JP5795947B2 - Exhaust gas recirculation device for supercharged engine - Google Patents

Description

  The present invention relates to an engine with a supercharger, and more particularly to an exhaust gas recirculation device for an engine with a supercharger that recirculates exhaust gas discharged from the engine to an exhaust passage to an intake passage.

  Conventionally, as this type of technology, for example, an exhaust gas recirculation device for a supercharged engine described in Patent Document 1 below is known. In an engine equipped with a supercharger, this device is provided with an EGR passage that connects a downstream side of a turbine provided in an exhaust passage and an upstream side of a compressor provided in an intake passage. Is provided with an EGR regulating valve. An exhaust bypass passage that bypasses the turbine is provided in the exhaust passage, and an exhaust bypass valve is provided in the exhaust bypass passage. Further, an EGR passage that connects an exhaust passage downstream of the turbine and the catalyst and an intake passage downstream of the compressor and the cooler is provided. An EGR valve is provided in the EGR passage. When the supercharger is operated, the EGR adjustment valve is opened to recirculate the exhaust gas flowing through the exhaust passage to the intake passage upstream of the compressor. On the other hand, at the time of non-supercharging when the supercharger is not operated, the exhaust gas flowing through the exhaust passage is recirculated to the intake passage downstream of the cooler by opening the EGR valve.

JP 2011-69305 A

  However, in the apparatus described in Patent Document 1, since the negative pressure generated in the intake passage at the time of supercharging is relatively small, only a small amount of exhaust gas can be recirculated to the intake passage through the EGR passage. Therefore, it is desired to return an appropriate amount of exhaust gas to the intake passage even during supercharging.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas recirculation of a supercharged engine that enables an appropriate amount of exhaust gas recirculation gas to recirculate to an intake passage when the supercharger is operated. To provide an apparatus.

In order to achieve the above object, an invention according to claim 1 is provided in an engine provided with a supercharger in an intake passage, and a throttle valve is provided in the intake passage on the downstream side of the supercharger. In an exhaust gas recirculation apparatus for a supercharger-equipped engine having an exhaust gas recirculation passage that recirculates a part of the exhaust gas discharged to the exhaust gas passage as an exhaust gas recirculation gas to an intake air passage on the downstream side of the throttle valve. A branch passage, a bypass passage connecting the upstream side and the downstream side of the turbocharger in the intake passage, and an ejector that generates negative pressure in the bypass passage are connected to the bypass passage through the ejector. and it is, ejector, the air that has been supercharged by the supercharger flowing from the upstream side of the bypass passage is introduced as a working fluid to generate a negative pressure, discharge from the outlet of the branch passage And purpose to be flowing out by inhaling the recirculated gas to the downstream side of the bypass passage.

According to the configuration of the invention, when the supercharger is operated, a pressure difference is generated in the intake air between the upstream side and the downstream side of the supercharger in the intake passage, and a pressure difference is also generated between both ends of the bypass passage. . This pressure difference causes air to flow through the bypass passage, and negative pressure is generated in the ejector by the air flow. Therefore, negative pressure by the ejector acts on the outlet of the branch passage, and a part of the exhaust gas discharged from the engine to the exhaust passage flows as exhaust recirculation gas to the intake passage through the exhaust recirculation passage, branch passage, ejector and bypass passage. . Further, when the supercharging pressure by the supercharger increases, the negative pressure generated by the ejector increases accordingly. Therefore, the exhaust gas recirculation gas flow rate flowing from the exhaust gas recirculation passage and the branch passage to the bypass passage increases, and the exhaust gas recirculation gas flow rate flowing to the intake passage increases. Here, since the bypass passage is provided by bypassing a part of the intake passage, the bypass passage and the ejector do not affect the intake resistance of the intake passage. Further, when the supercharger is not operated, a pressure difference is hardly generated in the intake air between the upstream side and the downstream side of the supercharger in the intake passage, and the pressure difference between both ends of the bypass passage is reduced. At this time, the negative pressure generated in the intake passage on the downstream side of the throttle valve acts on the outlet of the exhaust gas recirculation passage, and the exhaust gas recirculation gas flows to the intake passage through the exhaust gas recirculation passage.

In order to achieve the above object, the invention according to claim 2 is the invention according to claim 1, wherein the flow rate of the exhaust recirculation gas is adjusted downstream from the branch position of the branch passage in the exhaust recirculation passage. The purpose is to provide an exhaust recirculation gas flow rate control valve.

According to the configuration of the above invention, in addition to the operation of the invention according to claim 1, when the supercharger is not in operation, the flow rate of the exhaust recirculation gas flowing through the exhaust recirculation passage to the intake passage is controlled by the exhaust recirculation gas flow control valve. Adjusted by.

In order to achieve the above object, the invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2 , an opening / closing valve for opening and closing the branch passage is provided in the branch passage. .

According to the configuration of the invention described above, in addition to the operation of the invention according to claim 1 or 2 , the exhaust recirculation gas flows into the branch passage by opening the branch passage by the on-off valve when the supercharger is operated, and the ejector and bypass The exhaust gas recirculation gas flows to the intake passage through the passage. On the other hand, by closing the branch passage by the opening / closing valve, the flow of the exhaust gas recirculation gas from the exhaust gas recirculation passage to the branch passage is blocked, and the reverse flow of the intake air from the bypass passage to the branch passage is blocked.

In order to achieve the above object, according to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, air flowing from the supercharger is introduced into the intake passage on the downstream side of the supercharger. A cooler for cooling is provided, the upstream side of the bypass passage is connected to the intake passage on the downstream side of the cooler, and the downstream side of the bypass passage is connected to the intake passage on the upstream side of the supercharger And

According to the configuration of the invention, in addition to the operation of the invention according to any one of claims 1 to 3 , air cooled by the cooler also flows to the bypass passage when the supercharger is operated. Therefore, even if the exhaust gas recirculation gas flowing from the branch passage to the bypass passage through the ejector merges with the air flowing from the intake passage to the bypass passage, the temperature of the exhaust gas recirculation gas flowing through the bypass passage does not rise more than necessary. .

According to the first aspect of the present invention, an appropriate amount of the exhaust gas recirculation gas can be recirculated to the intake passage when the supercharger is operated, and an appropriate amount of the exhaust gas recirculation gas is sucked through the exhaust gas recirculation passage when the supercharger is not operated. It can be refluxed to the passage.

According to the invention described in claim 2, in addition to the effect of the invention according to claim 1, during non-operation of the turbocharger, appropriately adjusting the exhaust gas recirculation flow rate of the gas recirculated from the exhaust passage to the intake passage Can do. Further, when the supercharger is operated, the backflow of air from the intake passage to the exhaust gas recirculation passage can be prevented, and adverse effects on the negative pressure acting on the exhaust gas recirculation passage from the ejector through the branch passage can be prevented.

According to the invention of claim 3 , in addition to the effect of the invention of claim 1 or 2 , when the supercharger is not in operation, the exhaust gas recirculation gas is reliably recirculated from the exhaust passage to the intake passage through the exhaust recirculation passage. Can be made.

According to the invention described in claim 4 , in addition to the effects of the invention described in any one of claims 1 to 3 , the ejector and the bypass passage can be protected from overheating.

1 is a schematic configuration diagram illustrating a supercharged engine system including an exhaust gas recirculation device according to an embodiment. Sectional drawing which shows an ejector concerning the embodiment. The schematic block diagram which shows the engine system with a supercharger which concerns on another embodiment and contains an exhaust gas recirculation apparatus.

  Hereinafter, an embodiment of an exhaust gas recirculation device for an engine with a supercharger according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a supercharged engine system including an exhaust gas recirculation (EGR) device in this embodiment. This engine system includes a reciprocating engine 1. An intake passage 3 is connected to the intake port 2 of the engine 1, and an exhaust passage 5 is connected to the exhaust port 4. An air cleaner 6 is provided at the inlet of the intake passage 3. A supercharger 7 for boosting the intake air in the intake passage 3 is provided between the exhaust passage 5 and the intake passage 3 downstream of the air cleaner 6.

  The supercharger 7 includes a compressor 8 disposed in the intake passage 3, a turbine 9 disposed in the exhaust passage 5, and a rotating shaft 10 that connects the compressor 8 and the turbine 9 so as to be integrally rotatable. The supercharger 7 rotates the turbine 9 with the exhaust gas flowing through the exhaust passage 5 and integrally rotates the compressor 8 via the rotary shaft 10, thereby boosting the intake air in the intake passage 3, that is, performing supercharging. It has become.

  An exhaust bypass passage 11 that bypasses the turbine 9 is provided in the exhaust passage 5 adjacent to the supercharger 7. A waste gate valve 12 is provided in the exhaust bypass passage 11. By adjusting the exhaust gas flowing through the exhaust bypass passage 11 by the wastegate valve 12, the flow rate of the exhaust gas supplied to the turbine 9 is adjusted, and the rotational speeds of the turbine 9 and the compressor 8 are adjusted. The supercharging pressure is adjusted.

  In the intake passage 3, a cooler 13 is provided between the compressor 8 of the supercharger 7 and the engine 1. The cooler 13 is for cooling the intake air that has been pressurized by the compressor 8 to a high temperature. A surge tank 3 a is provided in the intake passage 3 between the cooler 13 and the engine 1. A throttle valve 14 is provided downstream of the cooler 13 and upstream of the surge tank 3a.

  A catalytic converter 15 for purifying exhaust gas is provided in the exhaust passage 5 on the downstream side of the turbine 9. Further, an EGR passage 21 which is an exhaust gas recirculation passage of the present invention is provided between the exhaust passage 5 on the downstream side of the catalytic converter 15 and the surge tank 3a. That is, the outlet 21a of the EGR passage 21 is connected to the surge tank 3a on the downstream side of the throttle valve 14 in order to recirculate a part of the exhaust gas flowing through the exhaust passage 5 to the intake passage 3 through the EGR passage 21 as EGR gas. Is done. In this embodiment, the inlet 21 b of the EGR passage 21 is connected to the exhaust passage 5 on the downstream side of the catalytic converter 15. A part of the exhaust gas discharged from the engine 1 to the exhaust passage 5 is recirculated to the intake passage 3 through the EGR passage 21 as EGR gas.

  The upstream side and the downstream side of the supercharger 7 in the intake passage 3 are connected by an intake bypass passage 22. That is, an intake bypass passage 22 that bypasses the compressor 8 is provided between the intake passage 3 on the downstream side of the compressor 8 having a high supercharging pressure and the intake passage 3 on the upstream side of the compressor 8. In this embodiment, the upstream side of the intake bypass passage 22 is connected to the intake passage 3 downstream of the cooler 13 and upstream of the throttle valve 14. The downstream side of the intake bypass passage 22 is connected to the intake passage 3 upstream of the compressor 8 and downstream of the air cleaner 6.

  The intake bypass passage 22 is provided with an ejector 23 that generates a negative pressure by the air flowing through the passage 22. FIG. 2 shows a schematic configuration of the ejector 23 in a sectional view. The ejector 23 includes an outer pipe 31. A decompression chamber 31 a is provided on the air inlet side of the outer pipe 31. A diffuser 31 b is provided on the air outlet side of the outer pipe 31. Further, on the air inlet side of the outer pipe 31, a nozzle 32 that is disposed in the decompression chamber 31a and injects intake air is provided. The tip 32a of the nozzle 32 is disposed toward the diffuser 31b. The outer pipe 31 is provided with a suction port 31d for sucking EGR gas into the decompression chamber 31a corresponding to the decompression chamber 31a. A branch passage 25 described later is connected to the suction port 31d. The upstream side of the intake bypass passage 22 is connected to the inlet 32 b of the nozzle 32, and the downstream side of the intake bypass passage 22 is connected to the outlet 31 c of the outer pipe 31.

  The above-described ejector 23 introduces air flowing through the intake bypass passage 22 into the nozzle 32 as a working fluid, injects air from the tip 32a of the nozzle 32 to generate a low pressure supersonic flow, and applies a negative pressure to the decompression chamber 31a. generate. That is, when the turbocharger 7 is operated, the intake air is boosted by the compressor 8, thereby generating a pressure difference between the intake passage 3 upstream of the compressor 8 and the intake passage 3 downstream of the compressor 8. . Therefore, a pressure difference is generated between the upstream side and the downstream side of the intake bypass passage 22, and different intake air flows through the intake bypass passage 22 between the inlet 32 b of the nozzle 32 of the ejector 23 and the outlet 31 c of the outer pipe 31. Pressure acts. As a result, air flows into the intake bypass passage 22 and air is injected from the tip 32a of the nozzle 32, whereby a negative pressure is generated in the decompression chamber 31a, and EGR gas is sucked into the decompression chamber 31a from the suction port 31d. . Then, the sucked EGR gas is discharged from the outlet 31c of the outer pipe 31 together with the intake air through the diffuser 31b. The magnitude of the negative pressure generated in the decompression chamber 31a can vary depending on the magnitude of the supercharging pressure by the supercharger 7.

In the middle of the EGR passage 21, an EGR cooler 24 for cooling the EGR gas flowing through the passage 21 is provided. The EGR passage 21 on the downstream side of the EGR cooler 24 is provided with a branch passage 25 that branches from the passage 21. The outlet 25 a of the branch passage 25 is connected to the intake bypass passage 22 via the ejector 23. That is, the outlet 25 a of the branch passage 25 is connected to the suction port 31 d of the ejector 23. Accordingly, when the supercharger 7 is operated, a negative pressure is generated in the decompression chamber 31 a of the ejector 23, so that the negative pressure acts on the branch passage 25. Due to the action of this negative pressure, EGR gas is led out from the EGR passage 21 to the branch passage 25, and the EGR gas flows from the ejector 23 to the intake passage 3 through the intake bypass passage 22. The EGR gas flowing into the intake passage 3 is introduced into the combustion chamber of the engine 1 together with the intake air via the compressor 8 and the intake passage 3 and the like.

In this embodiment, an EGR valve 26 as an exhaust gas recirculation gas flow rate adjustment valve of the present invention for adjusting the flow rate of EGR gas is provided downstream of the branch position of the branch passage 25 in the EGR passage 21. The EGR valve 26 is configured to adjust the EGR flow rate flowing through the EGR passage 21 by operating the valve body 26b by the actuator 26a to adjust the opening degree of the EGR passage 21.

  In this embodiment, the branch passage 25 is provided with a VSV 27 as an on-off valve of the present invention for opening and closing the branch passage 25. The VSV 27 is configured to selectively open and close the branch passage 25 by operating the valve body 27b by the actuator 27a.

  According to the exhaust gas recirculation device for a supercharged engine in this embodiment described above, when the engine 1 is in operation and the supercharger 7 is operating, the intake passage 3 downstream of the supercharger 7 is positive pressure. It becomes. Here, in the surge tank 3 a, negative pressure does not act on the outlet 21 a of the EGR passage 21, and EGR gas does not flow from the exhaust passage 5 to the intake passage 3 through the EGR passage 21. At this time, a pressure difference is generated in the intake air between the upstream side and the downstream side of the supercharger 7 in the intake passage 3, and a pressure difference is also generated between both ends of the intake bypass passage 22. Due to this pressure difference, air flows into the intake bypass passage 22, and negative pressure is generated in the ejector 23 by the air flow. Therefore, negative pressure by the ejector 23 acts on the branch passage 25. Accordingly, when the VSV 27 is opened, a part of the exhaust gas discharged from the engine 1 to the exhaust passage 5 becomes EGR gas through the EGR passage 21, the branch passage 25, the ejector 23 and the intake bypass passage 22. To flow. For this reason, an appropriate amount of EGR gas can be recirculated to the intake passage 3 when the supercharger 7 is operated.

  In this embodiment, when the supercharging pressure by the supercharger 7 increases, the pressure difference between both ends of the intake bypass passage 22 increases, and the negative pressure generated by the ejector 23 increases accordingly. Therefore, the flow rate of EGR gas flowing from the exhaust passage 5 to the EGR passage 21 and the branch passage 25 increases, and the flow rate of EGR gas flowing to the intake passage 3 increases. Here, since the intake bypass passage 22 is provided by bypassing a part of the intake passage 3, the intake bypass passage 22 and the ejector 23 do not affect the intake resistance of the intake passage 3. For this reason, EGR gas can be recirculated to the intake passage 3 without increasing the intake resistance of the intake passage 3 when the supercharger 7 is operated. Further, the EGR gas flow rate can be increased according to the increase in the supercharging pressure.

  On the other hand, in this embodiment, when the engine 1 is in operation and the supercharger 7 is not operating, negative pressure acts on the intake passage 3. For this reason, it becomes difficult for a pressure difference to be generated in the intake air between the upstream side and the downstream side of the supercharger 7 in the intake passage 3, and the pressure difference between both ends of the intake bypass passage 22 becomes small. At this time, negative pressure generated in the surge tank 3 a on the downstream side of the throttle valve 14 acts on the outlet 21 a of the EGR passage 21. Accordingly, when the EGR valve 26 is opened, a part of the exhaust gas flowing through the exhaust passage 5 flows to the surge tank 3a through the EGR passage 21 as EGR gas due to the negative pressure acting on the EGR passage 21. For this reason, when the supercharger 7 is not in operation, an appropriate amount of EGR gas can be returned to the intake passage 3 through the EGR passage 21. At this time, the flow rate of the EGR gas recirculated to the intake passage 3 can be arbitrarily adjusted by adjusting the opening degree of the EGR valve 26.

  In this embodiment, an EGR valve 26 for adjusting the EGR gas flow rate is provided downstream of the branch position of the branch passage 25 in the EGR passage 21. Therefore, when the supercharger 7 is not in operation, the flow rate of EGR gas flowing to the intake passage 3 via the EGR passage 21 is adjusted by the EGR valve 26. For this reason, when the supercharger 7 is not operated, the flow rate of the EGR gas recirculated from the exhaust passage 5 to the intake passage 3 can be appropriately adjusted.

  On the other hand, when the supercharger 7 is operated, the positive pressure acting on the EGR passage 21 from the surge tank 3a can be shut off by closing the EGR valve 26. For this reason, when the supercharger 7 is operated, the backflow of air to the EGR passage 21 can be prevented, and the negative pressure acting on the EGR passage 21 from the ejector 23 through the branch passage 25 can be prevented. . As a result, the EGR gas can be properly recirculated from the EGR passage 21 to the intake passage 3 through the branch passage 25, the ejector 23 and the intake bypass passage 22.

  In this embodiment, when the supercharger 7 is operated, the branch passage 25 is opened by the VSV 27, whereby EGR gas flows through the branch passage 25, and EGR gas flows through the ejector 23 and the intake bypass passage 22 into the intake passage 3. On the other hand, by closing the branch passage 25 by the VSV 27 when the supercharger 7 is not in operation, the flow of EGR gas from the EGR passage 21 to the branch passage 25 is blocked, and the intake air from the intake bypass passage 22 to the branch passage 25 is blocked. The reverse flow is blocked. For this reason, when the supercharger 7 is not operating, the EGR gas can be reliably recirculated from the exhaust passage 5 to the intake passage 3 through the EGR passage 21.

  In this embodiment, when the supercharger 7 is operated, the air cooled by the cooler 13 also flows to the intake bypass passage 22. Therefore, even if the EGR gas flowing from the branch passage 25 to the intake bypass passage 22 through the ejector 23 merges with the air flowing from the intake passage 3 to the intake bypass passage 22, the temperature of the EGR gas may rise more than necessary. Absent. For this reason, the ejector 23 and the intake bypass passage 22 can be protected from overheating.

  In this embodiment, since the inlet 21b of the EGR passage 21 is connected to the downstream side of the catalytic converter 15 in the exhaust passage 5, the exhaust gas that has passed through the catalytic converter 15 and has a reduced pressure is used as the EGR gas. . For this reason, the EGR gas can be properly recirculated through the EGR passage 21, the branch passage 25, the ejector 23, and the intake bypass passage 22 even in a high supercharging pressure region. Further, foreign matters such as deposits contained in the exhaust gas are removed by the catalytic converter 15 and then flow into the EGR passage 21. This is advantageous as a countermeasure against deposits related to the EGR passage 21, the EGR valve 26, the branch passage 25, the VSV 27, the ejector 23, and the intake bypass passage 22. Moreover, in this embodiment, the connection of the EGR rate can be improved when the supercharger 7 is switched from the non-operating state to the operating state.

  In addition, this invention is not limited to the said embodiment, A part of structure can also be changed suitably and implemented in the range which does not deviate from the meaning of invention.

  For example, in the above embodiment, the inlet 21b of the EGR passage 21 is connected to the exhaust passage 5 on the downstream side of the catalytic converter 15. However, as shown in the schematic configuration diagram of the engine system in FIG. May be connected to the exhaust passage 5 on the upstream side of the turbine 9 of the supercharger 7.

  The present invention is an engine with a supercharger and can be used for an engine system provided with an EGR device.

1 Engine 3 Intake Passage 3a Surge Tank 5 Exhaust Passage 7 Supercharger 8 Compressor 9 Turbine 13 Cooler 14 Throttle Valve 21 EGR Passage (Exhaust Recirculation Passage)
21a Outlet 21b Inlet 22 Intake bypass passage 23 Ejector 25 Branch passage 25a Outlet 26 EGR valve (exhaust recirculation gas flow control valve)
27 VSV (open / close valve)

Claims (4)

Provided in an engine equipped with a supercharger in the intake passage, a throttle valve is provided in the intake passage on the downstream side of the supercharger, and a part of the exhaust gas discharged from the engine to the exhaust passage is exhausted and recirculated In the exhaust gas recirculation device for a supercharged engine provided with an exhaust gas recirculation passage that recirculates to the intake passage on the downstream side of the throttle valve as gas ,
A branch passage branched from the exhaust gas recirculation passage;
A bypass passage connecting the upstream side and the downstream side of the supercharger in the intake passage;
An ejector for generating a negative pressure in the bypass passage, wherein the outlet of the branch passage is connected to the bypass passage through the ejector, and the ejector flows from the upstream side of the bypass passage. Air that is supercharged by a feeder is introduced as a working fluid to generate negative pressure, and the exhaust gas recirculation gas is sucked from the outlet of the branch passage and flows out downstream of the bypass passage. Exhaust gas recirculation device for a powered engine. Downstream of the branch position of the branch passage in the exhaust gas recirculation passage, supercharging of claim 1, wherein the exhaust recirculation gas exhaust recirculation gas flow rate regulating valve for regulating the flow rate of is provided Exhaust gas recirculation device for engine equipped aircraft. The exhaust gas recirculation device for an engine with a supercharger according to claim 1 or 2 , wherein an opening / closing valve for opening and closing the branch passage is provided in the branch passage. The intake passage on the downstream side of the supercharger is provided with a cooler for cooling the air flowing from the supercharger, and the upstream side of the bypass passage is connected to the intake passage on the downstream side of the cooler. The exhaust gas recirculation device for a supercharged engine according to any one of claims 1 to 3 , wherein a downstream side of the bypass passage is connected to the intake passage on the upstream side of the supercharger. .

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