JP4029827B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Description

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

  An exhaust gas recirculation device for an internal combustion engine is disclosed in Patent Document 1. In this exhaust gas recirculation device, exhaust gas discharged from the combustion chamber to the exhaust passage is recirculated from the exhaust passage downstream of the exhaust turbocharger to the intake passage upstream of the compressor of the exhaust turbocharger.

JP 2000-8835 A JP 2000-8964 A Japanese Patent No. 31168776

  Incidentally, in the internal combustion engine described in Patent Document 1, the intercooler is disposed in the intake passage downstream of the compressor of the exhaust turbocharger. When an internal combustion engine is mounted in an engine room of a vehicle, generally, a main body of the internal combustion engine is disposed in a central region in the engine room, and an intercooler is disposed in an outer region in the engine room. For this reason, in an internal combustion engine having an intercooler in the intake passage as in the internal combustion engine described in Patent Document 1, the path of the intake passage from the position of the intake passage where the exhaust gas recirculates to the combustion chamber is relatively long.

  By the way, when the internal combustion engine is requested to accelerate, in order to cause the internal combustion engine to perform the requested acceleration, it is necessary to quickly increase the amount of air taken into the combustion chamber. In this case, in the internal combustion engine described in Patent Document 1, the amount of exhaust gas recirculated to the intake passage is quickly reduced. However, as described above, in the internal combustion engine described in Patent Document 1, since the distance of the intake passage from the position of the intake passage where the exhaust gas is recirculated to the combustion chamber is relatively long, the exhaust gas recirculated to the intake passage When the amount is reduced, exhaust gas remains in the intake passage to the combustion chamber. Therefore, even if the amount of exhaust gas recirculated to the intake passage is quickly reduced, the amount of exhaust gas actually sucked into the combustion chamber does not immediately decrease, and therefore the air actually sucked into the combustion chamber The amount does not increase instantly.

  Further, there is known an internal combustion engine in which so-called low-temperature combustion (refer to the description of an embodiment of the present invention described later and Patent Document 3 for details of this combustion) is performed when the engine required load is low. . Here, when low temperature combustion is performed, the amount of exhaust gas recirculated into the combustion chamber is very large. Therefore, if the internal combustion engine is required to accelerate during low-temperature combustion, the amount of exhaust gas recirculated into the combustion chamber must be reduced immediately in order to achieve the desired acceleration. I must. However, as described above, even if the amount of exhaust gas recirculated to the intake passage is immediately reduced at once, the amount of exhaust gas actually sucked into the combustion chamber is not immediately reduced. As described above, when the internal combustion engine is requested to accelerate during low-temperature combustion, there is a high demand for reducing the amount of exhaust gas actually taken into the combustion chamber immediately.

  Furthermore, contrary to the case described above, there are cases where it is desired to immediately increase the amount of exhaust gas recirculated into the combustion chamber. In such a case, even if the amount of exhaust gas recirculated to the intake passage is immediately increased, the amount of exhaust gas recirculated into the combustion chamber does not increase immediately for the same reason as described above.

  That is, in the conventional internal combustion engine, when it is required to greatly change the amount of exhaust gas recirculated into the combustion chamber, the amount of exhaust gas recirculated into the combustion chamber cannot be greatly changed as required. .

  Accordingly, an object of the present invention is to change the amount of exhaust gas recirculated into the combustion chamber as quickly as possible when it is required to greatly change the amount of exhaust gas recirculated into the combustion chamber. .

In order to solve the above problems, in a first aspect of the invention, an exhaust gas that recirculates exhaust gas to a combustion chamber of an internal combustion engine that includes an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger. In the exhaust gas recirculation device comprising an exhaust gas recirculation passage that recirculates exhaust gas to the intake passage upstream of the compressor, the recirculation device passes through the vicinity of the main body of the internal combustion engine from the intake passage between the compressor and the intercooler. A bypass passage extending to the intake passage downstream of the intercooler is provided, and the exhaust gas currently recirculated to the combustion chamber when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount. If the difference between the amount and the predetermined amount is greater than or equal to a predetermined value, first, The amount of exhaust gas recirculated to the intake passage is set to the predetermined amount and substantially all of the gas flows into the combustion chamber via the bypass passage, and then recirculates to the intake passage via the exhaust recirculation passage. The amount of exhaust gas is maintained at the predetermined amount, and the amount of gas passing through the bypass passage is gradually reduced.

In the second invention, in the first invention, the bypass passage passes through the vicinity of the cooling water passage in the cylinder head of the internal combustion engine.
Further, according to a third invention, in the first invention, the bypass passage passes through the outside of the cylinder head of the internal combustion engine, the second passage passes through the vicinity of the cooling water passage in the cylinder head of the internal combustion engine, Means for controlling the amount of gas passing through the first passage and the second passage.
In a fourth aspect, the internal combustion engine according to any one of the first to third aspects, wherein the amount of exhaust gas in the combustion chamber is greater than the amount of exhaust gas at which the generation amount of soot peaks. An internal combustion engine that selectively executes a first combustion that hardly occurs and a second combustion in which the amount of exhaust gas in the combustion chamber is smaller than the amount of exhaust gas at which the amount of generated soot reaches a peak. When the combustion is switched between the first combustion and the second combustion, the difference between the amount of the exhaust gas currently recirculated to the combustion chamber and the predetermined amount is equal to or greater than the predetermined value.

In order to solve the above problems, in a fifth aspect of the invention, there is provided an exhaust gas recirculation device for recirculating exhaust gas to a combustion chamber of an internal combustion engine having an intercooler disposed in the intake passage, wherein the exhaust gas is recirculated to the intake passage. In the exhaust gas recirculation apparatus having an exhaust gas recirculation passage for recirculation, the vicinity of the main body of the internal combustion engine from the intake passage upstream of the intercooler to the intake passage downstream of the intercooler at the junction point of the intake passage and the exhaust recirculation passage And a predetermined amount of exhaust gas recirculated to the combustion chamber when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount. When the difference from the determined amount is equal to or greater than a predetermined value, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is set as the predetermined amount. The amount of gas passing through the bypass passage is then increased, and then the amount of exhaust gas recirculated to the intake passage via the exhaust recirculation passage is maintained at the predetermined amount and the amount of gas passing through the bypass passage is maintained. Reduce the amount gradually.
According to a sixth aspect, in the fifth aspect, the internal combustion engine includes the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas at which the generation amount of soot reaches a peak, and soot is hardly generated. An internal combustion engine that selectively executes the second combustion in which the amount of exhaust gas in the combustion chamber is smaller than the amount of exhaust gas at which the amount of generated soot reaches a peak, and between the first combustion and the second combustion The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the combustion is switched and the predetermined amount is equal to or greater than the predetermined value.

In order to solve the above problems, according to a seventh aspect of the present invention, there is provided an exhaust gas recirculation device that recirculates exhaust gas to a combustion chamber of an internal combustion engine having an intercooler disposed in an intake passage. In the exhaust gas recirculation apparatus having an exhaust gas recirculation passage for recirculation, the vicinity of the main body of the internal combustion engine from the intake passage upstream of the intercooler to the intake passage downstream of the intercooler at the junction point of the intake passage and the exhaust recirculation passage And a predetermined amount of exhaust gas recirculated to the combustion chamber when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount. When the difference from the determined amount is equal to or greater than a predetermined value, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is set as the predetermined amount. The bypass passage increases the amount of gas through the further the bypass passage is passed through the cooling water passage near the cylinder head of an internal combustion engine with.
According to an eighth aspect of the present invention, in the seventh aspect, the internal combustion engine includes the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas at which the generation amount of soot peaks, and soot is hardly generated. An internal combustion engine that selectively executes the second combustion in which the amount of exhaust gas in the combustion chamber is smaller than the amount of exhaust gas at which the amount of generated soot reaches a peak, and between the first combustion and the second combustion The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the combustion is switched and the predetermined amount is equal to or greater than the predetermined value.

In order to solve the above-described problems, in a ninth aspect of the invention, an exhaust gas that recirculates exhaust gas to a combustion chamber of an internal combustion engine that includes an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger. In the exhaust gas recirculation device comprising an exhaust gas recirculation passage that recirculates exhaust gas to the intake passage upstream of the compressor, the recirculation device passes through the vicinity of the main body of the internal combustion engine from the intake passage between the compressor and the intercooler. A bypass passage extending to the intake passage downstream of the intercooler is provided, and the exhaust gas currently recirculated to the combustion chamber when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount. If the difference between the amount and the predetermined amount is equal to or greater than a predetermined value, the intake air is passed through the exhaust gas recirculation passage. The amount of exhaust gas recirculated to the exhaust gas is set to the predetermined amount, the amount of gas passing through the bypass passage is increased, and then the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is set. While maintaining the predetermined amount, the amount of gas passing through the bypass passage is gradually reduced.
According to a tenth aspect, in the ninth aspect, the internal combustion engine includes a first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas at which the amount of generated soot reaches a peak, and soot is hardly generated. An internal combustion engine that selectively executes the second combustion in which the amount of exhaust gas in the combustion chamber is smaller than the amount of exhaust gas at which the amount of generated soot reaches a peak, and between the first combustion and the second combustion The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the combustion is switched and the predetermined amount is equal to or greater than the predetermined value.

In order to solve the above-mentioned problems, in an eleventh aspect of the invention, an exhaust gas that recirculates exhaust gas to a combustion chamber of an internal combustion engine including an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger. In the exhaust gas recirculation device comprising an exhaust gas recirculation passage that recirculates exhaust gas to the intake passage upstream of the compressor, the recirculation device passes through the vicinity of the main body of the internal combustion engine from the intake passage between the compressor and the intercooler. A bypass passage extending to the intake passage downstream of the intercooler is provided, and the exhaust gas currently recirculated to the combustion chamber when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount. If the difference between the amount and the predetermined amount is greater than or equal to a predetermined value, the intake air is passed through the exhaust gas recirculation passage. The amount of exhaust gas recirculated to the passage is set to the predetermined amount and the amount of gas passing through the bypass passage is increased. Further, the bypass passage is passed near the cooling water passage in the cylinder head of the internal combustion engine. The
According to a twelfth aspect, in the eleventh aspect, the internal combustion engine includes the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and soot is hardly generated. An internal combustion engine that selectively executes the second combustion in which the amount of exhaust gas in the combustion chamber is smaller than the amount of exhaust gas at which the amount of generated soot reaches a peak, and between the first combustion and the second combustion The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the combustion is switched and the predetermined amount is equal to or greater than the predetermined value.

According to the first invention, when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount, the amount of exhaust gas currently recirculated to the combustion chamber and the predetermined amount are determined. When the difference between the quantities is greater than or equal to a predetermined value, gas is drawn into the combustion chamber via the bypass passage. Here, the length of the bypass passage is shorter than the length of the intake passage extending from the inlet of the bypass passage through the intercooler to the outlet of the bypass passage. Therefore, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly.
Furthermore, according to the first invention, when it is required to reduce the amount of exhaust gas recirculated to the combustion chamber, once almost all the gas is once flowed into the combustion chamber via the bypass passage. The amount of gas passing through the bypass passage is gradually reduced. That is, the amount of gas passing through the intercooler gradually increases. According to this, the exhaust gas remaining in the intake passage upstream of the bypass passage from the intake passage downstream of the bypass passage through the intercooler gradually decreases. Of course, at this time, the amount of gas passing through the intercooler increases only gradually, so that the amount of exhaust gas recirculated to the combustion chamber is suppressed from greatly deviating from the predetermined amount.
Further, according to the second invention, the gas flowing into the combustion chamber via the bypass passage can be cooled.
Furthermore, according to the third aspect, it is possible to control whether or not the gas flowing into the combustion chamber via the bypass passage is cooled.
According to the fourth aspect of the present invention, when the combustion is switched between the first combustion and the second combustion in which the exhaust gas amount in the combustion chamber is greatly different, the amount of gas passing through the bypass passage is increased. Therefore, at this time, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly. In particular, according to the fourth aspect, when the combustion is switched from the first combustion to the second combustion, that is, when acceleration is required, the amount of exhaust gas in the combustion chamber decreases more quickly, and the combustion chamber As the amount of air increases more quickly, the acceleration response when acceleration is required increases.

According to the fifth and ninth inventions, when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount, the amount of exhaust gas currently recirculated to the combustion chamber and the above-mentioned pre- When the difference from the predetermined amount is greater than or equal to a predetermined value, gas is drawn into the combustion chamber through the bypass passage. Here, the length of the bypass passage is shorter than the length of the intake passage extending from the inlet of the bypass passage through the intercooler to the outlet of the bypass passage. Therefore, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly.
Further, according to the fifth and ninth inventions, when it is required to reduce the amount of exhaust gas recirculated to the combustion chamber, the amount of gas once introduced into the combustion chamber through the bypass passage is increased. After being done, the amount of gas passing through the bypass passage is gradually reduced. That is, the amount of gas passing through the intercooler gradually increases. According to this, the exhaust gas remaining in the intake passage upstream of the bypass passage from the intake passage downstream of the bypass passage through the intercooler gradually decreases. Of course, at this time, the amount of gas passing through the intercooler increases only gradually, so that the amount of exhaust gas recirculated to the combustion chamber is suppressed from greatly deviating from the predetermined amount.

Further, according to the sixth and tenth aspects, when the combustion is switched between the first combustion and the second combustion in which the exhaust gas amount in the combustion chamber is greatly different, the amount of gas passing through the bypass passage is reduced. To be more. Therefore, at this time, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly. In particular, according to the sixth and tenth inventions, when the combustion is switched from the first combustion to the second combustion, that is, when acceleration is required, the amount of exhaust gas in the combustion chamber decreases more quickly. Since the amount of air in the combustion chamber increases more quickly, the acceleration response when acceleration is required increases.

According to the seventh and eleventh inventions, when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount, the amount of exhaust gas currently recirculated to the combustion chamber and the above-mentioned pre- When the difference from the predetermined amount is greater than or equal to a predetermined value, gas is drawn into the combustion chamber through the bypass passage. Here, the length of the bypass passage is shorter than the length of the intake passage extending from the inlet of the bypass passage through the intercooler to the outlet of the bypass passage. Therefore, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly.
In addition to the above, in the seventh and eleventh inventions, the gas flowing into the combustion chamber via the bypass passage can be cooled.

Further, according to the eighth and twelfth inventions, when the combustion is switched between the first combustion and the second combustion in which the amount of exhaust gas in the combustion chamber is greatly different, the amount of gas passing through the bypass passage is reduced. To be more. Therefore, at this time, the amount of exhaust gas in the gas sucked into the combustion chamber becomes the predetermined amount more quickly. In particular, according to the eighth and twelfth inventions, when the combustion is switched from the first combustion to the second combustion, that is, when acceleration is required, the amount of exhaust gas in the combustion chamber decreases more quickly. Since the amount of air in the combustion chamber increases more quickly, the acceleration response when acceleration is required increases.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall view of an internal combustion engine equipped with an exhaust gas recirculation device of the present invention. In FIG. 1, 1 is a main body of an internal combustion engine (hereinafter referred to as “engine main body”), 2 is a combustion chamber, 3 is a fuel injection valve, and 4 is a fuel temporarily stored at a high pressure. A reservoir (so-called common rail) 5 is an intake branch pipe, and 6 is an exhaust branch pipe. The illustrated internal combustion engine is a compression ignition type internal combustion engine.

  The intake branch pipe 5 is connected to a common intake pipe 7. An intercooler 8 for cooling the gas flowing in the intake pipe 7 is disposed in the intake pipe 7. A compressor 10 of an exhaust turbocharger 9 is disposed in the intake pipe 7 upstream of the intercooler 8. A throttle valve 11 is arranged in the intake pipe 7 upstream of the compressor 10 of the exhaust turbocharger 9. On the other hand, the exhaust branch pipe 6 is connected to a common exhaust pipe 12. An exhaust turbine 13 of the exhaust turbocharger 9 is disposed in the exhaust pipe 12. Further, in the exhaust pipe 12 downstream of the exhaust turbine 13, a filter 13a for carrying a NOx catalyst for reducing and purifying nitrogen oxide (NOx) in the exhaust gas and for collecting particulates in the exhaust gas is disposed. Has been.

  A passage (hereinafter referred to as “EGR passage”) 14 for passing exhaust gas extends from the exhaust pipe 12 downstream of the filter 13 a to the intake pipe 7 between the compressor 10 and the throttle valve 11 of the exhaust turbocharger 9. . An EGR cooler 15 for cooling the exhaust gas flowing through the EGR passage 14 is disposed in the EGR passage 14. Further, a valve (hereinafter referred to as “EGR control valve”) 16 for controlling the flow rate of the exhaust gas flowing through the EGR passage 14 is disposed in the EGR passage 14 downstream of the EGR cooler 15.

  A bypass passage 17 extends from the intake pipe 7 between the compressor 10 of the exhaust turbocharger 9 and the intercooler 8 to the intake pipe 7 downstream of the intercooler 8. The bypass passage 17 passes close to the cylinder head of the engine body 1 (for example, immediately next to the cylinder head or just above the cylinder head). On the other hand, the intercooler 8 needs to be disposed at a position adjacent to the radiator in front of the engine room when the engine body 1 is mounted in the engine room of the vehicle. Located in the place.

  Further, a bypass valve 18 for controlling the flow rate of gas passing through the bypass passage 17 is disposed in the bypass passage 17. When the bypass valve 18 is in the position shown in FIG. 2 (A), gas flows as shown by the arrow in FIG. 2 (A), and no gas flows into the bypass passage 17; It flows into the combustion chamber 2 through the intercooler 8. On the other hand, when the bypass valve 18 is in the position shown in FIG. 2B, the gas flows as indicated by the arrow in FIG. 2B, and a part of the gas passes through the bypass passage 17 and is in the combustion chamber. 2 flows into the combustion chamber 2 through the intercooler 8. Then, by controlling the bypass valve 18 between the position shown in FIG. 2A and the position shown in FIG. 2B, the flow rate of the gas flowing into the combustion chamber 2 through the bypass passage 17 is controlled. Can be controlled. In this case, the closer the bypass valve 18 is to the position shown in FIG. 2B, the greater the flow rate of the gas flowing into the combustion chamber 2 through the bypass passage 17 due to the difference in flow path resistance.

  Next, control of the internal combustion engine of the present embodiment will be described. In the present embodiment, the amount of EGR gas (exhaust gas amount) in the combustion chamber 2 is larger than the amount of EGR gas at which soot generation peaks, and the first combustion in which soot is hardly generated (hereinafter referred to as “low temperature combustion”). ), And the second combustion (combustion normally performed conventionally, hereinafter referred to as “normal combustion”) in which the amount of EGR gas in the combustion chamber 2 is smaller than the amount of EGR gas at which the generation amount of soot reaches a peak ) Is selectively performed according to the engine demand load. Below, this low temperature combustion is demonstrated. FIG. 3 shows the opening of the throttle valve 11 (hereinafter referred to as “throttle opening”) and the EGR rate when the required load of the internal combustion engine is low and the fuel injection timing from the fuel injection valve 3 is constant. That is, the change in output torque when the air-fuel ratio A / F (horizontal axis in FIG. 3) is changed by changing the ratio of the amount of exhaust gas to the total amount of gas sucked into the combustion chamber 2). And the experiment example which showed the change of discharge | emission amount of smoke, HC, CO, NOx is represented. As can be seen from FIG. 3, in this experimental example, the EGR rate increases as the air-fuel ratio A / F decreases. When the air-fuel ratio A / F is less than the theoretical air-fuel ratio (≈14.6), the EGR rate is 65% or more.

  As shown in FIG. 3, when the air-fuel ratio A / F is reduced by increasing the EGR rate, the EGR rate becomes around 40%, and when the air-fuel ratio A / F becomes about 30, the smoke The amount of generation begins 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 decreased, this time, the smoke rapidly decreases, the EGR rate is set to 65% or more, and when the air-fuel ratio A / F is close to 15.0, the smoke is reduced. Nearly zero. That is, almost no soot is generated. At this time, the output torque of the engine slightly decreases, and the amount of NOx generated becomes considerably low. On the other hand, at this time, the generation amount of HC and CO starts to increase.

  FIG. 4 shows the mixed gas of exhaust gas and air necessary for making the temperature of the fuel and the surrounding gas lower than the soot generation temperature when exhaust gas is used as the inert gas. The amount, the ratio of the amount of air in the mixed gas, and the ratio of the amount of exhaust gas in the mixed gas are shown. In FIG. 4, the vertical axis indicates the total intake gas amount sucked into the combustion chamber 2, and the chain line Y indicates the total intake gas that can be sucked into the combustion chamber 2 when supercharging is not performed. The abscissa indicates the required load.

  In FIG. 4, the ratio of air (that is, the amount of air in the mixed gas) indicates the amount of air necessary for completely burning 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 the exhaust gas (that is, the amount of exhaust gas in the mixed gas) is lower than the temperature at which soot is formed when the injected fuel is burned and the temperature of the gas around it. It shows the minimum amount of exhaust gas required to reach temperature. This exhaust gas amount is approximately 55% or more in terms of EGR rate, and is 70% or more in the example shown in FIG. That is, if the ratio of the air quantity and the exhaust gas quantity in the total intake gas quantity sucked into the combustion chamber 2 (indicated by the solid line X in FIG. 4) is set to a ratio as shown in FIG. The temperature of the fuel and the surrounding gas is lower than the soot generation temperature, and so no soot is generated. Further, the amount of NOx generated at this time is about 10 p.p.m. (or less), and therefore the amount of NOx generated is extremely small.

  If the fuel injection amount 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 soot generation temperature, heat absorption by the exhaust gas is performed. The amount must be increased. Therefore, as shown in FIG. 4, the amount of exhaust gas must be increased as the amount of injected fuel increases. That is, the amount of exhaust gas needs to be increased as the required load increases.

  By the way, when supercharging is not performed, the upper limit of the total intake gas amount sucked into the combustion chamber 2 (solid line X in FIG. 4) is Y. Therefore, in FIG. 4, in the region where the required load is larger than Lo, the air-fuel ratio cannot be maintained at the stoichiometric air-fuel ratio unless the ratio of exhaust gas is reduced as the required load increases. In other words, when supercharging is not 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 larger than Lo, the EGR rate decreases as the required load increases. Thus, in a region where the required load is larger than Lo, the temperature of the fuel and the surrounding gas cannot be maintained at a temperature lower than the soot generation temperature.

  However, as shown in FIG. 1, when the exhaust gas is recirculated into the intake pipe 7 upstream of the compressor 10 of the exhaust turbocharger 9 via the EGR passage 14, the EGR rate is increased in a region where the required load is larger than Lo. Can be maintained at 55 percent or more (eg, 70 percent), and thus the temperature of the fuel and the surrounding gas can be maintained below the soot formation temperature. That is, if the exhaust gas is recirculated so that the EGR rate in the intake pipe becomes, for example, 70%, the EGR rate of the intake gas boosted by the compressor 10 of the exhaust turbocharger 9 also becomes 70%. Thus, the temperature of the fuel and the surrounding gas can be maintained at a temperature lower than the soot generation temperature up to a limit that can be increased by the compressor 10. Therefore, the operating range of the engine that can cause low temperature combustion can be expanded. When the EGR rate is set to 55% or more in the region where the required load is larger than Lo, the EGR control valve 16 is fully opened and the throttle valve 11 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. However, the amount of NOx generated can be reduced to around 10 p.pm (or less) while preventing the generation of soot, and the amount of air can be made larger than the amount of air shown in FIG. (That is, even if the average value of the air-fuel ratio is made lean from 17 to 18), the generation amount of NOx can be reduced to around 10 p.pm (or less) while preventing the generation of soot.

  That is, when the air-fuel ratio is made rich, the fuel becomes excessive, but since the combustion temperature is suppressed to a low temperature, the excess fuel does not grow to soot, and soot is generated. Absent. At this time, only a very small amount of NOx is generated. On the other hand, even when the average air-fuel ratio is lean (or 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 combustion temperature is suppressed to a low temperature. As a result, almost no soot is produced and very little 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. In addition, the amount of NOx generated 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, it is possible to suppress the temperature of the fuel during combustion in the combustion chamber 2 and the temperature of the gas around it to a temperature at which hydrocarbon growth stops halfway (hereinafter referred to as “hydrocarbon growth stop temperature”). Limited to medium and low load operation with relatively low heat generation. Therefore, in the embodiment of the present invention, at the time of engine low load operation, the temperature of the fuel during combustion and the surrounding gas temperature is suppressed to the hydrocarbon growth stop temperature or lower and the first combustion (low temperature combustion) is performed. Thus, during the engine high load operation, the second combustion (normal combustion) is performed. Here, as is clear from the above description, the low temperature combustion means that the amount of inert gas in the combustion chamber 2 is larger than the amount of inert gas at which the amount of generated soot reaches a peak, and soot is almost generated. Normal combustion refers to combustion in which the amount of inert gas in the combustion chamber 2 is smaller than the amount of inert gas at which the amount of soot peaks.

  FIG. 5 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. In FIG. 5, the vertical axis L indicates the amount of depression of the accelerator pedal (that is, the required load), and the horizontal axis N indicates the engine speed. Further, in FIG. 5, X (N) indicates a first boundary that divides the first operation region I and the second operation region II, and Y (N) indicates the first operation region I and The 2nd boundary which divides 2nd operation area 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 from the second operation region II to the first operation region I. The operation region change determination is performed based on the second boundary Y (N).

  That is, when the engine operating state is in the first operating region I and low temperature combustion is performed, if the required load L exceeds the first boundary X (N) that is a function of the engine speed N, It is determined that the operation region has moved to the second operation 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.

  Next, operation control in the first operation region I and the second operation region II will be schematically described with reference to FIG. FIG. 6 shows the throttle opening with respect to the required load L, the opening of the EGR control valve 16 (hereinafter referred to as “EGR opening”), the EGR rate, the air-fuel ratio, the injection timing, and the injection amount. As shown in FIG. 6, in the first operation region I where the required load L is low, the throttle opening is gradually increased from nearly fully closed to about 2/3 as the required load L increases. The EGR opening is gradually increased from near full close to full open as the required load L increases. In the example shown in FIG. 6, 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, in the first operating region I, the throttle opening and the EGR opening are controlled so that the EGR rate becomes approximately 70% and the air / fuel ratio becomes a slightly lean air / fuel ratio. 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 the idling operation, the throttle valve 11 is closed to near full closure, and at this time, the EGR control valve 16 is also made to close to full close. When the throttle valve 11 is closed close to being fully closed, the pressure in the combustion chamber 2 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 in the combustion chamber 2 is reduced, so that the vibration of the engine body 1 is reduced. That is, at the time of idling operation, the throttle valve 11 is closed to almost fully closed in order to suppress vibration of the engine body 1.

  On the other hand, when the operating state of the engine changes from the first operating region I to the second operating region II, the throttle opening is increased stepwise from about 2/3 opening in the fully open direction. At this time, in the example shown in FIG. 6, the EGR rate is decreased stepwise from approximately 70% to 40% or less, and the air-fuel ratio is increased stepwise. That is, since the EGR rate exceeds the EGR rate range (see FIG. 6) that generates a large amount of smoke, a large amount of smoke is generated when the operating state of the engine changes from the first operating region I to the second operating region II. It does not occur.

  In the second operation region II, normal combustion is performed. In the second operation region II, the throttle valve 11 is kept fully open except for a part thereof, and the opening degree of the EGR control valve 16 is gradually reduced as the required load L increases. In the second 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. 7A shows the target air-fuel ratio A / F in the first operation region I. FIG. In FIG. 7A, each of the curves indicated by A / F = 15.5, A / F = 16, A / F = 17, and A / F = 18 has a target air-fuel ratio of 15.5,16, respectively. , 17 and 18, and the air-fuel ratio between the curves is determined by proportional distribution. As shown in FIG. 7A, the air-fuel ratio is lean in the first operating region I, and further, in the first operating region I, the target air-fuel ratio A / F is lean.

  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 decreases. When the EGR rate is lowered, the air-fuel ratio increases. Therefore, as shown in FIG. 7A, the target air-fuel ratio A / F increases as the required load L decreases. 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 of the present invention, the target air-fuel ratio A / F decreases as the required load L decreases. Is increased.

  The target air-fuel ratio A / F shown in FIG. 7A is stored in advance in the ROM in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 7B. Yes. Further, as shown in FIG. 8A, the target opening ST of the throttle valve 11 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. As a function of the engine speed N, it is stored in advance in the ROM in the form of a map, and the target opening of the EGR control valve 16 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. As shown in FIG. 8B, the degree SE is stored in advance in the ROM in the form of a map as a function of the required load L and the engine speed N.

  FIG. 9A shows the target air-fuel ratio A / F when normal combustion is performed. In FIG. 9A, the curves indicated by A / F = 24, A / F = 35, A / F = 45, A / F = 60 are the target air-fuel ratios 24, 35, 45, 60. The target air-fuel ratio A / F shown in FIG. 9 (A) is stored in advance in the ROM in the form of a map as a function of the required load L and the engine speed N as shown in FIG. 9 (B). . Further, as shown in FIG. 10A, the target opening ST of the throttle valve 11 required for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. As a function of the engine speed N, it is stored in advance in the ROM in the form of a map, and the target opening of the EGR control valve 16 necessary for setting the air-fuel ratio to the target air-fuel ratio A / F shown in FIG. As shown in FIG. 10B, the degree SE is stored in advance in the ROM in the form of a map as a function of the required load L and the engine speed N.

  Further, when normal combustion is being performed, the fuel injection amount Q is calculated based on the required load L and the engine speed N. As shown in FIG. 11, the fuel injection amount Q is stored in advance in the ROM in the form of a map as a function of the required load L and the engine speed N.

  Next, control of the bypass valve 18 of this embodiment will be described. In this embodiment, when the change rate of the target EGR rate is smaller than a predetermined value (that is, when the change of the target EGR rate is relatively small), the bypass valve 18 is shown in FIG. The first operating position (hereinafter also referred to as “fully closed position”). When the change rate of the target EGR rate is smaller than a predetermined value, for example, in the example shown in FIG. 6, even if the required load L changes relatively large, the operation region is the first operation region I. This is when the operation region is maintained in one of the operation regions without switching between the first operation region and the second operation region. According to the present embodiment, when the rate of change of the target EGR rate is smaller than a predetermined value, all the mixed gas of air and exhaust gas does not go through the bypass passage 17 but goes through the intake pipe 7. It is caused to flow into the combustion chamber 2.

  On the other hand, when the change rate of the target EGR rate is larger than the predetermined value, the bypass valve 18 is set to the second operating position (hereinafter also referred to as “bypass position”) shown in FIG. . When the change rate of the target EGR rate is larger than the predetermined value, in the example shown in FIG. 6, when the operation region is switched from the first operation region I to the second operation region, This is when the region switches from the second operation region II to the first operation region I. For example, when the operation region is switched from the first operation region I to the second operation region II, the throttle opening is increased at a stretch and the EGR opening is decreased at a stretch.

  When the throttle opening and the EGR opening are thus changed, the amount of exhaust gas flowing into the intake pipe 7 is reduced at a stretch. Here, the EGR rate in the gas in the intake pipe 7 in the vicinity of the EGR control valve 16 decreases to the target EGR rate at a relatively early stage. However, even at this stage, the EGR rate in the gas in the intake pipe 7 downstream of the EGR control valve 16 (for example, the intake pipe 7 downstream of the intercooler 8) has not decreased to the target EGR rate. Here, when the bypass valve 18 is in the fully closed position, the gas flows into the combustion chamber 2 only through the intercooler 8, so that the operation region is changed from the first operation region I to the second operation region. Until a relatively long time has elapsed since switching to II, the EGR rate in the gas flowing into the combustion chamber 2 is not the target EGR rate.

  FIG. 12A shows this. That is, FIG. 12A shows the ratio of air in the gas when the bypass valve 18 is in the fully closed position even when the rate of change of the target EGR rate is greater than the predetermined value. Is shown. In the example shown in FIG. 12A, the target EGR rate decreases at a stretch at time t0. When the target EGR rate suddenly decreases at time t0, the ratio of the air in the gas at the confluence of the EGR passage 14 and the intake pipe 7 is substantially at time t0 as shown by the solid line A in FIG. It starts to rise from that point. However, the ratio of air in the gas in the vicinity of the intercooler 8 begins to rise only at time t4 as shown by the solid line B in FIG. 12A, and the ratio of air in the gas flowing into the combustion chamber As indicated by the solid line C in FIG. 12A, the ratio starts to increase only at time t8.

  However, according to the present embodiment, when the operation region is switched from the first operation region I to the second operation region II, the bypass valve 18 is set to the bypass position, so the bypass passage 17 is provided in the combustion chamber 2. Gas also flows through. Here, the length of the bypass passage 17 is considerably shorter than the length of the intake pipe 7 from the bypass passage 17 (hereinafter referred to as “bypass inlet”) 17a to the bypass outlet (hereinafter referred to as “bypass outlet”) 17b. The EGR rate in the gas flowing into the combustion chamber 2 becomes the target EGR rate at a relatively early stage.

  In other words, for example, when acceleration is required for the internal combustion engine, it is necessary to increase the amount of air flowing into the combustion chamber 2. Therefore, when the operation region is in the first operation region I and the internal combustion engine is requested to accelerate, the operation region is switched from the first operation region I to the second operation region II. At this time, the throttle opening is increased, the EGR opening is decreased, and the amount of air in the gas increases. However, immediately after the throttle opening is increased and the EGR opening is reduced, exhaust gas remains in the intake pipe 7 from the bypass inlet 17a to the bypass outlet 17b. If the bypass valve 18 remains in the fully closed position, the fuel flows into the combustion chamber 2 for a certain period (in FIG. 12A, the period from time t0 to time t8) after the internal combustion engine is requested to accelerate. The amount of air to do does not increase.

  On the other hand, according to the present embodiment, when the internal combustion engine is requested to accelerate, the bypass valve 18 is set to the bypass position, so that the amount of air flowing into the combustion chamber 2 increases relatively quickly. Therefore, according to this embodiment, the acceleration performance of the internal combustion engine is improved.

  FIG. 12B shows this. That is, the ratio of air in the gas when the bypass valve 18 is set to the bypass position when the rate of change of the target EGR rate is greater than the predetermined value is shown. Similar to FIG. 12A, also in FIG. 12B, the target EGR rate decreases at a stretch at time t0. When the target EGR rate is rapidly reduced at time t0, the ratio of the air in the gas at the confluence of the EGR passage 14 and the intake pipe 7 is substantially the time t0 as shown by the solid line A in FIG. It starts to rise from that point. Then, the ratio of air in the gas flowing into the combustion chamber starts to rise at time t1, as indicated by the solid line D in FIG. That is, in the example shown in FIG. 12B, the ratio of air in the gas flowing into the combustion chamber starts to rise earlier than in the example shown in FIG. Note that the ratio of air in the gas near the intercooler 8 starts to increase at time t4 as shown by the solid line B in FIG. 12B (the rate of increase in the ratio of air here is shown in FIG. 12). It is smaller than that of the solid line B in (A)).

  Immediately after the internal combustion engine is requested to accelerate, the amount of air in the gas flowing into the combustion chamber 2 does not immediately reach the required amount. Is more likely to misfire. According to this embodiment, when the internal combustion engine is requested to accelerate, the amount of gas flowing into the combustion chamber 2 without passing through the intercooler 8 increases, so the average temperature of the gas flowing into the combustion chamber 2 is relatively Become expensive. Therefore, according to the present embodiment, the misfire of combustion in the combustion chamber 2 can be suppressed by the amount that the average temperature of the gas flowing into the combustion chamber 2 becomes higher.

  Furthermore, in this embodiment, part of the gas flows into the combustion chamber 2 through the intercooler 8. According to this, the exhaust gas remaining in the intake pipe 7 from the bypass inlet 17a to the bypass outlet 17b is gradually removed therefrom.

  Further, if the bypass passage 17 is configured so that the flow passage resistance of the bypass passage 17 is lower than the flow passage resistance of the intake pipe 7 passing through the intercooler 8, the bypass valve 18 is more bypassed when the bypass valve 18 is set to the bypass position. Gas easily flows into the passage 17.

  In the above-described embodiment, when the operation region is switched from the first operation region I to the second operation region II, the bypass valve 18 is set to the bypass position, but the EGR rate changes when the operation region is switched. And a request for the temperature of the gas flowing into the combustion chamber 2 (since no means for positively cooling the gas is arranged in the bypass passage 17, the cooling rate of the gas passing through the bypass passage 17 is small). In consideration, when the operation region is switched, the bypass valve 18 may be set to a position between the fully closed position and the bypass position.

  For example, when the change rate of the EGR rate is larger than the predetermined value, the bypass valve 18 may be closer to the fully closed position as the change rate of the EGR rate is smaller. In this case, the amount of gas flowing through the bypass passage 17 and flowing into the combustion chamber 2 is relatively smaller than the amount of gas flowing through the intercooler 8 and flowing into the combustion chamber 2. Further, when the change rate of the EGR rate is larger than the predetermined value, the bypass valve 18 may be brought closer to the fully closed position as the required temperature of the gas flowing into the combustion chamber 2 is lower. Also in this case, the amount of gas flowing through the bypass passage 17 and flowing into the combustion chamber 2 is relatively smaller than the amount of gas flowing through the intercooler 8 and flowing into the combustion chamber 2.

  In the present embodiment, when the operation state is switched between the first operation state I and the second operation state II, as described above, after the bypass valve 18 is once set to the bypass position (or After a certain period of time has elapsed since the bypass valve 18 was set to the bypass position, the bypass valve 18 is gradually brought closer to the fully closed position.

  FIG. 13 is a view showing a configuration around the bypass passage 17 in the internal combustion engine provided with the exhaust gas circulation device of the second embodiment. The configuration other than the configuration shown in FIG. 13 is the same as the configuration of the first embodiment. In the present embodiment, a bypass valve 18 is disposed at the bypass inlet 17a.

  In this embodiment, when the bypass valve 18 is in the first operating position (fully closed position) shown in FIG. 14 (A), the gas flows as shown by the arrow in FIG. 14 (A). All the gas flows into the combustion chamber 2 through the intercooler 8. On the other hand, when the bypass valve 18 is in the second operating position (bypass position) shown in FIG. 14B, the gas flows as shown by the arrows in FIG. Flows into the combustion chamber 2 through the bypass passage 17.

  Control of the bypass valve 18 of this embodiment is the same as that of the first embodiment. That is, also in this embodiment, when the rate of change of the EGR rate is smaller than a predetermined value, the bypass valve 18 is set to the fully closed position shown in FIG. On the other hand, when the change rate of the EGR rate is larger than the predetermined value, the bypass valve 18 is set to the bypass position shown in FIG. When the bypass valve 18 is set to the bypass position, after the bypass valve 18 is set to the bypass position (or after a certain period of time has elapsed after the bypass valve 18 is set to the bypass position), the bypass valve 18 is gradually completed. Move closer to the closed position.

  In the present embodiment, when the internal combustion engine is requested to accelerate (that is, when it is required to reduce the amount of exhaust gas in the gas), the bypass valve 18 is set to the bypass position, and then the bypass valve 18. By gradually approaching the fully closed position, exhaust gas in the intake pipe 7 from the bypass inlet 17a to the bypass outlet 17b is gradually removed from there.

  FIG. 15 is a diagram illustrating a configuration around the bypass passage 17 in the internal combustion engine including the exhaust gas circulation device according to the third embodiment. The configuration other than the configuration shown in FIG. 15 is the same as the configuration of the first embodiment. In the present embodiment, another bypass passage (hereinafter referred to as “bypass branch passage”) 19 branches from the bypass passage 17. The bypass branch passage 19 passes through the vicinity of the cooling passage in the cylinder head of the internal combustion engine and joins the bypass passage 17 again. Cooling water for cooling the internal combustion engine is passed through the cooling passage in the cylinder head. Therefore, the gas passing through the bypass branch passage 19 is cooled by the cooling water in the cooling passage. In the present embodiment, the bypass valve 18 is disposed where the bypass branch passage 19 branches from the bypass passage 17.

  In this embodiment, when the bypass valve 18 is in the first operating position (fully closed position) shown in FIG. 16 (A), the gas flows as shown by the arrow in FIG. 16 (A). All the gas flows into the combustion chamber 2 through the intercooler 8. On the other hand, when the bypass valve 18 is in the second operating position shown in FIG. 16B (hereinafter referred to as “cooling bypass position”), the gas flows as shown in FIG. All the gas that has flowed into the bypass passage 17 flows into the combustion chamber 2 through the bypass branch passage 19. Further, when the bypass valve 18 is in the third operating position shown in FIG. 16C (hereinafter referred to as “partial cooling bypass position”), the gas flows as shown in FIG. A part of the gas flowing into the bypass passage 17 flows into the combustion chamber 2 through the bypass branch passage 19, and the remaining gas flowing into the bypass passage 17 flows into the combustion chamber 2 through only the bypass passage 17.

  Next, control of the bypass valve 18 of this embodiment will be described. In this embodiment, when the rate of change of the EGR rate is smaller than a predetermined value, the bypass valve 18 is set to the fully closed position shown in FIG. On the other hand, when the change rate of the EGR rate is larger than the predetermined value and the gas temperature is higher than the required temperature, the bypass valve 18 is set to the cooling bypass position shown in FIG. That is, since it is necessary to cool the gas when the gas temperature is higher than the required temperature, all the gas flowing into the bypass passage 17 is cooled by the cooling water in the cooling passage with the bypass valve 18 as the cooling bypass position. is there. For example, when the gas temperature is relatively high, and smoke may be generated in the combustion chamber 2, the gas flowing into the bypass passage 17 is cooled with the bypass valve 18 as a cooling bypass position. .

  Further, when the rate of change of the EGR rate is larger than the predetermined value and the gas temperature is lower than the required temperature, the bypass valve 18 is set to the partial cooling bypass position shown in FIG.

  When the bypass valve 18 is set to the cooling bypass position or the partial cooling bypass position, the bypass valve 18 is set to the cooling bypass position or the partial cooling bypass position (or the bypass valve 18 is set to the cooling bypass position or the partial cooling bypass position). Thereafter, after a certain time has elapsed), the bypass valve 18 is gradually brought closer to the fully closed position.

  FIG. 17 is a diagram illustrating a configuration around the bypass passage 17 in the internal combustion engine including the exhaust gas circulation device of the fourth embodiment. The configuration other than the configuration shown in FIG. 17 is the same as the configuration of the first embodiment. In the present embodiment, similarly to the third embodiment, another bypass passage (bypass branch passage) 19 is branched from the bypass passage 17. The bypass branch passage 19 passes through the vicinity of the cooling passage in the cylinder head of the internal combustion engine and joins the bypass passage 17 again. Cooling water for cooling the internal combustion engine is passed through the cooling passage in the cylinder head. Therefore, the gas passing through the bypass branch passage 19 is cooled by the cooling water in the cooling passage.

  In the present embodiment, a bypass valve (hereinafter referred to as “first bypass valve”) 20a is disposed at the bypass inlet 17a. Further, in the present embodiment, a bypass valve (hereinafter referred to as “second bypass valve”) 20 b is also arranged where the bypass branch passage 19 branches from the bypass passage 17.

  In the present embodiment, when the first bypass valve 20a is in the first operating position (fully closed position) shown in FIG. 18 (A), the gas flows as shown in FIG. 18 (A). All the gas flows into the combustion chamber 2 through the intercooler 8. In this case, the second bypass valve 20b may be in any position.

  On the other hand, the first bypass valve 20a is in the second operating position (bypass position) shown in FIG. 18 (B) and the second bypass valve 20b is in the first operation shown in FIG. 18 (B). When in the position (cooling bypass position), the gas flows as shown in FIG. 18B, all the gas flows into the bypass passage 17, and all the gas passes through the bypass branch passage 19 to the combustion chamber. Flows into 2.

  Further, the first bypass valve 20a is in the second operating position (bypass position) shown in FIG. 18C, and the second bypass valve 20b is in the second operation shown in FIG. 18C. When in the position (partial cooling bypass position), the gas flows as shown in FIG. 18C, all the gas flows into the bypass passage 17, and a part of it burns through the bypass branch passage 19. It flows into the chamber 2 and the remaining gas flows into the combustion chamber 2 only through the bypass passage 17.

  Next, control of the bypass valve of this embodiment will be described. In the present embodiment, when the rate of change of the EGR rate is smaller than a predetermined value, the first bypass valve 20a is set to the first operating position shown in FIG.

  On the other hand, when the rate of change of the EGR rate is larger than the predetermined value and the gas temperature is higher than the required temperature, the first bypass valve 20a is set to the bypass position shown in FIG. The 2 bypass valve 20b is set to the cooling bypass position shown in FIG. According to this, all the gases are cooled by the cooling water in the cooling passage.

  Further, when the rate of change of the EGR rate is larger than the predetermined value and the gas temperature is lower than the required temperature, the first bypass valve 20a is set to the bypass position shown in FIG. The 2 bypass valve 20b is set to the partial cooling bypass position shown in FIG.

  When the first bypass valve 20a is set to the bypass position, after the first bypass valve 20a is set to the bypass position (or after a certain time has elapsed after the first bypass valve 20a is set to the bypass position), 1 The bypass valve 20a is gradually brought closer to the fully closed position.

  In the above-described embodiment, by changing the position where the bypass valve is arranged, for example, all the gas flows into the combustion chamber 2 through the bypass branch passage 19 or all the gas passes through the bypass passage 17. It is also possible to allow only the gas to flow into the combustion chamber 2 or allow all gas to flow into the combustion chamber 2 only through the intercooler 8.

1 is an overall view of an internal combustion engine including an exhaust gas circulation device according to a first embodiment of the present invention. (A) is a figure which shows a bypass valve when it exists in a 1st operation position (fully closed position), (B) is a figure which shows a bypass valve when it exists in a 2nd operation position (bypass position). . It is the figure which showed the relationship between the air fuel ratio A / F at the time of low load driving | operation, throttle opening, etc. FIG. It is a figure which shows the relationship between a request | requirement load, total intake gas amount, etc. It is a figure which shows the area | region I in which low temperature combustion is performed, and the area | region II in which normal combustion is performed. It is a figure which shows the relationship between the request | requirement load L, throttle opening, etc. FIG. (A) is a figure which shows the relationship between the engine speed N in the 1st driving | operation area | region, the required load L, and air-fuel ratio A / F, (B) is the engine speed N and the required load in the 1st driving | operation area | region. It is a figure which shows the map of the air fuel ratio A / F of the function with L. (A) is a figure which shows the map of throttle opening ST of the function of the engine speed N and the request | requirement load L in the 1st operation area, (B) is the engine speed N and the request | requirement in the 1st operation area. It is a figure which shows the map of EGR opening degree SE of the function with the load L. FIG. (A) is a figure which shows the relationship between the engine speed N in the 2nd driving | operation area | region, the required load L, and air-fuel ratio A / F, (B) is the engine speed N in the 2nd driving | operation area | region, and a required load. It is a figure which shows the map of the air fuel ratio A / F of the function with L. (A) is a diagram showing a map of the throttle opening ST as a function of the engine speed N and the required load in the second operating region, and (B) is the engine speed N and the required load in the second operating region. It is a figure which shows the map of EGR opening degree SE of a function with L. FIG. 5 is a diagram showing a map of a fuel injection amount Q as a function of an engine speed N and a required load L in a second operation region. (A) is a figure which shows transition of the ratio of the air in gas when a bypass valve is maintained in a fully closed position when the rate of change of target EGR rate becomes larger than a predetermined value, ( B) is a diagram showing a transition of the ratio of air in the gas when the bypass valve is set to the bypass position when the change rate of the target EGR rate becomes larger than a predetermined value. It is a figure which shows the structure of the bypass passage periphery of the internal combustion engine provided with the exhaust-air-circulation apparatus of 2nd Embodiment of this invention. (A) is a figure which shows a bypass valve when it exists in a 1st operation position (fully closed position), (B) is a figure which shows a bypass valve when it exists in a 2nd operation position (bypass position). . It is a general view of the internal combustion engine provided with the exhaust gas circulation apparatus of 3rd Embodiment of this invention. (A) is a figure which shows a bypass valve when it exists in a 1st operation position (fully closed position), (B) is a figure which shows a bypass valve when it exists in a 2nd operation position (cooling bypass position). Yes, (C) is a diagram showing the bypass valve when in the third operating position (partial cooling bypass position). It is a figure which shows the structure of the periphery of the bypass valve of the internal combustion engine provided with the exhaust-air-circulation apparatus of 4th Embodiment of this invention. (A) is a view showing the first bypass valve in the first operating position (fully closed position), (B) is the first bypass valve in the second operating position (bypass position) and It is a figure which shows the place which has a 2nd bypass valve in a 1st operation position (cooling bypass position), (C) is a 1st bypass valve in a 2nd operation position, and a 2nd bypass valve is a 2nd It is a figure which shows the place which exists in an operation position (partial cooling bypass position).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Engine body 2 ... Combustion chamber 7 ... Intake pipe 14 ... EGR passage 16 ... EGR control valve 17 ... Bypass passage 18, 20a, 20b ... Bypass valve 19 ... Bypass branch passage

Claims (12)

  An exhaust gas recirculation device for recirculating exhaust gas to a combustion chamber of an internal combustion engine comprising an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger, wherein the exhaust gas is exhausted into the intake passage upstream of the compressor An exhaust gas recirculation device comprising an exhaust gas recirculation passage for recirculating gas comprises a bypass passage extending from an intake passage between the compressor and the intercooler to a suction passage downstream of the intercooler through the vicinity of the main body of the internal combustion engine. The difference between the amount of exhaust gas currently recirculated to the combustion chamber and the predetermined amount when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount If the value is equal to or greater than a predetermined value, first, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is determined in advance. The amount of exhaust gas that flows into the combustion chamber via the bypass passage and then recirculates to the intake passage via the exhaust recirculation passage. And an exhaust gas recirculation device characterized by gradually reducing the amount of gas passing through the bypass passage.   The exhaust gas recirculation apparatus according to claim 1, wherein the bypass passage is passed through a vicinity of a cooling water passage in a cylinder head of the internal combustion engine.   The bypass passage has a first passage through the outside of the cylinder head of the internal combustion engine, a second passage through the vicinity of the cooling water passage in the cylinder head of the internal combustion engine, and an amount of gas passing through the first passage and the second passage. The exhaust gas recirculation apparatus according to claim 1, further comprising a control means.   In the internal combustion engine, the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and the amount of soot generated in the combustion chamber peaks. The internal combustion engine that selectively executes the second combustion that is less than the amount of exhaust gas, and when the combustion is switched between the first combustion and the second combustion, The exhaust gas recirculation apparatus according to any one of claims 1 to 3, wherein a difference between the amount of exhaust gas present and the predetermined amount is not less than the predetermined value.   An exhaust gas recirculation device that recirculates exhaust gas to a combustion chamber of an internal combustion engine that includes an intercooler disposed in an intake passage, the exhaust gas recirculation device including an exhaust gas recirculation passage that recirculates exhaust gas to the intake passage. A bypass passage extending downstream from the intake passage upstream of the intercooler and from the intake passage downstream of the intercooler to the intake passage downstream of the intercooler and passing through the vicinity of the main body of the internal combustion engine is returned to the combustion chamber. The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the amount of exhaust gas to be made to be a predetermined amount and the predetermined amount is a predetermined value If this is the case, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is set to the predetermined amount and the amount of gas passing through the bypass passage is increased. Next, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is maintained at the predetermined amount, and the amount of gas passing through the bypass passage is gradually reduced. Exhaust gas recirculation device.   In the internal combustion engine, the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and the amount of soot generated in the combustion chamber peaks. The internal combustion engine that selectively executes the second combustion that is less than the amount of exhaust gas, and when the combustion is switched between the first combustion and the second combustion, 6. The exhaust gas recirculation apparatus according to claim 5, wherein a difference between the amount of exhaust gas present and the predetermined amount is equal to or greater than the predetermined value.   An exhaust gas recirculation device that recirculates exhaust gas to a combustion chamber of an internal combustion engine that includes an intercooler disposed in an intake passage, the exhaust gas recirculation device including an exhaust gas recirculation passage that recirculates exhaust gas to the intake passage. A bypass passage extending downstream from the intake passage upstream of the intercooler and from the intake passage downstream of the intercooler to the intake passage downstream of the intercooler and passing through the vicinity of the main body of the internal combustion engine is returned to the combustion chamber. The difference between the amount of exhaust gas currently recirculated to the combustion chamber when the amount of exhaust gas to be made to be a predetermined amount and the predetermined amount is a predetermined value If this is the case, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is set to the predetermined amount and the amount of gas passing through the bypass passage is increased. It was further exhaust gas recirculation system in which the bypass passage is characterized by being passed through a cooling water passage near the cylinder head of an internal combustion engine.   In the internal combustion engine, the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and the amount of soot generated in the combustion chamber peaks. The internal combustion engine that selectively executes the second combustion that is less than the amount of exhaust gas, and when the combustion is switched between the first combustion and the second combustion, The exhaust gas recirculation apparatus according to claim 7, wherein a difference between the amount of exhaust gas present and the predetermined amount is not less than the predetermined value.   An exhaust gas recirculation device for recirculating exhaust gas to a combustion chamber of an internal combustion engine comprising an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger, wherein the exhaust gas is exhausted into the intake passage upstream of the compressor An exhaust gas recirculation device comprising an exhaust gas recirculation passage for recirculating gas comprises a bypass passage extending from an intake passage between the compressor and the intercooler to a suction passage downstream of the intercooler through the vicinity of the main body of the internal combustion engine. The difference between the amount of exhaust gas currently recirculated to the combustion chamber and the predetermined amount when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount If it is equal to or greater than a predetermined value, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is determined in advance. And the amount of gas passing through the bypass passage is increased, and then the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is maintained at the predetermined amount and the bypass passage is An exhaust gas recirculation device characterized by gradually reducing the amount of gas passing therethrough.   In the internal combustion engine, the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and the amount of soot generated in the combustion chamber peaks. The internal combustion engine that selectively executes the second combustion that is less than the amount of exhaust gas, and when the combustion is switched between the first combustion and the second combustion, The exhaust gas recirculation apparatus according to claim 9, wherein the difference between the amount of exhaust gas present and the predetermined amount is equal to or greater than the predetermined value.   An exhaust gas recirculation device for recirculating exhaust gas to a combustion chamber of an internal combustion engine comprising an exhaust turbocharger and an intercooler disposed in an intake passage downstream of the compressor of the exhaust turbocharger, wherein the exhaust gas is exhausted into the intake passage upstream of the compressor An exhaust gas recirculation device comprising an exhaust gas recirculation passage for recirculating gas comprises a bypass passage extending from an intake passage between the compressor and the intercooler to a suction passage downstream of the intercooler through the vicinity of the main body of the internal combustion engine. The difference between the amount of exhaust gas currently recirculated to the combustion chamber and the predetermined amount when the amount of exhaust gas recirculated to the combustion chamber is required to be a predetermined amount If it is equal to or greater than a predetermined value, the amount of exhaust gas recirculated to the intake passage through the exhaust recirculation passage is determined in advance. The amount of gas passing through the bypass passage increases, further exhaust gas recirculation system in which the bypass passage is characterized by being passed through a cooling water passage near the cylinder head of an internal combustion engine as well as the amount.   In the internal combustion engine, the first combustion in which the amount of exhaust gas in the combustion chamber is larger than the amount of exhaust gas in which the generation amount of soot reaches a peak, and the amount of soot generated in the combustion chamber peaks. The internal combustion engine that selectively executes the second combustion that is less than the amount of exhaust gas, and when the combustion is switched between the first combustion and the second combustion, The exhaust gas recirculation apparatus according to claim 11, wherein the difference between the amount of exhaust gas present and the predetermined amount is greater than or equal to the predetermined value.

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