Engine intake system structure

Abstract

This engine intake system structure is provided with an EGR passage 31 which includes a surge tank 11 in an intake passage 6, has branch pipes 12 that divert intake air from the surge tank 11 to each cylinder, and which recirculates a portion of exhaust gas, serving as EGR gas, to the intake passage 6 inside an EGR ring 41 on an upstream side of the surge tank 11, wherein a tubular EGR introduction passage portion 45 provided in a downstream end portion of the EGR passage 31 is connected to the EGR ring 41 to recirculate the EGR gas to the intake passage 6 inside the EGR ring 41, and is provided with a second surge tank for temporarily storing the EGR gas.

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] In the multi-cylinder engine described in Patent Document 1, an EGR passage is connected to a branch passage (branch pipe) of an intake manifold located at the most downstream of the intake passage, and EGR gas (exhaust gas recirculation) is introduced into each branch passage.

[0004] Furthermore, in Patent Document 1, multiple branch passages are arranged in parallel, an EGR passage is provided extending in a direction intersecting the branch passages, and gas supply ports to each branch passage are provided at the downstream end of the EGR passage, lined up in the extension direction of the EGR passage.

[0005] Furthermore, in Patent Document 1, the flow path cross-sectional area of ​​the EGR passage just before it connects to each branch passage is configured to become smaller from the upstream side to the downstream side, making it easier for EGR gas to flow approximately evenly into each branch passage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-121540 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, since the structure is such that EGR gas is supplied to the intake air in each branch passage respectively, even if the flow path cross-sectional area of ​​the EGR passage is set to become smaller toward the downstream side, when, for example, the engine operation fluctuates, the EGR gas may not flow appropriately into each branch passage in relation to the intake air volume, and the concentration of EGR gas in each cylinder may differ or fluctuate.

[0008] The present invention has been made in consideration of such problems, and its object is to provide an engine intake system structure that can homogenize the concentration of exhaust recirculation gas in the intake air introduced into multiple cylinders. [Means for solving the problem]

[0009] In order to achieve the above object, the engine intake system structure according to the present invention is an intake system structure for an engine, which includes a first surge tank in an intake passage, a branch passage for dividing intake air from the first surge tank to each cylinder, and an exhaust recirculation passage for recirculating a part of the exhaust gas to the intake passage as exhaust recirculation gas, the exhaust recirculation passage is connected to an introduction portion for introducing the exhaust recirculation gas into the intake passage upstream of the first surge tank, and includes a second surge tank for storing the exhaust recirculation gas having a smaller volume than the first surge tank, and the first surge tank and the second surge tank are formed integrally. The second surge tank is formed by a tubular introduction passage portion that closes the downstream end of the exhaust recirculation passage, the introduction portion has the intake passage therein, and a peripheral wall forms a part of the inner wall that is the downstream end side of the introduction passage portion, and is formed by a tubular intake pipe having an opening in the peripheral wall, the intake pipe is disposed offset to one side in the flow path width direction with respect to a center position in the flow path width direction of the introduction passage portion, and is connected to a tank inlet provided on the one side of the first surge tank, there is a gap between the inner wall on the other side in the flow path width direction of the introduction passage portion and the peripheral wall, and the opening is provided in at least one of the peripheral walls in the flow path width direction of the exhaust recirculation gas in the introduction passage portion or on the other side in the flow path width direction. It is characterized by:

[0010] As a result, since the second surge tank is provided in the exhaust recirculation passage, the first surge tank and the second surge tank can be configured compactly, and even when the supply amount of exhaust recirculation gas is small, the exhaust recirculation gas is temporarily stored in the second surge tank before being introduced into the intake passage, the pressure of the exhaust recirculation gas is increased, and the exhaust recirculation gas is stably supplied to the intake passage upstream of the first surge tank, and the mixture of the intake air and the exhaust recirculation gas in the intake passage can be promoted. Furthermore, by temporarily storing the intake air mixed with the exhaust recirculation gas in the first surge tank, the mixture of the intake air and the exhaust recirculation gas is promoted in the first surge tank, and the exhaust recirculation gas in the intake air can be homogenized and supplied to each branch passage. Also, the introduction portion for introducing the exhaust gas recirculation gas into the intake passage and the second surge tank can be realized with a simple structure. The exhaust gas recirculation gas flowing through the introduction passage reaches the intake pipe, and flows around the gap between the inner wall of the introduction passage on one side in the flow path width direction and the peripheral wall of the intake pipe along the peripheral wall of the intake pipe. Then, the exhaust gas recirculation gas is introduced into the intake passage in the intake pipe from the opening, which generates a swirling flow of the exhaust gas recirculation gas in the intake pipe, and promotes mixing of the intake air and the exhaust gas recirculation gas.

[0015] Preferably, the first surge tank has a wall surface to which the intake passage is connected and which extends in a plane, and the second surge tank is formed along the wall surface of the first surge tank and so as to surround a side surface of the intake passage.

[0016] This allows the second surge tank to be configured simply and compactly along the wall surface of the first surge tank. Effect of the Invention

[0021] According to the engine intake system structure of the present invention, even when the supply amount of EGR gas is small, the EGR gas is temporarily stored in the second surge tank to increase the pressure of the EGR gas, and the EGR gas is stably supplied to the intake passage upstream of the first surge tank, thereby stabilizing the concentration of the EGR gas in the intake air. Furthermore, by temporarily storing the intake air mixed with the EGR gas in the first surge tank, the mixture of the intake air and the EGR gas is promoted in the first surge tank, and the EGR gas in the intake air can be homogenized and supplied uniformly to each branch passage. This makes it possible to introduce intake air with a homogenized concentration of exhaust gas recirculated into each cylinder of the engine, thereby improving the effectiveness of exhaust gas recirculation. [Brief description of the drawings]

[0022] [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. 2 is a vertical cross-sectional view of an intake system accessory of the engine. [Diagram 3] FIG. 2 is a vertical cross-sectional view of an intake system accessory of the engine. [Figure 4] FIG. 2 is a cross-sectional view of an intake system accessory of the engine. [Diagram 5] FIG. 11 is a vertical cross-sectional view of an intake system accessory according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 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 the engine 3, as viewed from the left side in the vehicle width direction when mounted on the vehicle. Fig. 3 is a vertical cross-sectional view of the intake system accessory of the engine 3. Fig. 4 is a horizontal cross-sectional view of the intake system accessory of the engine 3. Fig. 3 is a cross-sectional view of the AA portion shown in Fig. 2. Fig. 4 is a cross-sectional view of the BB portion shown in Fig. 3.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] A throttle valve 10 is provided in the intake passage 6. In addition, between the throttle valve 10 of the intake passage 6 and the intake manifold 5, a surge tank 11 (first surge tank) is provided.

[0028] 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 (branch 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 2 to 4, an adapter 40 and an EGR ring 41 (inlet portion / intake pipe) 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. 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 end of the EGR ring 41 is connected to a tank inlet 42 provided in the upper wall 11a of the surge tank 11.

[0036] The surge tank 11 is formed in a generally rectangular box shape, and a tank inlet 42 is provided at a generally central position in the left-right direction of an upper wall 11a and at the front part of the vehicle.

[0037] Four tank discharge ports 43 are arranged side by side in the left-right direction at a position on the vehicle rear side of the bottom wall 11b of the surge tank 11 corresponding to the number of cylinders of the engine 3. 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.

[0038] 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.

[0039] 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.

[0040] 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, and has an EGR inlet passage portion 45 (inlet passage portion, second surge tank) formed to surround the side surface of the EGR ring 41.

[0041] The EGR introduction passage 45 has a tubular shape with a rectangular vertical cross section, a front-to-rear width (for example, several cm) that is approximately the same as or slightly larger than the diameter of the EGR ring 41, and a rectangular shape with the vertical width smaller than the left-to-right width.

[0042] The EGR introduction passage 45 extends to the right in the vehicle width direction beyond the outer wall surface of the EGR ring 41 on the right side in the vehicle width 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. Furthermore, a gap of, for example, about 1 cm is formed between the right inner wall surface at the tip end side in the extension direction of the EGR introduction passage 45 (the forward side in the flow direction) and the right outer wall surface of the EGR ring 41, and 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 right, rear, and left parts of the outer wall surface (circumferential wall) of the EGR ring 41.

[0043] Furthermore, a ring hole 50 (opening) 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 (opening) is provided in the right part. 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 in the EGR ring 41.

[0044] The vertical cross-sectional area of ​​the EGR introduction passage 45, i.e., the flow passage area, is formed to be larger than the flow passage area of ​​the EGR passage 31 upstream of the EGR introduction passage 45. As a result, the EGR introduction passage 45 is adjacent to the upstream side of the ring holes 50, 51 of the EGR ring 41 and functions as a surge tank (second surge tank) that temporarily stores EGR gas.

[0045] Further, the volume of the internal space that functions as a surge tank in the EGR introduction passage portion 45 is set to be smaller than the volume of the surge tank 11 .

[0046] 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.

[0047] 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.

[0048] In addition, adjacent to the upstream side of the ring holes 50, 51 of the EGR ring 41, i.e., adjacent to the upstream side of the introduction position of EGR gas from the EGR passage 31 to the intake passage 6, the EGR passage 31 is provided with an EGR introduction passage portion 45 which functions as a surge tank for storing EGR gas.

[0049] Therefore, the EGR gas is temporarily stored in the EGR introduction passage 45 before being introduced into the intake passage 6, and the EGR gas is stably supplied to the intake passage 6, thereby promoting mixing of the intake air and the exhaust gas recirculated gas in the intake passage 6. Furthermore, by temporarily storing the intake air mixed with the exhaust gas recirculated gas in the surge tank 11, mixing of the intake air and the EGR gas is promoted in the surge tank 11, and the EGR gas in the intake air is homogenized and can be supplied to each branch pipe 12 uniformly.

[0050] This makes it possible to introduce intake air with a homogenized concentration of EGR gas into each cylinder of the engine 3, thereby improving the effectiveness of the EGR device 30.

[0051] In addition, since the EGR introduction passage 45 has a smaller volume than the surge tank 11, even in an engine operating state or a transient operating state in which the amount of EGR gas supplied is small, the EGR introduction passage 45 can increase the pressure of the EGR gas, thereby enabling a stable supply of EGR gas to the intake passage 6.

[0052] Furthermore, since the surge tank 11 and the EGR introduction passage portion 45 are formed integrally, the surge tank 11 and the second surge tank in the EGR introduction passage portion 45 can be constructed compactly.

[0053] In addition, the surge tank 11 has an upper wall 11a to which the intake passage 6 is connected and which extends in a plane, and the EGR introduction passage portion 45 is formed along the upper wall 11a of the surge tank 11, so that the second surge tank can be constructed simply and compactly along the wall surface of the surge tank 11.

[0054] Further, a tubular EGR introduction passage 45 with a closed tip is provided at the downstream end of the EGR passage 31, and the EGR ring 41 forms part of the inner wall on the tip side of this EGR introduction passage 45. In other words, by passing the tubular EGR ring 41 having ring holes 50, 51 through the EGR introduction passage 45 near its tip, an EGR gas introduction section that introduces EGR gas into the intake passage can be realized with a simple configuration.

[0055] The EGR ring 41 is disposed offset toward the front of the vehicle, which is one side of the flow path width direction, with respect to the center position of the EGR introduction passage 45 in the flow path width direction (vehicle front-rear direction), and there is a gap between an inner wall of the EGR introduction passage 45 on the other side of the flow path width direction, which is the rear side of the vehicle, and a peripheral wall of the EGR ring 41. The ring holes 50, 51 of the EGR ring 41 are provided on the right side and the rear side of the vehicle in the vehicle width direction of the peripheral wall of the EGR ring 41.

[0056] As a result, the EGR gas flowing through the EGR introduction passage 45 reaches the EGR ring 41, and flows along the outer wall of the EGR ring 41, between the inner wall of the EGR introduction passage 45 on the vehicle rear side and the EGR ring 41. The EGR gas is then introduced into the intake passage 6 inside the EGR ring 41 through ring holes 50, 51 of the EGR ring 41, generating a swirling flow of EGR gas in the intake passage 6, and promoting mixing of the intake air and the EGR gas.

[0057] The present invention is not limited to the above embodiment. For example, in the above embodiment, the lower end of the EGR ring 41 is located at approximately the same vertical position as the inner wall surface of the upper wall 11a of the surge tank 11. However, as shown in FIG. 5, the EGR ring 41 may be extended downward so that the lower end 41a of the EGR ring 41 protrudes downward from the inner wall surface of the upper wall 11a of the surge tank 11.

[0058] In this way, by extending the EGR ring 41 downward, the distance from the ring holes 50, 51, which are the EGR gas introduction positions in the EGR ring 41, to the inside of the surge tank 11 is extended, and it is possible to promote mixing of the intake air and the EGR gas in the EGR ring 41. In addition, since the distance between the lower end of the EGR ring 41 and the bottom wall 11b of the surge tank 11 is shortened, the intake air containing the EGR gas that has flowed from the EGR ring 41 into the surge tank 11 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.

[0059] Alternatively, 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.

[0060] 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]

[0061] 3 Engine 6 Intake passage 11 Surge tank (first surge tank) 12 Branch pipe (branch passage) 31 EGR passage (exhaust recirculation passage) 45 EGR inlet passage (inlet passage, second surge tank) 41 EGR ring (introduction part, intake pipe) 50, 51 Ring hole (opening)

Claims

1. An intake system structure for an engine, comprising: a first surge tank in an intake passage; a branch passage for dividing intake air from the first surge tank to each cylinder; and an exhaust gas recirculation passage for recirculating a portion of exhaust gas to the intake passage, the exhaust gas recirculation passage includes a second surge tank that is connected to an introduction portion that introduces the exhaust gas recirculation gas into the intake passage upstream of the first surge tank and that stores the exhaust gas recirculation gas and has a volume smaller than that of the first surge tank, The first surge tank and the second surge tank are integrally formed, the second surge tank is formed by a tubular introduction passage portion that closes a downstream end of the exhaust gas recirculation passage, the introduction section has the intake passage therein, and a peripheral wall of the introduction section forms a part of an inner wall of the introduction passage section on the downstream end side, and is formed by a tubular intake pipe having an opening on the peripheral wall, The intake pipe is the inlet passage portion is offset in one direction in the width direction of the flow passage with respect to a center position in the width direction of the flow passage portion, The first surge tank is connected to a tank inlet provided on the one side of the first surge tank, a gap is provided between an inner wall of the introduction passage portion on the other side in the flow path width direction and the peripheral wall, an intake passage portion that is provided in the peripheral wall and arranged to face the exhaust gas recirculation gas flow direction of the exhaust gas recirculation gas passage;

2. the first surge tank has a wall surface to which the intake passage is connected and which extends in a plane; 2. The engine intake system structure according to claim 1, wherein the second surge tank is formed along the wall surface of the first surge tank and so as to surround a side surface of the intake passage.

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