JP2007218187A - Exhaust circulation device of turbocharged engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust circulation device of a turbocharged engine, efficiently cooling EGR gas. <P>SOLUTION: In the exhaust circulation device of a turbocharged engine, an exhaust recirculation passage is provided with first and second exhaust circulation passages 17, 18 connected with exhaust manifolds, and the exhaust circulation passages are respectively provided with first and second exhaust circulations coolers 20, 21 for cooling circulated exhaust. After the exhaust from one exhaust manifold 2a is cooled by the exhaust circulation cooler 20 of one exhaust circulation passage 17 connected with the exhaust manifold 2a, the exhaust flows back in the other exhaust circulation passage 18 to be cooled by the exhaust circulation cooler 21 disposed to the exhaust circulation passage 18, and the back-flow exhaust is mixed with the exhaust from the other exhaust manifold 2b so as to flow back in one exhaust circulation passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in an exhaust gas recirculation device for a turbocharged engine.

  Today, an exhaust gas recirculation device (EGR device) that recirculates exhaust gas to the intake side of the engine (hereinafter referred to as “EGR”) as EGR gas in order to reduce NOx generated during diesel engine combustion is known. ing.

  Since NOx is produced by the reaction of oxygen and nitrogen in the air under high-temperature exhaust gas, this exhaust gas recirculation device lowers the combustion temperature with EGR and suppresses the generation of NOx.

  Conventionally, many vehicles are equipped with a turbocharger for the purpose of improving engine output, and an exhaust gas recirculation device is also attached to a turbocharged engine equipped with a turbocharger.

  The EGR of the turbocharged engine is performed using a pressure difference from the upstream side of the turbocharger turbine to the downstream side of the compressor. In the turbocharged engine, the supply pressure is higher than the exhaust pressure. There is an operation region (especially a low speed and high load region), and there is a possibility that EGR cannot be sufficiently performed in this operation region.

  Therefore, as an exhaust gas recirculation device for a turbocharged engine that solves such a problem and enables EGR even in a high load range, one disclosed in Patent Document 1 is known.

This exhaust gas recirculation system divides an exhaust manifold of an engine equipped with a turbocharger into a first exhaust manifold and a second exhaust manifold for each cylinder whose exhaust strokes do not overlap each other, In addition, an exhaust gas recirculation passage is connected between the two exhaust manifolds and a turbine housing of the turbocharger. A nozzle portion whose cross section gradually decreases toward the exhaust gas merging portion of the turbine housing is connected to each exhaust manifold portion. Provided. The exhaust gas recirculation passages extend from the respective exhaust manifolds, and then gather into one exhaust gas recirculation passage, and are connected to an ejector provided at a connection portion between the intake air passage and the exhaust gas recirculation passage. An exhaust gas recirculation cooler and a check valve are installed from the exhaust manifold side in each exhaust gas recirculation passage connected to each exhaust manifold. By providing the check valve, the backflow of the exhaust gas to the other exhaust gas recirculation passage due to the exhaust pulse of one exhaust manifold is prevented.
JP 2005-147011 A

  However, the exhaust gas recirculation apparatus disclosed in Patent Document 1 includes exhaust gas recirculation coolers that are independent from each other in the exhaust gas recirculation passages connected to the respective exhaust manifolds. In order to cool, there exists a subject that an exhaust-gas recirculation cooler will enlarge and cost will be raised.

  In view of the above problems, an object of the present invention is to provide an exhaust gas recirculation device for a turbocharged engine that achieves downsizing of an exhaust gas recirculation cooler that cools exhaust gas recirculation gas.

  According to a first aspect of the present invention, an exhaust manifold of an engine provided with a turbocharger is divided into a first exhaust manifold and a second exhaust manifold for each cylinder whose exhaust strokes do not overlap each other, and the first and second exhausts are divided. In the exhaust gas recirculation apparatus for a turbocharged engine in which an exhaust gas recirculation passage is connected between the manifold and the intake air passage of the engine, the exhaust gas recirculation passage includes a first exhaust gas recirculation passage connected to the first exhaust manifold, The first and second exhaust gas recirculation comprises a second exhaust gas recirculation passage connected to the second exhaust manifold and a third exhaust gas recirculation passage formed by joining the first and second exhaust gas recirculation passages. The passages are provided with first and second exhaust gas recirculation coolers for cooling the recirculated exhaust gas, respectively, and the exhaust gas from one exhaust manifold is connected to the front of the connected one. After being cooled by the exhaust gas recirculation cooler in the exhaust gas recirculation passage, it flows out to the third exhaust gas recirculation passage, while a part flows back through the other exhaust gas recirculation passage, and the exhaust gas recirculation cooler provided therein The cooled and back-flowed exhaust gas is mixed with the exhaust gas from the other exhaust manifold and flows out to the third exhaust gas recirculation passage, while a part of the exhaust gas flows back through the one exhaust gas recirculation passage. It is characterized by that.

  A second invention is characterized in that, in the first invention, the first and second exhaust gas recirculation coolers are integrated and installed at a junction with the third exhaust gas recirculation passage.

  According to a third invention, in the first or second invention, an exhaust gas recirculation control valve that controls a recirculation amount of exhaust gas to the intake passage in the third exhaust recirculation passage, the third exhaust recirculation passage, An ejector is provided at the junction with the intake passage.

  According to a fourth invention, in the first or second invention, an exhaust gas recirculation control valve that controls a return amount of exhaust gas to the intake passage in the third exhaust gas return passage, the third exhaust gas return passage, An electric throttle valve is provided in the intake passage upstream of the junction with the intake passage, and the exhaust gas recirculation control valve and the electric throttle valve are cooperatively controlled according to the operating state of the engine. .

  In the first invention, the exhaust gas recirculated through the exhaust gas recirculation passages is cooled while reciprocating the exhaust gas recirculation coolers, so that the temperature of the exhaust gas can be lowered efficiently and the cooling of the exhaust gas can be improved. Can do.

  In the second invention, by integrating the exhaust gas recirculation coolers provided in the respective exhaust gas recirculation passages, weight reduction and cost reduction can be achieved.

  In the third aspect of the invention, the exhaust gas recirculation control valve and the ejector are provided at the junction of the third exhaust gas recirculation passage and the intake air passage, so that the exhaust gas recirculation can be performed more efficiently.

  In the fourth aspect of the present invention, an electrically controlled throttle valve is provided in the exhaust gas recirculation control valve and the intake passage upstream of the junction of the third exhaust recirculation passage and the intake passage, and the exhaust recirculation control valve and the electrically controlled throttle valve are provided. Since the cooperative control is performed according to the operating state of the engine, the exhaust gas recirculation can be controlled more finely.

  FIG. 1 shows a first embodiment of an exhaust gas recirculation system according to the present invention, wherein 1 is an in-line 6-cylinder diesel engine (hereinafter referred to as “engine”), 2 is an exhaust manifold attached to the engine 1, and an exhaust manifold 2 For each cylinder where the exhaust strokes do not overlap each other, for example, the first exhaust manifold 2a mounted on the # 1 to # 3 cylinder side and the second exhaust manifold 2b mounted on the # 4 to # 6 cylinder side. It is divided. Then, as shown in FIG. 2, a flange portion 3c forming exhaust gas outlets 3a, 3b of both exhaust manifolds 2a, 2b is partitioned by a partition wall 2c, and a turbocharger (hereinafter simply referred to as a variable nozzle turbine). The exhaust gas is connected to a so-called “one-port” exhaust gas merging portion (scroll portion) 6 in the turbine housing 9 alternately from both exhaust gas outlets 3a and 3b. Is coming out.

  As shown in FIG. 2, the exhaust gas outlets 3 a, 3 b of the exhaust manifolds 2 a, 2 b are formed as tapered nozzle parts 4, 5 whose cross section gradually decreases toward the exhaust gas merging part 6. . Exhaust gas exhausted from the # 1 to # 3 cylinders side is increased in flow rate at the nozzle unit 4 and flows out to the exhaust gas merging unit 6, and exhaust gas exhausted from the # 4 to # 6 cylinders side is discharged from the nozzle unit The flow rate is increased at 5 and flows out to the exhaust gas junction 6. With this configuration, an exhaust pulse from the first exhaust manifold 2a or the second exhaust manifold 2b does not escape to the second exhaust manifold 2b or the first exhaust manifold 2a.

  Further, as shown in FIG. 2, the turbine housing 9 is provided with a throttle portion 8 that is throttled in a venturi shape immediately downstream of the exhaust gas merging portion 6, and each exhaust manifold that has flowed out to the exhaust gas merging portion 6. Exhaust gases from 2a and 2b are further discharged at a reduced speed through the exhaust passage 10 after rotating the turbine 7a of the turbocharger 7 by further increasing the flow velocity at the throttle 8.

  As shown in FIG. 1, a compressor 7 b that is directly connected to the turbine 7 a is mounted in the intake passage 11, and the compressor 7 b that rotates in the turbine 7 a compresses the intake air, so that the supercharged intake air is taken in from the intake passage 11. It is sent to the engine 1 through the manifold 12.

  As in the prior art, the intake passage 11 is provided with an intercooler 13 that lowers the temperature of the intake air supercharged by the turbocharger 7 and improves the charging efficiency of the intake air, and the intake passage on the upstream side of the compressor 7b. 11, an air filter 14 is attached. On the other hand, a silencer 15 is mounted in the exhaust passage 10 on the downstream side of the turbine 7a.

  EGR passages (exhaust gas recirculation passages) 17 to 19 are connected between the first and second exhaust manifolds 2a and 2b and an ejector 16 attached to the intake passage 11 on the downstream side of the intercooler 13.

  The first EGR passage 17 is connected to the first exhaust manifold 2a, the second EGR passage 18 is connected to the second exhaust manifold 2b, and exhaust gas flows from each exhaust manifold. The first EGR passage 17 and the second EGR passage 18 are fitted with the first and second EGR coolers 20 and 21, and both the EGR passages 17 and 18 join downstream to connect to the ejector 16 as a third EGR passage 19. An EGR valve 24 that controls the recirculation amount of EGR gas and a check valve 26 that prevents intake air from flowing back from the intake passage 11 to the third EGR passage 19 are sequentially attached to the third EGR passage 19 from the exhaust manifold 2 side. The

  Then, the EGR gas flowing through the EGR passages 17 to 19 is pulled by the intake air flowing through the throat portion 16 a of the ejector 16 and is returned from the intake passage 11 to the intake manifold 12.

  Next, the operation of this embodiment will be described.

  The intake air purified by the air filter 14 is sent to the compressor 7b of the turbocharger 7 and supercharged. The intake air supercharged by the turbocharger 7 is supplied to the intake manifold 12 of the engine 1 via the intercooler 13 and the ejector 16. Further, when the check valve 26 is opened, the EGR gas flowing into each of the EGR passages 17 to 19 is pulled by the intake air flowing through the throat portion 16a of the ejector 16 and returned to the intake manifold 12. In addition, the first and second EGR coolers 20 and 21 can lower the temperature of the EGR gas flowing into the EGR passages 17 to 19 to suppress the deterioration of smoke during combustion, thereby reducing NOx.

  In the present embodiment, the exhaust manifold 2 is divided into a first exhaust manifold 2a and a second exhaust manifold 2b for each cylinder whose exhaust strokes do not overlap each other, and the first and second exhaust manifolds 2 are connected to the turbine housing 9. 2 As shown in FIG. 2, the exhaust gas outlets 3a and 3b of the exhaust manifolds 2a and 2b are tapered nozzle parts 4 and 5 whose cross section gradually decreases toward the exhaust gas merging part 6 on the downstream side. A venturi-shaped throttle 8 is provided immediately downstream of the exhaust gas merging portion 6 of the turbine housing 9.

  For this reason, the exhaust gas exhausted from the first exhaust manifold 2a side flows out to the exhaust gas merging portion 6 with the flow velocity increased by the nozzle portion 4, and the exhaust gas exhausted from the second exhaust manifold 2b side is After the flow rate is increased by the nozzle unit 5 and flows out to the exhaust gas merging unit 6 respectively, the flow rate is further increased by the throttle unit 8 and flowed out to the turbine 7a, where the exhaust from the first exhaust manifold 2a or the second exhaust manifold 2b The pulse does not escape to the second exhaust manifold 2b or the first exhaust manifold 2a.

  Further, the exhaust gas discharged from one exhaust manifold passes through the throat 8 to increase the flow velocity, draw the exhaust gas in the other exhaust manifold, lower the pressure in the other exhaust manifold, and reduce the pumping loss. be able to.

  For example, the EGR gas discharged from the first exhaust manifold 2a and flowing through the first EGR passage 17 is cooled by the first EGR cooler 20, and the EGR gas discharged from the first EGR cooler 20 flows into the third EGR passage 19, A part thereof flows back through the second EGR passage 18 and flows into the second EGR cooler 21 installed in the second EGR passage 18 to be further cooled. Then, the EGR gas discharged from the second exhaust manifold 2 b and flowing through the second EGR passage 18 is mixed with the EGR gas flowing backward from the first exhaust manifold, cooled by the second EGR cooler 21, and discharged from the second EGR cooler 21. The EGR gas flows into the third EGR passage 19, and a part thereof flows back through the first EGR passage 17 and flows into the first EGR cooler 20 installed in the first EGR passage 17, and is further cooled. In this manner, the process of reciprocating the EGR gas between the first and second EGR coolers 20 and 21 is sequentially repeated.

  Therefore, the EGR gas discharged from one exhaust manifold is cooled by the EGR cooler installed in the EGR passage connected to one exhaust manifold, while flowing backward through the EGR passage connected to the other exhaust manifold. Further, the EGR cooler installed in the other EGR passage is further cooled. As described above, the EGR gas reciprocates between the two EGR coolers 20 and 21 to sufficiently cool the EGR gas, and then flows into the EGR passage 19. The cooled EGR gas is recirculated to the intake air, and the NOx emission amount can be reduced. In addition, since the EGR gas can be cooled using two EGR coolers, the performance required for each EGR cooler can be reduced, and the size and cost can be reduced.

  Further, an ejector 16 is provided at the junction of the third EGR passage 19 and the intake passage 11, and the flow rate of the intake air flowing through the ejector 16 is increased to draw in the EGR gas, thereby increasing the EGR amount and reducing the NOx amount. Reduction can be achieved.

  Instead of providing the ejector 16 at the junction between the third EGR passage 19 and the intake passage 11, an electric throttle valve is provided upstream of the intake passage 11 at the junction and the throttle is adjusted according to the operating state of the engine 1. It is also possible to perform EGR control more finely by coordinating the opening of the valve with the opening of the EGR control valve 24.

  FIG. 3 shows a second embodiment of the exhaust gas recirculation apparatus of the present invention, and will be described based on a comparison with the first embodiment shown in FIG. In the second embodiment, instead of the EGR coolers 20 and 21 respectively installed in the EGR passages 17 and 18 in the first embodiment, the EGR cooler 27 is added to the junction where the EGR passages 17 and 18 merge. It is characterized by providing. Other configurations are the same as those in the first embodiment.

  FIG. 4 is a configuration diagram of the EGR cooler 27 used in the second embodiment.

  The EGR cooler 27 has a covered cylindrical main body, and the inside is partitioned into three compartments 27a to 27c by partition walls 28a and 28b in the central axis direction. The second compartment 27b partitioned in the middle is formed to be the largest, and the EGR passages 17 and 18 are connected to the second compartment 27b, and EGR gas is introduced into the second compartment 27b.

  A predetermined number of circular tubes 27d through which the refrigerant flows are spanned between the first compartment 27a and the third compartment 27c in the axial direction, and the first and first refrigerants are respectively passed to the lid portions 27f and 27g of the main body. Refrigerant passages 29a and 29b for inflow and outflow into the three compartments 27a and 27c are connected. Therefore, for example, the refrigerant introduced into the first compartment 27a from one refrigerant flow path 29a flows into the third compartment 27c after flowing through the circular tube 27d, and then flows from the other refrigerant flow path 29b. Discharged.

  When the EGR gas flowing into the second compartment 27b flows through the gap 27e between the circular tubes 27d, the EGR gas contacts the circular tube 27d and exchanges heat with the refrigerant flowing through the circular tube 27d. The heat is absorbed and cooled. The EGR gas whose temperature has been lowered is discharged from the EGR passage 19 that opens to the second compartment 27 b and travels toward the ejector 16.

  Since the EGR passages 17 and 18 are connected to the first and second exhaust manifolds 2a and 2b, respectively, in which the exhaust strokes of the cylinders do not overlap, exhaust gas flows from one exhaust manifold (for example, the first exhaust manifold 2a). When exhausted, EGR gas is introduced into the second compartment 27b from the EGR passage 17, cooled through the circular tube 27d, discharged from the EGR passage 19, and part of the EGR passage 18 is reversed.

  On the other hand, when the exhaust gas is discharged from the other second exhaust manifold 2b, the EGR gas is introduced into the EGR passage 18, and is introduced into the second compartment 27b together with the EGR gas that has flowed back through the EGR passage 18, and the circular tube 27d. The air flows through the space and is cooled and discharged from the EGR passage 19, and a part thereof flows back into the EGR passage 17. Thus, part of the EGR gas reciprocates in the second compartment 27b, so that the EGR gas dissipates heat and the cooling efficiency can be improved.

  Further, by installing the EGR cooler 27 at the junction of the first and second EGR passages 17 and 18 and the third EGR passage 19, only one EGR cooler 27 may be provided, and the layout around the engine becomes easy. Moreover, weight reduction and cost reduction can be achieved.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

It is explanatory drawing of the exhaust gas recirculation apparatus which concerns on 1st Embodiment. It is a principal part expanded sectional view of the connection part of a turbocharger and an exhaust manifold. It is explanatory drawing of the exhaust gas recirculation apparatus which concerns on 3rd Embodiment. It is a block diagram of an EGR cooler.

Explanation of symbols

1: Engine 3: Exhaust manifold 2a: First exhaust manifold 2b: Second exhaust manifold 7: Turbocharger 8: Throttle section 9: Turbine housing 10: Exhaust passage 11: Intake passage 12: Intake manifold 16: Ejector 16a: Throat 17, 18, 19: First to third EGR passages 20, 21: First and second EGR coolers 24: EGR valve 26: Check valve 27: EGR coolers 29a, 29b: Refrigerant flow path

Claims (4)

An exhaust manifold of an engine equipped with a turbocharger is divided into a first exhaust manifold and a second exhaust manifold for each cylinder whose exhaust strokes do not overlap each other, and the first and second exhaust manifolds and the intake passage of the engine In the exhaust gas recirculation device of the turbocharged engine that connects the exhaust gas recirculation passage between
The exhaust gas recirculation passage includes a first exhaust gas recirculation passage connected to the first exhaust manifold, a second exhaust gas recirculation passage connected to the second exhaust manifold, and the first and second exhaust gas recirculation passages. Comprising a third exhaust gas recirculation passage formed by
The first and second exhaust gas recirculation passages are respectively provided with first and second exhaust gas recirculation coolers for cooling the recirculated exhaust gas.
The exhaust from one of the exhaust manifolds is cooled by the exhaust gas recirculation cooler of one of the connected exhaust gas recirculation passages, and then flows out to the third exhaust gas recirculation passage, while part of the exhaust gas recirculation passage is the other And is cooled by the exhaust gas recirculation cooler provided in this,
The exhaust gas that has flowed backward is mixed with the exhaust gas from the other exhaust manifold and flows out into the third exhaust gas recirculation passage, while a part of the exhaust gas flows back through the exhaust gas recirculation passage. Exhaust gas recirculation device of turbocharged engine.   2. The exhaust gas recirculation device for a turbocharged engine according to claim 1, wherein the first and second exhaust gas recirculation coolers are integrated and installed at a junction with the third exhaust gas recirculation passage. An exhaust gas recirculation control valve for controlling a return amount of exhaust gas to the intake passage in the third exhaust gas recirculation passage;
3. The exhaust gas recirculation device for a turbocharged engine according to claim 1, wherein an ejector is provided at a junction between the third exhaust gas recirculation passage and the intake passage. An exhaust gas recirculation control valve for controlling a return amount of exhaust gas to the intake passage in the third exhaust gas recirculation passage;
An electrically controlled throttle valve is provided in the intake passage upstream of the junction of the third exhaust gas recirculation passage and the intake passage;
3. The exhaust gas recirculation device for a turbocharged engine according to claim 1, wherein the exhaust gas recirculation control valve and the electric throttle valve are cooperatively controlled according to an operating state of the engine.

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