average air-fuel ratio is lean, or even when the air-fuel ratio is the stoichiometric air-fuel ratio, a small amount of soot is generated if the combustion temperature is high, but in the present invention the soot is suppressed to a low temperature so Almost no generation. Furthermore, only a very small amount of NOx is generated.

  Thus, when low-temperature combustion is performed, soot is hardly generated regardless of the air-fuel ratio, that is, whether the air-fuel ratio is rich, the stoichiometric air-fuel ratio, or the average air-fuel ratio is lean. , NOx generation is extremely small. Therefore, considering the improvement of the fuel consumption rate, it can be said that it is preferable to make the average air-fuel ratio lean at this time.

  By the way, the temperature of the fuel during combustion in the combustion chamber and the surrounding gas temperature can be suppressed to a temperature equal to or lower than the temperature at which the growth of hydrocarbons stops midway, only when the engine medium-low load operation has a relatively small amount of heat generated by combustion. Therefore, in the embodiment according to the present invention, at the time of engine low load operation, the temperature of the fuel at the time of combustion and the surrounding gas temperature is controlled to be equal to or lower than the temperature at which hydrocarbon growth stops halfway, and low temperature combustion is performed. In some cases, normal combustion, which is conventionally performed, is performed. Note that the low-temperature combustion here refers to combustion in which the amount of inert gas in the combustion chamber is larger than the amount of inert gas at which soot generation peaks, and soot is hardly generated, as is apparent from the above description. Ordinary combustion, which is normally performed conventionally, refers to combustion in which the amount of inert gas in the combustion chamber is smaller than the amount of inert gas in which the amount of generated soot reaches a peak.

  FIG. 5 is a diagram showing the smoke concentration FSN, the low temperature combustion region and the normal combustion region in a specific operating state, and FIG. 6 is a conceptual diagram showing the low temperature combustion region and the normal combustion region. Using FIG. 5 and FIG. 6 and the like, low-temperature combustion, which is a combustion in which the amount of inert gas in the combustion chamber is larger than the amount of inert gas at which soot generation peaks, and soot is hardly generated, and the amount of soot generated is The normal combustion in which the amount of inert gas in the combustion chamber is smaller than the peak amount of inert gas will be described. As shown in FIG. 5, there are a low temperature combustion region and a normal combustion region on the high EGR rate side and the low EGR rate side of the EGR rate where the generation amount of soot peaks. In addition, when low temperature combustion is performed, the injection timing is advanced compared to when normal combustion is performed. Therefore, as shown in FIG. 5, the low temperature combustion region is advanced compared to the normal combustion region.

  In FIG. 6, the broken line P indicates that the amount of soot generation peaks when the EGR rate is increased, and the solid line Q indicates that the amount of soot generation becomes almost zero when the EGR rate is further increased. Show. As can be seen from FIGS. 2 and 6, when the EGR rate is increased or decreased to switch between normal combustion and low-temperature combustion on the more advanced side than normal combustion, it passes through a point where the amount of soot generated reaches a peak. Further, when the EGR rate is increased with the injection timing kept constant as shown in FIG. 2, a peak occurs in the amount of smoke generated as shown by the broken line P in FIG. In FIG. 6, if the EGR rate is increased to switch from the normal combustion region to the low temperature combustion region on the more advanced side than the normal combustion region, it passes over the broken line P, so that a peak occurs in the amount of smoke generated during the increase of the EGR rate. Will occur.

  FIG. 7 shows a first operation region I in which low-temperature combustion is performed and a second operation region II in which normal combustion is performed by a conventional combustion method. In FIG. 7, the vertical axis L indicates the amount of depression of the accelerator pedal 50, that is, the required load, and the horizontal axis N indicates the engine speed. In FIG. 7, X (N) indicates the first boundary between the first operation region I and the second operation region II, and Y (N) indicates the first operation region I and the second operation region. A second boundary with region II is shown. The change determination of the operation region from the first operation region I to the second operation region II is performed based on the first boundary X (N), and the change from the second operation region II to the first operation region I is performed. The change determination of the operation region is performed based on the second boundary Y (N).

  That is, if the required load L exceeds the first boundary X (N) that is a function of the engine speed N when the engine operating state is in the first operating region I and low-temperature combustion is being performed, the operating region Is determined to have moved to the second operating region II, and normal combustion is performed. Next, when the required load L becomes lower than the second boundary Y (N) that is a function of the engine speed N, it is determined that the operating region has shifted to the first operating region I, and low temperature combustion is performed again.

  The reason for providing the two boundaries of the first boundary X (N) and the second boundary Y (N) on the lower load side than the first boundary X (N) is as follows. . The first reason is that the combustion temperature is relatively high on the high load side of the second operation region II, and at this time, even if the required load L becomes lower than the first boundary X (N), the low temperature combustion cannot be performed immediately. Because. That is, low temperature combustion is not started immediately unless the required load L is considerably low, that is, when the required load L is lower than the second boundary Y (N). The second reason is to provide hysteresis with respect to a change in the operation region between the first operation region I and the second operation region II.

  By the way, when the engine operating region is in the first operating region I and low-temperature combustion is performed, soot is hardly generated, and instead, the unburned hydrocarbon is in the form of soot precursor or the previous state. It is discharged from the combustion chamber 5. At this time, the unburned hydrocarbons discharged from the combustion chamber 5 are satisfactorily oxidized by the catalyst having an oxidation function (occlusion reduction type NOx catalyst) carried on the filter 25. At the same time, exhaust particulates are collected by the filter 25.

  This NOx catalyst has, for example, alumina as a carrier, and on this carrier, for example, alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, alkaline earth such as barium Ba, calcium Ca, lanthanum La, yttrium Y, etc. At least one selected from such rare earths and a noble metal such as platinum Pt are supported.

  FIG. 8 shows the output of the air-fuel ratio sensor 27. As shown in FIG. 8, the output current I of the air-fuel ratio sensor 27 varies according to the air-fuel ratio A / F. Therefore, the air-fuel ratio can be known from the output current I of the air-fuel ratio sensor 27.

  Next, operation control in the first operation region I and the second operation region II will be schematically described with reference to FIG.

  FIG. 9 shows the opening degree of the throttle valve 20, the opening degree of the EGR control valve 31, the EGR rate, the air-fuel ratio, the injection timing, and the injection amount with respect to the required load L. As shown in FIG. 9, in the first operation region I where the required load L is low, the opening degree of the throttle valve 20 is gradually increased from nearly fully closed to about 2/3 opening degree as the required load L increases. As the required load L increases, the opening degree of the EGR control valve 31 is gradually increased from nearly fully closed to fully opened. In the example shown in FIG. 9, in the first operating region I, the EGR rate is approximately 70%, and the air-fuel ratio is a slightly lean air-fuel ratio.

  In other words, the opening degree of the throttle valve 20 and the opening degree of the second EGR control valve 31 are controlled so that the EGR rate is approximately 70% in the first operation region I and the air / fuel ratio becomes a slightly lean air / fuel ratio. Is done. In the first operation region I, fuel injection is performed before the compression top dead center TDC. In this case, the injection start timing θS is delayed as the required load L is increased, and the injection completion timing θE is also delayed as the injection start timing θS is delayed.

  During idle operation, the throttle valve 20 is closed to near full close, and at this time, the second EGR control valve 31 is also closed to close to full close. When the throttle valve 20 is closed to near full close, the pressure in the combustion chamber 5 at the start of compression becomes low, so the compression pressure becomes small. When the compression pressure is reduced, the compression work by the piston 4 is reduced, so that the vibration of the engine body 1 is reduced. That is, during idle operation, the throttle valve 20 is closed to close to the fully closed state in order to suppress vibration of the engine body 1.

  On the other hand, when the operating range of the engine is changed from the first operating range I to the second operating range II, the opening degree of the throttle valve 20 is increased stepwise from about 2/3 opening degree to the full opening direction. At this time, in the example shown in FIG. 9, the EGR rate is decreased in a step-like manner from approximately 70% to 40% or less, and the air-fuel ratio is increased in a step-like manner. That is, since the EGR rate jumps over the EGR rate range (FIG. 5) that generates a large amount of smoke, a large amount of smoke is generated when the engine operating region changes from the first operating region I to the second operating region II. There is no.

  In the second operation region II, normal combustion is performed. In the second operation region II, the throttle valve 20 is held in a fully opened state except for a part thereof, and the opening degree of the second EGR control valve 31 is gradually reduced as the required load L increases. In this operation region II, the EGR rate decreases as the required load L increases, and the air-fuel ratio decreases as the required load L increases. However, the air-fuel ratio is made a lean air-fuel ratio even when the required load L increases. In the second operation region II, the injection start timing θS is set near the compression top dead center TDC.

  FIG. 10A shows the target air-fuel ratio A / F in the first operation region I. In FIG. 10A, each of the curves indicated by A / F = 15.5, A / F = 16, A / F = 17, A / F = 18 has a target air-fuel ratio of 15.5, 16, 17 respectively. , 18, and the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 10 (A), the air-fuel ratio is lean in the first operating region I, and in the first operating region I, the target air-fuel ratio A / F is made lean as the required load L becomes lower. The

  That is, the lower the required load L, the smaller the amount of heat generated by combustion. Therefore, low temperature combustion can be performed even if the EGR rate is reduced as the required load L is reduced. When the EGR rate is decreased, the air-fuel ratio increases, and therefore the target air-fuel ratio A / F is increased as the required load L decreases as shown in FIG. As the target air-fuel ratio A / F increases, the fuel consumption rate improves. Therefore, in order to make the air-fuel ratio as lean as possible, in the embodiment according to the present invention, the target air-fuel ratio A / F increases as the required load L decreases. .

  The target air-fuel ratio A / F shown in FIG. 10 (A) is stored in advance in the ROM 42 in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 10 (B). . Further, the target opening ST of the throttle valve 20 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. 10A is the required load L and the engine speed as shown in FIG. As a function of N, it is stored in advance in the ROM 42 in the form of a map, and the opening degree SEL of the first EGR control valve 64 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. The target total opening degree SE, which is the sum of the opening degree SEH of the second EGR control valve 31 and the ROM 42 in advance in the form of a map as a function of the required load L and the engine speed N as shown in FIG. Is stored within. The ratio between the opening degree SEL of the first EGR control valve 64 and the opening degree SEH of the second EGR control valve 31 will be described in detail later.

  FIG. 12A shows the target air-fuel ratio A / F when normal combustion is performed. In FIG. 12A, the curves indicated by A / F = 24, A / F = 35, A / F = 45, and A / F = 60 indicate the target air-fuel ratios 24, 35, 45, and 60, respectively. ing. The target air-fuel ratio A / F shown in FIG. 12 (A) is stored in advance in the ROM 42 in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 12 (B). Further, the target opening ST of the throttle valve 20 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. 12A is the required load L and the engine speed as shown in FIG. As a function of N, it is stored in advance in the ROM 42 in the form of a map, and the opening degree SEL of the first EGR control valve 64 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. As shown in FIG. 13 (B), the target opening degree SE is stored in advance in the ROM 42 in the form of a map as a function of the required load L and the engine speed N.

  When normal combustion is being performed, the fuel injection amount Q is calculated based on the required load L and the engine speed N. The fuel injection amount Q is stored in advance in the ROM 42 in the form of a map as a function of the required load L and the engine speed N as shown in FIG.

  Next, operation control will be described with reference to FIG. Referring to FIG. 15, first, at step 100, it is judged if the flag I indicating that the engine operating state is the first operating region I is set. When the flag I is set, that is, when the operating state of the engine is the first operating region I, the routine proceeds to step 101, where it is determined whether or not the required load L has become larger than the first boundary X1 (N). Is done. When L ≦ X1 (N), the routine proceeds to step 103 where low temperature combustion is performed.

  That is, in step 103, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 11A, and the opening of the throttle valve 20 is set as the target opening ST. Next, at step 104, the target opening degree SE of the second EGR control valve 31 is calculated from the map shown in FIG. 11B, and the opening degree of the EGR control valve 31 is made the target opening degree SE. Next, at step 105, fuel injection is performed so that the air-fuel ratio shown in FIG. At this time, low temperature combustion is performed.

  On the other hand, when it is determined in step 101 that L> X (N), the routine proceeds to step 102 where the flag I is reset, and then the routine proceeds to step 108 where the second combustion is performed. That is, at step 108, the target opening ST of the throttle valve 20 is calculated from the map shown in FIG. 13A, and the opening of the throttle valve 20 is set as this target opening ST. Next, at step 109, the target opening degree SE of the second EGR control valve 31 is calculated from the map shown in FIG. 13B, and the opening degree of the EGR control valve 31 is made the target opening degree SE. Next, at step 110, fuel injection is performed so that the lean air-fuel ratio shown in FIG.

  When the flag I is reset, in the next processing cycle, the routine proceeds from step 100 to step 106, where it is determined whether or not the required load L has become lower than the second boundary Y (N). When L ≧ Y (N), the routine proceeds to step 108 where normal combustion is performed under a lean air-fuel ratio. On the other hand, when it is determined in step 106 that L <Y (N), the routine proceeds to step 107 where the flag I is set, and then the routine proceeds to step 103 where low temperature combustion is performed.

  By the way, in the above-described operation control of the internal combustion engine, the opening degree of the throttle valve 20 is set in Step 103 and Step 108, and the opening degree of the first EGR control valve 64 is set in Step 104 and Step 109. Yes. When the opening degree of the valve is set in this way, the intake gas and the recirculated exhaust gas flow at a flow rate corresponding to the set opening degree. Here, in the conventional internal combustion engine, the intake gas whose flow rate is adjusted by the throttle valve reaches the combustion chamber through the compressor and the intercooler of the turbocharger, and the EGR gas whose flow rate is adjusted by the EGR control valve is also Similarly, it passed through the compressor and intercooler of the turbocharger and reached the combustion chamber. For this reason, in the internal combustion engine of the prior art, since the new gas reaches the combustion chamber after pushing out the residual EGR gas such as the intercooler described above, the response is lacking. However, in the internal combustion engine of the present invention as shown in FIG. 1, the first EGR control valve 64 is provided downstream of the EGR gas compressor 65, and the EGR passage 61 is connected to the surge tank 12 positioned downstream of the intercooler 14. Since they are connected, EGR gas does not pass through the EGR gas compressor 65. Further, in FIG. 1, the EGR passage 61 is connected to the surge tank 12 positioned downstream of the intercooler 14, so that EGR gas does not pass through the intercooler 14. For this reason, the response of the internal combustion engine when the EGR control valve 64 is opened to increase the EGR gas amount can be enhanced.

  Similarly, the throttle valve 20 in FIG. 1 is provided downstream of the compressor 16 and the intercooler 14, and the EGR passage 61 is connected to a surge tank located downstream of the throttle valve 20. When the throttle valve 20 is opened during acceleration, no EGR gas is present in the compressor 16 and the intercooler 14 (there is no remaining), so new intake air is immediately supplied to the combustion chamber 5. For this reason, it becomes possible to improve the response of the internal combustion engine when the throttle valve 20 is opened to increase the intake gas amount.

  Further, in the embodiment shown in FIG. 1, an EGR gas compressor 65 driven by the exhaust turbine 23 of the exhaust turbocharger 15 is provided in the EGR passage 61, whereby a large amount of EGR gas is quickly supplied to the combustion chamber. can do. In the prior art, since both EGR gas and intake gas are supplied to the combustion chamber by a single compressor, it is difficult to supply a large amount of EGR gas when the required engine load is high. In the present invention, since the EGR gas compressor 65 for boosting the EGR gas is provided, a large amount of EGR gas can be supplied even when the engine required load is high, whereby the engine required load is high. Even so, low temperature combustion is possible.

  Further, during the lean control operation of the internal combustion engine provided with the NOx occlusion reduction catalyst described above, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is used to purify the NOx before the NOx absorption amount of the catalyst is saturated. Is temporarily rich to reduce the oxygen concentration of the exhaust gas flowing into the NOx occlusion reduction catalyst, and to perform rich spike control for releasing and reducing NOx. When the air-fuel ratio is temporarily made rich, the EGR gas amount is increased. However, when the engine required load is high, it is difficult to supply a large amount of EGR gas to the combustion chamber 5. However, as described above, in the present invention, by using the EGR gas compressor 65, a large amount of EGR gas can be supplied even when the engine required load is high. Expansion is also possible.

  Incidentally, the compressor 16 for the intake gas of the exhaust turbocharger 15 in the internal combustion engine is driven by the exhaust turbine 23. Since the air from the air cleaner 18 compressed by the compressor 16 is at an ordinary temperature, the material of the compressor 16 is not required to have heat resistance, but the exhaust gas passing through the exhaust turbine 23 is hot, so the material of the exhaust turbine 23 Heat resistance is required. As can be seen from FIG. 1, in the present invention, a part of the exhaust gas flowing through the exhaust passage passes through the EGR gas compressor 65 as EGR gas. That is, since the EGR gas itself is originally an exhaust gas, the temperature is high, and the exhaust gas is further heated by an oxidation reaction when passing through the catalytic converter 26, so the temperature of the EGR gas becomes considerably high. For this reason, when the EGR gas compressor 65 is formed from a material having low heat resistance such as that used for manufacturing the compressor 16, the EGR gas compressor 65 may be damaged by the high-temperature EGR gas. 1, an EGR cooler 62 as shown in FIG. 1 is provided upstream of the EGR gas compressor 65. Therefore, the EGR gas can be cooled by the EGR cooler 62 before passing through the EGR gas compressor 65. That is, since the temperature of the EGR gas entering the EGR gas compressor 65 is low, the EGR gas compressor 65 can be prevented from being damaged by heat even if the EGR gas compressor 65 is formed from a material having low heat resistance.

  Although the EGR gas compressor 65 driven by the exhaust turbine 23 of the exhaust turbocharger 15 is shown in the first embodiment, the EGR gas compressor 65 is not necessarily driven by the exhaust turbine 23. Alternatively, the motor may be driven by a separate drive source, for example, a separately provided motor.

  In the above-described embodiment, the EGR passage 61 is shown to be directly connected to the surge tank 12, but the present invention is applicable even when the EGR passage 61 is connected to the intake duct 13 located downstream of the intercooler 14. It is clear that it is included in the range.

1 is an overall view of a compression ignition type internal combustion engine of a first embodiment. It is a figure which shows the generation amount etc. of smoke and NOx. It is a figure which shows the relationship between the generation amount of smoke and an EGR rate. It is a figure which shows the relationship between the amount of injected fuel, and the amount of mixed gas. It is a figure which shows the smoke concentration FSN in a specific driving | running state, a low temperature combustion area | region, and a normal fuel area | region. It is a conceptual diagram which shows a low temperature combustion area | region and a normal combustion area | region. It is a figure which shows the 1st operation area | region I and the 2nd operation area | region II. It is a figure which shows the output of an air fuel ratio sensor. It is a figure which shows the opening degree etc. of a throttle valve. FIG. 3 is a diagram showing an air-fuel ratio and the like in a first operation region I. It is a figure which shows the map of target opening degree, such as a throttle valve of 1st embodiment. It is a figure which shows the air fuel ratio etc. in normal combustion. It is a figure which shows the map of target opening degree, such as a throttle valve. It is a figure which shows the map of fuel injection quantity. It is a flowchart for controlling the operation of the engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5 ... Combustion chamber 6 ... Fuel injection valve 14 ... Intercooler 15 ... Turbocharger 16 ... Compressor (intake gas compressor)
DESCRIPTION OF SYMBOLS 20 ... Throttle valve 23 ... Exhaust turbine 25 ... Filter 61 which supported the catalyst (Occlusion reduction type NOx catalyst) which has an oxidation function ... EGR passage (exhaust gas recirculation passage)
62 ... EGR cooler (cooling device)
64 ... EGR control valve (recirculation exhaust gas control valve)
65 ... EGR gas compressor (recirculation exhaust gas compressor)

Claims (4)

An exhaust gas recirculation device that recirculates exhaust gas discharged from the combustion chamber into the engine intake passage is provided, and when the amount of recirculated exhaust gas supplied to the combustion chamber is increased, the amount of soot generated is increased. As the amount of recirculated exhaust gas supplied into the combustion chamber increases further and gradually reaches a peak, the temperature of the fuel and the surrounding gas in the combustion chamber is lower than the soot generation temperature. Switching means for switching between low-temperature combustion in which soot is hardly generated and normal combustion in which the amount of inert gas supplied to the combustion chamber is smaller than the amount of inert gas in which the amount of soot reaches a peak, and the engine In an internal combustion engine comprising an intake gas compressor provided in an intake passage and a turbocharger driven by a turbine provided in an engine exhaust passage,
The exhaust gas circulation device includes an exhaust gas recirculation passage, a recirculation exhaust gas control valve capable of controlling the amount of recirculation exhaust gas flowing through the exhaust gas recirculation passage, and the recirculation gas in the exhaust gas recirculation passage. A recirculation exhaust gas compressor for boosting the circulation exhaust gas,
The recirculation exhaust gas control valve is provided downstream of the recirculation exhaust gas compressor, a throttle valve in the engine intake passage is disposed downstream of an intercooler provided in the intake passage of the internal combustion engine, and An internal combustion engine in which an outlet portion of the exhaust gas recirculation passage is connected to an intake passage downstream of the throttle valve.   The internal combustion engine of claim 1, wherein the recirculation exhaust gas compressor is driven by the turbine of the turbocharger.   The exhaust gas circulation device further includes a cooling device that cools the recirculation exhaust gas in the exhaust gas recirculation passage, and the cooling device includes an inlet portion of the exhaust gas recirculation passage and the recirculation exhaust gas compressor. The internal combustion engine of Claim 2 provided between these.   The internal combustion engine according to any one of claims 1 to 3, wherein an inlet portion of the exhaust gas recirculation passage is located downstream of a filter provided downstream of the turbine in the engine exhaust passage.

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