Engine intake system structure

Abstract

To provide an EGR introduction part structure for an engine capable of introducing intake air in which a concentration of exhaust recirculation gas is made uniform to a plurality of cylinders.SOLUTION: An intake system structure for an engine includes: a surge tank 11 provided in an intake passage 6; branch pipes 12 each branching a flow of intake air from the surge tank 11 into each cylinder; and an EGR passage 45 for introducing part of exhaust gas as EGR gas into the intake passage 6 in an EGR ring 41 from a ring hole 51 provided in the EGR ring 41 on the upstream side in the surge tank 11 toward the right side in the vehicle width direction. An upper wall 11a of the surge tank 11 includes a tank inflow port 42 connected to the EGR ring 41, and a lower wall 11b includes a tank discharge port 43 connected to the branch pipe 12. By protruding a lower end of the EGR ring 41 into the surge tank 11, a protruding part 41a extending in the surge tank 11 is provided on the right side in the vehicle width direction of a peripheral edge of the tank inflow port 42.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a structure of an exhaust gas recirculation gas introduction portion in an intake passage of a vehicle. [Background technology]

[0002] Many engines installed in vehicles are equipped with an EGR device (exhaust gas recirculation device) to improve exhaust performance. The EGR device has an EGR passage that connects the exhaust passage and the intake passage, and recirculates part of the exhaust gas (EGR gas) from the exhaust passage to the intake passage, lowering the oxygen concentration in the intake air. This lowers the temperature inside the engine's combustion chamber and suppresses the emission of NOx from the engine.

[0003] The multi-cylinder engine described in Patent Document 1 is structured to introduce EGR gas (exhaust gas recirculation) near the point where the intake passage is divided into each cylinder, and adopts a configuration in which the EGR gas is introduced in a substantially tangential direction from the outer periphery of the intake passage, which generates a swirling flow of EGR gas in the intake passage and promotes mixing of the EGR gas with the intake air. Furthermore, in the multi-cylinder engine described in Patent Document 2, a large-diameter main intake passage with low heat dissipation and a small-diameter secondary intake passage with high heat dissipation are provided between the EGR gas inlet and the engine cylinders, and the main intake passage has an opening / closing valve. When the engine is under low load, the opening / closing valve is closed and only the secondary intake passage is opened, thereby disclosing a technology for promoting mixing of the intake air and the EGR gas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3539246 [Patent Document 2] Japanese Patent Application Publication No. 5-99080 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the intake air amount and EGR gas amount are small, for example, during idling, the swirling flow of the EGR gas is weak and the EGR gas may flow directly into the branch passages to each cylinder, resulting in a biased flow of the EGR gas into some cylinders, even if the EGR gas is introduced tangentially to the intake passage as in Patent Document 1. In addition, Patent Document 2 has problems in that the intake resistance changes significantly due to the operation of the opening and closing valve, which may complicate engine control, and the parts cost increases due to the addition of the opening and closing valve.

[0006] The present invention has been made in consideration of such problems, and its purpose is to provide an EGR introduction structure for an engine that can introduce intake air with a uniform concentration of exhaust recirculated gas into multiple cylinders. [Means for solving the problem]

[0007] In order to achieve the above object, the intake system structure of the engine according to the present invention is an intake system structure of an engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas as exhaust gas recirculation gas to an intake passage, comprising: a surge tank provided in the intake passage; an upstream intake passage provided upstream of the surge tank and provided with a first inlet through which the exhaust gas recirculation gas is introduced; a plurality of downstream intake passages provided downstream of the surge tank and supplying intake air to each cylinder of the engine; and an exhaust gas recirculation passage that introduces the exhaust gas recirculation gas by shifting from the first inlet to one side within the upstream intake passage, wherein the surge tank has a tank inlet that is provided on an upstream tank wall surface and is connected to the upstream intake passage, and a wall portion extending into the surge tank is provided on the first side of the periphery of the tank inlet. The wall portion is inclined toward the opposite side from the one side toward the downstream side. It is characterized by:

[0008] As a result, the exhaust recirculation gas that has flowed into the upstream intake passage so as to be biased to one side is prevented from moving further to the one side than the wall when it flows into the surge tank. This prevents the exhaust recirculation gas from moving too much toward the wall of the surge tank. The exhaust recirculation gas collides with the wall, weakening the inertial force of the exhaust recirculation gas and promoting mixing with the intake air. Furthermore, by inclining the wall portion toward the opposite side from the one side as it approaches the downstream side, the exhaust gas recirculation gas can be easily guided along the wall portion to the opposite side of the wall portion even if the height of the wall portion is made lower, This makes it possible to make the concentration of exhaust gas recirculated gas uniform in the surge tank even under conditions where the intake volume and flow rate of exhaust gas recirculated gas are different. Moreover, the intake system structure of an engine according to the present invention is an intake system structure for an engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas to an intake passage as exhaust recirculation gas, comprising: a surge tank provided in the intake passage; an upstream intake passage provided upstream of the surge tank and provided with a first inlet through which the exhaust recirculation gas is introduced; a plurality of downstream intake passages provided downstream of the surge tank and supplying intake air to each cylinder of the engine; and an exhaust recirculation passage that introduces the exhaust recirculation gas by shifting the first inlet to one side of the upstream intake passage, wherein the surge tank has a tank inlet provided on an upstream tank wall surface and connected to the upstream intake passage, and a wall portion extending into the surge tank is provided on the one side of the periphery of the tank inlet, and the wall portion has a semicircular cross section perpendicular to the extension direction of the wall portion that is concave towards the one side. This prevents the exhaust recirculation gas from moving too far toward the wall of the surge tank, and the collision of the exhaust recirculation gas with the wall weakens the inertial force of the exhaust recirculation gas and promotes mixing with the intake air.Furthermore, by making the wall so that the cross section perpendicular to the extension direction of the wall is semicircular and concave on one side, the dispersion of the exhaust recirculation gas that collides with the wall is suppressed and the exhaust recirculation gas is more likely to be guided to the opposite side of the wall, making it possible to make the concentration of exhaust recirculation gas in the surge tank uniform even under conditions where the intake air volume and exhaust recirculation gas flow rate are different.

[0009] Preferably, the exhaust gas recirculation passage extends from a side opposite to the one side toward the first inlet, and the first inlet is provided in a region of the upstream intake passage opposite to the one side. As a result, the exhaust recirculation gas that has passed through the first inlet from the exhaust recirculation passage and flowed into the upstream intake passage flows toward the wall of the upstream intake passage on the opposite side to the first inlet. In this way, with a simple configuration, the exhaust recirculation gas can be introduced so as to be biased toward one side of the upstream intake passage.

[0010] Preferably, the intake passage further includes a second inlet provided in the region of the one side of the upstream intake passage, at least a portion of which opens toward the opposite side from the one side, for introducing exhaust recirculation gas into the upstream intake passage. As a result, the exhaust gas recirculation gas is introduced into the upstream intake passage from the second inlet toward the opposite side from the one side, making it easier for the exhaust gas recirculation gas to be introduced to the opposite side of the wall in the surge tank. Therefore, even if the height of the wall is low, the concentration of the exhaust gas recirculation gas in the surge tank can be made uniform.

[0011] Preferably, the wall portion is formed such that a downstream end of the upstream intake passage projects into the surge tank. This makes it easy to form a wall portion inside the surge tank. 。

[0013] good Preferably, the upstream intake passage extends in a protruding direction of the wall portion toward the surge tank. This causes the intake air to flow along the wall toward the surge tank, making it easier for the exhaust gas recirculation gas flowing toward the wall to mix with the intake air. Effect of the Invention

[0014] According to the engine intake system structure of the present invention, by shifting the exhaust recirculation gas to one side and flowing it into the upstream intake passage, and by providing a wall portion on one side, it is possible to make the concentration of exhaust recirculation gas uniform in the surge tank even under conditions where the intake air volume and exhaust recirculation gas flow rate are different, so that intake air with a uniform exhaust recirculation gas concentration can be introduced into multiple cylinders, improving the effectiveness of the exhaust recirculation device. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a front part of a vehicle according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a vertical sectional view of an intake system accessory of an engine according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is a vertical sectional view of an intake system accessory of the engine of the first embodiment. [Figure 4] FIG. 2 is a cross-sectional view of an intake system accessory of the engine of the first embodiment. [Diagram 5] FIG. 6 is a vertical sectional view of an intake system accessory of an engine according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a cross-sectional view of an intake system accessory of an engine according to a second embodiment. [Figure 7] FIG. 11 is a vertical sectional view of an intake system accessory of an engine according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic structural diagram of the front part of a vehicle 1 employing an intake system structure for an engine 3 according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of an intake system accessory disposed in front of an engine 3 according to a first embodiment of the present invention, as viewed from the right side in the vehicle width direction when mounted on a vehicle. FIG. 3 is a vertical cross-sectional view of the intake system accessory of the engine 3 according to the first embodiment. FIG. 4 is a horizontal cross-sectional view of the intake system accessory of the engine 3 according to the first embodiment. FIG. 3 is a cross-sectional view of the AA portion described in FIG. 2. FIG. 4 is a cross-sectional view of the BB portion described in FIG. 3.

[0017] As shown in Fig. 1, a vehicle 1 embodying the present invention is equipped with a power unit 4 including an engine 3 in an engine compartment 2 at the front. The vehicle 1 is a plug-in hybrid vehicle capable of operating in an EV mode, a series mode, and a parallel mode. The power unit 4 includes the engine 3 and a driving motor and a power generating motor generator (not shown). The driving motor and the power generating motor generator are disposed to the left of the engine 3 in the vehicle width direction. The power generating motor generator is also used as a starter motor for the engine 3.

[0018] The engine 3 is a four-cylinder engine, and is mounted transversely on the vehicle 1. An intake manifold 5 is provided on a front surface 3a of the engine 3, and an intake passage 6 is arranged therein. On the other hand, an exhaust manifold 7 is provided on the rear side of the engine 3, and an exhaust passage 8 is arranged therein. A throttle valve 10 is provided in the intake passage 6. A surge tank 11 is provided between the throttle valve 10 of the intake passage 6 and the intake manifold 5.

[0019] The throttle valve 10 is located at the upper part of the front surface 3a of the engine 3, and is disposed between a branch pipe 12 (downstream intake passage) connected to the second cylinder located in the center of the engine 3 in the vehicle width direction, and a branch pipe 12 connected to the third cylinder. The surge tank 11 is provided along the front surface 3a of the engine 3 and is disposed below the throttle valve 10. Branch pipes 12 of the intake manifold 5 are connected from the surge tank 11 to each cylinder. The branch pipes 12 are bent from the lower surface of the surge tank 11 toward the front side of the vehicle, extend upward adjacent to the front side of the surge tank 11, and are connected to intake ports 13 of each cylinder provided at the upper part of the front surface 3a of the engine 3.

[0020] Meanwhile, a front catalyst 20 is provided in the exhaust passage 8 downstream of the exhaust manifold 7. Also, a rear catalyst 21 is provided in the exhaust passage 8 downstream of the front catalyst 20. The front catalyst 20 and the rear catalyst 21 are exhaust purification catalysts such as three-way catalysts. The front catalyst 20 is relatively small, and is disposed adjacent to the rear surface of the engine 3. The front catalyst 20 is disposed close to the engine 3 so that exhaust gas from the engine 3 immediately flows into it, in order to improve exhaust purification performance during cold operation, such as immediately after the engine is started. The rear catalyst 21 is relatively large, and is disposed, for example, under the floor of the vehicle 1.

[0021] Furthermore, the engine 3 is equipped with an EGR device 30 (exhaust gas recirculation device). The EGR device 30 recirculates a portion of the exhaust gas to the intake passage 6, thereby reducing the oxygen concentration of the intake air and suppressing a rise in temperature inside the combustion chamber of the engine 3. This reduces NOx in the exhaust gas of the engine 3. The EGR device 30 includes an EGR passage 31 (exhaust gas recirculation passage) that connects the intake passage 6 and the exhaust passage 8, an EGR valve 34 that is interposed in the EGR passage 31 and adjusts the opening area of ​​the EGR passage 31, and an EGR cooler 32 that is provided in the EGR passage 31.

[0022] The EGR cooler 32 is a water-cooled cooler that lowers the temperature of EGR gas (exhaust gas recirculation gas), which is exhaust gas passing through the EGR passage 31, and is disposed along the rear surface of the engine 3. By lowering the temperature of the EGR gas, the EGR cooler 32 further suppresses the rise in temperature of the intake air into which the EGR gas has been introduced, thereby improving the NOx reduction effect of the EGR device 30. The EGR passage 31 runs from near the exhaust outlet of the front catalyst 20, passes through an EGR cooler 32, extends upward from the rear left part of the engine, wraps around to the front side of the engine 3, passes through an EGR valve 34 located on the upper left part of the engine, and is connected to the intake passage 6 between the throttle valve 10 and the surge tank 11.

[0023] 2 to 4, an adapter 40 and an EGR ring 41 (upstream intake passage) are provided between the throttle valve 10 and the surge tank 11 as part of the intake passage 6 of the engine 3. The adapter 40 and the EGR ring 41 are cylindrical and have approximately the same diameter, and the lower end of the adapter 40 and the upper end of the EGR ring 41 are connected to each other and extend in the vertical direction along the front surface of the engine 3. The upper end of the adapter 40 is connected to the throttle valve 10, and the lower part of the EGR ring 41 is connected to a tank inlet 42 provided in an upper wall 11a (upstream tank wall surface) of the surge tank 11.

[0024] The surge tank 11 is formed in a substantially rectangular box shape, and a tank inlet 42 is provided at a position slightly to the right in the vehicle width direction and toward the front of the vehicle (one side) from approximately the center position in the left-right direction (vehicle width direction) of the upper wall 11a. Four tank discharge ports 43 corresponding to the number of cylinders of the engine 3 are arranged side by side in the left-right direction at a position on the vehicle rear side (other side) of the lower wall 11b (downstream tank wall surface) of the surge tank 11. That is, in the surge tank 11, the tank inlet 42 and the tank discharge port 43 are arranged offset in the vehicle front-rear direction.

[0025] From each tank discharge port 43 of the surge tank 11 , a branch pipe 12 of the intake manifold 5 extends adjacent to the lower and front sides of the surge tank 11 toward the intake port 13 of the corresponding cylinder at the left or right position. The connection point between the EGR passage 31 in the EGR device 30 and the intake passage 6, that is, the point where the EGR gas is introduced into the intake passage 6, is located between the throttle valve 10 and the surge tank 11.

[0026] The EGR passage 31 downstream of the EGR valve 34 extends along the upper wall 11a of the surge tank 11 from the left in the vehicle width direction to the right in the vehicle width direction (one side), and has an EGR inlet passage portion 45 (exhaust gas recirculation passage inlet portion) formed to surround the side surface of the EGR ring 41. The EGR introduction passage portion 45 is a tubular member having a rectangular vertical cross section that is formed integrally with the upper wall 11a of the surge tank 11, and has a front-to-rear width (e.g., a few cm) that is approximately the same as or slightly larger than the diameter of the EGR ring 41, and is rectangular in shape with the vertical width smaller than the front-to-rear width.

[0027] The EGR introduction passage 45 extends slightly to the right in the vehicle width direction from the center position of the EGR ring 41 in the left-right direction. The EGR introduction passage 45 is disposed offset toward the rear of the vehicle with respect to the axis of the EGR ring 41. A gap of, for example, about 1 cm is formed between the rear inner wall surface of the EGR introduction passage 45 and the rear outer wall surface of the EGR ring 41. The front outer wall surface of the EGR ring 41 abuts against the front inner wall surface of the EGR introduction passage 45. That is, the internal space of the EGR introduction passage 45 faces the rear and left portions of the outer wall surface of the EGR ring 41.

[0028] Furthermore, a ring hole 50 (first inlet) is provided in the rear part of the outer wall surface of the EGR ring 41 facing the internal space of the EGR introduction passage portion 45, and a ring hole 51 (first inlet) is provided in the left part in the vehicle width direction. As a result, the EGR gas that has passed through the EGR valve 34 is introduced from the EGR introduction passage portion 45 through the ring holes 50 and 51 into the intake passage 6 in the EGR ring 41.

[0029] In detail, the EGR introduction passage 45 has a main body 45a (exhaust gas recirculation passage introduction portion) extending tangentially from the EGR ring 41 to the left in the vehicle width direction, and its left end in the vehicle width direction extends circumferentially along the outer wall of the EGR ring 41 to a position slightly to the right in the vehicle width direction from the center position in the vehicle width direction of the EGR ring 41. A ring hole 50 is provided in the EGR ring 41 at a position on the vehicle rear side that is a contact point with the EGR introduction passage 45, and a ring hole 51 is provided in the main body 45a.

[0030] Furthermore, the left half of the lower end of the EGR ring 41 in the vehicle width direction protrudes downward into the surge tank 11 to a position substantially equal to or slightly larger than the upper wall 11a of the surge tank 11, and the right half of the lower end of the EGR ring 41 in the vehicle width direction protrudes significantly downward into the surge tank 11 beyond the upper wall 11a. Note that a protruding portion 41a (wall portion) which is the right (one lateral) half in the vehicle width direction of the lower end (downstream end) of the EGR ring 41 has the same diameter as the upper portion of the EGR ring 41 and has a semicircular cross section recessed to the right in the vehicle width direction. The lower end and the left side of the protruding portion 41a in the vehicle width direction of the EGR ring 41 are open into the surge tank 11. As described above, in this embodiment, the throttle valve 10 and the intake manifold 5, which are intake system devices, are provided on the front surface 3a side of the engine 3 mounted transversely on the vehicle 1. In addition, a surge tank 11 is provided between the throttle valve 10 and the intake manifold 5. The branch pipes 12 of the intake manifold 5 are connected from the surge tank 11 to each cylinder, and the intake air is branched in the surge tank 11 and supplied to each cylinder via each branch pipe 12.

[0031] Furthermore, an EGR device 30 is provided that supplies EGR gas, which is a part of the exhaust gas, to the intake passage 6. The EGR gas is introduced into the intake air at an EGR ring 41 provided in the intake passage 6 between the throttle valve 10 and the surge tank 11. The EGR ring 41 has ring holes 50, 51 as inlets for EGR gas to the intake passage 6, with the ring hole 50 opening toward the front of the vehicle and the ring hole 51 opening toward the right in the vehicle width direction. On the other hand, each tank discharge port 43 that discharges the intake air from the surge tank 11 to the branch pipe 12 all faces upward.

[0032] Therefore, the EGR gas introduced into the intake passage 6 in the EGR ring 41 from the ring holes 50 and 51 is unlikely to flow directly toward either of the tank discharge ports 43 which are the inlets of the branch pipes 12 . In addition, the EGR introduction passage 45, which is the most downstream part of the EGR passage 31 that introduces the EGR gas to the intake passage 6, extends to the right in the vehicle width direction toward the EGR ring 41, and the ring hole 51 is provided in a part (area) on the left side of the EGR ring 41 in the vehicle width direction, so that most of the EGR gas that has passed through the EGR passage 31 passes through the ring hole 51 and flows into the EGR ring 41. This makes it easy for the EGR gas to be biased to the right side in the vehicle width direction in the EGR ring 41. However, since the lower end of the EGR ring 41 has a part on the right side in the vehicle width direction protruding and a part on the left side in the vehicle width direction that hardly protrudes and is open, the EGR gas that has moved toward the right side in the vehicle width direction through the EGR introduction passage 45 is suppressed from moving to the right side in the vehicle width direction by the protruding part 41a. Furthermore, the EGR gas and air are diffused to the left side in the vehicle width direction of the protruding part 41a of the EGR ring 41, and the amount of EGR gas flowing into the cylinder on the left side in the vehicle width direction increases.

[0033] This makes it possible to equalize the amount of EGR gas flowing from the surge tank 11 to each cylinder of the engine 3, and to introduce intake air with a uniform EGR gas concentration into each cylinder, thereby improving the effectiveness of the EGR device 30. In particular, by intentionally biasing the EGR gas to the right side in the vehicle width direction within the EGR ring 41 and directing the EGR gas to the left side in the vehicle width direction by the protruding portion 41a, it becomes possible to diffuse the EGR gas and promote its mixing with the intake air even if the intake air volume and the flow rate of the exhaust gas recirculated gas are small, and to make the concentration of the exhaust gas recirculated gas in the surge tank 11 uniform.

[0034] Furthermore, in this embodiment, a ring hole 50 is also provided on the vehicle rear side of the EGR ring 41, so that part of the EGR gas moving to the right in the vehicle width direction in the EGR introduction passage portion 45 flows into the EGR ring 41 toward the protruding portion 41a on the right in the vehicle width direction. Also, part of the EGR gas from the ring hole 50 changes direction toward the front of the vehicle and flows into the EGR ring 41. As a result, the EGR gas that flows into the EGR ring 41 from the ring hole 50 becomes a swirling flow in the EGR ring 41, which can promote mixing of the intake air and the EGR gas in the EGR ring 41.

[0036] The EGR introduction passage 45 has a piping shape that extends toward the right in the vehicle width direction and has a closed tip, and the EGR ring 41 penetrates the tip (right end) of the EGR introduction passage 45 to form an introduction section for EGR gas. This allows the introduction portion of the EGR gas into the intake passage 6 to be configured simply and compactly.

[0037] In addition, by extending the lower end portion of the EGR ring 41 on the right side in the vehicle width direction downward, a protrusion 41a, which is a wall portion that suppresses the movement of EGR gas to the right side in the vehicle width direction within the surge tank 11, can be easily formed. In addition, the protrusion 41a formed at the lower end of the cylindrical EGR ring 41 has a semicircular cross section perpendicular to the direction in which the protrusion 41a extends that is recessed toward the protrusion 41a, so that the EGR gas is guided toward the center to the left in the vehicle width direction without being dispersed by the protrusion 41a. This allows the protrusion 41a to effectively guide the EGR gas to the left in the vehicle width direction and promotes mixing of the intake air and the EGR gas.

[0038] In addition, since the EGR ring 41 extends downward toward the surge tank 11, which is the protruding direction of the protruding portion 41a, the intake air passing through the EGR ring 41 flows toward the surge tank 11 along the protruding portion 41a, making it easier for the EGR gas flowing toward the protruding portion 41a to mix with the intake air. Moreover, since the EGR introduction passage 45 is formed integrally with the upper wall 11a of the surge tank 11, the surge tank 11 and the EGR introduction passage 45 can be configured compactly. Moreover, the branch pipe 12 is configured to extend toward the front side of the vehicle along the lower wall 11b of the surge tank 11. Since the branch pipe 12 is connected to the rear side of the surge tank 11, the length of the branch pipe 12 in the front-rear direction of the vehicle can be secured to increase the bending radius, while the lengths of the surge tank 11 and the branch pipe 12 in the front-rear direction of the vehicle can be reduced. Therefore, the intake resistance in the branch pipe 12 can be reduced, and the structure of the intake system of the engine 3 can be configured compactly.

[0039] In addition, the tank inlet 42, which is the opening position of the lower end of the EGR ring 41, is offset from the tank discharge outlet 43, which is the opening position of the branch pipe 12 in the surge tank 11, in the vehicle fore-and-aft direction perpendicular to the inflow direction of the intake air from the tank inlet 42, and the bottom wall 11b of the surge tank 11 is located ahead of the opening side of the tank inlet 42. Therefore, the intake air containing EGR gas that flows into the surge tank 11 from the tank inlet 42 collides with the bottom wall 11b of the surge tank 11 and spreads in the vehicle front-rear direction and the vehicle width direction. Furthermore, by extending a part of the EGR ring 41 downward, the distance between the bottom end of the EGR ring 41 and the bottom wall 11b of the surge tank 11 is shortened, so that the intake air containing EGR gas that flows into the surge tank 11 from the bottom end of the right side part in the vehicle width direction of the EGR ring 41 is more likely to collide with the bottom wall 11b of the surge tank 11. This promotes mixing of the EGR gas in the surge tank 11 and further suppresses unevenness in the EGR gas concentration of the intake air supplied to each cylinder from each tank outlet 43.

[0040] In the above embodiment, the EGR ring 41 is provided with two ring holes 50, 51 for introducing EGR gas, but only the ring hole 51 on the EGR introduction passage 45 side may be provided, or only the ring hole 50 may be provided. By providing the protrusion 41a on the right side in the vehicle width direction of the lower end of the EGR ring 41, it becomes easier to introduce the EGR gas that has flowed into the EGR ring 41 from the ring hole 51 or the ring hole 50 from the surge tank 11 to the cylinder on the left side in the vehicle width direction, and unevenness in the EGR gas concentration of the intake air supplied to each cylinder can be suppressed.

[0041] Fig. 5 is a vertical cross-sectional view of an intake system accessory of an engine 3 according to a second embodiment of the present invention. Fig. 6 is a horizontal cross-sectional view of an intake system accessory of an engine 3 according to the second embodiment. The intake system accessories of the engine 3 according to the second embodiment of the present invention differ from the first embodiment in that the structure of the EGR introduction passage portion 45 and the ring hole of the EGR ring 41 are also provided at a position (region) on the right side in the vehicle width direction.

[0042] 5 and 6, the EGR introduction passage 45 includes a main body 45a extending leftward in the vehicle width direction from the EGR ring 41, and an extension 45b (exhaust gas recirculation passage extension) extending circumferentially along the outer wall of the EGR ring 41 on the right side in the vehicle width direction opposite to the main body 45a. The EGR ring 41 includes a ring hole 50 provided at a position on the rear side of the vehicle and a ring hole 51 provided at a position (region) on the left side in the vehicle width direction, as well as a ring hole 52 (second introduction port) provided at a position (region) on the right side in the vehicle width direction facing the extension 45b.

[0043] As a result, in the second embodiment, a portion of the EGR gas flows from the ring hole 52 into the EGR ring toward the left side in the vehicle width direction, making it easier for the EGR gas to flow into the cylinder on the left side in the vehicle width direction. Therefore, in this embodiment, by providing the ring hole 52, the amount of protrusion of the protruding portion of the EGR ring 41 can be made smaller than in the first embodiment.

[0044] In the above embodiment, three ring holes 50, 51, and 52 are provided in the EGR ring 41 to introduce EGR gas, but this is not limited to the above, and only two holes, either one of the ring holes 50 and 51 and the ring hole 52, may be provided. In this case as well, the amount of protrusion of the protruding portion of the EGR ring 41 can be reduced compared to the first embodiment.

[0045] FIG. 7 is a vertical cross-sectional view of an intake system accessory of an engine 3 according to a third embodiment of the present invention. The intake system accessories of the engine 3 according to the third embodiment of the present invention differ from those of the first embodiment in the shape of the protruding portion 41a of the EGR ring 41. 7, the protruding portion 41a of the EGR ring 41 of this embodiment is inclined toward the center as it extends downward. That is, the protruding portion 41a of the EGR ring 41 is inclined toward the left in the vehicle width direction as it extends downstream.

[0046] As a result, the EGR gas that flows into the EGR ring 41 and moves downward along the inner wall surface of the protruding portion 41a flows into the surge tank 11 along the inclined inner wall surface of the protruding portion 41a toward the left side in the vehicle width direction. This makes it easier for the EGR gas to flow into the cylinders on the left side in the vehicle width direction. In addition, the intake air that moves downward along the inner wall surface of the EGR ring 41 also flows into the surge tank 11 toward the center, i.e., toward the left side in the vehicle width direction, along the inclined inner wall surface of the protruding portion 41a, so that the EGR gas is guided to the left side in the vehicle width direction by the intake air, making it easier for the EGR gas to flow into the cylinders on the left side in the vehicle width direction. This makes it possible to further suppress the bias in the EGR gas concentration of the intake air supplied to each cylinder.

[0047] The present invention is not limited to the above embodiment. For example, in the above embodiment, the lower end of the EGR ring 41 protrudes into the surge tank 11 to form a wall, but a wall extending into the surge tank 11 may be provided separately from the EGR ring 41 on the right side of the periphery of the tank inlet in the vehicle width direction. Further, the detailed shape of the protruding portion 41a may be appropriately changed so as to suppress the EGR gas from moving to the right in the vehicle width direction inside the surge tank 11.

[0048] Further, in the above embodiment, the adapter 40 and the EGR ring 41 are separate structures, but the adapter 40 and the EGR ring 41 may be integrally formed. In the present embodiment, a plurality of tank discharge ports 43 are provided in accordance with the number of cylinders of the engine 3, but the present invention is not limited to this and the number of tank discharge ports 43 may be smaller than the number of cylinders of the engine 3.

[0049] In addition, in this embodiment, the present invention is applied to the engine 3 mounted on a plug-in hybrid vehicle, but the present invention can also be applied to engines mounted on hybrid vehicles or gasoline vehicles, or engines other than those mounted on vehicles. The present invention can be widely applied to engines equipped with an EGR device. [Explanation of symbols]

[0050] 3 Engine 6 Intake passage 11 Surge Tank 12 Branch pipe (downstream intake passage) 30 EGR device (exhaust gas recirculation device) 41 EGR ring (upstream intake passage) 41a Projection (wall) 42 Tank inlet 43 Tank outlet 45 EGR introduction passage (exhaust recirculation passage) 51 Ring hole (first inlet) 52 Ring hole (second inlet)

Claims

1. An intake system structure of an engine equipped with an exhaust gas recirculation device that recirculates a part of the exhaust gas to an intake passage as an exhaust gas recirculation gas, a surge tank provided in the intake passage; an upstream intake passage provided upstream of the surge tank and having a first inlet through which the exhaust gas recirculation gas is introduced; a plurality of downstream intake passages provided downstream of the surge tank and configured to supply intake air to each cylinder of the engine; an exhaust gas recirculation passage for introducing the exhaust gas recirculated gas into the exhaust gas recirculation passage, the exhaust gas recirculation passage being offset from the first inlet port toward one side of the upstream intake passage, the surge tank has a tank inlet that is provided on an upstream tank wall surface and is connected to the upstream intake passage, A wall portion is provided on the one side of a periphery of the tank inlet, the wall portion extending into the surge tank, The wall portion is inclined toward the opposite side from the one side toward the downstream side. An intake system structure for an engine.

2. An intake system structure of an engine equipped with an exhaust gas recirculation device that recirculates a portion of the exhaust gas to an intake passage as exhaust gas recirculation gas, a surge tank provided in the intake passage; an upstream intake passage provided upstream of the surge tank and having a first inlet through which the exhaust gas recirculation gas is introduced; a plurality of downstream intake passages provided downstream of the surge tank and configured to supply intake air to each cylinder of the engine; an exhaust gas recirculation passage for introducing the exhaust gas recirculated gas into the exhaust gas recirculation passage, the exhaust gas recirculation passage being offset from the first inlet port toward one side of the upstream intake passage, the surge tank has a tank inlet that is provided on an upstream tank wall surface and is connected to the upstream intake passage, A wall portion is provided on the one side of a periphery of the tank inlet, the wall portion extending into the surge tank, The wall portion has a cross section perpendicular to the extending direction of the wall portion that is semicircular and recessed toward the one side. An intake system structure for an engine.

3. The exhaust gas recirculation passage extends from the side opposite to the one side toward the first inlet, The first inlet is provided in a region opposite to the one side of the upstream intake passage.

3. The engine intake system structure according to claim 1 or 2.

4. The exhaust gas recirculation passage further includes a second inlet that is provided in the region of the one side of the upstream intake passage, at least a portion of which opens toward the opposite side from the one side, and that introduces exhaust gas recirculation gas into the upstream intake passage.

4. The engine intake system structure according to claim 3.

5. 5. The engine intake system structure according to claim 1, wherein the wall portion is formed such that a downstream end of the upstream intake passage projects into the surge tank.

6. 6. The engine intake system structure according to claim 1, wherein the upstream intake passage extends in a protruding direction of the wall portion toward the surge tank.

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