JP2011106361A - Exhaust gas recirculation device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device for an internal combustion engine having a catalyst unit easily mounted in front of an exhaust cooler and effectively reducing the exhaust pulsation so as to suppress the exhaust interference, in the internal combustion engine including two confluent exhaust pipes and a twin entry type exhaust turbocharger. <P>SOLUTION: This device includes: an EGR passage 51 with a first passage portion 51a connected to the confluent exhaust pipe 31a, a second passage portion 51b connected to the confluent exhaust pipe 31b, and a third passage portion 51c connected to an internal space in a surge tank 27, recirculating a part of exhaust gas through the passage portions 51a-51c to the intake side; and an EGR valve 52 with a three-way valve configuration interposed between the first and second passage portions 51a, 51b and the third passage portion 51c. Each of the first and the second passage portions 51a, 51b has a bellows-shaped plurality stages of annular recessed portions located on the minimum cross-sectional area side and annular projected portions located on the maximum cross-sectional area side, in a manner to vary the cross-sectional area of each passage between the maximum cross-sectional area and the minimum cross-sectional area a plurality of times. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is suitable for an exhaust gas recirculation device for an internal combustion engine, particularly for an internal combustion engine in which exhaust from a plurality of cylinders is divided into two systems and introduced into a twin entry type exhaust turbocharger so as to avoid exhaust interference. The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  In a four-cycle multi-cylinder internal combustion engine, if the exhaust pipes (exhaust passages) of all cylinders are gathered near their exhaust ports, exhaust interference occurs. Some exhaust gas is exhausted to two combined exhaust pipes so that exhaust gases from cylinders that are separated from each other are merged. In addition, when supercharging is performed with such an engine, a twin-entry type exhaust turbocharger that can take in the exhaust of both combined exhaust pipes without causing exhaust interference is effective. Therefore, an internal combustion engine using two combined exhaust pipes and a twin entry type exhaust turbocharger has been proposed (see, for example, Patent Document 1).

  On the other hand, it is known that an exhaust gas recirculation device that recirculates a part of exhaust gas to the intake side is effective in reducing exhaust emissions and improving fuel efficiency (see, for example, Patent Document 2).

JP-A-2005-330836 JP 2006-214275 A

  However, when an exhaust gas recirculation device is equipped in an engine equipped with the above-described two combined exhaust pipes and a twin entry type exhaust turbocharger, there are the following problems.

  For example, in an engine equipped with an exhaust gas recirculation device, when it is desired to dispose a catalyst unit for exhaust purification upstream of the exhaust cooler, a certain length of pipe length is required for two merged exhaust pipes because it is necessary to suppress exhaust interference. Therefore, it is not easy to mount the catalyst unit.

  On the other hand, if the lengths of the two combined exhaust pipes are shortened, the pulsation component of the exhaust gas disappears due to the exhaust interference and does not reach the turbine blades of the turbo, and the turbine operating efficiency is lowered, so that the engine torque is lowered. There is concern.

  Therefore, the present invention eliminates restrictions on mounting of a catalyst before the exhaust cooler and the like in an internal combustion engine having two merged exhaust pipes and a twin entry type exhaust turbocharger, and effectively reduces exhaust pulsation and exhaust. It is an object of the present invention to provide an exhaust gas recirculation device for an internal combustion engine that can suppress interference.

  In order to achieve the above object, an exhaust gas recirculation apparatus for an internal combustion engine according to the present invention (1) exhausts exhaust gases from a plurality of cylinders whose exhaust stroke order is adjacent to each other and exhausts them separately. A first merging exhaust pipe and a second merging exhaust pipe for merging exhaust gases from the cylinders, and a twin-entry type exhaust turbocharger connected to the first merging exhaust pipe and the second merging exhaust pipe. An exhaust gas recirculation device equipped in an internal combustion engine provided with a first passage portion connected to the first combined exhaust pipe, a second passage portion connected to the second combined exhaust pipe, and an intake air of the internal combustion engine A third passage portion connected to a pipe, and a part of the exhaust gas of the internal combustion engine is recirculated to the intake pipe through the first passage portion, the second passage portion, and the third passage portion. Exhaust recirculation passage and the exhaust recirculation A three-way exhaust recirculation valve interposed between the first passage portion and the second passage portion and the third passage portion of the passage, and the first passage portion and the second passage portion of the exhaust recirculation passage However, the annular recess located on the minimum cross-sectional area side and the annular convex part located on the maximum cross-sectional area side have a bellows shape so that each passage cross-sectional area is changed between the maximum cross-sectional area and the minimum cross-sectional area a plurality of times. It has a plurality of stages.

  With this configuration, in the first and second passage portions of the exhaust gas recirculation passage from the first confluence exhaust pipe and the second confluence exhaust pipe to the exhaust gas recirculation valve, the exhaust gas responds to multiple changes in the passage cross-sectional area. Thus, expansion and contraction are repeated. Accordingly, the pulsating component having a large flow velocity in both the passage portions is effectively attenuated, so that exhaust interference is effectively suppressed in the joining portion of both passage portions. In addition, since a plurality of bellows portions are used, there is no need to set the maximum cross-sectional area of the passage cross-sectional area excessively large or the minimum cross-sectional area excessively small, and the catalyst unit can be easily installed before the exhaust cooler. It can be mounted and excessive pressure loss does not occur. Furthermore, the function of cooling the exhaust gas is also generated by increasing the surface area of the bellows portion, so that the load on the exhaust cooler can be reduced and the expansion and contraction due to heat of the exhaust system components can be absorbed by the bellows portion. The three-way exhaust recirculation valve includes a valve-open state in which the first passage portion, the second passage portion, and the third passage portion are in communication, the first passage portion, the second passage portion, and the third passage. It is desirable to switch to a valve closing state that blocks communication between any of the passage portions.

In the exhaust gas recirculation apparatus for an internal combustion engine of the present invention, (2) where the number of stages of the plurality of stages is γ and the energy decay rate of the exhaust gas at each stage is β, the following equation (1-β) ^γ < It is preferable that the step number γ, the maximum cross-sectional area, and the minimum cross-sectional area are set so as to satisfy 0.1.

  With this configuration, it is possible to reliably suppress exhaust interference due to attenuation of exhaust pressure pulsation while selecting the number of bellows, the size of the bellows, and the like that are not easily restricted by mounting.

  According to the present invention, in an internal combustion engine equipped with two combined exhaust pipes and a twin entry type exhaust turbocharger, there is no restriction on mounting a catalyst before the exhaust cooler and the like, and exhaust pulsation is effectively reduced and exhaust is reduced. An exhaust gas recirculation device for an internal combustion engine that can suppress interference can be provided.

1 is a schematic block diagram of an exhaust gas recirculation device for an internal combustion engine according to an embodiment of the present invention. It is a principal part block diagram of the exhaust gas recirculation apparatus of the internal combustion engine which concerns on one Embodiment. It is a schematic cross section of the pipe shape of the 1st and 2nd passage part of the exhaust gas recirculation passage in the exhaust gas recirculation device of the internal-combustion engine concerning one embodiment. It is a figure which shows the energy loss characteristic of the expansion part of the 1st, 2nd channel | path part of the exhaust gas recirculation passage in the exhaust gas recirculation apparatus of the internal combustion engine which concerns on one Embodiment.

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

  1 to 3 show an exhaust gas recirculation device for an internal combustion engine according to an embodiment of the present invention.

  An engine 10 shown in FIG. 1 is a multi-cylinder internal combustion engine for vehicles, for example, a four-cylinder gasoline engine (hereinafter simply referred to as an engine), and has a plurality of cylinders 11.

  The engine 10 includes a well-known fuel injection device (not shown) that injects fuel into a combustion chamber (not shown in detail) in each cylinder 11, an intake device 12 that sucks air into the combustion chamber, and a combustion chamber. An exhaust device 13 for exhausting the exhaust gas, a twin-entry exhaust turbocharger 14 having an exhaust turbine 14T rotated by exhaust energy in the exhaust device 13 and an intake air compressor 14C rotating integrally therewith, and an exhaust gas And an exhaust gas recirculation device 15 that recirculates a part of the gas to the intake side and recirculates it. The fuel injection device supplies fuel into the combustion chamber at a timing and duty ratio corresponding to an injection command signal from a fuel pump that pumps fuel from a fuel tank (not shown) and an electronic control unit (hereinafter referred to as ECU) 30 described later. And a fuel injection valve that injects fuel.

  The intake device 12 includes an intake manifold 21, an intake pipe 22 that forms an intake passage upstream of the intake manifold 21, an air cleaner 23 that cleans intake air by a filter on the upstream side of the intake pipe 22, and an exhaust turbocharger 14, an intercooler 24 that cools the intake air heated by supercharging downstream of the intake air compressor 14 </ b> C, an air flow meter 25 that detects an intake air flow rate (fresh air intake amount), and intake air into the engine 10. A throttle valve 26 for adjusting the amount, and a surge tank 27 for suppressing pulsation of intake air on the upstream side of the intake manifold 21 are provided.

  The exhaust device 13 includes an exhaust manifold 31, an exhaust pipe 32 that forms an exhaust passage downstream of the exhaust manifold 31, and an air-fuel ratio sensor 33 that is mounted on the exhaust pipe 32 downstream of the exhaust turbine 14T of the exhaust turbocharger 14. And an exhaust aftertreatment device 34 incorporating an exhaust purification catalyst.

  Here, the exhaust manifold 31 includes a plurality of cylinders of the engine 10 whose exhaust periods (exhaust stroke order) are separated from each other, such as an exhaust port, for example, a first cylinder and a fourth cylinder (# in FIG. 1). 1 and # 4), the first combined exhaust pipe 31a connected to the exhaust port (not shown), and the exhaust ports of the remaining cylinders whose exhaust periods are separated from each other among the plurality of cylinders of the engine 10, such as the second cylinder and A second combined exhaust pipe 31b connected to an exhaust port (not shown) of the third cylinder (# 2, # 3 in FIG. 1) is formed, and these first and second combined exhaust pipes 31a, 31b are formed. Are independently connected to two nozzle passage portions (described later) of the twin entry type exhaust turbocharger 14. In other words, exhaust interference occurs between the cylinders (for example, the first cylinder and the third cylinder) in which the exhaust stroke order is adjacent and the exhaust valve opening periods partially overlap, so that the exhaust passage is divided into two systems and exhausted. The two systems of combined exhaust pipes 31a and 31b are arranged so that the exhaust gas is merged in the same system between the cylinders (for example, the first cylinder and the fourth cylinder) that are separated from each other without overlapping the opening periods of the exhaust valves. Is provided.

  In the air-fuel ratio sensor 33, for example, whether the oxygen concentration in the exhaust gas passing through the downstream exhaust pipe 32 is a value corresponding to the stoichiometric air-fuel ratio (the air-fuel ratio in which gasoline and air are completely burned and no surplus oxygen remains). It consists of an exhaust oxygen concentration sensor whose output changes depending on whether or not.

The exhaust aftertreatment device 34 is composed of, for example, a three-way catalyst, and reduces NOx in the exhaust gas to NO ₂ or NO and reacts with HC or CO in the exhaust gas to form N ₂ or oxidizes HC or CO. H ₂ O or CO ₂ . The engine 10 is feedback-controlled by the ECU 30 based on the detection information of the air-fuel ratio sensor 33, and is operated at a stoichiometric air-fuel ratio that provides good exhaust purification characteristics of the exhaust aftertreatment device 34.

  The intake air compressor 14 </ b> C and the exhaust turbine 14 </ b> T of the exhaust turbocharger 14 are integrally connected to each other in the rotation direction, and the exhaust turbine 14 </ b> T is rotated by exhaust energy in the exhaust device 13 and the intake air compressor in the intake device 12. 14C can be rotated, and supercharging can be performed in which more air is sucked into the engine 10 than natural intake air.

  Further, the exhaust turbocharger 14 introduces exhaust from the first cylinder and the fourth cylinder of the engine 10 into the exhaust turbine 14T, and squeezes and accelerates the first nozzle passage portion 14a, and the exhaust turbine. 14T has a second nozzle passage portion 14b for introducing exhaust from the second cylinder and the third cylinder of the engine 10 and accelerating by narrowing the flow path. The exhaust turbo supercharger 14 is configured to be a high turbine by supplying exhaust gas from the first nozzle passage portion 14a and the second nozzle passage portion 14b to the turbine rotor 14c of the exhaust turbine 14T without pressure drop due to exhaust interference. It can operate at operating efficiency.

  The exhaust gas recirculation device 15 includes an exhaust gas recirculation EGR passage 51 (exhaust gas recirculation passage) that bypasses the combustion chamber in the engine 10 and connects the exhaust passage in the exhaust manifold 31 and the intake passage in the intake manifold 21. The EGR valve 52 (three-way exhaust gas recirculation valve) that adjusts the exhaust gas recirculation amount through the EGR passage 51, the EGR cooler 53 (exhaust cooler) that cools the exhaust gas recirculating through the EGR passage 51, and the EGR cooler 53 EGR cooler pre-catalyst units 54 that purify the exhaust gas are respectively provided.

  Here, the EGR passage 51 is an exhaust gas recirculation passage that recirculates a part of the exhaust gas from the exhaust passage side of the engine 10 to the intake passage side, and the EGR cooler 53 uses a part of the EGR passage 51 as a cooling passage.

  Further, the EGR valve 52 can be switched between, for example, a valve opening state in which exhaust gas is recirculated to the intake passage side and a valve closing state in which the connection is cut off, and the length of the valve opening instruction signal from the ECU 30 per predetermined time. The opening degree can be controlled by the ratio (duty ratio). Of course, the EGR valve 52 may be of a type that changes the rotation angle of the rotary valve body from the fully open position to the fully closed position.

  The EGR cooler 53 cools the exhaust gas recirculated through the EGR passage 51 by heat exchange with cooling water passing through the cooling system of the engine 10.

  The EGR cooler pre-catalyst unit 54 is composed of, for example, an oxidation catalyst or a similar three-way catalyst.

  On the other hand, the EGR passage 51 includes a first passage portion 51a and a second passage portion 51b that extend from the first combined exhaust pipe 31a and the second combined exhaust pipe 31b of the exhaust manifold 31 to the EGR valve 52 that is a three-way valve, and EGR. The third passage 51c extends from the valve 52 to the surge tank 27, and a part of the exhaust gas of the engine 10 passes through the first passage 51a, the second passage 51b, and the third passage 51c. It can be recirculated to the intake passage side. Here, the first passage portion 51a is connected to the first combined exhaust pipe 31a of the exhaust manifold 31, the second passage portion 51b is connected to the second combined exhaust pipe 31b of the exhaust manifold 31, and the third passage portion 51c. Is connected to the internal space of the surge tank 27 which is a part of the intake passage of the engine 10.

  Further, as shown in FIGS. 2 and 3, the first passage portion 51a and the second passage portion 51b form similar pipes having substantially the same length, and the passage sectional area is set to the maximum sectional area A2. The small-diameter portion 51v located on the minimum cross-sectional area A1 side and the large-diameter portion 51p located on the maximum cross-sectional area A2 side are provided in a plurality of steps in a bellows shape so as to change a plurality of times between the minimum cross-sectional area A1 and the minimum cross-sectional area A1. That is, the first passage portion 51 a and the second passage portion 51 b are formed inside by the bellows portions 55 bw and 56 bw of the two exhaust recirculation pipes 55 and 56 that form the upstream portion of the EGR passage 51.

  More specifically, the passage cross-sectional area in the small diameter part 51v of the first passage part 51a and the second passage part 51b is the minimum cross-sectional area A1 or a value close to it in almost the entire region of the formation section p1 of the small diameter part 51v. The passage sectional area in the large diameter portion 51p of the first passage portion 51a and the second passage portion 51b is the maximum sectional area A2 or a value close thereto in almost the entire region of the formation section p2 of the large diameter portion 51p. The cross-sectional area of the third passage portion 51c of the EGR passage 51 is set to be twice or more the minimum cross-sectional area A1.

  In FIG. 3, the cross sections of the bellows portions 55 bw and 56 bw are illustrated in a substantially rectangular wave shape having a corner R. However, the corner R may not be provided, and conversely, a trochoidal curved cross section may be used. Moreover, the small diameter part 51v and the large diameter part 51p may each be substantially V-shaped.

However, in the 1st channel | path part 51a and the 2nd channel | path part 51b, the adjacent small diameter part 51v and the large diameter part 51p are made into one step bellows shape, the installation stage number is set to (gamma), The small diameter part 51v and large diameter of each stage are When the energy decay rate of the exhaust gas when passing through the portion 51p is β, the stage number γ and the ratio of the minimum cross-sectional area A1 to the maximum cross-sectional area A2 are set so as to satisfy the following equation (1): Each is set. This equation is set so that the total specific energy loss caused by the plurality of accordion-shaped small-diameter portions 51v and large-diameter portions 51p is close to that of the surge tank (1- (1-β) ^γ > 0.9). The conditions are shown.

(1-β) ^γ <0.1 (1)
However, the attenuation ratio β is defined as an energy loss ratio in each enlarged tube portion from the small diameter portion 51v to the large diameter portion 51p and an energy loss ratio in each contraction tube portion from the large diameter portion 51p to the next small diameter portion 51v. It is a combination.

  Here, since the flow of the exhaust gas in the EGR passage 51 is not so steep, the approximate specific energy loss can be estimated in the same manner as the energy loss in the expansion pipe and the reduction pipe for the incompressible fluid.

  That is, regarding the energy loss in the expanded pipe portion here, the exhaust gas traveling at the speed va in the small diameter portion 51v of the minimum cross section A1 enters the large diameter portion 51p of the maximum cross section A2 immediately after the small diameter portion 51v and expands. Assuming that the velocity va ′ is reached, the specific energy loss ΔE1 and the loss coefficient β1 that determines the specific energy loss ΔE1 can be expressed by the following equations (2) and (3), respectively. In this case, it can be said that the energy loss is large with respect to the pulsating component having a large velocity va.

^{ΔE1 = β1 · (va 2/} 2) ··· (2)
β1 = ξ · (1− (A1 / A2)) ² (3)
However, since the coefficient ξ in the equation (3) is a value close to 1, hereinafter, it is assumed that ξ = 1.

  As for the energy loss due to the reduced tube portion here, the exhaust gas traveling at a speed vb ′ in the large diameter portion 51p of the maximum cross sectional area A2 enters the small diameter portion 51v of the minimum cross sectional area A1 immediately thereafter, and is reduced. Assuming the speed vb, the specific energy loss ΔE2 and the loss coefficient β2 at that time can be expressed by the following equations (4) and (5), respectively.

^{ΔE2 = β2 · (vb 2/} 2) ··· (4)
β2 = (1 / c−1) ² (5)
Here, c is a contraction coefficient, and is a value corresponding to A3 / A1, where A3 is the minimum cross-sectional area of contraction flow when entering the small diameter portion 51v immediately after.

These loss coefficients β1 and β2 vary greatly depending on the pipe shape. For example, when there is a gentle inclination or a corner R in the contraction tube portion, energy loss due to the contraction tube becomes small.
Therefore, for example, when a gentle slope or corner R is added to the bellows part so as to easily suppress the influence of thermal distortion, the loss coefficient β2 in the reduction pipe part is considered to be sufficiently small, and the loss coefficient β1 in the expansion pipe part is set to each stage. The loss ratio β can be considered.
More specifically, for example, the cross-sectional area ratio A1 / A2 of the small diameter portion 51v and the large diameter portion 51p of the enlarged pipe portion is 0.5 (the diameter (passage inner diameter) d1 of the small diameter portion 51v and the diameter d2 of the large diameter portion 51p). When the ratio d1 / d2 is about 0.7) and the bellows step number γ is nine, the cross-sectional area ratio A1 / A2 is 0.4 (d1 / d2 is about 0.63), and the bellows step number γ is FIG. 4 shows the loss shown in FIG. 4 in the case of 6 stages or when the cross-sectional area ratio A1 / A2 is 0.3 (d1 / d2 is about 0.55) and the number of bellows stages γ is 4. When (1-β1) ^γ is obtained based on the data of the ratio β1, it becomes sufficiently smaller than 0.1, and a pulsation damping effect close to that of a surge tank can be expected.

In this way, when considering the attenuation of pulsation due to the plurality of stages of enlarged tube portions, the cross-sectional area ratio A1 / A2, which is the ratio of the minimum cross-sectional area A1 and the maximum cross-sectional area A2, is A1 / A2 <0.4 (d1 / d2 By setting so as to satisfy <0.63), it is possible to sufficiently suppress restrictions on mounting the exhaust gas recirculation device 15.
Further, the formation section p1 of the small diameter part 51v of each of the first passage part 51a and the second passage part 51b is not particularly limited, but has a length close to the diameter (passage inner diameter) d1 of the small diameter part 51v. The formation section p2 of the diameter portion 51p has a length close to the diameter (passage inner diameter) d2 of the large diameter portion 51p.

  As shown in FIG. 2, the EGR valve 52 includes two inlet ports 52 a and 52 b to which the first passage portion 51 a and the second passage portion 51 b of the EGR passage 51 are connected, and a third passage portion 51 c of the EGR passage 51. The outlet port 52c is connected to the first passage portion 51a of the EGR passage 51, and is configured as a three-way solenoid valve interposed between the second passage portion 51b and the third passage portion 51c. . Further, the EGR valve 52 includes a valve-open state in which the first passage portion 51a, the second passage portion 51b, and the third passage portion 51c are in communication with each other, and the first passage portion 51a, the second passage portion 51b, and the third passage portion 51c. The valve can be switched to a closed state in which communication between the two is cut off.

  Specifically, the EGR valve 52 includes a valve opening position [I] that allows the inlet ports 52a and 52b to communicate with the outlet port 52c, and a valve closing position [II] that blocks the inlet ports 52a and 52b and the outlet port 52c individually. A valve body 52v that can be switched to the valve body 52, a spring 52p that normally biases the valve body 52v in the valve closing direction, and an electromagnetic operation section 52s that can drive the valve body 52v in the valve opening direction. . The configuration of such a three-way valve itself is the same as a known one, but the electromagnetic operation unit 52s is excited and driven by a valve opening instruction signal per predetermined time from the ECU 30, and the EGR valve 52 is turned on by a valve opening instruction signal. The opening can be set according to the duty ratio.

  The EGR cooler 53 has a cooling passage structure similar to that of the EGR cooler described in, for example, JP-A-2006-348873, and the EGR cooler pre-catalyst unit 54 is for purification described in, for example, JP-A-2005-240641 The passage structure is the same as that of the catalyst.

  Next, the operation will be described.

  In the exhaust gas recirculation apparatus for an internal combustion engine of the present embodiment configured as described above, the first passage of the EGR passage 51 from the first combined exhaust pipe 31a and the second combined exhaust pipe 31b of the exhaust manifold 31 when the engine 10 is operated. Exhaust gas with exhaust pulsation flows into the portion 51a and the second passage portion 51b.

  At this time, the exhaust gas passing through the inside of the first passage portion 51a and the second passage portion 51b of the EGR passage 51 is expanded from the small diameter portion 51v to the large diameter portion 51p, and from the large diameter portion 51p to the next stage. Pulsating component having a large flow velocity inside both the passage portions 51a and 51b, which passes through each of the contraction pipe portions to the small-diameter portion 51v and repeats expansion and contraction a plurality of times in accordance with changes in the respective passage sectional areas. Is effectively attenuated to such an extent that it flows into the surge tank. Therefore, when the EGR valve 52 is opened, when the two systems of combined exhaust gas passing through the first passage portion 51a and the second passage portion 51b are further merged inside the EGR valve 52 and gather for all the cylinders, both passage portions The exhaust gas from 51a and 51b has already sufficiently attenuated the pulsation component, and the exhaust interference is effectively suppressed.

  In the present embodiment, each of the first passage portion 51a and the second passage portion 51b has a configuration having a plurality of bellows-like portions including the adjacent small diameter portion 51v and large diameter portion 51p as one step. There is no need to set the maximum cross-sectional area A2 of the passage cross-sectional area excessively large or the minimum cross-sectional area A1 excessively small, and the passage length to the EGR cooler pre-catalyst unit 54 can be shortened. Therefore, the EGR cooler pre-catalyst unit 54 can be easily mounted in front of the EGR cooler 53.

  In addition, since the surface areas serving as heat dissipation surfaces of the bellows portions 55bw and 56bw of the two exhaust gas recirculation pipes 55 and 56 are increased, exhaust gas having a high exhaust temperature passing through the first passage portion 51a and the second passage portion 51b is generated. The function to cool will also arise and the cooling load of the EGR cooler 53 can also be reduced. In addition, expansion and contraction (distortion) due to heat of the exhaust system parts can be effectively absorbed by the bellows portions 55bw and 56bw of the two exhaust recirculation pipes 55 and 56, and cracks of peripheral parts can be prevented. it can.

Furthermore, in this embodiment, when the number of stages of the plurality of bellows-like parts including the adjacent small-diameter part 51v and large-diameter part 51p as one stage is γ, and the energy decay rate of the exhaust gas at each stage is β. , (1-β) ^γ <0.1, the step number γ, the maximum cross-sectional area A2 and the minimum cross-sectional area A1 are set, respectively. Exhaust interference due to the attenuation of exhaust pressure pulsation can be reliably suppressed while selecting the passage inner diameter dimensions d1, d2, and the like.

  As described above, in the present embodiment, in the engine 10 including the two combined exhaust pipes 31a and 31b and the twin entry type exhaust turbocharger 14, the restriction on mounting the EGR cooler pre-catalyst unit 54 and the like is eliminated. Thus, it is possible to provide the exhaust gas recirculation device 15 that can effectively reduce the exhaust pulsation and suppress the exhaust interference.

  Further, in the present embodiment, when the EGR valve 52 is closed, the first passage portion 51a and the second passage portion 51b are blocked so that exhaust interference is reliably prevented and engine torque is prevented from being lowered. The

  In the present embodiment, the EGR valve 52 is disposed upstream of the EGR cooler 53 (on the first and second combined exhaust pipe sides), but the EGR valve 52 is downstream of the pre-EGR cooler catalyst unit 54. (The side away from the first and second combined exhaust pipes) or further downstream of the EGR cooler 53. In this case, the first passage portion 51a and the second passage portion 51b corresponding to the two merged exhaust pipes 31a and 31b are formed longer on the upstream side than the EGR valve 52. Therefore, for example, an exhaust gas recirculation pipe similar to the two exhaust gas recirculation pipes 55 and 56 is provided between the EGR cooler pre-catalyst unit 54 and the EGR cooler 53, and the first passage portion 51a and the second passage portion 51b are provided as the EGR cooler. Also between the front catalyst unit 54 and the EGR cooler 53, the respective passage cross-sectional areas can be changed a plurality of times between the maximum cross-sectional area A2 and the minimum cross-sectional area A1. In that case, the cross-sectional area ratio A1 / A2 can be set relatively large.

  In the above-described embodiment, the engine 10 is a gasoline engine. However, a diesel engine may be used, and an arbitrary four-cycle engine using a different fuel may be used. Further, the catalyst unit before the exhaust cooling air is not limited to the oxidation catalyst or the three-way catalyst, but may be a NOx storage catalyst or a diesel particulate filter.

  As described above, the exhaust gas recirculation device for an internal combustion engine according to the present embodiment is a restriction on mounting an exhaust cooler pre-catalyst or the like in an internal combustion engine including two combined exhaust pipes and a twin entry type exhaust turbocharger. In addition, an exhaust gas recirculation device for an internal combustion engine that can effectively reduce exhaust pulsation and suppress exhaust interference can be provided, and exhaust from a plurality of cylinders can be provided to avoid exhaust interference. This is useful for exhaust gas recirculation devices that are installed in internal combustion engines that are divided into two systems and introduced into twin-entry exhaust turbochargers.

10 Engine (Internal combustion engine)
11 cylinder 12 intake device 13 exhaust device 14 exhaust turbocharger 14C intake air compressor 14T exhaust turbine 15 exhaust recirculation device 21 intake manifold 22 intake pipe (intake passage)
27 Surge tank (intake passage)
30 ECU (Electronic Control Unit)
31 Exhaust manifold 31a First combined exhaust pipe 31b Second combined exhaust pipe 32 Exhaust pipe (exhaust passage)
51 EGR passage (exhaust gas recirculation passage)
51a 1st channel | path part 51b 2nd channel | path part 51c 3rd channel | path part 51p Large diameter part (annular convex part)
51v Small diameter part (annular recess)
52 EGR valve (3-way exhaust recirculation valve)
52a, 52b Inlet port 52c Outlet port 53 EGR cooler (exhaust cooler)
54 EGR cooler front catalyst unit (catalyst)
55, 56 Exhaust gas recirculation pipe 55bw, 56bw Bellows A1 Minimum cross-sectional area A2 Maximum cross-sectional area p1, p2 Formation section

Claims (2)

A first merging exhaust pipe and a second merging exhaust pipe for separately evacuating exhaust gases from a plurality of cylinders whose exhaust stroke order is adjacent and merging exhaust gases from a plurality of cylinders whose exhaust stroke orders are separated from each other; An exhaust gas recirculation device equipped in an internal combustion engine comprising a twin-entry exhaust turbocharger connected to the first combined exhaust pipe and the second combined exhaust pipe,
A first passage portion connected to the first combined exhaust pipe, a second passage portion connected to the second combined exhaust pipe, and a third passage portion connected to an intake pipe of the internal combustion engine; An exhaust gas recirculation passage capable of recirculating a part of engine exhaust gas to the intake pipe through the first passage portion, the second passage portion, and the third passage portion;
A three-way exhaust recirculation valve interposed between the first passage portion and the second passage portion and the third passage portion of the exhaust recirculation passage;
An annular recess located on the minimum cross-sectional area side so that the first passage portion and the second passage portion of the exhaust gas recirculation passage change each passage cross-sectional area a plurality of times between the maximum cross-sectional area and the minimum cross-sectional area. And an exhaust gas recirculation device for an internal combustion engine having a plurality of annular convex portions located on the maximum cross-sectional area side in a bellows shape. When the number of stages in the plurality of stages is γ and the energy decay rate of the exhaust gas in each stage is β, the following equation (1-β) ^γ <0.1
2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the stage number γ, the maximum cross-sectional area, and the minimum cross-sectional area are set so as to satisfy the following equation.

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