JP2005344675A - Exhaust gas recirculation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR device capable of performing both a remarkable reduction in NOx by the re-circulation of exhaust gases and an increase in engine performance by supercharging and also coping with future strict exhaust emission controls by realizing a high EGR rate even in an engine with a turbocharger. <P>SOLUTION: The inside of a turbine scroll 15 of the turbocharger 2 is also divided by partition walls 16 all around the periphery so that the inside can be continued with the outlet flow passage of an exhaust manifold demarcated by partition walls to prevent the interference of exhaust gas from occurring in each cylinder. A turbine scroll flow passage 15A connected to one side outlet flow passage from which recirculation exhaust gas is extracted among the divided turbine scroll flow passages 15A and 15B is formed to be smaller in flow passage cross sectional area than the turbine scroll flow passage 16B connected to the other side outlet flow passage from which the recirculation exhaust gas is not extracted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an EGR device.

  2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side so that the combustion temperature is increased. So-called exhaust gas recirculation (EGR) is performed in which the generation of NOx is reduced by lowering.

  In general, when this type of exhaust gas recirculation is performed, an EGR pipe is used between an appropriate position of the exhaust passage extending from the exhaust manifold to the exhaust pipe and an appropriate position of the intake passage extending from the intake pipe to the intake manifold. The exhaust gas is recirculated through the EGR pipe.

  In addition, if the exhaust gas recirculated to the engine is cooled in the middle of the EGR pipe, the temperature of the exhaust gas is reduced and the volume thereof is reduced, so that the combustion temperature is effectively reduced without significantly reducing the output of the engine. Since the generation of nitrogen oxides can be reduced, a water-cooled EGR cooler is provided in the middle of an EGR pipe for recirculating exhaust gas to the engine.

  FIG. 7 shows an example of the EGR device for performing the above-described exhaust gas recirculation. In FIG. 7, reference numeral 1 denotes an engine that is a diesel engine. The engine 1 includes a turbocharger 2 and is not shown. From the intercooler 5 to the intake manifold 6, the intake air 3 pressurized by the compressor 2 a is sent to the intercooler 5 for cooling. The intake air 3 is guided and distributed to each cylinder 7 of the engine 1 (the case of in-line 6 cylinders is illustrated in FIG. 7).

  The exhaust gas 8 discharged from each cylinder 7 of the engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 9, and the exhaust gas 8 driving the turbine 2b is discharged out of the vehicle through the exhaust pipe 10. I have to do it.

  An end portion of the exhaust manifold 9 in the arrangement direction of the cylinders 7 and one end portion of the intake pipe 4 connected to the intake manifold 6 are connected by an EGR pipe 11. Part of 8 is extracted and can be led to the intake pipe 4 as exhaust gas 8 'for recirculation.

  Here, the EGR pipe 11 is equipped with an EGR valve 12 for opening and closing the EGR pipe 11 as appropriate, and an EGR cooler 13 for cooling the recirculation exhaust gas 8 ′. Then, the temperature of the recirculation exhaust gas 8 ′ can be lowered by exchanging heat between the cooling water (not shown) and the recirculation exhaust gas 8 ′.

  In FIG. 7, reference numeral 14 denotes a partition that divides the exhaust flow path for the front three cylinders and the exhaust flow path for the rear three cylinders in the exhaust manifold 9, and the partition 14 overlaps part of the exhaust stroke. The exhaust interference between the cylinders 7 is suppressed and exhaust pulsation can be efficiently sent to the turbine 2b.

On the other hand, as disclosed above, an EGR device in which a part of the exhaust gas 8 is extracted from the exhaust manifold 9 of the engine 1 equipped with the turbocharger 2 and recirculated to the intake pipe 4 is disclosed in, for example, a patent. There is literature 1.
JP 2001-123889 A

  However, in the EGR device equipped in the engine 1 with the turbocharger 2 as described above, the pressure difference from the exhaust side is reduced because the intake side is supercharged, and a high EGR rate can be realized. In particular, in a high load region, there is a region in which the supercharging pressure by the turbocharger 2 becomes higher than the exhaust pressure. Therefore, a part of the exhaust gas 8 is recirculated from the exhaust manifold 9 to the intake pipe 4. There was a possibility that it could not be circulated.

  As a countermeasure when the supercharging pressure becomes higher than the exhaust pressure in this way, it is conceivable to lower the supercharging pressure by executing the intake throttle, but if excessive intake throttling is performed in a high load region, etc. As a result, the amount of fresh air is drastically insufficient, resulting in poor combustion in the cylinders and deterioration in fuel consumption, and the improvement in engine performance by the turbocharger 2 is also impaired.

  In view of such circumstances, the present invention can achieve a high EGR rate even in an engine equipped with a turbocharger, and can achieve both a significant reduction in NOx due to exhaust gas recirculation and an improvement in engine performance due to supercharging, The aim is to provide an EGR device that can meet future strict exhaust gas regulations.

The present invention is an EGR device in which a part of exhaust gas is extracted from one side of an exhaust manifold of an engine equipped with a turbocharger and recirculated to an intake pipe,
The exhaust manifold is partitioned by partition walls so that exhaust interference of each cylinder does not occur, and the turbine scroll of the turbocharger is also divided over the entire circumference by the partition so as to be continuous with the outlet flow path of the exhaust manifold. The turbine scroll flow path connected to the outlet flow path on the one side where the exhaust gas for recirculation is extracted out of the turbine scroll flow paths thus formed is connected to the outlet flow on the other side where the exhaust gas for recirculation is not extracted. The present invention is directed to an EGR apparatus characterized in that the flow path cross-sectional area is smaller than the turbine scroll flow path connected to the road.

  According to the above means, the following operation can be obtained.

  When configured as described above, the back pressure in the turbine scroll passage connected to the outlet passage on the side of the exhaust manifold where the exhaust gas for recirculation is withdrawn is on the side where the exhaust manifold for exhaust gas on the exhaust manifold is not withdrawn. As a result, a sufficient pressure difference from the exhaust side is ensured even if the intake side is supercharged, resulting in a higher EGR rate than before. Will be realized.

  In the EGR device, a large number of nozzle vanes capable of adjusting the angle can be disposed in the throat portion of the turbine scroll flow path.

  Further, in the EGR device, a large number of nozzle vanes capable of adjusting the angle are arranged in the respective throat portions of the respective turbine scroll passages divided by the partition walls, and the angle adjustment of each nozzle vane is independently performed for each turbine scroll passage. In this case, the opening degree of each nozzle vane is narrowed down in the turbine scroll passage on the side where the exhaust gas for recirculation in the turbine scroll of the turbocharger is extracted. If the opening cross-sectional area of the throat portion is reduced by the above, the back pressure in the turbine scroll flow path in which the opening cross-sectional area of the throat portion is reduced is further increased, and the pressure on the side for extracting the exhaust gas for recirculation of the exhaust manifold is increased. Increases further, and the pressure difference between the intake and exhaust sides is further increased to achieve a higher EGR rate. It is possible to.

  On the other hand, in the turbine scroll passage on the side where exhaust gas for recirculation is not extracted in the turbine scroll of the turbocharger, each nozzle vane is made up to compensate for the turbine driving force that is insufficient due to the narrowing in the opposite turbine scroll passage. By adjusting the angle and setting an appropriate opening, the efficiency of the turbocharger can be maximized as long as the supercharging pressure does not exceed the pressure on the exhaust manifold recirculation exhaust gas extraction side. It will be.

  And if the efficiency as a turbocharger can be increased in this way, it becomes possible to increase the intake amount that had to be throttled for EGR so far, and excessive intake throttling in high load areas etc. is unnecessary As a result, combustion failure in the cylinder and deterioration of fuel consumption are avoided, and engine performance is improved by the turbocharger.

  According to the EGR device of the present invention, a high EGR rate can be realized even in an engine equipped with a turbocharger, and both NOx reduction by exhaust gas recirculation and engine performance improvement by supercharging can be achieved at the same time. It is possible to achieve an excellent effect of being able to cope with strict exhaust gas regulations.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 6 show an example of an embodiment for carrying out the present invention. The parts denoted by the same reference numerals as those in FIG. 7 represent the same components, and the basic configuration is the same as the conventional one shown in FIG. However, as shown in FIGS. 1 to 6, the feature of this illustrated example is that it is continuous with the outlet flow path of the exhaust manifold 9 that is partitioned by the partition wall 14 so that the exhaust interference of each cylinder 7 does not occur. Thus, the inside of the turbine scroll 15 of the turbocharger 2 is also divided over the entire circumference by the partition wall 16, and one side of the divided turbine scroll flow paths 15A, 15B for extracting the recirculation exhaust gas 8 ′ ( The turbine scroll flow path 15A connected to the outlet flow path on the side where the EGR pipe 11 is connected in FIG. 7 does not extract the recirculation exhaust gas 8 ′ (the EGR pipe 11 in FIG. 7). Contact By the flow path cross-sectional area of the turbine scroll passage 15B which is connected to the outlet passage of yet not side) and is in point configured to be smaller.

  That is, the conventional turbine scroll flow paths 15A and 15B are divided into two equal parts by the partition wall 16 so as to have the same flow path cross-sectional area as shown in FIGS. 2 (b) and 3 (b). As shown in FIGS. 2A and 3A, the flow passage cross-sectional area of the turbine scroll flow passage 15A is made smaller than the flow passage cross-sectional area of the turbine scroll flow passage 15B.

  Further, in the case of the illustrated example, a plurality of nozzle vanes 18a and 18b whose angles can be adjusted are disposed in the throat portions 17a and 17b of the turbine scroll flow paths 15A and 15B divided by the partition wall 16, respectively. The angle adjustment of each nozzle vane 18a, 18b can be controlled independently for each of the turbine scroll passages 15A, 15B.

  Here, each of the nozzle vanes 18a and 18b is adjusted in angle by different angle adjusting mechanisms, but the mechanisms themselves may be of the same type, so that the angle adjusting mechanism of the nozzle vane 18a will be described below. It demonstrates referring FIG. 4, and omits the description about the angle adjustment mechanism of the nozzle vane 18b.

  That is, as shown in FIG. 4, each nozzle vane 18a is disposed so as to surround the turbine wheel 19, and is attached to the nozzle ring plate 20 via a pin 21 so as to be tiltable. The angle of each nozzle vane 18a corresponds to the nozzle. The link plate 22 is changed in conjunction with the circumferential displacement of the link plate 22 with respect to the ring plate 20, and the link plate 22 is rotated via the link 25 by the tilting operation of the lever 24 by the actuator 23. It has become so.

  Next, the operation of the illustrated example will be described.

  When the turbocharger 2 configured as described above is employed in an engine 1 as shown in FIG. 7, a turbine scroll passage connected to an outlet passage on the side of the exhaust manifold 9 where the exhaust gas 8 ′ for recirculation is extracted. As a result of the back pressure at 15A being higher than the back pressure of the turbine scroll passage 15B connected to the outlet passage on the side where the exhaust gas 8 'for recirculation of the exhaust manifold 9 is not extracted, the intake side is supercharged. However, a sufficient pressure difference from the exhaust side is ensured, and a higher EGR rate than before is realized.

  Further, in the illustrated example, a large number of nozzle vanes 18a and 18b whose angles can be adjusted are disposed in the throat portions 17a and 17b of the turbine scroll flow paths 15A and 15B divided by the partition wall 16, respectively. , 18b can be controlled independently for each of the turbine scroll passages 15A, 15B, so that the exhaust gas 8 'for recirculation in the turbine scroll 15 of the turbocharger 2 is extracted. In the turbine scroll flow path 15A, as schematically shown in FIG. 5, when the opening cross-sectional area of the throat portion 17a is reduced by reducing the opening of each nozzle vane 18a to a small size, the opening cross-sectional area of the throat portion 17a is reduced. The back pressure in the turbine scroll flow path 15A is further increased, and the exhaust manifold 9 is restored. Was withdrawn upward pressure on the side further to perform the ring for the exhaust gas 8 ', it is possible to achieve a higher EGR rate further increasing the pressure difference between the intake side and the exhaust side.

  On the other hand, in the turbine scroll passage 15B on the side where the exhaust gas 8 ′ for recirculation in the turbine scroll 15 of the turbocharger 2 is not extracted, the turbine drive that is insufficient due to the narrowing in the turbine scroll passage 15A on the opposite side described above. If each nozzle vane 18b is angle-adjusted to compensate for the force and an appropriate opening is set, the pressure on the side of the exhaust manifold 9 where the recirculation exhaust gas 8 'is withdrawn is within the range where the supercharging pressure does not exceed, The efficiency as the turbocharger 2 is maximized.

  Here, in order to increase the efficiency of the turbocharger 2, basically, the rotational speed of the exhaust gas 8 in the turbine 2b is increased by reducing the opening degree of each nozzle vane 18b to increase the rotational speed of the turbine 2b. However, if the opening degree of each nozzle vane 18b is narrowed too much, the inflow resistance of the exhaust gas 8 to the turbine 2b increases and the rotational speed of the exhaust gas 8 decreases, so each nozzle vane. 18b needs to be narrowed down to an appropriate opening degree.

  However, even if the efficiency of the turbocharger 2 is increased, the pressure on the side where the exhaust gas 8 'for recirculation of the exhaust manifold 9 is extracted due to excessive increase of the supercharging pressure on the compressor 2a side in a high load region or the like. If there is a possibility that the boost pressure will rise more than necessary, it is necessary to avoid the loss of a sufficient pressure difference from the It should be noted that the efficiency of the turbocharger 2 may need to be appropriately suppressed by slightly opening the opening of each nozzle vane 18b, as schematically shown in FIG.

  If the efficiency of the turbocharger 2 can be increased in this way, it becomes possible to increase the intake amount that had to be throttled for EGR so far, and excessive intake throttling in a high load region or the like will occur. As a result, the combustion failure in the cylinder 7 and the deterioration of the fuel consumption are avoided, and the engine performance by the turbocharger 2 is improved.

  In this way, even an engine equipped with a turbocharger 2 can achieve a high EGR rate, which can achieve both significant reduction of NOx by recirculation of exhaust gas and improvement of engine performance by supercharging. Can also respond.

  Note that the EGR device of the present invention is not limited to the above-described illustrated example, and the angle adjustment is made so that the partition 16 is not only the throat portions 17a and 17b, and the nozzle vanes 18a and 18b are not divided and integrated. Of course, various modifications can be made without departing from the gist of the present invention, such as possible arrangement.

It is sectional drawing which shows an example of the form which implements this invention. It is II-II sectional drawing of FIG. It is III-III sectional drawing of FIG. It is the schematic which shows an example of the angle adjustment mechanism of the nozzle vane of FIG. It is a conceptual diagram explaining the state which made the opening degree of the nozzle vane of FIG. 1 small. It is a conceptual diagram explaining the state which enlarged the opening degree of the nozzle vane of FIG. It is the schematic which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Turbocharger 4 Intake pipe 7 Cylinder 8 Exhaust gas 8 'Recirculation exhaust gas 9 Exhaust manifold 10 Exhaust pipe 11 EGR pipe 14 Partition 15 Turbine scroll 15A Turbine scroll path 15B Turbine scroll path 16 Partition 17a Throat part 17b Throat section 18a Nozzle vane 18b Nozzle vane

Claims (3)

An EGR device that extracts a part of exhaust gas from one side of an exhaust manifold of an engine equipped with a turbocharger and recirculates it to an intake pipe,
The exhaust manifold is partitioned by partition walls so that exhaust interference of each cylinder does not occur, and the turbine scroll of the turbocharger is also divided over the entire circumference by the partition so as to be continuous with the outlet flow path of the exhaust manifold. The turbine scroll flow path connected to the outlet flow path on the one side where the exhaust gas for recirculation is extracted out of the turbine scroll flow paths thus formed is connected to the outlet flow on the other side where the exhaust gas for recirculation is not extracted. An EGR device configured to have a flow path cross-sectional area smaller than a turbine scroll flow path connected to a road.   The EGR device according to claim 1, wherein a number of nozzle vanes capable of adjusting an angle are disposed in a throat portion of the turbine scroll passage.   A large number of nozzle vanes capable of adjusting the angle are arranged in each throat portion of each turbine scroll flow path divided by the partition wall, and the angle adjustment of each nozzle vane can be controlled independently for each turbine scroll flow path. The EGR device according to claim 1.

Images