JP5550503B2 - Engine exhaust gas recirculation system - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device that recirculates a part of exhaust gas from an exhaust passage of an engine to an EGR passage.

  Conventionally, as this type of exhaust gas recirculation device, an exhaust passage and an intake passage are connected by an EGR passage to supply a part of exhaust gas (EGR gas) flowing through an exhaust passage of an engine to the intake passage, and the EGR flows through the EGR passage. There is disclosed an EGR device in which an EGR cooler for cooling gas is provided in the EGR passage, and an EGR valve for adjusting the flow rate of EGR gas supplied from the EGR passage to the intake passage is provided in the EGR passage (for example, Patent Documents). 1). In this EGR device, a plurality of EGR coolers are provided in the EGR passage, and an EGR valve is disposed between any two adjacent EGR coolers among the plurality of EGR coolers. For example, when the first and second EGR coolers are provided in series in the EGR passage, and an EGR valve is disposed between these EGR coolers, the first EGR cooler positioned upstream of the EGR valve causes the EGR gas to flow from 100 ° C. The second EGR cooler, which is cooled to a high temperature and located downstream of the EGR valve, is configured to cool the EGR gas to 100 ° C. or lower.

  In the EGR device configured as described above, the exhaust gas temperature at the inlet of the second EGR cooler is higher than the condensation temperature and the solidification temperature of the moisture and hydrocarbon components contained in the EGR gas, so that the EGR gas passes through the EGR valve. In addition, there is no adhesion of condensed water (acid) or hydrocarbon components. Then, the EGR gas temperature at the outlet of the second EGR cooler becomes lower than the condensation temperature and solidification temperature (about 100 ° C.) of the hydrocarbon component contained in the EGR gas, and this gas becomes the temperature of the EGR gas supplied to the intake passage. . As a result, even if the EGR gas is cooled to a temperature equal to or lower than the condensation temperature or solidification temperature of the hydrocarbon component by the second EGR cooler downstream of the EGR valve, the EGR valve does not malfunction.

Japanese Patent Laying-Open No. 2006-200381 (Claim 1, paragraphs [0015], [0021] to [0023], [0029], [0030], FIG. 1)

  However, in the conventional EGR device shown in Patent Document 1, the EGR gas is cooled to about 100 ° C. or less by the second EGR cooler, the moisture in the EGR gas is condensed to generate condensed water, and hydrocarbons are generated. Condensate is generated by condensing components, but condensate or condensate or a mixture of these flows into a specific cylinder of the engine, increasing the variation in EGR rate between each cylinder of the engine and reducing engine performance There is a risk that the engine may be damaged by a water hammer caused by the condensation of condensed water on a specific cylinder.

  An object of the present invention is to introduce engine condensate separated from EGR gas almost uniformly into each cylinder of the engine, thereby suppressing variations in the EGR rate between the cylinders and preventing engine performance from being deteriorated. It is to provide a recirculation device.

The first aspect of the present invention is that, as shown in FIGS. 1 and 2, an EGR pipe 17 that recirculates a part of the exhaust gas flowing through the exhaust passage 13 of the engine 11 to the intake passage 12 as EGR gas, and an EGR pipe 17 An EGR cooler 22 that cools the EGR gas that is provided and flows through the EGR pipe 17, an EGR valve 23 that is provided in the EGR pipe 17 and adjusts the flow rate of the EGR gas that passes through the EGR pipe 17, and EGR according to the operating condition of the engine 11 In an exhaust gas recirculation device for an engine having a controller 33 for controlling the valve 23, a gas-liquid that is provided in the EGR pipe 17 and is cooled by the EGR cooler 22 to separate the condensate 26 generated in the EGR cooler 22 from the EGR gas. The separation means 24 and the condensate 26 separated by the gas-liquid separation means 24 are supplied to each intake port 21 of the engine 11. A condensed liquid supply passage 27 leading to, provided condensate supply passage 27 and the on-off valve 28 for opening and closing the condensate supply passage 27 is provided in the intake port 21a and a temperature sensor 32 for detecting the temperature of the intake port 21a further comprising, wherein the controller 33 is configured to control the opening and closing valve 28 on the basis of the detection output of the temperature sensor 32.

  The second aspect of the present invention is an invention based on the first aspect, and as shown in FIG. 2, the gas-liquid separation means 24 side of the condensate supply passage 27 is positioned higher than the intake port 21a side. Further, the condensate supply passage 27 has a height difference.

The third aspect of the present invention is an invention based on the first aspect, and further, as shown in FIG. 1, the EGR cooler 22 is connected in series to the EGR pipe 17 from the exhaust passage 13 to the intake passage 12 in order. The EGR valve 23 is provided in the EGR pipe 17 between the first EGR cooler 22a and the second EGR cooler 22b, and EGR gas is 150 ° C. or more in the first EGR cooler 22a. The second EGR cooler 22b is cooled to a predetermined temperature of less than 100 ° C. after being cooled to the predetermined temperature.

In the exhaust gas recirculation device according to the first aspect of the present invention, the gas-liquid separation means separates the condensate generated in the EGR gas from the EGR gas by cooling the EGR gas with the EGR cooler, and the separated condensation Since the liquid is guided to each intake port of the engine through the condensate supply passage, the condensate is guided to each cylinder of the engine almost evenly. As a result, variations in the EGR rate between the cylinders of the engine can be suppressed, so that a decrease in engine performance can be prevented and a water hammer caused by condensing condensed water in a specific cylinder can be prevented. Further, since the controller controls the on-off valve based on the detection output of the temperature sensor, it is possible to prevent the condensate from being led to the intake port when the engine is cold, such as immediately after the engine is started. As a result, it is possible to prevent a decrease in engine performance.

  In the exhaust gas recirculation device according to the second aspect of the present invention, since the condensate supply passage has a height difference so that the gas-liquid separation means side of the condensate supply passage is positioned higher than the intake port side, the gas-liquid separation means The condensate separated from the EGR gas is guided to each intake port by its own weight. As a result, it is not necessary to use power such as a pump for supplying the condensate to the intake port.

In the exhaust gas recirculation device according to the third aspect of the present invention, the EGR gas is cooled to a predetermined temperature of 150 ° C. or higher by the first EGR cooler and then cooled to a predetermined temperature of less than 100 ° C. by the second EGR cooler. Condensate is not generated by the EGR valve provided in the EGR pipe between the cooler and the second EGR cooler. As a result, the valve shaft and valve seal of the EGR valve are not fixed due to the adhesion of the condensate or corrosion due to acid.

It is the block diagram seen from the arrow A of FIG. 2 which shows the state which fractured | ruptured the cylinder head of the engine of this invention embodiment, and fractured | ruptured the principal part of the intake manifold and the exhaust manifold. It is the BB sectional view taken on the line of FIG.

  Next, an embodiment for carrying out the present invention will be described with reference to the drawings. As shown in FIG. 1, an intake pipe 12b is connected to the intake port 21a of the diesel engine 11 via an intake manifold 12a, and an exhaust pipe 13b is connected to the exhaust port 21b via an exhaust manifold 13a. The intake manifold 12a and the intake pipe 12b constitute an intake passage 12, and the exhaust manifold 13a and the exhaust pipe 13b constitute an exhaust passage 13. The intake pipe 12b is provided with a compressor housing 14a of the turbocharger 14 and a water-cooled intercooler 16 that cools the intake air compressed by the turbocharger 14. The exhaust pipe 13b is provided with a turbine housing 14b of the turbocharger 14. The compressor rotor 14c is rotatably accommodated in the compressor housing 14a, and the turbine rotor 14d is rotatably accommodated in the turbine housing 14b. The compressor rotor blade 14c and the turbine rotor blade 14d are connected by a shaft 14e, and the compressor rotor blade 14c rotates through the turbine rotor blade 14d and the shaft 14e by the energy of the exhaust gas discharged from the engine 11, and the compressor rotor blade 14c. , The intake air in the intake pipe 12b is compressed. In addition, the code | symbol 15 in FIG. 1 is the air cleaner attached to the intake upstream end of the intake pipe 12a.

  On the other hand, the exhaust manifold 13a and the intake pipe 12b are connected to bypass the engine 11 by the EGR pipe 17. Specifically, one end of the EGR pipe 17 is connected to the exhaust manifold 13 a, and the other end of the EGR pipe 17 is connected to an EGR gas mixing unit 18 provided in the intake pipe 12 b on the intake downstream side of the intercooler 16. As a result, part of the exhaust gas in the exhaust manifold 13a of the engine 11 is recirculated as EGR gas through the EGR pipe 17 to the EGR gas mixing unit 18 of the intake pipe 12b, and the EGR mixed with the intake air in the EGR gas mixing unit 18 The gas is introduced into each cylinder 19a through the intake manifold 12a and the intake port 21a. Here, the engine 11 includes a cylinder block 19 (FIG. 2) in which each cylinder 19 a (FIG. 1) is provided at a predetermined interval, and a cylinder head 21 (FIG. 1 and FIG. 1) attached to the upper surface of the cylinder block 19. 2). The intake port 21a and the exhaust port 21b are provided on opposite side surfaces of the cylinder head 21 (FIG. 1). The intake manifold 12a is attached to the side surface of the cylinder head 21 so as to communicate with the intake port 21a (FIGS. 1 and 2), and the exhaust manifold 13a is attached to the side surface of the cylinder head 21 so as to communicate with the exhaust port 21b (see FIG. FIG. 1).

  The EGR pipe 17 is provided with an EGR cooler 22 for cooling the EGR gas flowing through the EGR pipe 17 (FIGS. 1 and 2). In this embodiment, the EGR cooler 22 includes first and second EGR coolers 22a and 22b provided in series in the EGR pipe 17 in order from the exhaust manifold 13a toward the intake pipe 12b. The first EGR cooler 22a has the ability to cool the EGR gas passing through the EGR pipe 17 to a predetermined temperature of 150 ° C. or higher (for example, about 160 ° C.), and the second EGR cooler 22b is EGR discharged from the first EGR cooler 22a. It has the ability to cool the gas to a predetermined temperature below 100 ° C. (for example, about 80 ° C.). An EGR valve 23 is provided in the EGR pipe 17 between the first EGR cooler 22a and the second EGR cooler 22b. The EGR valve 23 is configured to adjust the flow rate of EGR gas recirculated from the exhaust manifold 13a through the EGR pipe 17 to the intake pipe 12b. In this embodiment, the EGR valve 23 is constituted by a butterfly valve. Specifically, the EGR valve 23 includes a valve case 23a formed in a cylindrical shape having a diameter larger than that of the EGR pipe 17, a rotation shaft 23b rotatably inserted in the valve case 23a, and the rotation A disc-shaped valve main body 23c fixed to the shaft 23b and capable of changing the opening degree in the valve case 23a, and the valve main body 23c is driven via the rotating shaft 23b to gradually or continuously increase the opening degree in the valve case 23a. The valve drive means 23d (FIG. 1) which changes automatically. As the valve driving means 23d, a stepping motor with a reduction gear, a servo motor with a reduction gear, or the like is used.

  On the other hand, the gas-liquid separation means 24 is provided in the EGR pipe 17 downstream of the EGR gas from the second EGR cooler 22b (FIGS. 1 and 2). In this embodiment, the gas-liquid separation means 24 has a filter (not shown) using a metal mesh or plastic mesh of a predetermined mesh. This filter is accommodated in a separation short pipe 24a having a diameter larger than that of the EGR pipe 17, and a liquid reservoir 24b is provided at a lower portion of the separation short pipe 24a. The condensate 26 (FIG. 2) cooled by the second EGR cooler 22b and generated in the second EGR cooler 22b is separated from the EGR gas by the filter, and the separated condensate 26 is stored in the liquid reservoir 24b. Configured to be Further, the condensate 26 separated by the gas-liquid separation means 24 is configured to be guided to each intake port 21a of the engine 11 through the condensate supply passage 27 (FIGS. 1 and 2). The condensate supply passage 27 includes a lead-out pipe 27a whose base end is connected to the bottom of the liquid reservoir 24b, and extends in the longitudinal direction along the lower surface of the intake manifold 12a. A distribution pipe 27b having a tip connected thereto, a plurality of supply short pipes 27c (FIG. 2) projecting from the position of the distribution pipe 27b facing each cylinder 19a toward the cylinder head 21, and the cylinder head 21 A plurality of communication holes 27d are formed to connect each short supply pipe 27c and each intake port 21a. The gas-liquid separation means 24 is provided at a position higher than the cylinder head 21 (FIG. 2). Thus, the condensate supply passage 27 is provided with a height difference so that the gas-liquid separation means 24 side of the condensate supply passage 27 is positioned higher than the intake port 21a side. Further, the outlet pipe 27a of the condensate supply passage 27 is provided with an on-off valve 28 for opening and closing the outlet pipe 27a. This on-off valve 28 is an electromagnetic valve that opens and closes the outlet pipe 27a (FIG. 1).

  The engine 11 is provided with a rotation sensor 29 for detecting the rotation speed of the engine 11, a load sensor 31 for detecting the load of the engine 11, and a water temperature sensor 35 for detecting the coolant temperature of the engine 11 (FIG. 1). ). The intake port 21a is provided with a temperature sensor 32 that detects the temperature of the intake port 21a. The detection outputs of the rotation sensor 29, load sensor 31, temperature sensor 32, and water temperature sensor 35 are connected to the control input of the controller 33, and the control output of the controller 33 is connected to the valve drive means 23d of the EGR valve 23 and the on-off valve 28. Is done. The controller 33 is provided with a memory 34. In this memory 34, the optimum opening degree of the EGR valve 23 corresponding to the respective detection outputs of the rotation sensor 29, the load sensor 31 and the water temperature sensor 35 is stored as a map. Further, the memory 34 stores the temperature (for example, 80 ° C.) of the intake port 21a that opens and closes the on-off valve 28.

  Operation | movement of the exhaust gas recirculation apparatus of the engine 11 comprised in this way is demonstrated. The controller 33 opens the EGR valve 23 at a predetermined opening based on the operating state of the engine 11, that is, the detection outputs of the rotation sensor 29 and the load sensor 31. Further, when the controller 33 detects that the temperature sensor 32 is equal to or higher than a predetermined temperature (for example, 80 ° C.), the controller 33 opens the on-off valve 28 based on the detection output of the temperature sensor 32. When the controller 33 controls the valve driving means 23d to open the EGR valve 23 by a predetermined amount, a part of the exhaust gas flows into the EGR pipe 17 as EGR gas. The EGR gas is first cooled to about 150 ° C. by the first EGR cooler 22 a and then flows into the EGR valve 23. Since the temperature of the EGR gas flowing into the EGR valve 23 is 150 ° C. or higher, moisture and hydrocarbon components contained in the EGR gas are not condensed. As a result, since the condensate 26 does not adhere to the rotating shaft 23b, the valve body 23c, etc. of the EGR valve 23, the rotating shaft 23b or the like due to the attachment of the condensate 26 to the rotating shaft 23b, the valve body 23c, etc. A situation of malfunction of the valve body 23c or the like does not occur.

  The EGR gas that has passed through the EGR valve 23 is cooled to about 80 ° C. by the second EGR cooler 22b. At this time, since the temperature of the EGR gas in the second EGR cooler 22b is less than 100 ° C., the moisture and hydrocarbon components contained in the EGR gas are condensed and the condensate 26 is generated. The condensate 26 is separated from the EGR gas by the gas-liquid separation means 24 and accumulated in the liquid reservoir 24b, and then flows into the distribution pipe 27b through the outlet pipe 27a of the condensate supply passage 27 by its own weight, and further supplied. The gas flows into the intake ports 21a through the short pipes 27c and the communication holes 27d and is vaporized. At this time, the condensate is provided by making a difference in level to the introduction pipe 27a so that the gas-liquid separation means 24 side of the introduction pipe 27a of the condensate supply passage 27 is positioned higher than the intake port 21a side, and inclining with a predetermined downward gradient. 26, and the leading end of the introduction pipe 27a is connected to the center in the longitudinal direction of the distribution pipe 27b, so that the condensate 26 is supplied to each cylinder 19a almost equally and the condensate 26 is supplied to each intake port. The condensate 26 can be supplied to each cylinder 19a without using power such as a pump for supplying to 21a. On the other hand, the EGR gas that has passed through the gas-liquid separation means 24 flows into the EGR gas mixing section 18 and is mixed with the intake air, and then flows into each cylinder 19a. As a result, variations in the EGR rate between the cylinders 19a of the engine 11 can be suppressed, so that deterioration of the engine 11 performance can be prevented. Further, since the intake air temperature of each intake port 21a is reduced due to the vaporization of the condensate 26, the volume efficiency of the engine 11 can be improved and the maximum combustion temperature of the fuel in each cylinder 21a of the engine 11 can be kept low. Can be suppressed.

  On the other hand, immediately after the engine 11 is started, the controller 33 determines that the engine 11 is in the warm-up operation based on the detection outputs of the rotation sensor 29, the load sensor 31, and the water temperature sensor 35, and has a relatively small opening. Open the EGR valve 23. Further, when the controller 33 detects that the temperature sensor 32 is lower than a predetermined temperature (for example, 80 ° C.), the controller 33 closes the on-off valve 28 based on the detection output of the temperature sensor 32. By opening the EGR valve 23 with a relatively small opening, a part of the exhaust gas is recirculated to the intake pipe 12b through the EGR pipe 17 as EGR gas. The maximum combustion temperature of the fuel is kept low, and the generation of NOx is suppressed. Further, by closing the on-off valve 28, even if the condensate 26 is separated from the EGR gas by the second EGR cooler 22b, the condensate 26 is not supplied to each intake port 21a. Is not further reduced by vaporization of the condensate 26. As a result, it is possible to prevent a decrease in the performance of the engine 11 immediately after the engine 11 is started. Here, even if the on-off valve 28 is closed, the amount of EGR gas passing through the second EGR cooler 22b of the EGR pipe 17 is small and the warm-up time is relatively short. Therefore, the gas-liquid separation means 24 is separated from the EGR gas. The amount of the condensate 26 collected in the liquid reservoir 24b is small, and the condensate 26 does not overflow from the liquid reservoir 24b.

  In the above embodiment, a diesel engine is used as the engine. However, a gasoline engine may be used as long as the engine includes an exhaust gas recirculation device. In the above embodiment, two EGR coolers are provided in series with the EGR pipe. However, one EGR cooler may be provided in the EGR pipe, or three EGR coolers or four or more EGR coolers may be provided in the EGR pipe. May be provided in series. Furthermore, in the above embodiment, a filter using a metal mesh or a plastic mesh having a predetermined mesh is used as the gas-liquid separating means. However, an apparatus that separates the condensate from the EGR gas by centrifugation may be used.

11 Diesel engine (engine)
DESCRIPTION OF SYMBOLS 12 Intake passage 13 Exhaust passage 17 EGR pipe 21a Intake port 22 EGR cooler 22a 1st EGR cooler 22b 2nd EGR cooler 23 EGR valve 24 Gas-liquid separation means 26 Condensate 27 Condensate supply passage 28 On-off valve 32 Temperature sensor 33 Controller

Claims (3)

An EGR pipe (17) that recirculates a part of the exhaust gas flowing through the exhaust passage (13) of the engine (11) to the intake passage (12) as EGR gas, and the EGR pipe (17) provided in the EGR pipe (17) An EGR cooler (22) that cools the EGR gas flowing through the EGR pipe, an EGR valve (23) that is provided in the EGR pipe (17) and adjusts the flow rate of the EGR gas that passes through the EGR pipe (17), and the engine (11 In an exhaust gas recirculation device for an engine comprising a controller (33) for controlling the EGR valve (23) in accordance with the operation status of
Gas-liquid separation means (24) provided in the EGR pipe (17) and cooled by the EGR cooler (22) and separating the condensate (26) generated in the EGR cooler (22) from the EGR gas;
A condensate supply passage (27) for guiding the condensate (26) separated by the gas-liquid separation means (24) to each intake port (21a) of the engine (11) ;
An on-off valve (28) provided in the condensate supply passage (27) for opening and closing the condensate supply passage (27);
The temperature further comprising a temperature sensor (32) for detecting the intake port provided in the intake port (21a) (21a),
An exhaust gas recirculation device for an engine, wherein the controller (33) controls the on-off valve (28) based on a detection output of the temperature sensor (32) .   The height difference is given to the said condensate supply path (27) so that the said gas-liquid separation means (24) side of the said condensate supply path (27) may become a position higher than the said intake port (21a) side. Engine exhaust gas recirculation device.   The EGR cooler (22) includes first and second EGR coolers (22a, 22b) provided in series in the EGR pipe (17) in order from the exhaust passage (13) to the intake passage (12). The EGR valve (23) is provided in an EGR pipe (17) between the first EGR cooler (22a) and the second EGR cooler (22b), and the EGR gas is 150 ° C. in the first EGR cooler (22a). The engine exhaust gas recirculation device according to claim 1, wherein the exhaust gas recirculation device is configured to be cooled to a predetermined temperature of less than 100 ° C by the second EGR cooler (22b) after being cooled to the predetermined temperature.

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