JP2010090806A - Exhaust gas recirculation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation system wherein a mixture gas from which condensate produced in the mixture gas of intake air and EGR gas has been removed is supplied to the intake system of an engine. <P>SOLUTION: The exhaust gas recirculation system 101 is used for the engine 1 provided with a turbocharger 2. The system 101 is provided with: an intake passage 11 communicating with an intake port 2aa of the turbocharger 2; an EGR gas passage 41 which is connected to an EGR connection 11b in the intake passage 11 so as to recirculate the exhaust gas to the intake passage 11 as EGR gas; and a variable vane 21 which is placed between an EGR connection 11b in the intake passage 11 and an intake port 2aa of the turbocharger 2, and causes swirl flow swirling along the internal circumference of the intake passage 11 in compressor suction gas flowing in the intake passage 11, and being composed of suction air to the intake passage 11 and the EGR gas. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation system used for an internal combustion engine including a supercharger.

  In recent years, emission regulations of nitrogen oxides (NOx) in engines such as automobiles have become stricter. However, in a diesel engine, combustion is performed in a state where the air is excessive with respect to the stoichiometric air-fuel ratio. Therefore, a three-way catalyst used in a gasoline engine may be used to reduce nitrogen oxide emissions. Can not. Therefore, in a diesel engine, an EGR system that lowers the combustion temperature in the engine and suppresses the generation of nitrogen oxides by recirculating part of the exhaust gas as EGR gas to the intake system of the engine and mixing it with the intake mixed gas. Commonly used.

  In particular, in diesel engines, nitrogen oxides (NOx) can be reduced by recirculating EGR gas to the intake system of the engine and lowering the combustion temperature in an operating region where there is sufficient oxygen for combustion. Can be increased. On the other hand, when a large amount of EGR gas is recirculated, the temperature of the mixed gas supplied to the combustion chamber increases, and the combustion temperature of the engine cannot be effectively reduced. Moreover, when the amount of oxygen is insufficient, soot is generated. Therefore, when the volume of the mixed gas that can be supplied into the engine cylinder is the same, even if a large amount of EGR gas is supplied by cooling the high-temperature EGR gas that is refluxed and reducing the volume of the EGR gas, Sufficient oxygen can be supplied while lowering the combustion temperature. Therefore, an EGR cooler is provided in the EGR gas passage that is recirculated to the engine.

  For example, in Patent Document 1, a turbocharger connected to an intake manifold and an exhaust manifold of an engine is provided. Further, an inlet portion is connected in the middle of the exhaust pipe connected to the turbine housing on the exhaust side of the turbocharger, and an outlet portion is provided in the middle of the intake pipe connected to the compressor housing on the intake side of the turbocharger. A connected EGR gas pipe is provided. Furthermore, the EGR gas pipe has a soot trap for capturing solid soot contained in the EGR gas flowing through the inside from the inlet portion toward the outlet portion, an EGR cooler for cooling the EGR gas, and EGR EGR rate control valves for controlling the gas recirculation amount are sequentially provided, and these constitute an EGR gas recirculation circuit, that is, an EGR system together with the EGR gas pipe. This EGR system recirculates exhaust gas that has passed through a turbo turbine upstream of a turbocharger compressor, and is called LPL (Low Pressure Loop) -EGR. Since LPL-EGR uses the exhaust gas after passing through the turbo turbine as EGR gas, the exhaust gas energy is recovered and effectively used to improve the turbocharger supercharging pressure, and the EGR gas before supercharging. Since it recirculates to the intake passage, it has a feature that enables a large amount of EGR gas to recirculate.

Japanese Patent Laid-Open No. 5-71428

However, in the EGR gas recirculation circuit of Patent Document 1, an EGR cooler is provided as means for reducing the temperature of the recirculating EGR gas, but condensed water is generated when the EGR gas is cooled in the EGR cooler. Further, the EGR gas generates condensed water due to a temperature difference from the intake air when mixed with the outside air taken into the engine, that is, the intake air. In the LPL-EGR system, a large amount of EGR gas is recirculated to low-temperature intake air before supercharging, so that a large amount of condensed water is generated.
When this large amount of condensed water is contained in the mixed gas of EGR gas and intake air and is sucked into the compressor housing of the turbocharger, the impeller of the compressor wheel is damaged by the sucked condensed water. There is a problem.
The EGR gas contains sulfur, oxygen, nitrogen and hydrogen. For this reason, condensed water may be mixed with these substances to form an acidic aqueous solution such as sulfuric acid or nitric acid, or an alkaline aqueous solution such as ammonia water. When such an acidic or alkaline aqueous solution is sucked into the intake pipe, there is a problem that corrosion occurs in the turbocharger, the engine intake system, and the engine.

  The present invention has been made to solve such problems, and an exhaust gas recirculation system for supplying a mixed gas from which condensed water generated in a mixed gas of intake air and EGR gas is removed to an intake system of an engine. The purpose is to provide.

  An exhaust gas recirculation system according to the present invention is an exhaust gas recirculation system used for an internal combustion engine including a supercharger, and includes an intake passage communicating with an intake port of the supercharger and an EGR connection portion in the intake passage. EGR gas passage that is connected and recirculates as exhaust gas as EGR gas to the intake passage, and is provided between the EGR connection portion of the intake passage and the intake port of the supercharger, and intake air to the intake passage that circulates through the intake passage And a swirl flow generating means for generating a swirl flow swirling along the inner periphery of the intake passage in the mixed gas composed of EGR gas, and centrifugal separation between the intake port of the supercharger and the wing-like body in the intake passage And a gas-liquid separator that separates the gas and liquid. First, the EGR gas generates condensed water when cooled by the EGR cooler and when mixed with the intake air into the internal combustion engine. In view of this, this exhaust gas recirculation system uses a swirl flow generating means provided in the intake passage to prevent a mixed gas composed of EGR gas and intake air between the swirl flow generating means and the intake port of the supercharger in the intake passage. To generate a swirling flow. And the condensed water contained in mixed gas is centrifuged by this swirl | vortex flow in a gas-liquid separation part. Accordingly, the condensed water contained in the mixed gas, which is generated by being cooled by the EGR cooler and contained in the EGR gas, and the condensed water generated when the EGR gas is mixed with the intake air are Since the mixed gas is removed before being sucked into the intake port, it is possible to prevent the turbocharger and further the internal combustion engine from being damaged by the condensed water.

  The swirling flow generating means may be a rotatable wing-like body, and the rotating speed of the swirling flow generated in the mixed gas may be changed according to the rotation angle of the wing-like body. As a result, the rotating speed of the swirling flow of the mixed gas is changed by rotating the rotatable wing-like body, so that the rotating speed of the swirling flow is ensured regardless of the flow rate and flow velocity of the mixed gas flowing to the wing-like body. can do. Therefore, the rotational force of the swirling flow can be adjusted according to the operating conditions of the internal combustion engine, and the condensed water contained in the mixed gas can be effectively removed.

The gas-liquid separation unit may have a liquid discharge port for discharging the liquid inside the gas-liquid separation unit. Thereby, the condensed water centrifuged in the gas-liquid separator is discharged from the liquid outlet to the outside of the gas-liquid separator.
The gas-liquid separation unit may have a double-pipe gas-liquid separation structure. As a result, the gas-liquid separation part has a double-pipe gas-liquid separation structure, so that the condensed gas is effectively removed by the swirling flow of the mixed gas composed of the EGR gas and the intake air.

  An air amount detecting means for detecting the intake air amount to the intake passage, an EGR rate calculating means for calculating an EGR rate based on the operating conditions of the internal combustion engine, and a condensed water generation amount calculation for calculating a condensed water generation amount in the mixed gas And the intake water amount detected by the air amount detection means, the EGR rate calculated by the EGR rate calculation means, and the condensed water generation amount calculated by the condensed water generation amount calculation means. Rotation angle determination means for determining the rotation angle of the wing-like body that generates the swirling flow that separates the two. Thereby, the rotation angle of the wing body can be determined in accordance with the operating conditions of the internal combustion engine, and the condensed water contained in the mixed gas can be removed. Furthermore, by controlling the wing body in accordance with the operating conditions of the internal combustion engine, the wing body becomes an intake resistance and affects the internal combustion engine at the time of high rotation of the internal combustion engine or when EGR gas does not flow into the intake passage, etc. Since the airfoil is controlled so as to reduce the intake pressure loss due to the airfoil, the performance of the internal combustion engine can be improved.

  Furthermore, an air amount detecting means for detecting the intake air amount to the intake passage, an EGR rate calculating means for calculating an EGR rate based on the operating conditions of the internal combustion engine, and a condensed water generation for calculating the amount of condensed water generated in the mixed gas Included in the mixed gas based on the amount of intake air detected by the amount calculating means and the air amount detecting means, the EGR rate calculated by the EGR rate calculating means, and the amount of condensed water generated calculated by the condensed water generation amount calculating means First rotation angle calculation means for calculating a first reference value that is a rotation angle of a wing body that generates a swirling flow for separating condensed water, and first pressure detection means for detecting a first pressure at the intake port of the supercharger A second pressure detecting means for detecting a second pressure in a passage for supplying a mixed gas from the supercharger to the internal combustion engine, and a compressor for calculating a compressor pressure ratio that is a ratio of the second pressure to the first pressure Based on the intake air amount detected by the pressure ratio calculation means, the air amount detection means, the EGR rate calculated by the EGR rate calculation means, and the compressor pressure ratio calculated by the compressor pressure ratio calculation means, the intake air of the supercharger Second rotation angle calculation means for calculating a second reference value that is a rotation angle of the winged body that generates a swirling flow that prevents surging at the mouth, and a first reference value and a second rotation calculated by the first rotation angle calculation means You may provide the 3rd rotation angle determination means which selects one from the 2nd reference values calculated by an angle calculation means, and determines the rotation angle of a winged body. Thus, in accordance with the operating conditions of the internal combustion engine, the rotation angle of the airfoil that enables the removal of condensed water contained in the mixed gas is calculated, and the airfoil that enables the supercharger intake port to prevent surging The rotation angle of the body can be calculated. Then, by selecting one of the rotation angles of these two wings and determining the rotation angle of the wings, not only the separation of the condensed water from the mixed gas but also the surging in the supercharger can be prevented. .

  A method of recirculating exhaust gas according to the present invention includes a supercharger, an intake passage communicating with an intake port of the supercharger, and an EGR gas passage connected to the intake passage and recirculating to the intake passage as exhaust gas as EGR gas In the internal combustion engine, the exhaust gas is regenerated while generating a swirling flow in the mixed gas composed of the intake air and the EGR gas to the intake passage between the EGR gas passage in the intake passage and the intake port of the supercharger. (A) a step of detecting an intake air amount into the intake passage; (b) a step of calculating an EGR rate based on operating conditions of the internal combustion engine; and (c) an intake air and EGR gas. And (d) a swirling flow of the mixed gas based on the detected intake air amount, the calculated EGR rate, and the calculated condensed water generation amount. For separating the condensed water contained, and performing the step of determining the magnitude of the swirling flow. Thereby, the magnitude | size of a turning flow can be determined according to the driving | running condition of an internal combustion engine, and the condensed water contained in mixed gas can be removed.

  The exhaust gas recirculation method according to the present invention includes a supercharger, an intake passage communicating with the intake port of the supercharger, and an EGR connected to the intake passage and recirculated to the intake passage as exhaust gas as EGR gas. In an internal combustion engine having a gas passage, exhaust gas is generated while generating a swirling flow in a mixed gas composed of intake air and EGR gas into the intake passage between the EGR gas passage in the intake passage and the intake port of the supercharger. (A) detecting the amount of intake air into the intake passage, (b) calculating an EGR rate based on operating conditions of the internal combustion engine, (c) intake air and A step of calculating a condensed water generation amount in the mixed gas composed of EGR gas; and (d) a swirling flow of the mixed gas is mixed based on the detected intake air amount, the calculated EGR rate, and the calculated condensed water generation amount. A step of calculating a first magnitude of the swirl flow for separating condensed water contained in the gas; and (e) a first pressure at an intake port of the supercharger and a mixed gas from the supercharger to the internal combustion engine. Detecting a second pressure in the supply passage and calculating a compressor pressure ratio that is a ratio between the second pressure and the first pressure; and (f) a detected intake air amount, a calculated EGR rate, and a calculated And (g) calculating the second magnitude of the swirling flow to prevent surging of the swirling flow of the mixed gas at the intake port of the supercharger, and (g) step (d). Selecting one of the first swirl flow size and the second swirl flow size calculated in step (f) and determining the swirl flow size. To do.

  Thus, in accordance with the operating conditions of the internal combustion engine, the size of the swirling flow that enables the removal of condensed water contained in the mixed gas is calculated, and the swirling that enables the supercharger intake port to be prevented from surging. The magnitude of the flow can be calculated. Then, by selecting one of these two calculated swirl flow sizes and determining the swirl flow size, not only the separation of the condensed water from the mixed gas but also the prevention of surging in the supercharger is achieved. It becomes possible.

  According to the present invention, it is possible to supply a mixed gas from which condensed water generated in a mixed gas of intake air and EGR gas is removed to an intake system of an engine.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the following embodiment shows the form used for the vehicle carrying a diesel engine.
Embodiment First, the configuration of an internal combustion engine including an exhaust gas recirculation system 101 according to an embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 1, a diesel engine 1 as an internal combustion engine communicates with a turbocharger 2 as a supercharger, but communicates with a compressor housing 2a including a compressor wheel 2c therein by an engine intake passage 1b. The engine 1 communicates with a turbine housing 2b including a turbine wheel 2d therein through an engine exhaust passage 1c. The turbocharger 2 rotates the turbine wheel 2d by the exhaust gas supplied from the engine 1 through the engine exhaust passage 1c, and rotates the compressor wheel 2c connected to the turbine wheel 2d through the turbine shaft 2e. . Further, the intake air pressurized by the rotation of the compressor wheel 2c is supplied to the engine 1 via the engine intake passage 1b, and the output of the engine 1 is improved.

One end of the exhaust passage 3 is connected to the exhaust port 2ba in the turbine housing 2b of the turbocharger 2. Further, the other end of the exhaust passage 3 is connected to a muffler 4 that reduces exhaust noise during operation of the engine 1, and the exhaust gas in the exhaust passage 3 is discharged to the outside through the muffler 4.
Further, between the turbocharger 2 and the muffler 4, the exhaust passage 3 has a DPF (diesel particulate filter) device that is a filter that captures particulate matter contained in the exhaust gas, and nitrogen contained in the exhaust gas. An exhaust gas treatment device 5 including a catalyst device for reducing the oxide content is provided. Further, an exhaust temperature sensor 15 for detecting the temperature of the exhaust gas is provided between the exhaust gas processing device 5 and the muffler 4 in the exhaust passage 3. The exhaust temperature sensor 15 is electrically connected to the ECU 8 of the vehicle (not shown) and sends detected exhaust temperature information to the ECU 8.

On the other hand, a gas-liquid separator 6 that is a gas-liquid separator having a substantially cylindrical shape is provided at the intake port 2aa in the compressor housing 2a of the turbocharger 2.
Here, referring to FIG. 2, the gas-liquid separator 6 has a substantially cylindrical outer shell 6a whose cross-sectional area increases in two steps toward the air inlet 2aa. In the outer shell 6a, a cylindrical portion having a substantially cylindrical shape is constituted by two cylindrical portions, ie, a first cylindrical portion 6ab and a second cylindrical portion 6ac having a cylindrical shape having different cross-sectional areas. The second cylindrical portion 6ac has a cylindrical diameter smaller than that of the first cylindrical portion 6ab. Further, the first cylindrical portion 6ab and the second cylindrical portion 6ac are arranged in the order of the first cylindrical portion 6ab and the second cylindrical portion 6ac from the intake port 2aa side, and the axial centers thereof are the same in the axial direction. It is connected. The outer shell 6a has an end surface 6aa on the first cylindrical portion 6ab and an end surface 6ad on the second cylindrical portion 6ac.

  The gas-liquid separator 6 has a gas discharge path 6b that penetrates the end face 6aa on the intake port 2aa side of the turbocharger 2 and protrudes into the outer shell 6a. The gas discharge path 6b Externally connected to the intake port 2aa. The end 6ba of the gas discharge path 6b in the outer shell 6a extends to the middle of the first cylindrical part 6ab, and the diameter of the gas discharge path 6b is smaller than the diameter of the substantially cylindrical outer shell 6a. ing. Furthermore, the axial center of the gas exhaust path 6b is the same as the axial center of the first cylindrical portion 6ab. Therefore, the gas-liquid separator 6 is a double-tube type gas-liquid separator having a double-tube structure with the outer shell 6a and the gas discharge path 6b.

  Further, the second cylindrical portion 6ac of the outer shell 6a of the gas-liquid separator 6 has four variable fan blades 21 that are plate-like wings having a substantially fan shape along the inner peripheral surface of the second cylindrical portion 6ac. Are provided at equal intervals (see FIG. 3). The variable wing 21 is formed so that two substantially fan-shaped wing portions 21b are opposed to a cylindrical surface of a shaft portion 21a which is a rotation center axis thereof. Furthermore, the variable wing 21 is attached such that its shaft portion 21a is directed to the second cylindrical portion 6ac in the radial direction, and is further rotatable about the shaft portion 21a. Further, the shaft portion 21 a of each variable blade 21 protrudes outside the gas-liquid separator 6 and is connected to the control motor 22 (see FIG. 1) by a link mechanism (not shown), and rotates by the power of the control motor 22. It is like that. Further, the control motor 22 is electrically connected to the ECU 8 (see FIG. 1), and operates under the control of the ECU 8.

  Therefore, the variable blade 21 rotates from the end face 6ad of the gas-liquid separator 6 by rotating so that the central axis 21CL has an inclination angle α with respect to the axis of the second cylindrical portion 6ac of the gas-liquid separator 6. A swirling flow swirling in the direction A (see FIG. 3) is generated along the inner circumference of the second cylindrical portion 6ac and the first cylindrical portion 6ab with respect to the gas flowing toward the end face 6aa. That is, the variable blade 21 constitutes a swirl flow generating means. Further, the rotation speed of the generated swirling flow changes depending on the inclination angle α of the variable blade 21, that is, the rotation angle, thereby changing the rotating force of the swirling flow. As the inclination angle α increases, the rotational force of the swirling flow increases. Note that the swirl flow forms a spiral flow that swirls in the direction A (see FIG. 3) and travels from the end surface 6ad of the gas-liquid separator 6 toward the end surface 6aa. The speed in the rotational direction of the swirling flow on a plane perpendicular to the axis of the gas-liquid separator 6 is shown. Furthermore, the rotational force of the swirl flow indicates the force by which the swirl flow rotates in the direction of the rotation speed of the swirl flow. The direction A of the swirling flow is set to be the same direction as the rotation direction of the compressor wheel 2c.

Further, a liquid discharge path 6c is connected to the lower part of the first cylindrical portion 6ab of the outer shell 6a in the gas-liquid separator 6, and the liquid discharge path 6c opens inside the outer shell 6a at the liquid discharge port 6ca. ing. The liquid discharge port 6ca is disposed on the end surface 6aa side of the outer shell 6a from the end portion 6ba of the gas discharge path 6b, that is, on the intake port 2aa side of the turbocharger 2.
Returning to FIG. 1, a first pressure sensor 16 for detecting a first pressure, which is a pressure of gas sucked into the compressor housing 2 a via the intake port 2 aa, is provided at the intake port 2 aa of the turbocharger 2. Yes. The first pressure sensor 16 constitutes first pressure detection means.
Further, a compressor exhaust port 2ab which is a connection portion between the compressor housing 2a of the turbocharger 2 and the engine intake passage 1b has a pressure of gas discharged from the compressor housing 2a through the compressor exhaust port 2ab to the engine 1. A second pressure sensor 17 for detecting two pressures is provided. The second pressure sensor 17 constitutes second pressure detection means.
The first pressure sensor 16 and the second pressure sensor 17 are each electrically connected to the ECU 8, and send detected pressure value information to the ECU 8.

One end of the intake passage 11 is connected to an end face 6ad (see FIG. 2) facing the gas discharge path 6b in the gas-liquid separator 6. The diameter of the intake passage 11 is smaller than the diameter of the second cylindrical portion 6ac of the gas-liquid separator 6 (see FIG. 2). In the connection portion 11 a (see FIG. 2) of the intake passage 11 with the gas-liquid separator 6, the axis of the intake passage 11 is the same as the axis of the gas discharge path 6 b of the gas-liquid separator 6.
Here, the gas-liquid separator 6 forms a part of an intake passage, and the gas-liquid separator 6 and the intake passage 11 constitute an intake passage communicating with the intake port 2aa of the turbocharger 2.

The other end of the intake passage 11 is connected to the air cleaner 7 so that outside air is introduced into the intake passage 11 via the air cleaner 7. The air cleaner 7 captures dust, dust, foreign matter, and the like contained in the outside air and prevents them from entering the engine 1 and the turbocharger 2.
Further, in the intake passage 11, an air amount sensor 12, which is an air amount detection means for detecting the intake air amount of the outside air to the intake passage 11, and a temperature of the outside air sucked into the intake passage 11 are detected. An intake air temperature sensor 13 is provided. Each of the air amount sensor 12 and the intake air temperature sensor 13 is electrically connected to the ECU 8, and sends the detected intake air amount information and intake air temperature information to the ECU 8. The intake passage 11 is provided with a humidity sensor 14 for detecting the humidity of the outside air taken into the intake passage 11. The humidity sensor 14 is also electrically connected to the ECU 8 and sends the detected humidity information to the ECU 8.

Further, an EGR gas passage 41 is provided in which one end is connected between the exhaust gas processing device 5 and the muffler 4 in the exhaust passage 3 and the other end is connected to the EGR connection portion 11 b in the intake passage 11. Yes. The EGR gas passage 41 returns a part of the exhaust gas discharged from the engine 1 to the upstream of the compressor housing 2a of the turbocharger 2 that is an intake system of the engine 1 as EGR gas.
Further, an EGR cooler 51 for cooling the EGR gas is provided in the middle of the EGR gas passage 41. In the EGR gas passage 41, an EGR valve 61, which is an EGR opening / closing valve that opens and closes the EGR gas passage 41, is provided between the EGR cooler 51 and the intake passage 11. The EGR valve 61 is electrically connected to the ECU 8, and the flow path cross-sectional area of the EGR gas passage 41 can be changed from 0 to 100% under the control of the ECU 8.

  Therefore, the EGR system is configured by the EGR gas passage 41, the EGR cooler 51, and the EGR valve 61. The EGR system recirculates the exhaust gas treated by the DPF device and the catalyst device in the exhaust gas treatment device 5 to the upstream side of the turbocharger 2 and is called LPL (Low Pressure Loop) -EGR. The LPL-EGR has a feature that enables recirculation of a large amount of EGR gas at a low temperature and further improves the supercharging pressure of the turbocharger 2 by recovering and effectively using exhaust energy.

In addition, the liquid discharge path 6c of the gas-liquid separator 6 communicates with the inside of the liquid storage 71 for storing the liquid discharged from the liquid discharge path 6c. Further, one end of a liquid storage discharge path 81 is connected to the liquid reservoir 71, and the other end of the liquid storage discharge path 81 is connected to the exhaust passage 3 between the EGR gas passage 41 and the muffler 4. Connected. Therefore, the liquid in the liquid accumulator 71 is discharged upstream of the muffler 4 in the exhaust passage 3 via the liquid storage discharge path 81. Further, an opening / closing valve 91 for opening and closing the liquid storage discharge path 81 is provided in the middle of the liquid storage discharge path 81. The on-off valve 91 is electrically connected to the ECU 8, and the flow path cross-sectional area of the liquid storage discharge path 81 can be changed from 0 to 100% under the control of the ECU 8.
As described above, the exhaust gas recirculation system 101 according to the embodiment of the present invention includes the intake passage 11, the gas-liquid separator 6, the variable vane 21, and the EGR gas passage 41.

Next, the operation of the engine 1 including the exhaust gas recirculation system 101 and the exhaust gas recirculation system 101 according to the embodiment of the present invention will be described with reference to FIGS.
First, the operation of the engine 1 will be described.
Referring to FIG. 1, when the engine 1 is operating, outside air is drawn into the intake passage 11 via the air cleaner 7. Further, the sucked outside air, that is, the sucked air flows directly into the gas-liquid separator 6 through the suction passage 11. Then, the intake air that has flowed into the gas-liquid separator 6 is sucked into the compressor housing 2 a of the turbocharger 2.

  The intake air drawn into the compressor housing 2a of the turbocharger 2 is supercharged by the compressor wheel 2c in the compressor housing 2a and sent to the engine intake passage 1b. The sent intake air is supplied to the engine 1 in a supercharged state, and the fuel injected in the cylinder 1a of the engine 1 and the intake air are mixed and fueled by self-ignition. Thereafter, the exhaust gas is discharged into the engine exhaust passage 1c. The discharged exhaust gas flows into the turbine housing 2b of the turbocharger 2, and is discharged into the exhaust passage 3 while increasing the rotation of the internal turbine wheel 2d and the compressor wheel 2c connected to the turbine wheel 2d. The exhaust gas discharged into the exhaust passage 3 is discharged to the outside of the vehicle (not shown) via the muffler 4 after the contents of particulate matter and nitrogen oxides are reduced in the exhaust gas processing device 5.

Next, the operation of the exhaust gas recirculation system 101 will be described.
Referring to FIG. 1, a part of the exhaust gas that has passed through the exhaust gas processing device 5 flows into the EGR gas passage 41. The exhaust gas that flows in, that is, the EGR gas, is cooled by the EGR cooler 51 and then flows into the intake passage 11 via the EGR valve 61. The inflow EGR gas is mixed with the intake air sucked into the intake passage 11 through the air cleaner 7, flows into the gas-liquid separator 6, and then mixed with the intake air, It circulates similarly. The EGR gas generates condensed water when cooled by the EGR cooler 51, and flows into the intake passage 11 in a state including the generated condensed water. Further, when the EGR gas flowing into the intake passage 11 is mixed with the intake air in the intake passage 11, further condensed water is generated due to a temperature difference with the intake air. Therefore, the compressor intake gas, which is a mixed gas of EGR gas and intake air, flows into the gas-liquid separator 6 in a state including the condensed water generated in the EGR cooler 51 and the intake passage 11.

The amount of EGR gas flowing into the gas-liquid separator 6, that is, the amount of recirculation to the intake system of the engine 1 is adjusted by the ECU 8 by controlling the degree of opening and closing of the EGR valve 61.
Note that the ECU 8 stores in advance a predetermined EGR rate in accordance with operating conditions such as the rotational speed and load of the engine 1. Then, the ECU 8 calculates an EGR rate that conforms to the operating condition of the engine 1, and further, based on the intake air amount information detected by the air amount sensor 12, the recirculation amount of the EGR gas is calculated to the calculated EGR rate. The EGR valve 61 is controlled to fit. Therefore, ECU8 comprises the EGR rate calculation means. The EGR rate is indicated by EGR gas flow rate / (EGR gas flow rate + intake air amount).

  Next, when the variable blade 21 is in the state shown in FIG. 2 under the control of the ECU 8, the central shaft 21CL of the variable blade 21 is inclined by the inclination angle α with respect to the axis of the second cylindrical portion 6ac of the gas-liquid separator 6. It is in the state. At this time, the direction of the flow of the compressor intake gas composed of EGR gas and intake air flowing into the second cylindrical portion 6ac from the intake passage 11 is changed by the action of the variable vane 21. As shown in FIG. 3, a swirling flow in the direction A along the inner periphery of the second cylindrical portion 6ac is generated. As the inclination angle α of the variable vane 21 increases, the rotational speed of the swirling flow of the compressor intake gas due to the action of the variable vane 21 increases.

  The compressor suction gas that has generated the swirl flow flows toward the gas discharge path 6b while swirling along the inner circumferences of the second cylindrical portion 6ac and the first cylindrical portion 6ab, that is, flows in a spiral manner. . Then, the compressor intake gas is sucked into the turbocharger 2 from the intake port 2aa via the gas discharge path 6b. The centrifugal force generated by the rotation of the compressor intake gas causes the EGR cooler 51 (see FIG. 1) to cool and the condensed water contained in the EGR gas and the EGR gas are mixed with the intake air. The condensed water contained in the compressor suction gas is then centrifuged from the compressor suction gas and adheres to the inner peripheral surfaces of the first cylindrical portion 6ab and the second cylindrical portion 6ac of the gas-liquid separator 6. The effect of the separation of the condensed water contained in the compressor intake gas is increased by increasing the rotation speed of the swirling flow of the compressor intake gas.

Further, since the swirl flow of the compressor intake gas has a shape that expands in a spiral shape and its swirl radius increases, the flow rate and flow velocity of the compressor intake gas flowing to the variable blade 21 in the intake passage 11 are small. Even in this case, centrifugal force acts on the condensed water contained in the inside, and effective centrifugal separation of the condensed water is possible.
The adhering condensed water is formed into water droplets by the condensed water centrifugally separated from the compressor suction gas, and flows down to the bottom along the inner peripheral surface of the gas-liquid separator 6. The water droplets flowing down to the bottom part flow to the first cylindrical part 6ab, and are discharged to the outside of the gas-liquid separator 6 from the liquid discharge port 6ca provided at the bottom part of the first cylindrical part 6ab via the liquid discharge path 6c. .
In addition, since the gas discharge path 6b protrudes inside from the end surface 6aa of the gas-liquid separator 6 to form a double pipe structure, the condensed water that has been centrifuged does not flow into the gas discharge path 6b. . Therefore, only the compressor intake gas composed of the EGR gas and the intake air from which the condensed water is separated and removed flows into the gas discharge path 6b.
Therefore, the condensed water contained in the compressor intake gas is prevented from entering the turbocharger 2 and further the engine 1 (see FIG. 1).

  Referring to FIG. 1, the condensed water discharged from the gas-liquid separator 6 is stored in the liquid storage 71 through the liquid discharge path 6c. The accumulator 71 communicates with the exhaust passage 3 via the accumulator discharge path 81, and the water stored in the accumulator 71 is discharged between the EGR gas passage 41 and the muffler 4 in the exhaust passage 3. The The discharged water is steamed by the exhaust temperature of the exhaust gas and discharged outside the vehicle (not shown). In addition, the discharge flow rate of the water from the liquid reservoir 71 is adjusted by changing the flow path cross-sectional area of the liquid storage discharge path 81 by the opening / closing valve 91 provided in the liquid storage discharge path 81. Further, the opening / closing of the opening / closing valve 91 is controlled by the ECU 8 based on information such as a storage amount in the liquid storage 71 and an exhaust temperature in the exhaust passage 3.

  On the other hand, when the variable blade 21 is in the state shown in FIG. 4 under the control of the ECU 8, the central axis 21CL of the variable blade 21 is parallel to the axis of the second cylindrical portion 6ac of the gas-liquid separator 6 ( (See FIG. 5). At this time, the compressor intake gas composed of the EGR gas and the intake air that has flowed into the second cylindrical portion 6ac from the intake passage 11 directly flows into the gas discharge passage 6b through the second cylindrical portion 6ac and the first cylindrical portion 6ab. Then, the air is sucked into the turbocharger 2 through the intake port 2aa. Therefore, the compressor intake gas composed of the EGR gas and the intake air sucked into the gas-liquid separator 6 from the intake passage 11 is sucked into the intake port 2aa of the turbocharger 2 without generating a swirling flow.

  Note that the ECU 8 (see FIG. 1) indicates that the intake resistance received from the variable vanes 21 in the compressor intake gas sucked into the intake port 2aa is, for example, when the engine 1 (see FIG. 1) is in a high rotation state. 1), the variable blade 21 is controlled so as to be in the state shown in FIG. 4 in order to reduce the pressure loss due to the intake resistance. Further, the ECU 8 (see FIG. 1) controls the variable blade 21 to be in the state shown in FIG. 4 even when the EGR valve 61 is closed and the EGR gas does not flow from the EGR gas passage 41 to the intake passage 11. Further, at this time, since the intake pressure loss of the engine 1 (see FIG. 1) is reduced, the performance of the engine 1 (see FIG. 1) is improved.

Next, a detailed control method of the variable blade 21 will be described below.
Referring to FIG. 6, a flowchart for obtaining the inclination angle α (see FIG. 2) of the variable blade 21 is shown.
First, in step S1, intake air amount information detected by the air amount sensor 12 (see FIG. 1) is sent to the ECU 8 (see FIG. 1).
In step S2, the ECU 8 (see FIG. 1) calculates the EGR rate corresponding to the information based on the detected value of the intake air amount sent and the rotational speed or load of the engine 1 (see FIG. 1). To do. Further, the ECU 8 (see FIG. 1) determines the degree of opening / closing of the EGR valve 61 (see FIG. 1) so as to match the calculated EGR rate, and issues a command to the control motor 22 so as to match the determined degree of opening / closing. The feed EGR valve 61 (see FIG. 1) is operated.
Furthermore, it progresses to step S3 and ECU8 (refer FIG. 1) selects the step which advances next from either step S4 or S6. Therefore, the ECU 8 (see FIG. 1) selects step S4 when the opening degree of the EGR valve 61 (see FIG. 1) is larger than 0%. The ECU 8 (see FIG. 1) selects step S6 when the opening degree of the EGR valve 61 (see FIG. 1) is 0%.

In step S4, the ECU 8 (see FIG. 1) calculates a condensed water generation amount W in the compressor intake gas in which the EGR gas and the intake air are mixed.
Here, the calculation of the condensed water generation amount W is performed based on the flowchart shown in FIG. 7, and this calculation method will be described below.
First, in step S21, the intake air amount detected by the air amount sensor 12 (see FIG. 1) and the detected value of the intake air temperature by the intake temperature sensor 13 (see FIG. 1) are sent to the ECU 8 (see FIG. 1). The detected value of the intake air amount is the same as that in step S1 (see FIG. 6) described above.
In step S22, the ECU 8 (see FIG. 1) calculates the saturated water vapor amount of the intake air from the intake air temperature. Further, the ECU 8 (see FIG. 1) acquires the detected value of the humidity of the intake air detected by the humidity sensor 14 (see FIG. 1) provided in the intake passage 11, and the detected value of the humidity, the intake air amount, The amount of moisture in the intake air is calculated from the calculated saturated water vapor amount. The humidity detection value may be set to a fixed value in advance without providing the humidity sensor 14 (see FIG. 1). In this case, the fixed value of humidity is set so as to be calculated on the safe side, that is, the amount of condensed water generated, that is, on the side with a large amount of water, for example, set to a high value of 90%.

Next, in step S23, the ECU 8 (see FIG. 1) acquires the detected value of the exhaust gas temperature detected by the exhaust temperature sensor 15 (see FIG. 1) provided in the exhaust passage 3 (see FIG. 1). . The detected value of the exhaust gas temperature may be calculated from the intake air amount and the rotational speed of the engine 1 (see FIG. 1) without providing the exhaust temperature sensor 15 (see FIG. 1). A fuel injection amount to the engine 1 (see FIG. 1) is calculated from the intake air amount based on a preset air-fuel ratio, and a corresponding exhaust gas temperature is calculated from this fuel injection amount and the rotational speed of the engine 1 (see FIG. 1). Can be calculated.
In step S24, the ECU 8 (see FIG. 1) calculates the amount of water generated by the combustion of the injected fuel from the fuel injection amount. Further, the ECU 8 (see FIG. 1) calculates the moisture content in the exhaust gas from the sum of the moisture content by the fuel and the moisture content in the intake air calculated in step S22.

Next, it progresses to step S25 and ECU8 (refer FIG. 1) calculates an EGR rate. This EGR rate is the EGR rate calculated in step S2 (see FIG. 6).
Thereafter, the process proceeds to step S26, where the ECU 8 (see FIG. 1) determines the EGR gas from the intake air amount and intake air temperature detected in step S21, the exhaust gas temperature detected in step S23, and the EGR rate calculated in step S24. And the temperature of the compressor intake gas comprising intake air is calculated.
In step S27, the ECU 8 (see FIG. 1) determines the moisture content in the intake air calculated in step S22, the exhaust gas temperature detected in step S23, the moisture content in the exhaust gas calculated in step S24, and the step. The amount of moisture in the compressor intake gas is calculated from the EGR rate calculated in S25.

Further, the process proceeds to step S28, and the ECU 8 (see FIG. 1) calculates a dew point temperature corresponding to the moisture content in the compressor intake gas calculated in step S27. The dew point temperature is easily calculated by storing a map indicating the relationship between the saturated water vapor amount and the dew point temperature in advance in the ECU 8 (see FIG. 1) and using this map.
Finally, the process proceeds to step S29. The ECU 8 (see FIG. 1) calculates the amount of water condensed in the compressor intake gas from the difference between the dew point temperature calculated in step S28 and the compressor intake gas temperature calculated in step S26. The amount of condensed water can also be calculated from the difference between the amount of moisture in the compressor intake gas calculated in step S27 and the amount of saturated water vapor at the compressor intake gas temperature calculated in step S26.
Further, steps S21 to S29 are performed in series, and a series of steps S21 to S29 are repeated every predetermined unit period.
Therefore, ECU8 (refer FIG. 1) comprises the condensed water generation amount calculation means.

Returning to FIG. 6, following step S <b> 4, the process proceeds to step S <b> 5, where the ECU 8 (see FIG. 1) first calculates the compressor intake gas flow rate from the intake air amount sent in step S <b> 1 and the EGR rate calculated in step S <b> 2. The compressor intake gas amount G is calculated. Further, the ECU 8 (see FIG. 1) generates a swirl flow that enables separation of condensed water contained in the compressor intake gas from the compressor intake gas amount G and the condensed water generation amount W calculated in step S4. The inclination angle α (see FIG. 2) of the blade 21 is calculated, and the calculated inclination angle is set as a first reference angle α1 that is the first reference value.
Therefore, the ECU 8 (see FIG. 1) shows the relationship between the compressor intake gas amount G and the condensed water generation amount W and the first inclination angle α1 of the variable blade 21 (see FIG. 2) as shown in FIG. A map is stored.

  The curves Ca1, Ca2, Ca3, and Ca4 in the map of FIG. 8 indicate that the first inclination angle α1 of the variable wing 21 (see FIG. 2) is 0%, 20%, 40%, and 80% when 45 ° is 100%. In these cases, the upper limit of the relationship between the compressor intake gas amount G and the condensed water generation amount W that can separate the condensed water contained in the compressor intake gas is shown. Further, on the map, the region where the first inclination angle α1 is 100% is the region above the curve Ca4, the region 80% is below the curve Ca4 and above the curve Ca3, and the region 40% is below the curve Ca3 and the curve. The area above Ca2, 20% of the area is below the curve Ca2 and above the curve Ca1, and 0% of the area is below the curve Ca1. Therefore, the first inclination angle α1 is obtained from the region to which the point defined by the value of the compressor intake gas amount G and the value of the condensed water generation amount W belongs.

Therefore, for example, on this map, when the compressor intake gas amount G is the value g1 and the condensed water generation amount W is the value w1, the point corresponding to these is GW1, and the variable blade 21 ( The first inclination angle α1 (see FIG. 2) is 80%, that is, 36 °. Therefore, at this time, by setting the first inclination angle α1 of the variable blade 21 (see FIG. 2) to 36 °, the condensed water contained in the compressor intake gas is separated.
In this way, the ECU 8 (see FIG. 1) calculates the first inclination angle α1 of the variable blade 21 (see FIG. 2) based on the map of FIG. The ECU 8 (see FIG. 1) includes first rotation angle calculation means and rotation angle determination means for calculating and determining a first inclination angle α1, which is a first reference value of the rotation angle of the variable blade 21 (see FIG. 2). It is composed.

Accordingly, by increasing the first inclination angle α1 of the variable vane 21 (see FIG. 2) from the map of FIG. 8, the compressor intake gas contains the condensed water contained in the compressor intake gas in accordance with the increase in the condensed water generation amount W. It becomes possible to be separated.
The condensed water generation amount W is greatly affected by the EGR rate as described in step S4 (see FIG. 6). Therefore, it can be said that the map shown in FIG. 8 is a map for determining the first inclination angle α1 of the variable blade 21 (see FIG. 2) based on the EGR rate.
In step S5, the ECU 8 (see FIG. 1) calculates the first inclination angle α1 of the variable vane 21 (see FIG. 2), that is, the rotational force of the swirling flow generated in the compressor intake gas, that is, It can also be said that the rotational speed of the swirling flow is calculated.

Returning to FIG. 6, after step S5 is completed, the process proceeds to step S6. As described above, when the opening degree of the EGR valve 61 (see FIG. 1) is 0% in step S3, it is variable so that the condensed water contained in the compressor intake gas can be separated in steps S4 and S5. Since it is not necessary to calculate the first inclination angle α1 of the blade 21 (see FIG. 2), the process directly proceeds from step S3 to step S6. In this case, the first inclination angle α1 is set to 0 °.
In step S6, referring to FIG. 2, the ECU 8 (see FIG. 1) calculates the compressor pressure ratio Rp = Pim / Pin, which is the ratio of the outlet pressure Pim and the inlet pressure Pin in the compressor housing 2a of the turbocharger 2. . The outlet pressure Pim is a pressure at the compressor exhaust port 2ab of the compressor housing 2a, and is detected by the second pressure sensor 17 (see FIG. 1). The inlet pressure Pin is a pressure at the intake port 2aa of the compressor housing 2a and is detected by the first pressure sensor 16 (see FIG. 1).

Furthermore, detected pressure values at the intake port 2aa and the compressor exhaust port 2ab detected by the first pressure sensor 16 (see FIG. 1) and the second pressure sensor 17 (see FIG. 1) are sent to the ECU 8 (see FIG. 1). The compressor pressure ratio Rp is calculated by the ECU 8 (see FIG. 1). Therefore, ECU8 (refer FIG. 1) comprises the compressor pressure ratio calculation means which calculates compressor pressure ratio Rp.
Since the relationship between the outlet pressure Pim and the inlet pressure Pin depends on the shape of the compressor wheel 2c and the compressor housing 2a, these relationships can be set, for example, as Pin = Pim × Coefficient Ne. Thus, in order to detect the outlet pressure Pim and the inlet pressure Pin, the first pressure sensor 16 (see FIG. 1) is provided at the intake port 2aa of the compressor housing 2a, and the second pressure sensor 17 (see FIG. 1) is provided at the compressor exhaust port 2ab. However, it is only necessary to provide a pressure sensor in any one of them. Therefore, cost can be reduced.

  Returning to FIG. 6, after step S6 ends, the process proceeds to step S7. In step S7, the ECU 8 (see FIG. 1) determines the intake air amount 2aa of the compressor housing 2a of the turbocharger 2 from the compressor intake gas amount G calculated in step S5 and the compressor pressure ratio Rp calculated in step S6. An inclination angle α (see FIG. 2) of the variable blade 21 that generates a swirling flow capable of preventing surging is calculated. Further, the calculated inclination angle is set as a second inclination angle α2 that is the second reference value.

Here, surging will be described below.
Referring to FIG. 2, in the turbocharger 2, the inlet pressure Pin at the intake port 2aa of the compressor housing 2a is smaller than the outlet pressure Pim at the compressor exhaust port 2ab of the compressor housing 2a. For this reason, in the flow rate region where the flow rate of the compressor intake gas is small, the compressor intake gas once flowing into the compressor housing 2a flows backward in the compressor housing 2a, and thus the flow rate and pressure of the compressor intake gas sucked into the intake port 2aa are large. A fluctuating phenomenon occurs. Such a phenomenon is called surging. Due to this surging, the compressor wheel 2c vibrates violently and the stable operation of the turbocharger 2 is impaired.

Still referring to FIG. 10, a compressor map is shown. This compressor map is a plot of the compressor intake gas amount G against the compressor pressure ratio Rp for various rotational speeds of the compressor wheel 2c (see FIG. 2) in the turbocharger 2 (see FIG. 2).
In the map of FIG. 10, curves r1 to r4 plot the compressor intake gas amount G against the compressor pressure ratio Rp for each of the rotation speeds r1 to r4 of the compressor wheel 2c (see FIG. 2). Further, the curves e1 to e4 indicate the suction efficiency of the turbocharger 2, and the suction efficiency is the same in the same curve shape. The inhalation efficiency has a relationship of e1>e2>e3> e4.

  Curve Sa is a surge line indicating the compressor intake gas amount G at which surging occurs at various rotational speeds of the compressor wheel 2c (see FIG. 2). Therefore, by adding an action to the turbocharger 2 (see FIG. 2) that causes the surge line to transition from the curve Sa to the broken curve Sb, surging occurs by further lowering the lower limit value of the compressor intake gas amount G that causes surging. The surge limit can be improved. For example, by causing the compressor intake gas to generate a swirling flow in the same direction as the rotation direction of the compressor wheel 2c (see FIG. 2) upstream of the intake port 2aa (see FIG. 2) of the compressor housing 2a, the flow rate of the compressor intake gas is reduced. Even in a small flow rate region, the backflow of the compressor suction gas in the compressor housing 2a (see FIG. 2) can be suppressed, and the surge limit can be improved.

Returning to the contents of step S7, referring to FIG. 9, the ECU 8 (see FIG. 1) has the compressor intake gas amount G and the compressor pressure ratio Rp and the second inclination angle α2 of the variable vane 21 (see FIG. 2). A map showing the relationship is stored.
The curves Cb1, Cb2, Cb3, and Cb4 in the map of FIG. 9 indicate that the second inclination angle α2 of the variable wing 21 (see FIG. 2) is 0%, 20%, 40%, and 80% when 45 ° is 100%. In these cases, the relationship between the compressor intake gas amount G and the compressor pressure ratio Rp when the surge limit is reached at the intake port 2aa (see FIG. 2) of the turbocharger 2 is shown. Further, on the map, the region where the second inclination angle α2 is 100% is the region on the left side of the curve Cb4, the region of 80% is the region on the right side from the curve Cb4 and the region on the left side of the curve Cb3, and the region of 40% is on the right side from the curve Cb3. The region on the left side of the curve Cb2, the 20% region is on the right side of the curve Cb2, the region on the left side of the curve Cb1, and the region of 0% is on the right side of the curve Cb1. Therefore, the second inclination angle α2 is obtained from the region to which the point defined by the value of the compressor intake gas amount G and the value of the compressor pressure ratio Rp belongs.

Therefore, for example, on this map, when the compressor intake gas amount G is the value g1 and the compressor pressure ratio Rp is the value rp1, the corresponding point is GR1, and the variable blade 21 (see FIG. 2) is 40%, that is, 18 °. Therefore, at this time, by setting the second inclination angle α2 of the variable blade 21 (see FIG. 2) to 18 °, surging at the intake port 2aa (see FIG. 2) of the turbocharger 2 is prevented.
In this way, the ECU 8 (see FIG. 1) calculates the second inclination angle α2 of the variable blade 21 (see FIG. 2) based on the map of FIG. Moreover, ECU8 (refer FIG. 1) comprises the 2nd rotation angle calculation means which calculates 2nd inclination-angle (alpha) 2 which is the 2nd reference value of the rotation angle of the variable wing | blade 21 (refer FIG. 2).

Accordingly, by increasing the second inclination angle α2 of the variable vane 21 (see FIG. 2) from the map of FIG. 9, the intake port 2aa (see FIG. 2) of the turbocharger 2 corresponding to the increase in the compressor pressure ratio Rp. Surging in) can be prevented. Therefore, referring also to FIG. 10, increasing the second inclination angle α2 of the variable vane 21 (see FIG. 2) is the same as improving the surge limit.
9 can be said to be a map for determining the second inclination angle α2 of the variable blade 21 (see FIG. 2) based on the surge limit.
In step S7, the ECU 8 (see FIG. 1) calculates the second inclination angle α2 of the variable vane 21 (see FIG. 2), that is, the rotational force of the swirling flow generated in the compressor intake gas, that is, It can also be said that the rotational speed of the swirling flow is calculated.

  Next, after step S7 ends, the process proceeds to step S8. In step S8, the ECU 8 (see FIG. 1) calculates the first inclination angle α1 of the variable blade 21 (see FIG. 2) for separating the condensed water contained in the compressor intake gas calculated in step S5, and in step S7. From the calculated second inclination angle α2 of the variable blade 21 (see FIG. 2) for preventing surging at the intake port 2aa (see FIG. 2) of the turbocharger 2, the inclination angle α of the variable blade 21 (see FIG. 2). Is calculated. At this time, the ECU 8 (see FIG. 1) selects the larger one of the first inclination angle α1 and the second inclination angle α2 that is on the safe side and has the larger inclination angle. That is, the ECU 8 (see FIG. 1) selects an inclination angle in which the rotational force of the swirling flow of the compressor intake gas generated in the gas-liquid separator (see FIG. 2) is increased.

Thus, for example, in a certain operating state, when the compressor intake gas amount G is g1, the condensed water generation amount W is w1, and the compressor pressure ratio Rp is rp1, the point at which the first inclination angle α1 is determined from FIG. The point which determines 2nd inclination-angle (alpha) 2 from GW1 and FIG. 9 becomes GR1. The first inclination angle α1 at the point GW1 is 36 °, and the second inclination angle α2 at the point GR1 is 18 °. Therefore, at this time, the ECU 8 (see FIG. 1) selects 36 ° of the first inclination angle α1 as the inclination angle α (see FIG. 2) of the variable blade 21.
Therefore, ECU8 (refer FIG. 1) comprises the 3rd rotation angle determination means which determines inclination-angle (alpha) (refer FIG. 2) which is the rotation angle of the variable wing | blade 21. FIG.
Further, after step S8 ends, the process proceeds to step S9, where the ECU 8 (see FIG. 1) controls the control motor 22 (see FIG. 1) so as to conform to the inclination angle α (see FIG. 2) of the variable blade 21 calculated in step S8. Command) to operate the variable wing 21 (see FIG. 2).
Steps S1 to S9 are performed in series, and a series of steps S1 to S9 are repeated every predetermined unit period.

  As described above, the first inclination angle α1 of the variable blade 21 (see FIG. 2) capable of separating the condensed water contained in the compressor intake gas can be calculated by performing steps S1 to S5. Further, by executing steps S6 to S8, the second inclination angle α2 of the variable blade 21 (see FIG. 2) capable of preventing surging at the intake port 2aa (see FIG. 2) of the turbocharger 2 is calculated, and the compressor The inclination angle α (see FIG. 2) of the variable blade 21 that enables both separation of condensed water contained in the intake gas and prevention of surging can be calculated.

  Thus, the exhaust gas recirculation system 101 according to this embodiment is used in the engine 1 including the turbocharger 2, and the intake passage 11 communicating with the intake port 2aa of the turbocharger 2 and the EGR connection in the intake passage 11 The EGR gas passage 41 is connected to the portion 11b and recirculates the exhaust gas as EGR gas to the intake passage 11, and is provided between the EGR connection portion 11b of the intake passage 11 and the intake port 2aa of the turbocharger 2. And a variable vane 21 for generating a swirling flow swirling along the inner periphery of the intake passage 11 in the compressor intake gas composed of intake air and EGR gas to the intake passage 11.

  Therefore, first, the EGR gas generates condensed water at the time of cooling by the EGR cooler 51 and at the time of mixing with the intake air to the engine 1. In the exhaust gas recirculation system 101, the variable blade 21 causes a swirl flow between the variable blade 21 and the intake port 2aa in the gas-liquid separator 6 with respect to the compressor intake gas composed of EGR gas and intake air. generate. Therefore, the condensate contained in the compressor intake gas is centrifuged by this swirl flow. Therefore, the condensed water contained in the compressor intake gas generated by cooling by the EGR cooler 51 and contained in the EGR gas, and the condensed water generated when the EGR gas is mixed with the intake air are converted into the turbocharger. Since the compressor intake gas is removed before being sucked into the second intake port 2aa, the turbocharger 2 and the engine 1 can be prevented from being damaged by the condensed water.

  Further, since the variable blade 21 is rotatable, the rotational flow velocity of the swirling flow generated in the compressor intake gas can be adjusted by adjusting the inclination angle α. Further, by the control of the ECU 8 in steps S1 to S5, the inclination angle α of the variable blade 21 is calculated in accordance with the operating condition of the engine 1, and the calculated inclination angle α is applied to the variable blade 21, thereby compressing the compressor. Condensed water contained in the intake gas can be effectively removed. Further, the control of the ECU 8 makes it possible to change the variable wing 21 when the engine 1 rotates at a high speed, which affects the engine 1 and affects the engine 1 or when the EGR valve 61 is closed and the EGR gas does not flow into the intake passage 11. The blade 21 can be controlled by setting the inclination angle α to 0 ° so as to reduce the intake pressure loss of the engine 1. Therefore, it is possible not only to prevent damage to the turbocharger 2 and the engine 1 due to condensed water, but also to improve the performance of the engine 1.

  Further, in the exhaust gas recirculation system 101, the swirl flow of the compressor intake gas generated by the variable blade 21 has an effect of preventing surging in the turbocharger 2 as well as an effect of separating condensed water from the compressor intake gas. ing. Therefore, the control of the ECU 8 in steps S1 to S9 calculates the first inclination angle α1 of the variable vane 21 that enables the removal of the condensed water contained in the compressor intake gas in accordance with the operating conditions of the engine 1, and the turbo The second inclination angle α2 of the variable vane 21 that can prevent surging at the intake port 2aa of the charger 2 can be calculated. Furthermore, the larger one of the two first inclination angles α1 and second inclination angle α2 is selected, the inclination angle α of the variable blade 21 is determined, and applied to the variable blade 21, whereby the compressor intake gas Not only the separation of the condensed water but also the surging in the turbocharger 2 can be prevented.

Further, by providing a gas-liquid separator 6 having a liquid discharge port 6 ca for discharging condensed water inside between the intake passage 11 and the intake port 2 aa of the turbocharger 2, a compressor is provided in the gas-liquid separator 6. A swirling flow of the suction gas is generated, and the condensed water contained in the compressor suction gas is centrifuged. The centrifuged condensed water is discharged outside the gas-liquid separator 6 from the liquid discharge port 6ca. Is possible.
Further, by making the gas-liquid separator 6 have a double-pipe gas-liquid separation structure, the compressor intake gas can effectively remove the condensed water by the swirling flow. Furthermore, the double pipe type gas-liquid separation structure can prevent the condensed water separated from the compressor intake gas from flowing into the gas discharge path 6b and the intake port 2aa of the turbocharger 2.

Further, in the exhaust gas recirculation system 101, increasing the inclination angle α of the variable vane 21 has the effect of improving the separation effect of the condensed water from the compressor intake gas and the effect of improving the surge limit in the turbocharger 2. . Furthermore, the supercharging performance of the turbocharger 2 can be improved by improving the surge limit.
In the embodiment, the variable blade 21 is provided inside the gas-liquid separator 6, but is not limited to this, and the EGR connection portion 11 b and the gas-liquid separator 6 in the intake passage 11 are not limited to this. It may be provided between them.

  In the embodiment, the gas-liquid separator 6 has a double-pipe structure. However, the present invention is not limited to this, and the gas-liquid separator 6 includes the diameter of the intake passage 11 and the turbocharger 2. A single tube structure having a diameter larger than the diameter of the air inlet 2aa may be used. By making the diameter of the gas-liquid separator 6 larger than the diameter of the intake passage 11, the centrifugal force due to the internal swirl flow can be increased, and the condensed water contained in the compressor intake gas can be effectively separated. . Furthermore, by making the diameter of the gas-liquid separator 6 larger than the diameter of the intake port 2aa, it is possible to prevent the separated condensed water from flowing into the intake port 2aa.

Further, the shape and the number of the variable blades 21 are not limited to those in the embodiment, and may be any shape and number that cause the gas-liquid separator 6 to generate a swirling flow.
In the embodiment, only the turbocharger 2 is described as the supercharger. However, the present invention is not limited to this. The supercharger may be a supercharger.

1 is an overall system diagram showing a schematic configuration of an internal combustion engine including an exhaust gas recirculation system according to an embodiment of the present invention. It is a figure which shows the principal part of a structure of the exhaust-gas recirculation system which concerns on embodiment of this invention. It is a schematic diagram which shows the III-III cross section of FIG. In FIG. 2, it is a figure which shows the principal part of a structure of the exhaust-gas recirculation system which rotated the variable blade. It is a schematic diagram which shows the VV cross section of FIG. It is a flowchart which shows the flow of control of the variable blade in the exhaust-gas recirculation system which concerns on embodiment of this invention. It is a flowchart which shows the flow which calculates the condensed water generation amount in the flowchart of FIG. It is a figure which shows the relationship between the angle of a variable blade, the compressor intake gas amount, and the amount of condensed water generation in the exhaust-gas recirculation system which concerns on embodiment of this invention. It is a figure which shows the relationship between the angle of a variable blade, the compressor intake gas amount, and the compressor pressure ratio in the exhaust gas recirculation system which concerns on embodiment of this invention. It is a figure which shows the relationship between the compressor intake gas amount in the exhaust gas recirculation system which concerns on embodiment of this invention, a compressor pressure ratio, and a surge limit.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Engine (internal combustion engine), 2 Turbocharger (supercharger), 2aa Intake port (intake port), 6ca Liquid discharge port (liquid discharge port), 6 Gas-liquid separator (intake passage, gas-liquid separation part), 8 ECU (EGR rate calculation means, condensed water generation amount calculation means, rotation angle determination means, first rotation angle calculation means, compressor pressure ratio calculation means, second rotation angle calculation means, third rotation angle determination means), 11 intake passage (Intake passage), 11b connection part (EGR connection part), 12 air quantity sensor (air quantity detection means), 16 first pressure sensor (first pressure detection means), 17 second pressure sensor (second pressure detection means) , 21 Variable wing (swirl flow generating means, wing-like body), 41 Gas passage (EGR gas passage), 101 Exhaust gas recirculation system, Pim outlet pressure (second pressure), Pin inlet pressure (first pressure), Rp Compressor pressure ratio (compressor pressure ratio), α inclination angle (rotation angle), α1 first inclination angle (first reference value of rotation angle), α2 second inclination angle (second reference value of rotation angle).

Claims (8)

An exhaust gas recirculation system used for an internal combustion engine equipped with a supercharger,
An intake passage communicating with the intake port of the supercharger;
An EGR gas passage connected to an EGR connection portion in the intake passage and returning to the intake passage as an exhaust gas as an EGR gas;
The intake passage is provided between the EGR connection portion of the intake passage and the intake port of the supercharger, and the intake passage and the mixed gas composed of the EGR gas to the intake passage that flows through the intake passage A gas-liquid separating the gas-liquid by centrifugal separation between the intake port of the supercharger and the wing-like body in the intake passage in the swirl flow generating means for generating a swirl flow swirling along the inner periphery of the turbocharger A separation unit;
An exhaust gas recirculation system comprising. The swirl flow generating means is a rotatable wing-like body,
The exhaust gas recirculation system according to claim 1, wherein a rotational speed of the swirl flow generated in the mixed gas changes according to a rotation angle of the wing-like body. The exhaust gas recirculation system according to claim 1 or 2, wherein the gas-liquid separator has a liquid outlet for discharging the liquid inside the gas-liquid separator. The exhaust gas recirculation system according to claim 3, wherein the gas-liquid separation unit has a double-pipe gas-liquid separation structure. An air amount detecting means for detecting an intake air amount to the intake passage;
EGR rate calculating means for calculating an EGR rate based on operating conditions of the internal combustion engine;
A condensed water generation amount calculating means for calculating a condensed water generation amount in the mixed gas;
Based on the intake air amount detected by the air amount detection unit, the EGR rate calculated by the EGR rate calculation unit, and the condensed water generation amount calculated by the condensed water generation amount calculation unit, The exhaust gas recirculation system according to any one of claims 2 to 4, further comprising: a rotation angle determination unit that determines the rotation angle of the wing-like body that generates the swirl flow that separates the condensed water contained therein. An air amount detecting means for detecting an intake air amount to the intake passage;
EGR rate calculating means for calculating an EGR rate based on operating conditions of the internal combustion engine;
A condensed water generation amount calculating means for calculating a condensed water generation amount in the mixed gas;
Based on the intake air amount detected by the air amount detection unit, the EGR rate calculated by the EGR rate calculation unit, and the condensed water generation amount calculated by the condensed water generation amount calculation unit, First rotation angle calculation means for calculating a first reference value that is the rotation angle of the wing-like body that generates the swirling flow that separates the condensed water contained;
First pressure detecting means for detecting a first pressure at the intake port of the supercharger;
Second pressure detecting means for detecting a second pressure in a passage for supplying the mixed gas from the supercharger to the internal combustion engine;
Compressor pressure ratio calculating means for calculating a compressor pressure ratio that is a ratio of the second pressure to the first pressure;
Based on the intake air amount detected by the air amount detection means, the EGR rate calculated by the EGR rate calculation means, and the compressor pressure ratio calculated by the compressor pressure ratio calculation means, the supercharger Second rotation angle calculation means for calculating a second reference value that is the rotation angle of the wing-like body that generates the swirling flow that prevents surging at the intake port;
One of the first reference value calculated by the first rotation angle calculation means and the second reference value calculated by the second rotation angle calculation means is selected, and the rotation angle of the winged body is determined. The exhaust gas recirculation system according to any one of claims 2 to 4, further comprising third rotation angle determination means for performing the operation. In an internal combustion engine comprising a supercharger, an intake passage communicating with an intake port of the supercharger, and an EGR gas passage connected to the intake passage and returning to the intake passage as exhaust gas as EGR gas,
The exhaust gas is recirculated between the EGR gas passage in the intake passage and the intake port of the supercharger while generating a swirling flow in the mixed gas composed of the intake air and the EGR gas into the intake passage. A method of
(A) detecting an intake air amount into the intake passage;
(B) calculating an EGR rate based on operating conditions of the internal combustion engine;
(C) calculating a condensed water generation amount in a mixed gas composed of the intake air and the EGR gas;
(D) Based on the detected intake air amount, the calculated EGR rate, and the calculated condensed water generation amount, the swirling flow of the mixed gas separates the condensed water contained in the mixed gas. And recirculating the exhaust gas, wherein the step of determining the magnitude of the swirling flow is performed. In an internal combustion engine comprising a supercharger, an intake passage communicating with an intake port of the supercharger, and an EGR gas passage connected to the intake passage and returning to the intake passage as exhaust gas as EGR gas,
The exhaust gas is recirculated between the EGR gas passage in the intake passage and the intake port of the supercharger while generating a swirling flow in the mixed gas composed of the intake air and the EGR gas into the intake passage. A method of
(A) detecting an intake air amount into the intake passage;
(B) calculating an EGR rate based on operating conditions of the internal combustion engine;
(C) calculating a condensed water generation amount in a mixed gas composed of the intake air and the EGR gas;
(D) Based on the detected intake air amount, the calculated EGR rate, and the calculated condensed water generation amount, the swirling flow of the mixed gas separates the condensed water contained in the mixed gas. Calculating a first magnitude of the swirling flow;
(E) detecting a first pressure at the intake port of the supercharger and a second pressure in a passage for supplying the mixed gas from the supercharger to the internal combustion engine, and the second pressure and the first pressure, Calculating a compressor pressure ratio that is a ratio of
(F) Based on the detected intake air amount, the calculated EGR rate, and the calculated compressor pressure ratio, the swirling flow of the mixed gas prevents surging at the intake port of the supercharger. Calculating a second magnitude of the swirling flow for,
(G) selecting one of the first magnitude of the swirl flow calculated in step (d) and the second magnitude of the swirl flow calculated in step (f); A method of recirculating the exhaust gas comprising: determining the magnitude of the flow.

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