JP5895900B2 - Engine exhaust gas recirculation system - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an engine, and in particular, an EGR cooler for cooling the recirculated exhaust gas is disposed on an EGR passage for recirculating a part of the exhaust gas flowing through the exhaust passage to the intake passage. The present invention relates to an exhaust gas recirculation device for an engine provided with a cooler passage and a bypass passage that bypasses the EGR cooler.

  Conventionally, an exhaust gas recirculation apparatus provided with an EGR passage for recirculating a part of exhaust gas flowing through the exhaust passage of the engine to the intake passage in order to reduce the generation of nitrogen oxides, the warm-up effect of the intake air, etc. (EGR device) is well known.

  For example, an EGR device disclosed in Patent Literature 1 includes an EGR passage connecting an exhaust passage and an intake passage, a cooler passage provided with an EGR cooler that cools recirculated exhaust gas (EGR gas), and an EGR cooler. A bypass passage for bypassing, and a downstream portion of the cooler passage in the exhaust gas flow direction (in the present specification and claims, the terms “upstream” and “downstream” refer to the gas flowing there unless otherwise specified) A switching valve for switching both passages is provided at a connection portion between the bypass passage and the downstream portion of the bypass passage, and an EGR valve for controlling the exhaust gas recirculation amount is further downstream of the switching valve. Is provided. According to this EGR device, one of the low-temperature EGR gas that has passed through the cooler passage and the high-temperature EGR gas that has passed through the bypass passage is recirculated to the intake passage, and the recirculation amount is adjusted by the EGR valve. .

  Similarly, the EGR device disclosed in Patent Document 2 is provided with a cooler passage and a bypass passage as an EGR passage, and at the connection portion between the upstream portion of the cooler passage in the exhaust gas flow direction and the upstream portion of the bypass passage. , A two-way branch passage for branching the EGR gas into both passages at a predetermined flow ratio is disposed, and a low-temperature EGR gas that has passed through the cooler passage is connected to a downstream portion of the cooler passage and a downstream portion of the bypass passage; There is provided an exhaust gas mixture ratio control valve that merges the high temperature EGR gas that has passed through the bypass passage, and mixes so that a swirl flow is generated by a flap type valve. According to this EGR device, the low-temperature EGR gas from the cooler passage and the high-temperature EGR gas from the bypass passage are merged at a predetermined ratio and efficiently mixed by the flap type valve.

JP 2008-248878 A (paragraph 0039, FIG. 1) JP 2005-273564 A (paragraph 0030, paragraph 0032, paragraph 0054, FIG. 2)

  By the way, in recent years, in the field of gasoline engines, instead of spark ignition combustion (SI combustion) in which an air-fuel mixture is forcibly burned by spark ignition of a spark plug, high-temperature and high-pressure generated by compression of a piston is used. Practical application of compression self-ignition combustion (CI combustion) in which an air-fuel mixture is combusted by self-ignition under an environment is being promoted. CI combustion is combustion in which an air-fuel mixture is self-ignited simultaneously and frequently, and has an advantage that the combustion period is shorter and thermal efficiency is superior to SI combustion in which combustion gradually spreads due to flame propagation.

  However, CI combustion is difficult to occur in a low load region of an engine with a small amount of fuel injection and a small amount of heat generation, and the air-fuel mixture self-ignites early in a high load region of an engine with a large amount of fuel injection and a large amount of heat generation. There is a problem that abnormal combustion and excessive combustion noise occur due to excessively short period. Therefore, in order to expand the region in which proper CI combustion can be performed, it is necessary to recirculate an appropriate amount and temperature of EGR gas to the intake passage in accordance with the load and adjust the temperature of the combustion chamber with high accuracy.

  In this respect, in the EGR device of Patent Document 1, only one of the low temperature EGR gas that has passed through the cooler passage and the high temperature EGR gas that has passed through the bypass passage is recirculated to the intake passage. The temperature cannot be adjusted according to the load. In the EGR device of Patent Document 2, the low temperature EGR gas from the cooler passage and the high temperature EGR gas from the bypass passage are combined and mixed at a predetermined ratio. Since it is based on the two-way branch flow path that adjusts the opening of the passage at the same time, the flow rate of the low temperature EGR gas and the flow rate of the high temperature EGR gas cannot be adjusted independently of each other. Therefore, it is still difficult to accurately adjust the temperature of the EGR gas returning to the intake passage.

  In order to cope with this problem, an EGR valve that adjusts the flow rate of the EGR gas is disposed in each of the cooler passage and the bypass passage, and the junction portion where the downstream portion of the cooler passage and the downstream portion of the bypass passage merge. And at least in the operation region where the CI combustion is performed, the opening degree of each EGR valve can be controlled independently so that the temperature of the EGR gas merged and mixed in the merging portion falls within a predetermined temperature range. Proposed. According to this, the mixing ratio in the confluence | merging part of the low temperature EGR gas from a cooler channel | path and the high temperature EGR gas from a bypass channel can be adjusted with a high freedom degree. Therefore, the temperature of the EGR gas returning to the intake passage can be kept within a predetermined temperature range with high accuracy. As a result, for example, in an operation region where CI combustion is performed, an environment in which fuel self-ignites at an appropriate timing can be surely created, and the stability of CI combustion can be improved.

  But there are still problems to be solved. This is a problem caused by the fact that the cooler passage has a greater flow resistance than the bypass passage. Here, the flow resistance is a value representing the pressure loss by force. Specifically, since the EGR cooler disposed in the cooler passage is a water-cooled heat exchanger, the passage through which the EGR gas passes is formed in a tube shape having a small passage cross-sectional area. The EGR gas that has flowed into the cooler passage is divided into a large number of tubes in the EGR cooler and is cooled by heat exchange with cooling water in the process. Therefore, the flow resistance of the cooler passage is larger than the flow resistance of the bypass passage where such an EGR cooler is not provided, and the low temperature EGR valve provided in the cooler passage and the high temperature EGR valve provided in the bypass passage are Are opened at the same opening, the amount of EGR gas flowing through the cooler passage is smaller than the amount of EGR gas flowing through the bypass passage. As a result, it becomes difficult to accurately adjust the mixing ratio of the low-temperature EGR gas and the high-temperature EGR gas in the joining portion, and it is difficult to accurately adjust the temperature of the EGR gas returning to the intake passage.

  Such a problem is a problem that can occur not only in an engine in which CI combustion is performed, but also in an engine in which SI combustion is performed. Moreover, it is a problem that can occur not only in gasoline engines but also in diesel engines. In other words, regardless of the combustion mode or engine type, in order to expand the area where proper combustion can be performed, the low temperature EGR gas from the cooler passage and the high temperature EGR gas from the bypass passage are accurately metered and mixed. This is a problem that may occur when the temperature of the EGR gas returning to the intake passage is to be adjusted with high accuracy in accordance with operating conditions such as a load.

  The present invention has been made in view of the above circumstances, and in order to expand a region where proper combustion can be performed, an EGR valve is provided in each of the cooler passage and the bypass passage of the EGR passage, An object of the present invention is to provide an exhaust gas recirculation device for an engine in which the problem of a decrease in EGR gas metering and temperature control accuracy caused by a difference in flow resistance between a cooler passage and a bypass passage is suppressed.

  In order to solve the above problems, the present invention provides an EGR cooler for cooling the recirculated exhaust gas as an EGR passage for recirculating a part of the exhaust gas flowing through the exhaust passage of the engine to the intake passage. An exhaust gas recirculation device for an engine provided with a bypass cooler passage and a bypass passage that bypasses the EGR cooler, wherein the low temperature EGR is disposed in the cooler passage and adjusts the flow rate of exhaust gas flowing through the cooler passage A valve, a high-temperature EGR valve that adjusts the flow rate of exhaust gas that is disposed in the bypass passage and flows through the bypass passage, and a merging portion where the downstream portion of the cooler passage and the downstream portion of the bypass passage merge The outlet opening of the cooler passage on the merging portion side is arranged so that the flow path axes thereof are parallel to the outlet opening of the merging portion on the intake passage side. In addition, the outlet opening on the merging portion side of the bypass passage is disposed such that the flow path axis intersects the outlet opening on the intake passage side of the merging portion at a predetermined angle, A cylindrical member having an inlet opening on the outlet opening side of the cooler passage and having an outlet opening on the outlet opening side of the merging portion is accommodated, and the cylindrical member has an axis line of the outlet opening of the merging portion. An exhaust gas recirculation device for an engine arranged so as to be parallel to an axis (Claim 1).

  According to the present invention, the low-temperature EGR valve disposed in the cooler passage and the high-temperature EGR valve disposed in the bypass passage allow the low-temperature EGR gas that has passed through the cooler passage and the high-temperature EGR gas that has passed through the bypass passage to join each other. The mixing ratio can be adjusted with a high degree of freedom. Therefore, the temperature of the EGR gas returning to the intake passage can be kept within a predetermined temperature range with high accuracy. As a result, for example, in an operation region where CI combustion is performed, an environment in which fuel self-ignites at an appropriate timing can be surely created, and the stability of CI combustion can be improved.

  In addition, since the low-temperature EGR gas that has passed through the cooler passage whose flow resistance is larger than that of the bypass passage passes linearly through the merge portion, an increase in flow resistance caused by passing through the merge portion is suppressed. On the other hand, the high temperature EGR gas that has passed through the bypass passage whose flow resistance is smaller than that of the cooler passage cancels the directivity of the flow in the crossing direction, changes the direction of the merging portion, and passes through the merging portion. As a result, distribution resistance increases. Therefore, the difference in flow resistance between the cooler passage and the bypass passage is reduced, and the low-temperature EGR gas and the high-temperature EGR gas at the junction are controlled by independently controlling the low-temperature EGR valve in the cooler passage and the high-temperature EGR valve in the bypass passage. And the temperature of the EGR gas returning to the intake passage can be adjusted with high accuracy.

  As described above, according to the present invention, in order to expand the region where proper combustion can be performed, the EGR valve is provided in each of the cooler passage and the bypass passage of the EGR passage, and further, the flow resistance between the cooler passage and the bypass passage. Provided is an engine exhaust gas recirculation device in which the problem of a decrease in EGR gas metering and temperature control accuracy due to a difference is suppressed.

  Moreover, according to the present invention, due to the presence of the cylindrical member accommodated in the merging portion, the high temperature EGR gas that has entered the merging portion from the bypass passage collides with the peripheral surface of the cylindrical member, and then the upstream side of the merging portion. Returning to the outlet opening side of the cooler passage, enters the hollow space of the tubular member from the inlet opening of the tubular member, merges with the low-temperature EGR gas that enters the merging portion from the cooler passage, is mixed, and is mixed EGR gas From the outlet opening (outlet opening of the merging portion) of the cylindrical member to the outside of the merging portion, so that the mixing of the low temperature EGR gas and the high temperature EGR gas with the messy movement in the merging portion of such high temperature EGR gas Is promoted. Therefore, the low temperature EGR gas and the high temperature EGR gas are efficiently and uniformly mixed within a short moving distance in the low temperature EGR gas merge portion, and the mixed EGR gas is recirculated from the merge portion to the intake passage.

  In the present invention, preferably, the flow path axis of the outlet opening of the bypass passage is offset with respect to the axis of the cylindrical member (claim 2).

  According to this configuration, the hot EGR gas that has entered the merging portion from the bypass passage collides with the peripheral surface of the cylindrical member, and then a swirling flow is generated along the peripheral surface of the cylindrical member. It returns to the upstream side of the part, enters the hollow space of the tubular member from the inlet opening of the tubular member, merges with the low temperature EGR gas, and is mixed. Therefore, the swirling flow of the high-temperature EGR gas sufficiently stirs the low-temperature EGR gas and the high-temperature EGR gas, thereby further promoting the mixing of both EGR gases.

  In the present invention, preferably, a distribution passage branched for each cylinder is disposed between the merging portion and each of the independent intake passages of the plurality of cylinders, and an upstream portion of each distribution passage is at an outlet opening of the merging portion. The downstream portion is connected to each independent exhaust passage (Claim 3).

  According to this configuration, the EGR gas merged and mixed in the merging portion is supplied to the independent intake passages of the plurality of cylinders via the distribution passage, so that the EGR gas adjusted and adjusted in the merging portion is compared. Each cylinder is supplied to the combustion chamber in a short time. Therefore, the switching responsiveness of the EGR gas returning to the intake passage is improved, and it is possible to cope with a sudden load change.

  As described above, in the present invention, in order to expand the region where proper combustion can be performed, the EGR valve is provided in each of the cooler passage and the bypass passage of the EGR passage, and further the circulation between the cooler passage and the bypass passage. Provided is an engine exhaust gas recirculation device in which the problem of a decrease in EGR gas metering and temperature control accuracy due to a resistance difference is suppressed. Therefore, the present invention is not limited to an engine in which CI combustion is performed. Regardless of this, it contributes to the development and improvement of the technology of internal combustion engines.

It is a figure showing an important section of an engine concerning one embodiment of the present invention. It is a top view which shows the specific structure by the side of the intake passage of the exhaust gas recirculation apparatus with which the said engine is equipped. It is an arrow view from the code | symbol III of the said FIG. It is a perspective view from the exhaust passage side which shows the specific structure by the side of the intake passage of the said exhaust gas recirculation apparatus. It is an arrow view from the code | symbol V of the said FIG. FIG. 3 is a cross-sectional view taken along the arrow VI in FIG. It is a perspective view of the mixing plate accommodated in the mixer of the exhaust gas recirculation device. FIG. 7 is a cross-sectional view taken along the arrow VIII in FIG. 6. It is arrow sectional drawing from the code | symbol IX of the said FIG. It is a map which shows the relationship between the load of the said engine, and the filling gas component ratio in a combustion chamber. It is explanatory drawing of an effect | action of embodiment. It is sectional drawing which shows the structure of the mixer of the exhaust gas recirculation apparatus concerning other embodiment of this invention, Comprising: It is a thing similar to FIG.

(1) Overall Configuration FIG. 1 is a diagram showing a main part of an engine according to an embodiment of the present invention. The engine shown in the figure is a compression self-ignition engine, which is a four-cycle gasoline engine mounted on a vehicle as a power source for traveling. Specifically, this engine has an engine body 1 having a plurality of cylinders 2 (only one of which is shown in FIG. 1) arranged in a row in a direction orthogonal to the paper surface, and air is introduced into the engine body 1. An intake passage 20 for exhausting, an exhaust passage 30 for discharging exhaust gas generated in the engine body 1, and an exhaust gas recirculation device for returning a part of the exhaust gas flowing through the exhaust passage 30 to the intake passage 20 (EGR device) 40.

  The engine body 1 includes a cylinder block 3 in which a plurality of cylinders 2 are formed, a cylinder head 4 provided on the top of the cylinder block 3, and a piston 5 that is inserted into each cylinder 2 so as to be slidable back and forth. Have.

  A combustion chamber 10 is formed above the piston 5, and fuel is supplied to the combustion chamber 10 by injection from the injector 11. The injected fuel burns in the combustion chamber 10, and the piston 5 pushed down by the expansion force due to the combustion reciprocates in the vertical direction. In addition, since the engine of this embodiment is a gasoline engine, gasoline is used as fuel. However, all of the fuel does not have to be gasoline, and for example, a subcomponent such as alcohol may be included in the fuel (for example, a mixed fuel such as E3).

  The piston 5 is connected to a crankshaft 15 that is an output shaft of the engine body 1 via a connecting rod 16, and the crankshaft 15 rotates about the central axis in accordance with the reciprocating motion of the piston 5. Yes.

  An intake port 6 for introducing air (intake air) supplied from the intake passage 20 into the cylinder head 4 into the combustion chamber 10 of each cylinder 2 and an exhaust gas generated in the combustion chamber 10 of each cylinder 2 as an exhaust passage. An exhaust port 7 for leading to 30, an intake valve 8 for opening and closing the opening of the intake port 6 on the combustion chamber 10 side, and an exhaust valve 9 for opening and closing the opening of the exhaust port 7 on the combustion chamber 10 side are provided. Yes.

  The intake valve 8 and the exhaust valve 9 are driven to open and close in conjunction with the rotation of the crankshaft 15 by valve mechanisms 18 and 19 including a pair of camshafts and the like disposed in the cylinder head 4.

  The valve mechanism 18 for the intake valve 8 incorporates a variable mechanism 18a capable of continuously (steplessly) changing the lift amount of the intake valve 8. The variable mechanism 18a having such a configuration is already known as a continuously variable valve lift mechanism (CVVL) or the like. As a specific configuration example, a cam for driving the intake valve 8 is reciprocally rocked in conjunction with the rotation of the cam shaft. A link mechanism for dynamic movement, a control arm for variably setting the arrangement (lever ratio) of the link mechanism, and a swing amount of the cam (amount and a period for depressing the intake valve 8) by electrically driving the control arm And a stepping motor that changes the angle.

  The valve mechanism 19 for the exhaust valve 9 incorporates a switching mechanism 19a that enables or disables the function of depressing the exhaust valve 9 during the intake stroke. That is, the switching mechanism 19a has a function of enabling the exhaust valve 9 to be opened not only in the exhaust stroke but also in the intake stroke, and switching between performing or stopping the valve opening operation of the exhaust valve 9 during the intake stroke. Have.

  The switching mechanism 19a having such a configuration is already known, and as a specific example thereof, the exhaust valve 9 is operated during the intake stroke separately from a normal cam for driving the exhaust valve 9 (a cam for pushing the exhaust valve 9 during the exhaust stroke). And a so-called lost motion mechanism that enables or disables transmission of the driving force of the sub-cam to the exhaust valve 9.

  The cylinder head 4 includes an injector 11 that injects fuel toward the combustion chamber 10, and an ignition plug 12 that supplies ignition energy by spark discharge to the mixture of fuel and air injected from the injector 11. One set is provided for each cylinder 2.

  The injector 11 is provided in the cylinder head 4 so as to face the upper surface of the piston 5. A fuel supply pipe 13 is connected to each injector 11 of each cylinder 2, and fuel supplied through each fuel supply pipe 13 is injected from a plurality of injection holes (not shown) provided at the tip of the injector 11. It has come to be.

  More specifically, a supply pump 14, which is a plunger type fuel pump driven by the rotation of the crankshaft 15, is provided on the upstream side of the fuel supply pipe 13, and the supply pump 14 and the fuel supply pipe 13 are connected to each other. A common rail (not shown) for pressure accumulation common to all the cylinders 2 is provided between them. Then, the fuel accumulated in the common rail is supplied to the injectors 11 of the respective cylinders 2, so that a fuel having a high pressure of about 120 MPa at the maximum can be injected from each injector 11.

  The intake passage 20 includes a single common passage 21, a surge tank 24 having a predetermined volume connected to a downstream end of the common passage 21 (an end on the downstream side in the intake flow direction), and a downstream side from the surge tank 24. It has a plurality of independent passages (independent intake passages) 25 (only one of them is shown in FIG. 1) that extends and communicates with the intake port 6 of each cylinder 2. A throttle valve 29 that adjusts the flow rate of intake air flowing through the common passage 21 is provided upstream of the surge tank 24 in the common passage 21.

  The exhaust passage 30 includes a plurality of independent passages (independent exhaust passages) 31 (only one of which is shown in FIG. 1) communicating with the exhaust ports 7 of the respective cylinders 2, and downstream end portions of the independent passages 31. It has an exhaust collecting portion 32 in which (exhaust gas flow direction downstream end) gathers and one common passage 33 extending downstream from the exhaust collecting portion 32.

(2) Configuration of EGR Device Next, the configuration of the EGR device 40 will be described with reference to FIG.

  The EGR device (exhaust gas recirculation device) 40 has an EGR passage 41, a mixer (merging portion) 45, an EGR cooler 47, a cooler side EGR valve (low temperature EGR valve) 48, and a bypass side EGR valve (high temperature EGR valve) 49. ing.

  The EGR passage 41 is a passage for allowing the exhaust passage 30 and the intake passage 20 to communicate with each other and returning a part of the exhaust gas flowing through the exhaust passage 30 to the intake passage 20. The EGR passage 41 includes an upstream passage 42, a cooler passage 43, a bypass passage 44, and a distribution passage 46.

  The upstream passage 42 is the most upstream portion of the EGR passage 41 and branches from the exhaust collecting portion 32 of the exhaust passage 30.

  The cooler passage 43 and the bypass passage 44 are branched into two parts from the downstream end of the upstream passage 42. In the cooler passage 43, an EGR cooler 47 and a cooler side EGR valve 48 are arranged in this order from the upstream side. In the bypass passage 44, a bypass side EGR valve 49 is disposed. The bypass passage 44 is provided so as to bypass both the EGR cooler 47 and the cooler side EGR valve 48.

  The cooler-side EGR valve 48 is an electric valve, and adjusts the flow rate of exhaust gas (EGR gas) recirculated to the intake passage 20 through the cooler passage 43 according to the opening / closing operation thereof. Similarly, the bypass-side EGR valve 49 is an electric valve, and adjusts the flow rate of exhaust gas (EGR gas) recirculated to the intake passage 20 through the bypass passage 44 according to the opening / closing operation thereof.

  The downstream ends of the cooler passage 43 and the bypass passage 44 merge at the mixer 45, and the distribution passage 46 extends downstream from the mixer 45 and branches into a plurality of pipes corresponding to the number of independent intake passages 25 of each cylinder 2. (Only one of them is shown in FIG. 1) and is connected to each independent intake passage 25 on a one-to-one basis.

  In the EGR device 40 as described above, when both the cooler side EGR valve 48 and the bypass side EGR valve 49 are closed, the flow of the exhaust gas flowing through the EGR passage 41 is interrupted and recirculated to the intake passage 20. The amount of exhaust gas is substantially zero. On the other hand, when the cooler-side EGR valve 48 is opened and the bypass-side EGR valve 49 is closed, the exhaust gas passes through only the cooler passage 43 and is recirculated to the intake passage 20. For this reason, all the exhaust gas recirculated to the intake passage 20 becomes low-temperature exhaust gas cooled by the EGR cooler 47 (low-temperature EGR gas). When the bypass side EGR valve 49 is opened and the cooler side EGR valve 48 is closed, the exhaust gas passes through only the bypass passage 44 and is recirculated to the intake passage 20. For this reason, all of the exhaust gas recirculated to the intake passage 20 becomes high-temperature exhaust gas that is not cooled by the EGR cooler 47 (high-temperature EGR gas).

  When both the cooler side EGR valve 48 and the bypass side EGR valve 49 are opened from these states, the exhaust gas is divided into the cooler passage 43 and the bypass passage 44 and then recirculated to the intake passage 20. Therefore, the exhaust gas recirculated to the intake passage 20 is a mixture of the low temperature EGR gas cooled by the EGR cooler 47 and the high temperature EGR gas not cooled by the EGR cooler 47 (this is referred to as “mixed EGR gas”). Called).

  By the way, since the engine according to the present embodiment is a compression self-ignition engine in which CI combustion is performed, there is an advantage that the combustion period is short and the thermal efficiency is excellent. On the other hand, CI combustion hardly occurs in a low load region of the engine. There is a problem that in the high load region of the engine, the timing at which the air-fuel mixture self-ignites becomes too early, causing abnormal combustion and excessive combustion noise. Therefore, in order to expand the region in which proper CI combustion can be performed, it is necessary to recirculate an appropriate amount and temperature of EGR gas to the intake passage 20 according to the load and adjust the temperature of the combustion chamber 10 with high accuracy. is there.

  Specifically, in the present embodiment, as shown in FIG. 10, as the engine load changes from the minimum load Lmin to the maximum load Lmax, the gas components (fresh air, low-temperature EGR gas (see FIG. Among the high-temperature EGR gas (denoted as H-EGR in the figure)), the ratio of fresh air having the lowest temperature increases, and the ratio of EGR gas whose temperature is higher than that of fresh air decreases. Further, among the EGR gases, the ratio of the high temperature EGR gas is decreased, and the ratio of the low temperature EGR gas is increased. Thereby, in the compression self-ignition type engine concerning this embodiment, proper CI combustion is achieved over the whole engine load region.

  Returning to FIG. 1, the EGR cooler 47 is a water-cooled heat exchanger for cooling the EGR gas flowing through the cooler passage 43. That is, in the EGR cooler 47, the EGR gas is cooled by heat exchange with the cooling water introduced therein. Engine cooling water for cooling the engine body 1 is used as cooling water.

  Specifically, in the EGR cooler 47, the passage through which the EGR gas passes is formed in a tube shape having a small passage sectional area. The EGR gas that has flowed into the cooler passage 43 is divided into a large number of tubes in the EGR cooler 47, and is cooled by heat exchange with cooling water in the process. Therefore, the flow resistance of the cooler passage 43 is larger than the flow resistance of the bypass passage 44 in which no EGR cooler is provided. Here, the flow resistance is a value representing the pressure loss by force. Therefore, even if the cooler-side EGR valve 48 disposed in the cooler passage 43 and the bypass-side EGR valve 49 disposed in the bypass passage 44 are opened by the same opening, the amount of EGR gas (low-temperature EGR gas) flowing through the cooler passage 43 Is less than the amount of EGR gas (high temperature EGR gas) flowing through the bypass passage 44.

  As a result, it becomes difficult to accurately adjust the mixing ratio of the low-temperature EGR gas and the high-temperature EGR gas that merge in the mixer 45, and consequently, it is difficult to accurately adjust the temperature of the EGR gas returning to the intake passage 20. There's a problem. This leads to a problem that even if engine control is executed according to the characteristics shown in FIG. 10, proper CI combustion becomes difficult. Therefore, in the present embodiment, measures are taken to cope with the above problem. This will be described later.

  In the present embodiment, the intake passage 20 side of the EGR device 40 is specifically configured as shown in FIGS. That is, the number of cylinders 2, the number of independent intake passages 25 in the intake passage 20, and the number of distribution passages 46 in the EGR device 40 are four.

  The surge tank 24 and the four independent intake passages 25 in the intake passage 20 are formed by an intake manifold 28 (see FIGS. 2 and 3). The intake manifold 28 is coupled to the outer side surface of the cylinder head 4. An intake port 6 communicating with each independent intake passage 25 is formed in the cylinder head 4.

  A part of the upstream passage 42 of the EGR passage 41 is formed in the cylinder head 4 (see FIG. 2). A cooler passage 43 and a bypass passage 44 are formed outside the cylinder head 4 so as to branch from the downstream end of the upstream passage 42. The cooler passage 43 extends in the horizontal direction from the branch portion, and the bypass passage 44 extends in the horizontal direction after extending upward from the branch portion.

  The downstream part of the cooler passage 43 is inclined obliquely so as to rise toward the cooler-side EGR valve 48 (see FIG. 3). The EGR cooler 47 is disposed in the inclined portion of the cooler passage 43. The cooler side EGR valve 48 bends the low temperature EGR gas cooled by the EGR cooler 47 at an angle of 90 ° and supplies the bent low temperature EGR gas to the mixer 45.

  The downstream portion of the bypass passage 44 is inclined obliquely so as to rise from the bypass side EGR valve 49 toward the mixer 45 (see FIG. 3). The bypass passage 44 is connected to the side portion of the mixer 45 (see FIG. 2). The bypass-side EGR valve 49 bends the high temperature EGR gas supplied from the upstream portion of the bypass passage 44 at an angle of 90 ° and supplies it to the downstream portion of the bypass passage 44.

  The mixer 45 is located above the intake manifold 28 and is connected to the cooler-side EGR valve 48 at the downstream end of the cooler passage 43 slightly extending in the horizontal direction from the surface on the cylinder head 4 side in the cooler-side EGR valve 48. (See FIG. 2). That is, the cooler passage 43 is connected to the upstream end of the mixer 45.

  Four distribution passages 46 are branched from the lower part of the portion of the mixer 45 on the cylinder head 4 side, and are connected to the individual intake passages 25 of the respective cylinders 2 from the upper side in a one-to-one relationship outside the cylinder head 4 ( (See FIGS. 4 and 5).

  Thus, the mixer 45 is arranged at the highest position on the intake passage 20 side of the EGR device 40. Thereby, the condensed water generated in the EGR passage 41 by cooling the water contained in the EGR gas flows toward the cylinder 2 after passing through the mixer 45, and before passing through the mixer 45, the exhaust passage. It flows toward the 30 side. Thereby, it is suppressed that condensed water accumulates in the mixer 45.

(3) Configuration of Mixer Next, the configuration of the mixer 45 will be described with reference to FIGS.

  The mixer 45 is a part where the downstream end of the cooler passage 43 and the downstream end of the bypass passage 44 merge as described above.

  The mixer 45 has a merging case 51 including a cylindrical main body 51b. A flange portion 51a is provided at the upstream end portion of the merging case 51, and the end portion on the cylinder head 4 side of the cooler-side EGR valve 48 is coupled to the end portion on the cylinder head 4 side via a flange portion 51a. . As shown in FIGS. 6 and 8, the downstream end of the cooler passage 43 connected to the upstream end of the mixer 45 is formed in the case of the cooler EGR valve 48.

  The merging case 51 has an inlet opening (mixer inlet) 51d on the cooler passage 43 side and an outlet opening (mixer outlet) 51e on the intake passage 20 side. Both the openings 51d and 51e are circular, and the opening area of the outlet opening 51e is larger than the opening area of the inlet opening 51d. The merge case 51 is arranged so that the outlet opening 43a on the mixer 45 side of the cooler passage 43 and the inlet opening 51d on the cooler passage 43 side of the merge case 51 overlap each other when viewed from one side in the EGR gas flow direction. Yes. Hereinafter, the flow path axis (symbol A) of the openings 43a and 51d is referred to as a “mixer inlet flow path axis”.

  A flange portion 51c is provided at the downstream end portion of the merging case 51, and a mixing plate 52 as a cylindrical member is coupled via a flange portion 51c by bolts, nuts, and the like (not shown).

  The four distribution passages 46 of the EGR passage 41 are gathered together at their upstream end portions, and this gathering portion is particularly referred to as a discharge case 53. The flange portion 53 a of the discharge case 53 is coupled to the flange portion 52 a of the mixing plate 52. The discharge case 53 has a circular inlet opening 53b on the mixer 45 side, and four distribution passages 46 are connected to the intake passage 20 side (independent intake passage 25 side).

  The merge case 51 is arranged such that the inlet opening 53b on the mixer 45 side of the discharge case 53 and the outlet opening 51e on the intake passage 20 side of the merge case 51 overlap each other when viewed from one side in the EGR gas flow direction. Yes. Hereinafter, the flow path axis (reference numeral O) of both the openings 53b and 51e is referred to as a “mixer outlet flow path axis”. The four distribution passages 46 are arranged symmetrically in the cylinder row direction with respect to the flow path axis (reference numeral O) of the mixer outlet.

  As shown in FIG. 7, the mixing plate 52 includes a flat plate portion 52a and a tapered peripheral wall portion 52b. The flat plate portion 52 a is a portion that is coupled to the flange portion 51 c of the merging case 51. Therefore, the flat plate portion 52a is provided with a bolt hole 52e through which a bolt (not shown) is inserted.

  The tapered peripheral wall portion 52b is formed in a truncated cone shape so as to protrude from the flat plate portion 52a to the cooler passage 43 side. The tapered peripheral wall portion 52 b is disposed so as to enter the hollow space S of the merging case 51. The mixing plate 52 has an inlet opening 52c on the cooler passage 43 side and an outlet opening 52d on the intake passage 20 side. The inlet opening 52c on the cooler passage 43 side is formed at the protruding tip of the tapered peripheral wall portion 52b, and the outlet opening 52d on the intake passage 20 side is formed in the base portion of the tapered peripheral wall portion 52b. Both the openings 52c and 52d are circular, and the opening area of the outlet opening 52d is larger than the opening area of the inlet opening 52c.

  Since the tapered peripheral wall portion 52b is formed in the shape of a truncated cone, the hollow space 52s of the tapered peripheral wall portion 52b has a tapered shape on the cooler passage 43 side and a divergent shape on the intake passage 20 side, and has a funnel shape as a whole. Is formed.

  More specifically, the inlet opening 52c of the mixing plate 52 on the cooler passage 43 side is parallel to each other and the EGR gas so that the flow path axis coincides with the flow path axis (reference numeral A) of the mixer inlet. Are arranged so as to overlap each other when viewed from one side in the flow direction. Similarly, the outlet opening 52d on the side of the intake passage 20 of the mixing plate 52 is more specifically, so that the flow path axis coincides with the flow path axis (symbol O) of the mixer outlet. And it arrange | positions so that it may mutually overlap seeing from one side of the flow direction of EGR gas. As a result, the mixing plate 52 is disposed such that its axis coincides with the flow path axis (reference A) of the mixer inlet and the flow path axis (reference O) of the mixer outlet.

  6 and 7, reference numeral 52 f is a drain hole for draining condensed water accumulated in the mixer 45, more specifically, in the hollow space S of the merging case 51, to the cylinder 2 side.

  As described above, the downstream end portion of the bypass passage 44 connected to the side portion of the mixer 45 is specifically connected to the main body portion 51 b of the merging case 51. In this case, the downstream end of the bypass passage 44 is arranged so that the flow path axis (reference numeral B) of the outlet opening 44a on the mixer 45 side is orthogonal to the flow path axis (reference numeral O) of the mixer outlet, that is, 90. It arrange | positions so that it may cross | intersect at an angle (refer FIG. 8, FIG. 9). Further, the downstream end of the bypass passage 44 is connected to the axis of the mixing plate 52, that is, the bypass passage 44 with respect to the mixer inlet channel axis (reference A) and the mixer outlet channel axis (reference O). The flow path axis (reference numeral B) of the outlet opening 44a is offset upward (see FIGS. 6 and 9).

(4) Operation As described above, in the present embodiment, the exhaust gas that recirculates (EGR gas) serves as the EGR passage 41 for recirculating a part of the exhaust gas that flows through the exhaust passage 30 of the engine to the intake passage 20. An engine exhaust gas recirculation device (EGR device) 40 provided with a cooler passage 43 provided with an EGR cooler 47 for cooling the engine and a bypass passage 44 for bypassing the EGR cooler 47 has the following characteristic configuration. It was adopted.

  A low-temperature EGR valve 48 that adjusts the flow rate of the low-temperature EGR gas that is disposed in the cooler passage 43 and flows through the cooler passage 43, and the flow rate of the high-temperature EGR gas that is disposed in the bypass passage 44 and flows through the bypass passage 44. A high-temperature EGR valve 49 to be adjusted and a mixer 45 where the downstream end of the cooler passage 43 and the downstream end of the bypass passage 44 merge are provided.

  The outlet opening 43a on the mixer 45 side of the cooler passage 43 is arranged so that the flow path axes A and O are parallel to the outlet opening 51e on the intake passage 20 side of the mixer 45, and the bypass The outlet opening 44a on the mixer 45 side of the passage 44 is arranged such that the flow path axes B and O intersect with the outlet opening 51e on the intake passage 20 side of the mixer 45 at an angle of 90 °.

  In the mixer 45, a mixing plate 52 having an inlet opening 52c on the outlet opening 43a side of the cooler passage 43 and having an outlet opening 52d on the outlet opening 51e side of the mixer 45 is accommodated. The axis is arranged so as to be parallel to the flow path axis O of the outlet opening 51 e of the mixer 45.

  According to this configuration, the low temperature EGR valve 48 disposed in the cooler passage 43 and the high temperature EGR valve 49 disposed in the bypass passage 44 cause the low temperature EGR gas passed through the cooler passage 43 and the high temperature passed through the bypass passage 44. The mixing ratio of the EGR gas in the mixer 45 can be adjusted with a high degree of freedom. Therefore, the temperature of the EGR gas recirculated to the intake passage 20 can be kept within a predetermined temperature range with high accuracy. As a result, for example, in an operation region where CI combustion is performed, an environment in which fuel self-ignites at an appropriate timing can be surely created, and the stability of CI combustion can be improved.

  In addition, since the low-temperature EGR gas that has passed through the cooler passage 43 whose flow resistance is larger than that of the bypass passage 44 passes through the mixer 45 linearly, an increase in flow resistance due to passing through the mixer 45 is suppressed. The On the other hand, the high-temperature EGR gas that has passed through the bypass passage 44 whose flow resistance is smaller than that of the cooler passage 43 cancels the directivity of the flow in the orthogonal direction and changes direction and passes through the mixer 45. This increases the distribution resistance. Therefore, the difference in flow resistance between the cooler passage 43 and the bypass passage 44 is reduced, and the low temperature EGR valve 48 in the cooler passage 43 and the high temperature EGR valve 49 in the bypass passage 44 are controlled independently, thereby reducing the low temperature in the mixer 45. Adjustment of the mixing ratio of the EGR gas and the high temperature EGR gas, and hence the temperature of the EGR gas returning to the intake passage 20 can be adjusted with high accuracy.

  As described above, according to the present embodiment, the EGR valves 48 and 49 are provided in the cooler passage 43 and the bypass passage 44 of the EGR passage 41, respectively, in order to expand the region where proper CI combustion can be performed. An engine EGR device 40 is provided in which the problem of a decrease in the amount of EGR gas metering and temperature control caused by the flow resistance difference between the passage 43 and the bypass passage 44 is suppressed.

  As described above, in this embodiment, the cooler passage 43 is connected in parallel to the mixer 45, and the bypass passage 44 is connected so as to intersect the mixer 45. The effect obtained by this will be described with reference to FIG.

  FIG. 11A shows a case where the bypass passage 44 is connected in parallel to the mixer 45 and the cooler passage 43 is connected so as to intersect the mixer 45, unlike the present embodiment. In this case, the hot EGR gas that has passed through the bypass passage 44 travels straight through the mixer 45. That is, the high-temperature EGR gas that has entered from the mixer inlet 51 d exits from the mixer outlet 51 e without turning in the mixer 45. Therefore, the flow resistance of the high temperature EGR gas flowing through the bypass passage 44 does not increase. On the other hand, the low-temperature EGR gas that has passed through the cooler passage 43 cannot travel linearly through the mixer 45. That is, the low temperature EGR gas that has entered from the side of the mixer 45 cannot exit from the mixer outlet 51e unless the direction is changed in the mixer 45. Therefore, the flow resistance of the low temperature EGR gas flowing through the cooler passage 43 is further increased in addition to the flow resistance by the EGR cooler 47. As a result, the following problems occur.

  As shown in FIG. 11 (c), the opening degree of the cooler side EGR valve (low temperature EGR valve (referred to as C valve in the figure)) 48 is 100%, and bypass side EGR valve (high temperature EGR valve (referred to as H valve in the figure)). )) When the opening degree of 49 is controlled to 0%, the temperature of the mixed EGR gas coming out of the mixer outlet 51e becomes the temperature of the low-temperature EGR gas, the opening degree of the cooler side EGR valve 48 is 0%, and the bypass side EGR valve 49 is opened. When the degree is controlled to 100%, the temperature of the mixed EGR gas becomes the temperature of the high-temperature EGR gas, and the opening degree of the cooler side EGR valve 48 and the opening degree of the bypass side EGR valve 49 are each between 0% and less than 100%. When the control is performed so that the sum becomes 100%, the temperature of the mixed EGR gas changes between the temperature of the low temperature EGR gas and the temperature of the high temperature EGR gas.

  As shown in FIG. 11A, when the flow resistance of the high temperature EGR gas is small and the flow resistance of the low temperature EGR gas is large, for example, the opening degree of the cooler side EGR valve 48 is 100% and the bypass side EGR valve 49 Assuming that the opening degree is 0%, the EGR gas 49 that has flowed only in the cooler passage 43 until then has flowed in a large amount into the bypass passage 44 having a low flow resistance. As a result, as shown by a broken line in FIG. 11C, the temperature of the mixed EGR gas rises rapidly. That is, the temperature of the mixed EGR gas with respect to the opening degree of the EGR valves 48 and 49 does not change in proportion (does not change linearly), so that there is a problem that it is difficult to adjust the temperature of the mixed EGR gas recirculated to the intake passage 20.

  On the other hand, when the cooler passage 43 is connected in parallel to the mixer 45 and the bypass passage 44 is connected so as to intersect the mixer 45 as shown in FIG. The low temperature EGR gas travels straight through the mixer 45. That is, the low-temperature EGR gas that has entered from the mixer inlet 51d exits from the mixer outlet 51e without turning in the mixer 45. Therefore, the flow resistance of the low temperature EGR gas flowing through the cooler passage 43 does not increase. On the other hand, the high-temperature EGR gas that has passed through the bypass passage 44 cannot travel straight through the mixer 45. That is, the high temperature EGR gas that has entered from the side of the mixer 45 cannot exit from the mixer outlet 51e unless the direction is changed in the mixer 45. Therefore, the flow resistance of the high temperature EGR gas flowing through the bypass passage 44 increases. As a result, the difference in flow resistance between the cooler passage 43 and the bypass passage 44 is reduced, and the temperature of the mixed EGR gas is proportional to the opening degree of the EGR valves 48 and 49 as shown by the solid line in FIG. It changes (changes linearly). Thus, the C valve 48 in the cooler passage 43 and the H valve 49 in the bypass passage 44 are independently controlled, thereby adjusting the mixing ratio of the low temperature EGR gas and the high temperature EGR gas in the mixer 45, and consequently in the intake passage 20. The temperature of the refluxing EGR gas can be adjusted with high accuracy.

  Further, according to the present embodiment, due to the presence of the mixing plate 52 accommodated in the mixer 45, the high-temperature EGR gas that has entered the mixer 45 from the bypass passage 44 is applied to the peripheral surface (tapered peripheral wall portion 52b) of the mixing plate 52. After the collision, the mixing plate 52 returns to the upstream side of the mixer 45 (the outlet opening 43a side of the cooler passage 43) (see the arrow in the hollow space S in FIGS. 6 and 8), and the mixing plate 52 is hollow from the inlet opening 52c. The low-temperature EGR gas that has entered the space (merging chamber) 52s and entered the mixer 45 from the cooler passage 43 is mixed and mixed, and the mixed EGR gas passes through the outlet opening 52d of the mixing plate 52 (the outlet opening 51e of the mixer 45). Since it goes out of the mixer 45, the low temperature EGR gas is accompanied by such a turbulent movement of the high temperature EGR gas in the mixer 45. Mixed with the hot EGR gas is facilitated with. Therefore, the low-temperature EGR gas and the high-temperature EGR gas are efficiently and uniformly mixed during a short moving distance in the mixer 45 of the low-temperature EGR gas, and the mixed EGR gas is recirculated from the mixer 45 to the intake passage 20.

  Further, according to the present embodiment, the flow path axis B of the outlet opening 44 a of the bypass passage 44 is offset with respect to the axis of the mixing plate 52.

  According to this configuration, the high-temperature EGR gas that has entered the mixer 45 from the bypass passage 44 collides with the peripheral surface (tapered peripheral wall portion 52b) of the mixing plate 52 and then the peripheral surface (tapered peripheral wall portion 52b) of the mixing plate 52. A swirling flow is generated along the line (see the arrow in the hollow space S in FIG. 9), and in this state, the flow returns to the upstream side of the mixer 45 and the hollow space of the mixing plate 52 from the inlet opening 52c of the mixing plate 52 (merging chamber). 52s, merged with the low-temperature EGR gas, and mixed (see the arrow in the hollow space 52s in FIG. 9). Therefore, the swirling flow of the high-temperature EGR gas sufficiently stirs the low-temperature EGR gas and the high-temperature EGR gas, thereby further promoting the mixing of both EGR gases.

  Further, according to the present embodiment, the distribution passage 46 branched for each cylinder 2 is disposed between the mixer 45 and the independent intake passages 25 of the plurality of cylinders 2, and the upstream portion of each distribution passage 46 is Connected to the outlet opening 51 e of the mixer 45, the downstream portion is connected to each independent exhaust passage 25.

  According to this configuration, the EGR gas merged and mixed in the mixer 45 is supplied to the individual intake passages 25 of the plurality of cylinders 2 via the distribution passage 46, so that the EGR that is adjusted and temperature-controlled in the mixer 45 Gas is supplied to the combustion chamber 10 for each cylinder 2 in a relatively short time. Therefore, the switching response of the EGR gas returning to the intake passage 20 is improved, and it is possible to cope with a sudden change in load.

(5) Other Embodiments In the above embodiment, the outlet opening 43a of the cooler passage 43 and the outlet opening 51e of the mixer 45 are arranged so that the flow path axes A and O coincide with each other. You may arrange | position so that it may become parallel. Here, the predetermined interval is a predetermined interval within a range where the flow resistance of the cooler passage 43 does not increase significantly. Similarly, the inlet opening 52c of the mixing plate 52 and the flow path axis of the mixer inlet (reference A), the outlet opening 52d of the mixing plate 52 and the outlet opening 51e of the merging case 51, the axis of the mixing plate 52 and the flow path axis of the mixer inlet (A), the mixing plate 52 axis and the mixer outlet channel axis (O), and the outlet opening 53b of the discharge case 53 and the mixer outlet channel axis (O) are parallel to each other at a predetermined interval. You may arrange so that it may become.

  Moreover, in the said embodiment, although arrange | positioned so that the flow-path axis (code | symbol B) of the outlet opening 44a of the bypass channel 44 may be orthogonally crossed with respect to the flow-path axis (code | symbol O) of a mixer exit, other than 90 degrees You may arrange | position so that it may cross | intersect with a predetermined angle. Here, the predetermined angle is a predetermined angle within a range in which the flow resistance of the bypass passage 44 increases to the extent that the difference in flow resistance between the cooler passage 43 and the bypass passage 44 decreases.

  Moreover, in the said embodiment, although the mixing plate 52 had the truncated-cone-shaped taper surrounding wall part 52b, as shown in FIG. 12, the cylindrical surrounding wall part 52x may be sufficient. Also by this, the high-temperature EGR gas that has entered the mixer 45 from the bypass passage 44 collides with the peripheral surface (cylindrical peripheral wall portion 52x) of the mixing plate 52, and then returns to the upstream side (cooler passage 43 side) of the mixer 45. Thus, the hollow space (merging chamber) 52s of the mixing plate 52 can be entered from the inlet opening 52c of the mixing plate 52.

  In FIG. 12, a communication hole 52y that connects the hollow space S of the merging case 51 and the hollow space 52s of the mixing plate 52 is further formed in the cylindrical peripheral wall portion 52x. Although the high temperature EGR gas that has entered the mixer 45 from the bypass passage 44 can enter the hollow space 52s of the mixing plate, the communication hole 52y may not be formed.

  In the above embodiment, the engine is a compression self-ignition engine in which CI combustion is performed. However, a spark ignition engine in which SI combustion is performed, a diesel engine, or the like may be used. That is, the combustion form and the type of engine are not questioned. Among these, the most preferable result is obtained particularly in an engine that performs CI combustion using gasoline or alcohol-containing gasoline as fuel. A diesel engine is also preferable.

2 cylinder 4 cylinder head 6 intake port 8 intake valve 20 intake passage 21 common passage 24 surge tank 25 independent passage (independent intake passage)
28 Intake Manifold 29 Throttle Valve 30 Exhaust Passage 32 Exhaust Collecting Portion 40 EGR Device (Exhaust Recirculation Device)
41 EGR passage 42 Upstream passage 43 Cooler passage 43a Outlet opening 44 Bypass passage 44a Outlet opening 45 Mixer (merging section)
46 Distribution passage 47 EGR cooler 48 Cooler side EGR valve (low temperature EGR valve)
49 Bypass side EGR valve (High temperature EGR valve)
51 Junction case 51d Inlet opening (mixer inlet)
51e Outlet opening (mixer outlet)
52 Mixing plate (tubular member)
52a Flat plate portion 52b Tapered peripheral wall portion 52c Inlet opening 52d Outlet opening 52f Drain hole 52s Hollow space (merging chamber)
53 Discharge case A Flow channel axis at the mixer inlet (flow channel axis at the outlet opening of the cooler passage)
B Flow path axis of outlet opening of bypass passage O Flow path axis of mixer outlet (flow path axis of outlet opening of merging section)
S Hollow space

Claims (3)

As an EGR passage for returning a part of the exhaust gas flowing through the exhaust passage of the engine to the intake passage, a cooler passage provided with an EGR cooler for cooling the recirculated exhaust gas, and a bypass passage for bypassing the EGR cooler An exhaust gas recirculation device for an engine equipped with
A low temperature EGR valve that is disposed in the cooler passage and adjusts a flow rate of exhaust gas flowing through the cooler passage;
A high temperature EGR valve that is disposed in the bypass passage and adjusts the flow rate of exhaust gas flowing through the bypass passage;
A merging portion where the downstream portion of the cooler passage and the downstream portion of the bypass passage meet,
The outlet opening on the confluence portion side of the cooler passage is disposed so that the flow path axes thereof are parallel to the outlet opening on the intake passage side of the confluence portion, and the outlet on the confluence portion side of the bypass passage. The opening is disposed such that the flow path axis intersects with a predetermined angle with respect to the outlet opening on the intake passage side of the merging portion,
A tubular member having an inlet opening on the outlet opening side of the cooler passage and having an outlet opening on the outlet opening side of the merging part is accommodated in the merging part,
The exhaust gas recirculation device for an engine, wherein the cylindrical member is disposed so that an axis thereof is parallel to a flow axis of the outlet opening of the merging portion. The exhaust gas recirculation device for an engine according to claim 1,
An exhaust gas recirculation device for an engine, wherein a flow path axis of an outlet opening of the bypass passage is offset with respect to an axis of the cylindrical member. The engine exhaust gas recirculation apparatus according to claim 1 or 2,
A distribution passage branched for each cylinder is disposed between the merging portion and each independent intake passage of the plurality of cylinders.
An exhaust gas recirculation device for an engine, wherein an upstream portion of each distribution passage is connected to an outlet opening of the merging portion, and a downstream portion is connected to each independent exhaust passage.

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