JP5966589B2 - Low pressure loop EGR device - Google Patents

Description

  The present invention relates to a low-pressure loop EGR device that can stably reduce intake air temperature.

  In recent years, due to increasing interest in the environment, NOx (nitrogen oxides) contained in exhaust gas is provided by providing an EGR device (exhaust gas circulation device) that returns part of the exhaust gas of the engine (internal combustion engine) to the intake system of the engine. Various proposals have been made to reduce the above.

  The EGR device includes a low-pressure loop EGR device (see Patent Document 1) that returns low-pressure exhaust gas downstream of the exhaust purification device provided in the exhaust pipe of the engine to the intake intake pipe at the compressor inlet of the turbocharger, and high pressure at the engine outlet. There is known a high-pressure loop EGR device (see Patent Document 2) that directly returns the exhaust gas to the intake pipe at the engine inlet.

  The low-pressure loop EGR device shown in Patent Document 1 returns a part of the low-pressure exhaust gas at the outlet of the exhaust purification device as EGR gas to the intake intake pipe at the compressor inlet of the turbocharger and mixes it with fresh air, and the mixed intake air is compressed by the compressor. Therefore, the pressure difference between the exhaust gas pressure at the exhaust purification device outlet and the intake air pressure at the compressor inlet is stable, so that stable exhaust circulation is achieved. Has the advantage to be obtained.

  On the other hand, in the high-pressure loop EGR device shown in Patent Document 2, a part of the high-pressure exhaust gas at the engine outlet is directly returned to the intake pipe at the engine inlet as EGR gas. In some cases, the differential pressure between the gas pressure and the intake air pressure at the engine inlet cannot be stably obtained. For this reason, stable exhaust circulation may not be obtained.

  In the low-pressure loop EGR device shown in Patent Document 1, since the EGR gas is mixed with the fresh air introduced into the compressor, the temperature of the intake air supplied to the compressor rises, and the intake air is compressed by the compressor. As a result, the temperature of the intake air supplied to the engine further rises. When the temperature of the intake air supplied to the compressor rises, there is a problem that the compression rate of the compressor is lowered, and there is a problem that the heat load on the compressor impeller is increased. Further, when the temperature of the intake air supplied to the engine rises, there is a problem that the heat load on the intake pipe increases, and further, there is a problem that the intake amount of the engine intake decreases, and the exhaust gas temperature at the engine outlet rises. Therefore, there is a problem that the heat load on the turbine increases.

  In order to cope with such a problem, in the low-pressure loop EGR device, the temperature of the intake air supplied to the compressor is lowered by installing an EGR cooler in the EGR pipe to lower the temperature of the EGR gas, An intercooler is installed in the pipe to lower the temperature of the intake air supplied to the engine.

JP 2011-001893 A JP 2004-257329 A

  In the low-pressure loop EGR device shown in Patent Document 1, if the temperature of the intake air supplied to the compressor can be lowered even slightly, the compression rate of the compressor can be increased and the thermal load on the compressor impeller can be reduced. Furthermore, since the intake air temperature for the engine is reduced, the heat load on the intake pipe is reduced, the intake amount of the engine intake is increased, and the exhaust gas temperature at the engine outlet is lowered, so that the heat load on the turbine is reduced. Is obtained.

  However, the conventional low pressure loop EGR device has a problem that the intake air cannot be cooled to a temperature lower than the intake air temperature determined by the cooling capacity of the EGR cooler.

  On the other hand, in the high-pressure loop EGR device shown in Patent Document 2, a radiating fin is arranged in an intake pipe that returns a part of the high-pressure exhaust gas at the engine outlet as EGR gas. It describes that the intake air temperature is lowered.

  However, in the high-pressure loop EGR device, depending on the operating conditions, the differential pressure between the engine outlet and the engine inlet cannot be stably obtained, so that stable exhaust circulation may not be obtained, and the intake air of such a high-pressure loop EGR device may not be obtained. There is a problem that a stable cooling effect of the intake air cannot be expected even if heat radiating fins are installed on the pipe.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a low-pressure loop EGR device that can stably reduce the intake air temperature.

The present invention is a turbocharger having a turbine that is rotated by exhaust gas of an internal combustion engine, and a compressor that rotates together with the turbine and compresses intake air taken in by an intake intake pipe and supplies compressed intake air to the internal combustion engine through an intake pipe. A low-pressure loop EGR device comprising an EGR pipe for returning a part of exhaust gas downstream of the turbine of the turbocharger as EGR gas to the intake intake pipe of the compressor inlet,
Corresponding to swirling means for mixing EGR gas from the EGR pipe with swirling with respect to the intake air of the intake intake pipe and supplying the mixed gas to the compressor, and swirling flow formed inside the intake intake pipe by the swirling means. The present invention relates to a low-pressure loop EGR device including an intake air temperature reduction device having a radiating fin disposed on an outer peripheral surface of an intake intake pipe.

  In the low-pressure loop EGR device, the intake air temperature reducing device includes a throttle portion having a flow passage cross-sectional area that decreases toward the downstream side in the intake intake pipe so as to increase the swirling force of the swirling flow formed by the swirling means. It is preferable to have.

  In the low-pressure loop EGR device, the swiveling means may connect the EGR pipe to the intake intake pipe so that EGR gas is supplied from the tangential direction to the intake intake pipe.

  In the low-pressure loop EGR device, the swivel means may include a swivel guide fin for swirling the EGR gas supplied from the EGR pipe inside the intake intake pipe.

  Further, in the low-pressure loop EGR device, the intake air temperature reducing device may have a radiation fin disposed on an outer peripheral surface of the EGR pipe.

  In the low-pressure loop EGR device, the intake air temperature reducing device may have a radiating fin disposed on an outer peripheral surface of the intake pipe.

  According to the present invention, since the temperature of the intake air supplied to the compressor of the turbocharger can be lowered, the compression rate of the compressor can be increased, the thermal load on the compressor impeller can be reduced, and the temperature of the intake air supplied to the engine As a result, the heat load on the intake pipe is reduced, the intake amount of the engine intake is increased, and the exhaust gas temperature at the engine outlet is lowered, thereby reducing the heat load on the turbine. obtain.

(A) is the cutting | disconnection top view which shows one Example of the low voltage | pressure loop EGR apparatus which has an intake air temperature reduction device of this invention, (b) is the cutting | disconnection front view which looked at (a) from IB direction. (A) is the cutting | disconnection top view which shows the other Example of the low voltage | pressure loop EGR apparatus which has an intake air temperature reduction device of this invention, (b) is the cutting | disconnection front view which looked at (a) from the IIB direction. It is a cutting | disconnection top view which shows another Example of the low voltage | pressure loop EGR apparatus which has an intake air temperature reduction device of this invention. It is a mimetic diagram showing composition of an engine provided with a low-pressure loop EGR device which has an intake air temperature reducing device of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 4 shows an example of an engine (internal combustion engine) equipped with a low pressure loop EGR device having an intake air temperature reducing device of the present invention. In FIG. 4, the flow of exhaust gas and EGR gas is indicated by hatched arrows. The flow of intake air (compressed air) including air (fresh air) and EGR gas is indicated by white arrows.

  An engine 1 (internal combustion engine) shown in FIG. 4 is, for example, an in-line four-cylinder diesel engine, and an intake manifold 4 that distributes intake air (compressed air) from an intake pipe 3 to each cylinder 2 and each cylinder 2. The exhaust manifold 5 for collecting the exhaust gas is provided.

  The engine 1 is equipped with a turbocharger 6 that supercharges intake air into the intake manifold 4 using heat and pressure energy of exhaust gas from the exhaust manifold 5.

  The turbocharger 6 has a bearing housing 7, and a compressor 8 for compressing intake air is disposed on one side of the bearing housing 7 (left side in FIG. 4). A compressor housing 9 fixed to one side of the housing 7 and a compressor impeller 10 rotatably provided in the compressor housing 9 are provided. Further, on the other side of the bearing housing 7 (right side in FIG. 4), a turbine 11 that generates a rotational force using the pressure energy of the exhaust gas from the cylinder 2 is disposed. A turbine housing 12 fixed to the other side of the housing 7 and a turbine impeller 13 rotatably provided in the turbine housing 12 are provided. In the bearing housing 7, a turbine shaft 14 (rotor shaft) that integrally connects the compressor impeller 10 and the turbine impeller 13 coaxially is rotatably provided via a bearing 15.

  An intake intake pipe 17 having an air cleaner 16 is connected to the inlet (left side in FIG. 4) of the compressor 8 constituting the turbocharger 6, and the outlet (upper side in FIG. 4) of the compressor housing 9 is The intake pipe 3 connected to the intake manifold 4 is connected, and an intercooler 18 for cooling the intake air (compressed air) is disposed in the middle of the intake pipe 3.

  An exhaust conduit 19 that guides exhaust gas from the exhaust manifold 5 is connected to an inlet (upper side in FIG. 4) of the turbine housing 12 of the turbine 11 that constitutes the turbocharger 6. 4 is connected to an exhaust pipe 20, and an exhaust purification device 21 is disposed in the middle of the exhaust pipe 20.

  A low pressure loop EGR device 30 is formed between the exhaust pipe 20 downstream of the exhaust purification device 21 and the intake intake pipe 17 at the inlet of the compressor 8. In the low-pressure loop EGR device 30, one end of an EGR pipe 22 for taking out a part of the low-pressure exhaust gas as EGR gas is connected to the outlet of the exhaust purification device 21 of the exhaust pipe 20, and the other end of the EGR pipe 22 is connected to the other end. The intake intake pipe 17 is connected. An EGR cooler 23 is disposed in the middle of the EGR pipe 22, and the inside of the EGR pipe 22 is opened and closed on the downstream side of the EGR cooler 23 (the flow rate of EGR gas in the EGR pipe 22 is adjusted). An EGR valve 24 is provided.

  1 (a) and 1 (b) show an embodiment of a low-pressure loop EGR device 30 having an intake air temperature reducing device 28 of the present invention. In the connecting portion for connecting the intake intake pipe 17 to an EGR pipe 22, FIG. The EGR gas from the EGR pipe 22 generates EGR with respect to the axial center (center line) of the intake intake pipe 17 so that a swirl flow R having a swirl component in the same direction as the rotation direction of the compressor impeller 10 is generated. The shaft center (center line) of the piping 22 is eccentrically connected, and thereby, the turning means 25 is configured in which the EGR gas of the EGR piping 22 is supplied in a tangential direction from the opening 22a to the intake intake pipe 17. doing. The opening 22 a shown in FIG. 1B has a flat shape that is long in the axial direction of the intake intake pipe 17 with respect to the inner surface of the intake intake pipe 17, and the inner bottom surface of the intake intake pipe 17 from the bottom surface of the opening 22 a. A flat portion 17a extending in the axial direction of the EGR pipe 22 is formed in X until the EGR gas from the EGR pipe 22 is directed toward the inner surface (curved surface) of the intake intake pipe 17 through the flat portion 17a. It has been introduced smoothly. The EGR gas supplied to the intake intake pipe 17 from the opening 22a flows in the intake intake pipe 17 by forming a swirl flow R indicated by an arrow, and is mixed with intake air (fresh air) taken in from the air cleaner 16 while being mixed. Supplied to the impeller 10.

  Further, on the downstream side (compressor impeller 10 side) of the intake intake pipe 17 in the immediate vicinity of the opening 22 a of the EGR pipe 22, toward the downstream side so as to increase the turning force of the turning flow R formed by the turning means 25. A narrowed portion 26 having a reduced channel cross-sectional area is formed.

  An outer peripheral surface of the intake intake pipe 17 between the opening 22a of the EGR pipe 22 and the compressor housing 9 in the intake intake pipe 17 corresponds to a portion where the swirl flow R is formed inside the intake intake pipe 17. In addition, a plurality of heat dissipating fins 27 are arranged. The radiating fins 27 have a length corresponding to a portion where the swirl flow R is formed inside the intake intake pipe 17 and project radially outward from the outer surface of the intake intake pipe 17. Thus, they are arranged with a predetermined interval in the circumferential direction. The projecting height of the heat dissipating fins 27 is set to a predetermined height that can exert a heat dissipating effect. Here, it is preferable that the intake intake pipe 17 and the radiating fins 27 are made of a material having high thermal conductivity.

  The swivel means 25, the throttle portion 26 and the heat radiating fin 27 constitute an intake air temperature reducing device 28.

  The operation of the embodiment of FIG. 1 will be described with reference to FIG.

  When the exhaust gas from the exhaust manifold 5 is circulated through the exhaust conduit 19 to the turbine housing 12 of the turbine 11 during the operation of the engine 1 in FIG. 4, the turbine impeller 13 is utilized using the heat and pressure energy of the exhaust gas. Rotational force (rotational torque) is generated at the same time, and the compressor impeller 10 rotates integrally through the turbine shaft 14 along with the rotation of the turbine impeller 13. As a result, air (fresh air) taken into the compressor housing 9 from the intake intake pipe 17 is compressed by the compressor impeller 10, and the compressed intake air is supplied to the intake manifold 4 via the intake pipe 3. The intake air before being supplied to the intake manifold 4 is cooled by the intercooler 18.

  Further, when the EGR valve 22 is opened by the EGR valve 24 during operation of the engine 1 (the flow rate of EGR gas in the EGR pipe 22 is adjusted), the downstream side of the turbine 11 in the exhaust pipe 20 (in other words, A part of the exhaust gas flows into the EGR pipe 22 as EGR gas from the downstream side of the exhaust purification device 21 in the exhaust pipe 20. Then, the EGR gas that has flowed into the EGR pipe 22 is cooled by the EGR cooler 23 and supplied to the upstream side of the compressor 8 in the intake intake pipe 17 through the opening 22a.

  As described above, the EGR gas taken out from the downstream side of the turbine 11 in the exhaust pipe 20 during operation of the engine 1 is returned to the upstream side of the compressor 8 in the intake intake pipe 17, so that the low-pressure loop EGR device 30 is Thus, the combustion temperature of the engine 1 can be lowered, and the amount of NOx emissions can be reduced.

  Here, as shown in FIG. 1B, since the opening 22a of the EGR pipe 22 constitutes the turning means 25 that is eccentrically connected to the intake intake pipe 17, the EGR gas in the EGR pipe 22 is taken into the intake air. Supplied from the tangential direction with respect to the intake pipe 17, and thus a swirling force is given to the EGR gas to form a swirl flow R in the intake intake pipe 17. The swirl flow R swirls with a swirl component in the same direction as the rotation direction of the compressor impeller 10. By this swirl flow R, the intake air (fresh air) taken into the intake air intake pipe 17 via the air cleaner 16 and the EGR gas are uniformly mixed, and the uniform intake air temperature is maintained. It is introduced into the impeller 10.

  Further, a throttle portion 26 is formed downstream of the opening 22a of the EGR pipe 22 in the intake intake pipe 17 so that the sectional area of the intake intake pipe 17 gradually decreases toward the downstream side. The swirl force of the swirl flow R given to the EGR gas is further increased. By increasing the intake swirl force in this way, the temperature distribution of the intake air is made more uniform, and the intake performance of the compressor impeller 10 is also increased, so that the compression ratio of the compressor 8 is also increased.

  Here, since the radiating fins 27 are provided on the outer peripheral surface of the intake intake pipe 17 in which the swirl flow R is formed inside the intake intake pipe 17, the intake air flowing inside the intake intake pipe 17 is provided. Can be effectively reduced by the heat dissipating fins 27.

  That is, in the intake air intake pipe 17, EGR gas having a higher temperature than fresh air flows so as to surround the main flow of fresh air to form a swirl flow R, and the swirl flow R of EGR gas is the intake air intake pipe 17. Since the distance of contact with the inner surface of the intake air becomes longer, heat transfer between the EGR gas and the inner surface of the intake intake pipe 17 is promoted, and the heat transferred to the intake intake pipe 17 is effectively externalized by the radiating fins 27. Therefore, the temperature of the intake air is effectively reduced. Furthermore, since the flow velocity of the swirl flow R is increased by providing the throttle portion 26, the heat transfer between the EGR gas and the inner surface of the intake intake pipe 17 is further increased, and therefore the cooling effect of the intake air by the radiating fins 27 is further increased. Enhanced.

  Thus, since the temperature of the intake air in the intake air intake pipe 17 is lowered by the intake air temperature reducing device 28, the compression rate of the compressor 8 can be further increased, and the temperature of the compressor 8 is increased by the compression. The heat load on the compressor impeller 10 is also reduced. Furthermore, since the temperature of the intake air supplied to the engine 1 also decreases, the thermal load on the intake pipe 3 decreases, the intake amount of intake air in the engine 1 increases, and the exhaust gas temperature at the outlet of the engine 1 decreases. As a result, the heat load on the turbine 11 can also be reduced.

  In the above embodiment, the EGR cooler 23 is provided. However, due to the nature of the internal combustion engine and the vehicle, the intake air temperature in the intake air intake pipe 17 can be sufficiently lowered by the intake air temperature reducing device 28. In some cases, the EGR cooler 23 can be omitted.

  2A and 2B show another embodiment of the present invention. In FIGS. 2A and 2B, the position of the opening 22a of the EGR pipe 22 on the inner surface of the intake intake pipe 17 is shown. The turning guide fins 29 are provided so as to sandwich the opening 22a between the upstream side and the downstream side of the intake air. The swivel guide fin 29 has a height H equal to the height of the opening 22a in the radial direction of the intake intake pipe 17, and moves forward from the position of the opening 22a in the direction in which EGR gas is supplied. It is inclined with respect to a plane orthogonal to the axis of the intake intake pipe 17 at a required extending angle α to the downstream side in the intake air flow direction (compressor 8 side). 2 (b) extends from the position of the opening 22a to the flat portion 17a, and further extends from the flat portion 17a to a position of approximately a quarter of the inner surface of the intake intake pipe 17. The extension length of the turning guide fins 29 can be set arbitrarily.

  Further, the turning guide fins 29 are fixed to the surface perpendicular to the axis of the intake intake pipe 17 at a required mounting angle β toward the downstream side in the flow direction of the intake air (compressor 8 side). . FIG. 2A shows a case where the extension angle α and the attachment angle β of the turning guide fin 29 are the same angle, but the extension angle α and the attachment angle β of the turning guide fin 29 may be different. .

  FIG. 2A illustrates the case where the turning guide fin 29 is disposed so that the opening 22a of the EGR pipe 22 is sandwiched between the upstream side and the downstream side of the intake air. In addition, it may be provided on one of the downstream sides, or three or more turning guide fins 29 may be provided.

  In the embodiment of FIG. 2, since the turning guide fins 29 are provided, the EGR gas introduced into the intake intake pipe 17 from the opening 22 a is guided by the turn guide fins 29 and the intake intake pipe 17. Since the stable swirl flow R is reliably formed in the inside, the stable swirl flow R enhances the mixing of EGR gas with the intake air (fresh air) and the heat of the EGR gas with respect to the inner surface of the intake intake pipe 17 The heat dissipation effect of the heat dissipation fins 27 can be enhanced.

  FIG. 3 shows still another embodiment of the present invention, which is not provided with the throttle portion 26 as compared with the embodiment of FIGS. 1 and 2, and therefore, the intake intake pipe in the embodiment of FIG. 17 'has a constant pipe diameter from the part which has the opening 22a of the EGR piping 22 to the compressor housing 9 entrance. And the opening 22a part of the said EGR piping 22 comprises the turning means 25 by connecting from the tangential direction with respect to the intake intake pipe 17 'similarly to FIG.1 (b) and FIG.2 (b), Radiating fins 27 are provided on the outer periphery of the intake intake pipe 17 ′ having a constant diameter between the opening 22 a and the compressor housing 9. Therefore, in the embodiment of FIG. 3, the intake air temperature reducing device 28 is constituted by the turning means 25 and the heat radiating fins 27.

  In the embodiment of FIG. 3 as well, since the swirling means 25 forms a swirl flow R in the intake intake pipe 17, the swirl flow R improves the mixing of EGR gas and intake air (fresh air), and the intake air. The heat transfer of the EGR gas to the inner surface of the intake pipe 17 is promoted, and the heat radiation effect by the heat radiation fins 27 can be enhanced.

  In FIG. 4, the radiating fins 31 are arranged on the outer peripheral surface of the EGR pipe 22, and the configuration of the embodiment shown in FIGS. It is said.

  Furthermore, in FIG. 4, the radiation fin 32 is arrange | positioned in the outer peripheral surface between the compressor housing 9 and the intercooler 18 in the said intake pipe 3, In the structure of the Example shown in the said FIGS. The intake air temperature reducing device 28 includes the structure of the heat radiating fins 32.

  As shown in FIG. 4, if the radiating fins 31 are installed on the outer peripheral surface of the EGR pipe 22, the temperature of the EGR gas before mixing with the intake air in the intake intake pipe 17 can be lowered. Further, if the radiating fins 32 are installed on the outer peripheral surface of the intake pipe 3, the temperature of the intake air supplied to the engine 1 can be reduced, so that the heat load on the intake pipe 3 is reduced, The intake amount of intake air in the engine 1 is further increased, and the exhaust gas temperature at the outlet of the engine 1 is lowered, whereby the heat load on the turbine 11 can be further reduced.

  FIG. 4 shows a case where the heat radiation fin 31 for the EGR pipe 22 and the heat radiation fin 32 for the intake pipe 3 are provided in the configuration including the intake temperature reduction device 28 having the throttle portion 26. Also in the configuration of the intake air temperature reducing device 28 that does not include the throttle portion 26 shown in FIG. 3, the radiating fins 31 for the EGR pipe 22 and the radiating fins 32 for the intake pipe 3 can be provided.

  The low-pressure loop EGR device of the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the scope of the present invention.

1 engine (internal combustion engine)
DESCRIPTION OF SYMBOLS 3 Intake pipe 6 Turbocharger 8 Compressor 11 Turbine 17 Intake intake pipe 17 'Intake intake pipe 22 EGR piping 22a Opening 25 Turning means 26 Restriction part 27 Radiation fin 28 Intake temperature reduction device 29 Turning guide fin 30 Low pressure loop EGR device 31 Radiation fin 32 Radiation fin R Swirling flow

Claims (6)

A turbocharger comprising: a turbine that is rotated by exhaust gas of an internal combustion engine; and a compressor that rotates together with the turbine and compresses intake air taken in by an intake intake pipe and supplies the compressed intake air to the internal combustion engine through an intake pipe, A low-pressure loop EGR device comprising an EGR pipe for returning a part of exhaust gas downstream of a turbocharger turbine as EGR gas to an intake intake pipe at the compressor inlet;
Corresponding to swirling means for mixing EGR gas from the EGR pipe with swirling with respect to the intake air of the intake intake pipe and supplying the mixed gas to the compressor, and swirling flow formed inside the intake intake pipe by the swirling means. A low-pressure loop EGR device comprising an intake air temperature reduction device having a radiating fin disposed on an outer peripheral surface of the intake intake pipe.   The intake air temperature reducing device includes a throttle portion having a flow passage cross-sectional area that decreases toward a downstream side so as to increase a swirl force of swirl flow formed by the swirl means in the intake intake pipe. Item 2. The low-pressure loop EGR device according to Item 1.   3. The low-pressure loop EGR according to claim 1, wherein the swivel unit connects the EGR pipe to the intake intake pipe so that EGR gas is supplied from a tangential direction to the intake intake pipe. apparatus.   The said turning means is provided with the turning guide fin which gives turning to the EGR gas supplied from the said EGR piping inside the said intake pipe. Low pressure loop EGR device.   The low-pressure loop EGR device according to any one of claims 1 to 4, wherein the intake air temperature reduction device includes a heat radiation fin disposed on an outer peripheral surface of the EGR pipe.   The low-pressure loop EGR device according to any one of claims 1 to 5, wherein the intake air temperature reducing device includes a heat dissipating fin disposed on an outer peripheral surface of the intake pipe.

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