JP6146567B2 - Engine intake system structure - Google Patents

Description

  The present invention relates to an intake system structure for an engine that includes an intake passage communicating with a combustion chamber and an intercooler that is provided in the intake passage and cools intake air introduced into the combustion chamber.

  Generally, an intercooler for cooling intake air pressurized by a supercharger is provided in an intake passage of an engine equipped with a supercharger (such as a turbocharger). Some engines equipped with a supercharger include an exhaust gas recirculation (EGR) device that recirculates a part of exhaust gas to an intake passage before the supercharger and reburns it with fresh air.

  In the engine having such a configuration, when the intake air is cooled in the intercooler, moisture is condensed and condensed water is generated. Condensate water generated from the intercooler is removed, for example, by being discharged to the outside at a predetermined timing, etc., but a part of the condensed water is discharged from the intercooler to the intake passage on the downstream side and constitutes the intake passage It will adhere to the inner surface of the (intake pipe).

  The EGR gas supplied to the intake passage by exhaust gas recirculation may have a relatively high temperature, and the EGR gas contains a relatively large amount of moisture as water vapor. For this reason, in the case of intake air containing EGR gas, the condensed water tends to adhere to the intake pipe.

  If condensed water adheres to the intake pipe in this way, the intake pipe may be corroded by the condensed water. In addition, if a large amount of condensed water adhering to the intake pipe flows into the combustion chamber in the form of water droplets, there is a risk of causing torque fluctuations or exhaust gas deterioration, and furthermore, the engine may be damaged by the so-called water hammer phenomenon. There is also a risk of it.

  Various techniques for removing moisture in the intake air have been proposed. For example, a water droplet separator is provided on the downstream side of the air supply cooler (intercooler), and water in the air supply is removed by this water droplet separator (see, for example, Patent Document 1).

  Further, this Patent Document 1 describes re-evaporating water droplets that have passed through the water droplet separator by ejecting high-temperature bypass air supply to the air supply tube downstream of the intake air cooler via the bypass tube. ing.

Japanese Utility Model Publication No. 1-111141

  If much of the condensed water adhering to the intake pipe can be re-evaporated, it is considered that the above-described torque fluctuation and exhaust gas deterioration can be suppressed.

  However, just by injecting the bypass intake air into the intake pipe through the bypass passage connected to the intake pipe on the downstream side of the intercooler, it is not possible to re-evaporate much of the condensed water adhering to the inner wall surface of the intake pipe. difficult. Therefore, even with the technique described in Patent Document 1, there is a possibility that a large amount of condensed water still flows in the form of water droplets into the combustion chamber, and the intake pipe may be corroded by the condensed water.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an intake system structure for an engine that can suppress a large amount of condensed water from flowing into a combustion chamber in the form of water droplets. .

  In a first aspect of the present invention for solving the above-described problem, an intake air of an engine comprising: an intake passage communicating with a combustion chamber; and an intercooler connected to the intake passage for cooling the intake air introduced into the combustion chamber. A system structure in which one end is connected to a downstream intake passage which is the intake passage on the intake downstream side of the intercooler, and the other end is connected to a space higher in pressure than the pressure in the downstream intake passage. An engine intake system having a passage and having an outlet opening at one end of the connection passage toward the intercooler side and along an inner wall surface of the downstream intake passage. In the structure.

  In such a first aspect, since air is injected toward the intercooler side through the connection passage and along the inner wall surface of the downstream intake passage, the droplets attached to the inner surface of the downstream intake passage The condensed water is atomized and mixed with the intake air.

  According to a second aspect of the present invention, in the engine intake system structure of the first aspect, the outlet portion includes an inflow restricting portion that restricts inflow of intake air from the downstream intake passage to the outlet portion. It is in the intake system structure of the engine characterized by this.

  In the second aspect, invasion of condensed water from the downstream intake passage into the outlet portion can be suppressed, and corrosion of the intake pipe that forms the downstream intake passage including the outlet portion due to condensed water is suppressed.

  According to a third aspect of the present invention, in the intake system structure of the engine according to the second aspect, the opening area of the inflow restricting portion of the outlet portion is gradually narrowed toward the distal end side of the outlet portion. The engine intake system structure is characterized by

  In this 3rd aspect, since the opening area is narrowing gradually, the penetration | invasion of the condensed water from a downstream side intake passage into an exit part can be suppressed. Further, since the injection speed of the air injected into the downstream intake passage through the connection passage is increased, the droplet-shaped condensed water adhering to the inner surface of the downstream intake passage can be atomized more effectively. .

  According to a fourth aspect of the present invention, in the engine intake system structure according to the second or third aspect, the outlet portion includes a first intake pipe that forms the downstream intake passage, and the first intake pipe. The intake system structure of the engine is characterized in that it is formed between a second intake pipe provided and a spiral guide wall is provided at the inflow restricting portion of the outlet portion.

  In the fourth aspect, it is possible to suppress the intrusion of condensed water from the downstream side intake passage into the outlet portion by the guide wall. Further, since the guide wall is provided, the air passage distance in the outlet portion is increased, so that the condensed water that has entered the outlet portion can be effectively atomized and discharged to the downstream intake passage.

  According to a fifth aspect of the present invention, in the engine intake system structure according to any one of the first to fourth aspects, the other end of the connection passage is the intake passage upstream of the intercooler. The intake system structure of the engine is characterized by being connected to an upstream intake passage.

  In the fifth aspect, a connection passage can be formed by a passage that bypasses the intercooler, and there is no need to provide another device or the like for introducing high-pressure air into the downstream intake passage, thereby suppressing an increase in cost. Can do.

  As described above, according to the intake system structure of the engine of the present invention, the droplet-shaped condensed water adhering to the inner surface of the downstream intake passage is efficiently atomized or vaporized. Accordingly, it is possible to suppress a large amount of condensed water from flowing into the combustion chamber of the engine in the form of water droplets, and to suppress occurrence of torque fluctuations, exhaust gas deterioration, and the like.

It is a figure showing the whole engine composition concerning Embodiment 1 of the present invention. It is sectional drawing which shows the intake system structure of the engine which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the intake system structure of the engine which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the intake system structure of the engine which concerns on Embodiment 3 of this invention. It is sectional drawing which shows the intake system structure of the engine which concerns on other embodiment of this invention.

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

(Embodiment 1)
First, the overall configuration of the engine according to the first embodiment will be described. As shown in FIG. 1, the engine 10 according to the present embodiment is an in-line four-cylinder diesel engine (hereinafter simply referred to as “engine”) including four cylinders (combustion chambers) 11 arranged in series. An intake manifold 12 is connected to an intake port (not shown) of each cylinder 11, and an intake pipe 13 is connected to the intake manifold 12. On the other hand, an exhaust manifold 14 is connected to an exhaust port (not shown) of each cylinder 11, and an exhaust pipe 15 is connected to the exhaust manifold 14.

  In addition, an injector 16 for injecting fuel corresponding to each cylinder 11 is provided. Fuel is supplied to each injector 16 from a high-pressure fuel distribution pipe 17. Although illustration is omitted, the fuel supplied from the low-pressure fuel pump in the fuel tank is supplied to the high-pressure fuel distribution pipe 17 while being pressurized to a predetermined pressure by the high-pressure fuel pump.

  A turbocharger (supercharger) 18 is provided in the middle of the intake pipe 13 and the exhaust pipe 15. In the turbocharger 18, when exhaust gas flows from each cylinder (combustion chamber) 11, the turbine is rotated by the flow of the exhaust gas, and the compressor rotates with the rotation of the turbine, and the turbocharger 18 enters the turbocharger 18 from the intake pipe 13. Air is sucked in and pressurized.

  An air cleaner 19 and a first throttle valve 20 are provided in the intake pipe 13 upstream of the turbocharger 18. The air cleaner 19 is provided with a humidity sensor 21 that detects the humidity of the intake air. The first throttle valve 20 adjusts the amount of fresh air that has passed through the air cleaner 19 and, by this adjustment, the amount of exhaust gas (low pressure EGR gas) introduced into the intake pipe 13 via a low pressure EGR pipe described later. Amount) indirectly. An air flow sensor 22 that detects the intake air flow rate is provided on the downstream side of the air cleaner 19.

  An intercooler 23 for cooling the intake air is disposed in the intake pipe 13 on the downstream side of the turbocharger 18. The intake pipe 13 on the downstream side of the intercooler 23 is provided with a second throttle valve 25 that is an intake adjustment valve that opens and closes the intake pipe 13 by driving an electric actuator.

  The second throttle valve 25 adjusts the intake air amount (new air amount + low pressure EGR gas amount) that has passed through the intercooler 23, and exhaust gas introduced into the intake pipe 13 via the EGR pipe described later by this adjustment. The gas amount (EGR gas amount) is indirectly adjusted.

  One end of an EGR pipe (EGR flow path) 26 through which high-pressure exhaust gas (EGR gas) circulates is connected to the intake pipe 13 downstream of the second throttle valve 25. The other end of the EGR pipe 26 is connected to the upstream side of the turbocharger 18 of the exhaust pipe 15. An EGR cooler 27 is provided in the EGR pipe 26, and an EGR valve 28 is provided in a connection portion of the EGR pipe 26 with the intake pipe 13. When the EGR valve 28 is opened, a part of the high-pressure exhaust gas flowing upstream from the turbocharger 18 of the exhaust pipe 15 flows into the EGR pipe 26 and is cooled by the EGR cooler 27, and then the intake pipe 13. To be supplied. The EGR valve 28 may be provided so that the amount of EGR gas flowing from the EGR pipe 26 into the intake pipe 13 can be adjusted.

  Further, a diesel oxidation catalyst 31 that is an exhaust purification catalyst and a diesel particulate filter 32 that is an exhaust purification filter are arranged in order from the upstream side of the exhaust pipe 15 downstream of the turbocharger 18.

  A low-pressure EGR pipe (low-pressure EGR) in which a part of the low-pressure exhaust gas (low-pressure EGR gas) circulates downstream of the turbocharger 18 of the exhaust pipe 15, in this embodiment, downstream of the diesel particulate filter 32. One end of the (flow path) 33 is connected. The other end of the low pressure EGR pipe 33 is connected to the intake pipe 13 between the turbocharger 18 and the first throttle valve 20. The low pressure EGR pipe 33 is provided with a low pressure EGR cooler 34 and a low pressure EGR valve 35 as in the case of the EGR pipe 26. When the low pressure EGR valve 35 is opened, the low pressure EGR gas flowing downstream from the turbocharger 18 in the exhaust pipe 15 is cooled by the low pressure EGR cooler 34 and supplied to the intake pipe 13. Yes.

  A differential pressure sensor 36 is provided at both ends of the low pressure EGR pipe 33. The differential pressure sensor 36 detects the differential pressure between the pressure upstream of the turbocharger 18 in the intake pipe 13 and the pressure downstream of the turbocharger 18 in the exhaust pipe 15. That is, the flow rate and flow rate of the low pressure EGR gas flowing through the low pressure EGR pipe 33 are obtained from the detection result of the differential pressure sensor 36.

  By the way, in the engine 10 having such a configuration, when the intake air is cooled in the intercooler 23, moisture is condensed and condensed water is generated. In particular, when the low pressure EGR gas is circulated, condensed water is easily generated. Condensed water is discharged from the intercooler 23 to the outside at a predetermined timing, but part of the condensed water flows out to the downstream side of the intercooler 23 and adheres to the inner wall surface of the intake pipe (intake passage) 13. Then, due to the droplet-shaped condensed water adhering to the inner wall surface of the intake pipe 13, problems such as torque fluctuation, deterioration of exhaust gas, and corrosion of the intake pipe 13 may occur.

  Therefore, in the present invention, one end is connected to the downstream intake pipe (downstream intake passage) 13A which is the intake pipe 13 on the intake downstream side (downstream in the intake flow direction) of the intercooler 23, and the other end is connected to the downstream intake pipe. A connection passage connected to a space higher in pressure than the pressure in 13A is provided, and air (in this embodiment, “bypass intake” described below) is provided in the downstream intake pipe 13A through the connection passage in a direction opposite to the flow of intake air. ). Thereby, since the droplet-like condensed water adhering to the inner wall surface of the downstream side intake pipe 13A is atomized or vaporized, the occurrence of torque fluctuation or the like can be suppressed. Hereinafter, the intake system structure of the engine 10 according to the present embodiment will be described.

  In the intake system structure of the engine 10 of the present embodiment, the intercooler 23 is connected in the middle of the intake pipe 13 connected to each combustion chamber 11 as described above. Further, a bypass pipe (connection passage) 40 that bypasses the intercooler 23 is connected to the intake pipe 13. That is, one end side of the bypass pipe 40 is connected to the downstream side intake pipe 13A, and the other end side is an upstream side intake passage that is an upstream side intake passage of the intercooler 23 and is a higher pressure space than in the downstream side intake pipe 13A. (Upstream side intake passage) 13B is connected.

  Both ends of the bypass pipe 40 are connected to the downstream side intake pipe 13A and the upstream side intake pipe 13B in the vicinity of the intercooler 23, but the connection position of the other end of the bypass pipe 40 to the upstream side intake pipe 13B is The position may be a distance from the intercooler 23. However, the pressure of the portion where the bypass pipe 40 of the upstream side intake pipe 13B is connected needs to be higher than the pressure of the downstream side intake pipe 13A. For this reason, it is preferable that the other end of the bypass pipe 40 is connected to the upstream side intake pipe 13B on the downstream side of the turbocharger 18.

  In the present embodiment, as shown in FIG. 2, one end of the bypass pipe 40 is connected to the outlet 50 provided in the intake pipe 13. The bypass intake air flowing through the bypass pipe 40 flows into the outlet portion 50 and is injected into the downstream side intake pipe 13A from the opening 51 of the outlet portion 50. The outlet 50 is provided to open toward the intercooler 23 side and along the inner wall surface of the downstream side intake pipe 13A. That is, the opening 51 of the outlet portion 50 is formed in such a direction that bypass intake air injected from the outlet portion 50 flows along the inner wall surface of the downstream side intake pipe 13A.

  Specifically, the downstream intake pipe 13A, which is the intake passage on the downstream side of the intercooler 23, is formed with a first intake pipe 13a connected to the intercooler 23 and a smaller diameter than the first intake pipe 13a. One end side is constituted by a second intake pipe 13 b connected to the combustion chamber 11. The second intake pipe 13b is connected to the first intake pipe 13a in a state where the other end side is inserted into the first intake pipe 13a. The outlet 50 is a space between the first intake pipe 13a and the second intake pipe 13b, and is formed over the entire circumference of the downstream intake pipe 13A.

  Thus, in the intake system structure of the engine of the present embodiment, a connection passage is formed by the bypass pipe 40 and the outlet 50, and the inside of the downstream side intake pipe 13A passes from the upstream side intake pipe 13B via the connection path. Bypass intake is injected. That is, the bypass intake air supplied to the outlet 50 via the bypass pipe 40 is directed from the opening 51 of the outlet 50 toward the intercooler 23 side (upstream side) and along the inner wall surface of the first intake pipe 13a. Are injected into the downstream side intake pipe 13A.

  In the intake system structure of the engine according to the present embodiment described above, air (bypass intake) is injected from the opening 51 of the outlet portion 50 into the downstream intake pipe 13A in a direction opposite to the intake air flow at a predetermined timing. . By this bypass intake, the droplet-shaped condensed water adhering to the inner surface of the downstream side intake pipe (first intake pipe) 13A is atomized. In particular, by injecting the bypass intake air in the direction opposite to the flow of the intake air in the downstream side intake pipe 13A, a turbulent flow is formed in the downstream side intake pipe 13A and atomization of condensed water is promoted. Further, since the bypass intake air is hotter than the intake air flowing through the downstream side intake pipe 13A, a part of the condensed water may be vaporized, and the atomization of the condensed water is also promoted.

  In this embodiment, the connection passage is formed by the bypass pipe 40 that bypasses the intercooler 23. Thereby, it is not necessary to provide another device or the like to introduce high-pressure air into the downstream side intake pipe 13A, and an increase in cost can be suppressed.

  By causing the atomized or vaporized condensed water to flow into the combustion chamber 11 together with the intake air, problems such as torque fluctuation and exhaust gas deterioration can be suppressed. Further, since the condensed water is removed from the inner wall surface of the downstream side intake pipe 13A by injection of the bypass intake air, corrosion of the intake pipe 13 can be suppressed.

  An opening / closing valve (opening / closing means) 41 for opening and closing the bypass pipe 40 is provided in the middle of the bypass pipe 40, and the opening / closing valve 41 is appropriately controlled by the control unit 60. The controller 60 appropriately controls the on-off valve 41 according to the operating state of the engine 10, and as a result, appropriately controls the injection of the bypass intake air into the downstream intake pipe 13A. For example, based on the detection result of the airflow sensor 22 and the like, the control unit 60 opens the on-off valve 41 to allow the bypass intake to be taken into the downstream intake when the intake amount of the engine 10 is low (during low load operation). It is injected into the tube 13A. In the operating state of the engine with a small intake amount, the efficiency of the intercooler 23 is increased, the intake air is cooled well, and condensed water is likely to be generated. Therefore, the condensed water adhering to the inner wall surface of the downstream side intake pipe 13A can be atomized (or vaporized) more efficiently.

  Further, based on the detection result of the humidity sensor 21, the control unit 60 may open the on-off valve 41 and inject the bypass intake when the humidity of the intake air in the air cleaner 19 is higher than a predetermined value. As the humidity in the air cleaner 19 is higher, condensed water is more likely to be generated when the intake air is cooled by the intercooler 23. Therefore, by supplying the bypass intake air when the humidity is high, the condensed water adhering to the inner wall surface of the downstream side intake pipe 13A can be atomized (or vaporized) more efficiently.

(Embodiment 2)
FIG. 3 is a cross-sectional view illustrating an intake system structure of the engine according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

  The present embodiment is an example in which an inflow restricting portion that restricts the inflow of intake air from the downstream side intake pipe 13A is provided in the outlet portion 50, and the other configurations are the same as those in the first embodiment.

  Specifically, as shown in FIG. 3, the distal end portion on the other end side of the second intake pipe 13 b is formed so that the inner diameter gradually increases, and as a result, on the distal end side of the outlet portion 50, A gradually decreasing portion 52 is formed as an inflow restricting portion whose opening area gradually decreases toward the opening 51 side.

  In such a configuration of the present embodiment, since the gradually decreasing portion 52 is provided, that is, the opening 51 of the outlet portion 50 is narrowed, the intrusion of condensed water into the outlet portion 50 can be suppressed. . Further, since the opening 51 is narrowed, the injection speed of the bypass intake air injected from the outlet 50 into the downstream side intake pipe 13A is increased, so that the mist of condensed water adhering to the inner surface of the downstream side intake pipe 13A. Can be promoted.

(Embodiment 3)
FIG. 4 is a cross-sectional view showing the intake system structure of the engine according to the third embodiment. In addition, the same code | symbol is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

  The present embodiment is another example of the inflow restricting portion provided in the outlet portion 50, and the other configuration is the same as that of the above-described embodiment.

  Specifically, as shown in FIG. 4, a spiral guide wall 55 is provided in the outlet 50 formed between the first intake pipe 13a and the second intake pipe 13b. And in this embodiment, the part in which the guide wall 55 of the exit part 50 was provided comprises an inflow control part. The inside of the outlet portion 50 is partitioned by the spiral guide wall 55, and the bypass intake air that has flowed into the outlet portion 50 from the bypass pipe 40 is guided by the guide wall 55 and flows along the guide wall 55. It is injected into the intake pipe 13A. The bypass intake air injected into the downstream side intake pipe 13A flows toward the intercooler 23 along the inner wall surface of the downstream side intake pipe 13A while forming a swirling flow, and atomizes condensed water.

  In such a configuration, intrusion of condensed water into the outlet 50 is suppressed by the guide wall 55. Further, the provision of the guide wall 55 increases the passage distance of the bypass intake air in the outlet portion 50. For this reason, even when condensed water intrudes into the outlet 50, the condensed water that has entered the outlet 50 can be efficiently atomized and discharged from the outlet 50 by injection of bypass intake air.

(Other embodiments)
Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. The present invention can be modified as appropriate without departing from the spirit of the present invention.

  In the above-described embodiment, the example in which the outlet 50 is provided between the first intake pipe 13a and the second intake pipe 13b has been described. However, the configuration of the outlet 50 is not limited to this. Absent.

  For example, the outlet portion 50 may be configured by the bypass pipe 40. That is, when the bypass pipe 40 is connected to the downstream side intake pipe 13 </ b> A in a predetermined direction, the connection part of the bypass pipe 40 with the downstream side intake pipe 13 </ b> A constitutes the outlet 50. Specifically, as shown in FIG. 5A, in the axial direction of the downstream side intake pipe 13A, the bypass pipe 40 is inclined toward the downstream side of the downstream side intake pipe 13A by a predetermined angle. Further, as shown in FIG. 5B, in the radial direction of the downstream side intake pipe 13A, the bypass pipe 40 extends in the tangential direction of the downstream side intake pipe 13A.

  In such a configuration, the bypass intake air injected from the bypass pipe 40 into the downstream intake pipe 13A forms a swirling flow along the inner wall surface of the downstream intake pipe 13A toward the intercooler 23 side. Will flow. That is, the connection portion of the bypass pipe 40 with the downstream side intake pipe 13A constitutes an outlet 50 that opens toward the intercooler 23 side and along the inner wall surface of the downstream side intake pipe 13A.

  Of course, even in such a configuration, the condensed water adhering to the inner wall surface of the downstream side intake pipe 13A can be efficiently atomized or vaporized, as in the above-described embodiment. Occurrence of torque fluctuations or the like can be suppressed. Furthermore, since the condensed water is removed from the inner wall surface of the downstream side intake pipe 13A by the injection of the bypass intake air, corrosion of the downstream side intake pipe 13A can also be suppressed.

  In the above-described embodiment, the other end of the bypass pipe 40 is illustrated as being connected to the upstream intake pipe 13B in the vicinity of the inlet of the intercooler 23. However, the other end of the bypass pipe 40 is not necessarily the upstream intake pipe. It may not be connected to 13B. The other end of the bypass pipe 40 only needs to be connected to a position where a bypass intake air having a predetermined temperature or higher and a predetermined pressure or higher can be injected into the downstream intake pipe 13A. For example, the other end of the bypass pipe 40 may be connected to the EGR pipe 26. For example, the other end of the bypass pipe 40 may be connected to a space whose pressure is higher than the pressure in the downstream side intake pipe 13A by a compressor or the like provided separately.

10 Engine 11 Combustion chamber (cylinder)
12 Intake manifold 13 Intake pipe 13A Downstream intake pipe 13B Upstream intake pipe 13a First intake pipe 13b Second intake pipe 14 Exhaust manifold 15 Exhaust pipe 16 Injector 17 High-pressure fuel distribution pipe 18 Turbocharger 19 Air cleaner 20 First Throttle valve 21 Humidity sensor 22 Air flow sensor 23 Intercooler 25 Second throttle valve 26 EGR pipe 27 EGR cooler 28 EGR valve 31 Diesel oxidation catalyst 32 Diesel particulate collection filter 33 Low pressure EGR pipe 34 Low pressure EGR cooler 35 Low pressure EGR Valve 36 Differential pressure sensor 40 Bypass pipe (connection passage)
41 On-off valve 50 Outlet part 51 Opening 52 Decreasing part (inflow restricting part)
55 Guide wall 60 Control unit

Claims (5)

An intake passage communicating with the combustion chamber;
An intercooler connected to the intake passage for cooling the intake air introduced into the combustion chamber;
An intake system structure of an engine comprising
One end is connected to a downstream intake passage that is the intake passage on the intake downstream side of the intercooler, and the other end has a connection passage connected to a space higher in pressure than the pressure in the downstream intake passage,
An intake system structure for an engine, wherein an outlet portion that opens toward the intercooler side and along the inner wall surface of the downstream intake passage is provided at the one end of the connection passage. The intake system structure for an engine according to claim 1,
An intake system structure for an engine, wherein the outlet portion includes an inflow restricting portion that restricts inflow of intake air from the downstream intake passage to the outlet portion. The intake system structure for an engine according to claim 2,
An intake system structure for an engine, wherein an opening area of the inflow restricting portion of the outlet portion is gradually narrowed toward a front end side of the outlet portion. The engine intake system structure according to claim 2 or 3,
The outlet portion is formed between a first intake pipe forming the downstream intake passage and a second intake pipe provided in the first intake pipe;
An intake system structure for an engine, wherein the inflow restricting portion of the outlet portion is provided with a spiral guide wall. The intake system structure for an engine according to any one of claims 1 to 4,
An intake system structure for an engine, wherein the other end of the connection passage is connected to an upstream intake passage which is the intake passage upstream of the intercooler.

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