JP2005273558A - Internal combustion engine with exhaust gas recirculation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine equipped with an exhaust gas circulation system capable of supplying each of a plurality of cylinders with a mixed stream uniform in the mixing ratio of EGR gas and intake air. <P>SOLUTION: In the internal combustion engine with the exhaust gas recirculation (EGR) system having an EGR passage 1 for returning EGR gas 1a obtained by extracting a part of exhaust gas from an exhaust passage of the engine, to an air supply passage 6, a protrusion 11 is provided projecting into the air supply passage 6 downstream of a confluence part 1b of the EGR passage and air supply passage and upstream of a combustion chamber to deflect a stream in an intake air rate increasing direction to a stream which flows into the combustion chamber 9 into which a stream with a large mixing ratio of EGR gas tends to flow. The generation of smoke is thereby prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is applied to a diesel engine or the like, and includes an EGR passage that recirculates EGR (exhaust gas recirculation) gas obtained by extracting a part of exhaust gas from an exhaust passage of an engine (internal combustion engine) to an air supply passage. The present invention relates to an internal combustion engine with an exhaust gas recirculation (EGR) device.

An exhaust gas recirculation (EGR) device is an effective means for reducing nitrogen oxides (NOx) in exhaust gas in a diesel engine. The exhaust gas recirculation device is configured to recirculate EGR (exhaust gas recirculation) gas obtained by extracting a part of exhaust gas from the exhaust passage of the engine through the EGR passage to the air supply passage.
In such a diesel engine, from the viewpoint of preventing generation of harmful components such as NO _x and PM and smoke, the mixing of EGR gas and the intake air of the air supply passage is promoted, and a plurality of cylinders are provided on the downstream side. It is necessary to supply a mixed flow with a uniform mixing ratio of EGR gas and intake air to each cylinder.

  However, a means for promoting the mixing of the EGR gas and the intake air in the air supply passage has not been particularly employed. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-2134), a protrusion that guides the flow of the supply air in the supply port and guides it tangentially to the wall surface of the combustion chamber is provided to form a good swirl flow. It is described.

That is, in Patent Document 1, in a combustion chamber having a first air supply port and a second air supply port, the first air supply port is provided with a swirl control valve, and the flow of intake air is diverted to the second air supply port. Protrusions that lead to the combustion chamber in a tangential direction are provided, and through the through holes for directing the intake air to the spark plug, a step for positively guiding the intake air and fuel spray is formed at the inlet of the through holes. Accordingly, there is described means for increasing the fuel in the vicinity of the spark plug, thereby improving the ignitability and the combustion state, and reducing the fuel in the vicinity of the wall surface to reduce the HC emission amount.
Japanese Patent Laid-Open No. 11-2134

  However, the internal combustion engine disclosed in Patent Document 1 is not an internal combustion engine with an exhaust gas recirculation (EGR) device, and the EGR gas and the intake air in the supply passage are downstream of the EGR gas and the supply passage. It is not intended to promote mixing.

Conventionally, mixing of the EGR gas and the intake air is not sufficiently performed at the joint portion of the EGR gas and the supply passage, and the EGR gas and the intake air flow downstream in a layered state while being separated, and a plurality of cylinders are provided downstream. In the case of an internal combustion engine equipped with an engine, there is a bias in the mixing ratio of EGR gas and intake air for each cylinder, which makes it easy for smoke to be generated in a cylinder supplied with a mixed flow with a high ratio of EGR gas, and for intake. the cylinder air ratio is high mixed flow is supplied, the combustion temperature rises, there is a problem that the NO _X generation density becomes high.

  FIG. 4 is a schematic elevational view of an internal combustion engine equipped with a conventional exhaust gas recirculation device. 01a is an EGR gas partially led from an exhaust passage (not shown), and passes through the EGR passage 01 to introduce intake air 06a. Are joined by an opening 01b and an air supply passage 06 leading to a cylinder (not shown) (two in each supply passage system, and four in total in this apparatus). The mixed flow of EGR gas and intake air is introduced into the combustion chamber through the supply ports 02a and 02b. Reference numerals 05a and 05b denote air supply flanges connected to a combustion chamber (not shown).

In this device, the EGR gas 01a merges with the intake air 06a through the opening 01b, but does not mix much with the intake air after merging, and flows in a layered manner near the supply passage wall surface on the opening 01b side. The air supply port 02a tends to be supplied with a mixed flow having a high EGR gas mixing ratio, while the other air supply port 02b is supplied with a mixed flow having a low EGR gas mixing ratio.
For this reason, smoke is likely to occur in a cylinder supplied with a mixed flow having a high EGR gas ratio, and combustion temperature rises in a cylinder supplied with a mixed flow having a high intake air ratio, and NO _X, PM, etc. There is a problem that the generation concentration of harmful components becomes high.

In an internal combustion engine with an exhaust gas recirculation (EGR) device, conventionally, no means for promoting the stirring of the mixed flow at the air supply passage opening of the EGR passage has been adopted, and the above-mentioned causes due to the poor stirring of the mixed flow No problems were pointed out.
The inventors of the present invention have found the above-mentioned problem and have reached the present invention in order to solve the problem. That is, in view of the problems of the prior art, the present invention supplies a mixed flow having a uniform mixing ratio of EGR gas and intake air to each of a plurality of cylinders without causing an increase in engine manufacturing cost with a very simple structure. An object of the present invention is to provide an internal combustion engine equipped with an exhaust gas recirculation device.

The present invention achieves such an object, and its means includes a plurality of cylinders, and supplies EGR (exhaust gas recirculation) gas obtained by extracting a part of the exhaust gas from the exhaust passage of the engine. In an internal combustion engine with an exhaust gas recirculation device provided with an EGR passage that recirculates to the passage, a flow that protrudes into a supply passage on the downstream side of the joining portion of the EGR passage and the supply passage and flows into a predetermined cylinder A projection is provided that causes a throttle action and deflects the flow in a direction that increases the ratio of intake air.
In such means, preferably, the projection is provided on the wall surface of the air supply passage near the inlet of the air supply port of the predetermined cylinder. More preferably, another protrusion may be provided on the air supply wall surface on the downstream side of the merging portion and on the merging side.

In the present invention, the direction that protrudes into the supply passage on the downstream side of the supply passage side confluence portion of the EGR passage and causes the throttle action to flow into the predetermined combustion chamber and increases the proportion of intake air By providing a projection for deflecting the flow, the suction air is deflected against the surface of the projection so that the intake air flows into a predetermined cylinder on the downstream side of the joint portion, and causes a throttling action on the flow. As a result, the flow speed is increased to cause further intake air inflow, and these actions can be combined to increase the intake air mixing ratio in the mixed flow flowing into a predetermined cylinder.
At the same time, a turbulent flow (vortex) is generated due to the pressure loss due to the throttling action, and the effect of mixing and stirring the layered EGR gas and the intake air can be obtained.

Therefore, the ratio of EGR gas can be reduced with respect to the cylinder located at a position where the ratio of EGR gas increases in the inflowing mixed flow with respect to a plurality of arranged cylinders. And the intake air are mixed and stirred as a whole, so that a mixed flow with a uniform mixing ratio of EGR gas and intake air can be supplied to each cylinder as a whole, and the mixing ratio varies among the cylinders. Can be eliminated.
Therefore, in the present invention, there is mainly an effect that smoke can be effectively prevented, and not only that, but also control for reducing emission of harmful components such as NO _x and PM can be performed with high accuracy. As a result, there is also an effect that generation of these harmful components can be prevented.

  Preferably, by providing the protrusion on the wall surface of the air supply passage near the inlet of the air supply port of the predetermined cylinder, the above effect can be exhibited more significantly. By providing the protrusion on the supply passage wall surface on the downstream side of the merging portion and on the merging side, a synergistic effect of the mixing / stirring effect of the EGR gas and the intake air by the separate protrusion can be exhibited.

As described above, according to the present invention, a throttle action is generated for a flow that protrudes into a supply passage on the downstream side of a joining portion of the EGR passage and the supply passage, and flows into a predetermined cylinder, and is suctioned. By providing a projection that deflects the flow in the direction of increasing the air ratio, it is possible to effectively prevent a mixed flow having a high EGR gas mixing ratio from flowing into some cylinders, thereby preventing the generation of smoke. As a whole, there is also the promotion of mixing and stirring of EGR gas and intake air. As a whole, the mixing ratio of EGR gas and intake air in a mixed flow supplied to a plurality of cylinders is set for each combustion chamber. It can be made uniform, and control for reducing the amount of harmful components such as NO _x and PM can be systematically performed.
Furthermore, in the present invention, a simple structure in which only a protrusion is provided in the air supply passage is sufficient, and the cost is low and remodeling is extremely easy.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
1 is a partially sectional elevational view of a portion corresponding to FIG. 4 (conventional example) according to a first embodiment of the present invention, and FIG. 2 is an air supply in a diesel engine with an exhaust gas recirculation device according to the first embodiment. FIG. 3 is a partially sectional elevational view of a portion corresponding to FIG. 1 according to the second embodiment of the present invention.

In FIGS. 1 and 2 showing the first embodiment (in this embodiment, two cylinders are provided per one supply passage, and a total of four cylinders are provided), 9 is an engine (diesel engine). Combustion chambers 7 are air supply valves provided in the respective combustion chambers, and 2 is an air supply port opened and closed by the air supply valve 7. An air supply passage 6 guides the intake air 6 a to the combustion chamber 9 through the air supply port 2.
8 is an exhaust valve provided in each combustion chamber 9, and exhaust gas 4 a generated in the combustion chamber 9 is exhausted to the exhaust passage 4 through the exhaust port 3. An exhaust port 3 is opened and closed by the exhaust valve 8.

Reference numeral 1 denotes an EGR passage which extracts a part of the exhaust gas 4a branched from the EGR intake port 1c of the exhaust passage 4 and flowing through the exhaust passage 4 as the EGR gas 1a, and an opening 1b provided in the air supply passage 6 Then, the EGR gas 1a is supplied to the air supply passage 6. Reference numeral 1d denotes an EGR valve provided in the EGR passage 1 for controlling the flow rate of the EGR gas 1a.
In FIG. 1, reference numeral 11 denotes a downstream side of the opening 1 b that is a confluence of the EGR passage 1 and the air supply passage 6, and is provided on the wall of the air supply passage near the entrance of the air supply port 2 a of the combustion chamber (not shown). 11 a is a mixed flow mixed and stirred by the protrusion 11.

In the first embodiment, the EGR gas 1a which is a part of the exhaust gas taken in from the EGR intake port 1c of the exhaust passage 4 enters the opening 1b which is a junction point between the EGR passage 1 and the air supply passage 6. Supplied.
The EGR gas 1a supplied from the opening 1b to the passage 6 is directed in the direction of the combustion chamber 9 and tends to flow in a layered manner along the wall surface of the air supply passage on the merging side. A flow having a relatively high mixing ratio of the intake air flowing near the center in the air supply passage 6 strikes the surface of the projection 11 and is deflected toward the air supply port 2a.
Further, the projection 11 exerts a throttling effect on the flow, and the flow is accelerated by the throttling effect. As a result, the intake air further flows into the air supply port 2a side, and at the same time, a pressure loss or the like occurs, resulting in turbulence ( As a result, the EGR gas 4a and the intake air 6a are mixed and stirred, and a mixed flow 11a having a uniform mixing ratio is obtained.

In the first embodiment, the projection 11 can effectively prevent a mixed flow having a large mixing ratio of EGR gas from flowing into the air supply port 2a, and at the same time, the projection 11 can prevent the EGR gas 1a and the intake air 6a from flowing. Since mixing and agitation are also promoted, a mixed gas having a uniform mixing rate is supplied to the other combustion chambers.
Therefore, first of all, smoke generation is effectively prevented as a main purpose, and there is also an effect that the control for reducing the emission amount of harmful components such as NO _x and PM can be performed with high accuracy.
Furthermore, with the extremely simple and inexpensive structure in which only the protrusion 11 is provided on the wall surface of the air supply passage 6, the above effects can be obtained, and modification to existing equipment can be easily performed.

FIG. 3 shows a second embodiment of the present invention. In the second embodiment, as shown in the drawing, in addition to the projection 11 similar to that of the first embodiment, another projection 12 is provided. The protrusion 12 is a protrusion provided on the confluence portion-side air supply passage wall immediately downstream of the opening 1 b, which is the confluence portion of the EGR passage 1 and the air supply passage 6.
The EGR gas 1a supplied from the opening 1b to the passage 6 is directed in the direction of the combustion chamber 9 and tends to flow in a layered manner along the air supply passage wall surface on the merging side. It is deflected to the center side of the passage 6.
Further, the projection 12 exerts a throttling effect on the flow, causing an increase in speed, pressure loss, etc. due to the throttling effect, resulting in turbulence (vortex), whereby the EGR gas 4a and the intake air 6a are mixed and stirred, and the opening In the vicinity of the portion 1b, the mixed flow 11a has a uniform mixing ratio.

The mixed flow 11a is further deflected by the protrusion 11 so that a flow having a relatively large mixing ratio of the intake air at the relatively central portion in the air supply passage 6 is deflected toward the air supply port 2a, and is accelerated by the throttle action of the protrusion 11 to be sucked. Further inflow of air to the supply port 2a side occurs. At the same time, pressure loss or the like occurs, and mixing and stirring are further promoted.
Therefore, according to the second embodiment, the flow deflection action by the two protrusions 11 and 12 and the mixing and agitation action of the mixed flow by the throttling effect are synergistically exhibited. Can be achieved.

As described above, according to the present invention, in an internal combustion engine that includes a plurality of cylinders and includes an exhaust gas recirculation device, each of the plurality of cylinders has an extremely simple structure without causing an increase in engine manufacturing cost. On the other hand, it is possible to supply a mixed gas having a uniform mixing ratio of EGR gas, whereby it is possible to suppress the generation of NO _x , smoke and the like with a simple and inexpensive structure.

It is a partial cross-sectional schematic elevation view of the air supply and exhaust system in the first embodiment of the present invention. It is a schematic sectional drawing of the air supply and exhaust system in the diesel engine with an exhaust-gas recirculation apparatus which concerns on the said 1st Example. It is a partial cross-sectional schematic elevation view of the air supply and exhaust system in the second embodiment of the present invention. It is a schematic elevation view of an air supply and exhaust system in an internal combustion engine provided with a conventional exhaust gas recirculation device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 EGR passage 1a EGR gas 1b Opening part 1c EGR intake 2 Supply air port 3 Exhaust port 4 Exhaust passage 6 Supply air passage 6a Intake air 7 Supply valve 8 Exhaust valve 9 Combustion chamber 11, 12 Protrusion 11a Mixed flow

Claims (3)

  Equipped with multiple cylinders and equipped with an exhaust gas recirculation device with an EGR passage that recirculates EGR (exhaust gas recirculation) gas extracted from the exhaust passage of the engine to the supply air passage In an internal combustion engine, a direction that causes a throttling effect on a flow that protrudes into an air supply passage downstream of the joining portion of the EGR passage and the air supply passage and that flows into a predetermined cylinder, and increases the proportion of intake air An internal combustion engine with an exhaust gas recirculation device, characterized in that a projection for deflecting the flow is provided on the internal combustion engine.   2. The internal combustion engine with an exhaust gas recirculation device according to claim 1, wherein the protrusion is provided on a wall surface of an air supply passage in the vicinity of an inlet of an air supply port of the predetermined cylinder.   2. The internal combustion engine with an exhaust gas recirculation device according to claim 1, wherein another protrusion is provided on the wall surface of the air supply passage on the downstream side of the merging portion and on the merging side.

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