JP2005232996A - Exhaust gas recirculating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maximally omit a vibration countermeasure of an exhaust gas recirculating passage, while enhancing vehicle mountability by reducing the size of an exhaust gas recirculating device in an exhaust gas recirculating system. <P>SOLUTION: This system is composed of an inner pipe 3a and an outer pipe 3b arranged in a position at a predetermined interval from an outside surface of the inner pipe 3a; and is constituted so as to recirculate a part of exhaust gas to an intake passage 2 via an exhaust manifold 3 of a double tube structure connected to an exhaust port 1b of an engine 1, a communicating hole 30 formed in the inner pipe 3a, and a space between the inner pipe and the outer pipe positioned upstream of the communicating hole 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas recirculation system in which a pumping loss of an internal combustion engine is reduced to improve fuel consumption and nitrogen oxides contained in the exhaust gas are reduced.

2. Description of the Related Art Conventionally, exhaust gas recirculation systems (hereinafter referred to as EGR devices) in which part of exhaust gas from an internal combustion engine (engine) is recirculated to intake air to reduce nitrogen oxides (NOx) are widely known. In such an EGR device, the pumping loss of the engine is also reduced, so that the fuel consumption can be improved.
In general, in an EGR device, an intake passage and an exhaust passage of an engine are connected by an exhaust gas recirculation passage (hereinafter referred to as an EGR passage), and exhaust gas (EGR gas) is recirculated into the intake passage through the EGR passage. . Further, an EGR valve for controlling the recirculation amount of the EGR gas is provided in the middle of the EGR passage, and the exhaust gas is controlled by controlling the lift amount (opening degree) of the EGR valve according to the operating state of the engine. The amount of reflux is controlled.

  FIG. 3 is a schematic diagram showing an example of a conventional EGR device, where 101 is an engine, 102 is an intake passage (intake manifold), 103 is an exhaust passage (exhaust manifold), and 104 is arranged downstream of the exhaust passage 103. Catalyst. The exhaust passage 103 has a double-pipe structure for the purpose of promoting the temperature rise and keeping the temperature of the catalyst 104. For this reason, the exhaust passage 103 includes an inner tube 103a and an outer tube 103b. In the example shown in FIG. 3, one end of the EGR passage 105 is connected to the exhaust passage 103 downstream from the catalyst 104, and the exhaust gas discharged from the engine 101 is once purified by the catalyst 104, The part is recirculated to the intake passage 102 via the EGR passage 105. Reference numeral 106 denotes an EGR valve interposed on the EGR passage 105.

In addition to the one shown in FIG. 3, for example, Patent Literature 1 and Patent Literature 2 also disclose techniques related to the EGR device.
Of these, Patent Document 1 discloses that the exhaust manifold is covered with a heat shield cover so that the exhaust passage has a double-pipe structure, and in order to recirculate hot EGR gas as much as possible, A technique in which an EGR passage is disposed is disclosed.

In Patent Document 2, the exhaust passage has a double-pipe structure composed of an inner tube and an outer tube, and exhaust flows through both the inner space of the inner tube and the space between the inner tube and the outer tube. A technique in which an EGR passage is connected to a space between a pipe and an outer pipe is disclosed.
JP 2002-21647 A JP 2002-161738 A

  However, the conventional technique described with reference to FIG. 3 requires an EGR passage formed by a relatively long dedicated pipe to recirculate the exhaust gas. Therefore, the layout is limited in an engine room with a relatively small space. Difficult to do and complicated. Further, since the vibration of the EGR passage due to the vibration of the engine 1 becomes large, it is necessary to take a countermeasure against vibration in the EGR passage, and there is a problem that the cost increases accordingly.

In the technique of Patent Document 2, a part of the space between the inner pipe and the outer pipe is used as the EGR passage. However, as in the conventional technique shown in FIG. In addition to the problem that the layout of the EGR passage becomes difficult because a long EGR passage is required, there is a problem that it is necessary to take measures against vibration in the EGR passage.
Furthermore, in the technique of Patent Document 1, although the EGR passage is not exposed to the outside of the engine, problems relating to layout, cost, and the like that must be formed by another pipe still remain.

  The present invention was devised in view of such problems, and an object of the present invention is to provide an exhaust gas recirculation system that improves vehicle mountability and can suppress vibration measures as much as possible.

  For this reason, the present invention comprises an exhaust port formed in a cylinder head of an internal combustion engine, an inner tube and an outer tube provided at a predetermined distance from the outer surface of the inner tube, and is connected to the exhaust port. A part of the exhaust gas is removed from the internal combustion engine through a space between the exhaust manifold having a double pipe structure, a communication hole formed in the inner pipe, and the inner pipe and the outer pipe located upstream of the communication hole. The exhaust gas recirculation device is configured to recirculate to the intake passage of the engine (claim 1).

The exhaust gas recirculation system according to claim 1, wherein the exhaust gas recirculation device is formed on an outer surface of the cylinder head positioned between the inner tube and the outer tube connected to a side surface of the cylinder head. It has the 1st channel | path formed in the said cylinder head so that it may go to the said intake channel from 1 opening (Claim 2), It is characterized by the above-mentioned.
3. The exhaust gas recirculation system according to claim 2, wherein the first passage has a second opening formed on the outer surface of the cylinder head opposite to the outer surface of the cylinder head in which the first opening is formed. It is preferable that a second passage for connecting the second opening and the intake passage is provided.

  The exhaust gas recirculation system according to claim 2, further comprising a catalyst that is disposed in the inner pipe and that can purify the exhaust gas that passes through the inner pipe, and the outer pipe extends at least to a position where the catalyst is interposed. It is preferable that the communication hole is formed in the inner pipe located downstream of the catalyst.

  According to the exhaust gas recirculation system of the present invention, since the exhaust gas recirculation device is not exposed to the outside, there is an advantage that the downsizing can be achieved and the layout when mounted on the vehicle becomes easy. Further, since the long exhaust gas recirculation passage exposed outside the internal combustion engine as in the prior art becomes unnecessary, the exhaust gas recirculation passage is hardly affected by the vibration of the engine, and the vibration countermeasure can be omitted as much as possible. is there.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(1) Description of the first embodiment.
First, an exhaust gas recirculation system according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing the overall configuration. In FIG. 1, 1 is an engine (internal combustion engine), and 2 is an intake manifold (intake passage). ) 3 is an exhaust manifold (exhaust passage). Further, as shown in the figure, an exhaust purification catalyst (catalyst) 4 for purifying exhaust gas discharged from the engine 1 is provided on the downstream side of the exhaust manifold 3. In the present embodiment, the catalyst 4 is a three-way catalyst that purifies three components of HC, CO, and NOx in the exhaust gas.

  Here, as is well known, the catalyst 4 such as a three-way catalyst cannot sufficiently purify the exhaust gas below a predetermined activation temperature. Therefore, as shown in the figure, the exhaust manifold 3 has a double-pipe structure for the purpose of promoting temperature rise and keeping the temperature of the catalyst 4. More specifically, the exhaust manifold 3 includes an inner pipe 3a connected to the exhaust port 1b and an outer pipe 3b formed so as to cover the inner pipe 3a. The inner pipe 3a and the outer pipe The space between 3b functions as a heat insulation layer (thermal insulation layer).

  The engine 1 is also provided with an exhaust gas recirculation device (EGR device) 7 that recirculates part of the exhaust gas to the intake manifold 2. Here, the EGR device 7 mainly includes an EGR passage (exhaust gas recirculation passage) 5 interposed between the intake manifold 2 and the exhaust manifold 3, and an EGR valve 6 interposed on the EGR passage 5. And a controller (not shown) for controlling the operating state of the EGR valve 6. Then, the controller outputs a signal for controlling the operation of the EGR valve 6 based on the operating state of the engine 1, and the opening degree of the EGR valve 6 is controlled based on the control signal from the controller. Is to be controlled.

  Next, the main part of the present apparatus will be described. In the exhaust gas recirculation system, the configuration of the EGR passage 5 is characteristic. Here, the EGR passage 5 includes a first EGR passage (second passage) 51 having one end connected to the intake manifold 2 and a second EGR passage (first passage) 52 having one end connected to the other end of the first EGR passage 51. And a third EGR passage 53 having one end connected to the other end of the second EGR passage 52.

  Among these, the EGR valve 6 is interposed in the first EGR passage 51. Further, as shown in the figure, the second EGR passage 52 is formed in the cylinder head 1 a so as to penetrate the cylinder head 1 a of the engine 1. The second EGR passage 52 is formed, for example, by arranging a pipe or the like in the cylinder head 1a. The second EGR passage 52 is formed with openings at both ends of the pipe (on the intake side surface and the exhaust side surface of the cylinder head 1a). First and second openings) 21 and 22 are formed.

The third EGR passage 53 is formed integrally with the exhaust manifold 3 of the engine 1, and the space between the inner pipe 3a and the outer pipe 3b of the manifold 3 described above also functions as the third EGR passage 53. Is configured to do.
Incidentally, as shown in the figure, the outer tube 3b is formed to extend further downstream than the end portion of the inner tube 3a while covering the inner tube 3a. On the other hand, the end portion of the inner pipe 3a is formed as an opening, and the catalyst 4 is interposed in the opening. With this configuration, the inner pipe 3a and the third EGR passage 53 are communicated with each other via the communication hole 30 on the downstream side of the catalyst 4, thereby a part of the exhaust gas purified by the catalyst 4. Flows into the third EGR passage 53 as EGR gas.

Further, as shown in FIG. 1, in the top view, the upstream end side of the outer tube 3b is connected to the cylinder head 1a so as to cover the exhaust side surface of the cylinder head 1a. A space (the third EGR passage 53) between the outer pipe 3b and the second EGR passage 52 is connected.
With such a configuration, the exhaust gas discharged from the engine 1 is supplied to the catalyst 4 through the inner pipe 3 a of the exhaust manifold 3, and harmful components in the exhaust gas are purified in the catalyst 4. Thereafter, most of the exhaust gas flows downstream of the exhaust manifold 3 and is discharged into the atmosphere through a muffler (not shown). A part of the exhaust gas is taken into the third EGR passage 53 from the end portion of the inner pipe 3a as EGR gas. The periphery of the inner pipe 3a is covered with such EGR gas, and the third EGR passage 53 functions as a heat insulating layer, whereby the inside of the inner pipe 3a and the catalyst 4 are maintained at a high temperature, and the temperature of the catalyst 4 is increased. The effect and the heat retention effect are enhanced.

  The EGR gas in the third EGR passage 53 flows into the first EGR passage 51 through the second EGR passage 52 formed in the cylinder head 1a, and is returned to the intake manifold 2 from the first EGR passage 51. By supplying EGR gas together with fresh air to the combustion chamber of the engine 1, the combustion in the combustion chamber becomes slow and the generation of NOx is suppressed.

  Therefore, according to the exhaust gas recirculation system according to the first embodiment of the present invention, the second EGR passage 52 is formed in the cylinder head 1a, and the third EGR passage 53 is formed integrally with the exhaust manifold 3, thereby The 2EGR passage 52 and the third EGR passage 53 are not exposed or projected outside the engine 1 including the exhaust manifold 3, and there is an advantage that the EGR passage 5 can be greatly reduced in size. Therefore, the layout when mounted on the vehicle becomes easy. Further, as described above, the second EGR passage 52 is formed in the cylinder head 1a, and the third EGR passage is formed integrally with the exhaust manifold 3, thereby reducing the number of parts of the EGR passage 5 and the EGR device main body. There is an advantage that the cost can be reduced.

In the exhaust gas recirculation system according to the present embodiment, the EGR passage 5 is hardly affected by the vibration of the engine 1 because there are few portions exposed to the outside. For this reason, there is no need to take measures against vibration in the EGR passage 5, and there is an advantage that the cost can be reduced.
In addition, since the space between the inner tube 3a and the outer tube 3b functions as the third EGR passage 53, when high-temperature exhaust gas (EGR gas) flows through the third EGR passage 53, the inner tube 3a and the outer tube 3b The heat insulation layer in the space between them can be kept at a high temperature, and the temperature reduction of the exhaust gas passing through the inside of the inner pipe 3a can be suppressed. Therefore, the exhaust gas holding a high temperature can be caused to flow into the catalyst 4 and the catalyst 4 can be quickly raised to the activation temperature even at the time of cold start. Can be increased. Further, exhaust gas purification performance is improved by raising the temperature of the catalyst 4 earlier. Further, since the inner pipe is maintained at a high temperature, combustion of the soot component in the exhaust gas is promoted, and further purification of the exhaust gas and the EGR gas can be achieved.

  Further, since the EGR gas that has flowed into the space between the inner pipe 3a and the outer pipe 3b is cooled by the outside air, it is possible to promote a decrease in the temperature of the EGR gas returned to the intake manifold 2. Therefore, the combustion temperature in the engine 1 is lowered, and the production of nitrogen oxides NOx can be greatly suppressed, and further purification of exhaust gas can be realized from this viewpoint. Moreover, since the exhaust gas temperature recirculated to the intake manifold 2 is lowered, there is an advantage that the volumetric efficiency of intake air is improved and fuel efficiency is improved.

  Further, as in the present embodiment, by connecting the inner pipe 3a and the third EGR passage 53 on the downstream side of the catalyst 4, clean exhaust gas once purified by the catalyst 4 is passed through the intake manifold 2 via the EGR 5. There is also an advantage that it can be refluxed.

(2) Description of the second embodiment.
Next, a second embodiment of the present invention will be described. In the second embodiment, portions that are configured differently from the above-described first embodiment will be mainly described, and portions that are configured in the same manner as the first embodiment are denoted by the reference numerals used in the first embodiment. The description is omitted as much as possible while being used as it is.

FIG. 2 is a schematic view showing the overall configuration. In the second embodiment, the exhaust gas in the inner pipe 3a is guided from the upstream side of the catalyst 4 to the third EGR passage. It differs from 1st Embodiment only by the point from which the position of the hole 30 differs.
That is, in the first embodiment described above, the inner pipe 3a and the third EGR passage 53 are configured to communicate with each other on the downstream side of the catalyst 4 (see FIG. 1), but in the second embodiment, FIG. As shown in FIG. 3, a partition wall 9 is provided between the inner tube 3a and the outer tube 3b in order to prevent the exhaust gas that has passed through the catalyst 4 from flowing into the third EGR passage 53. An opening 30 is formed at a position upstream of the position where the catalyst 4 of the inner pipe 3 is disposed, and a part of the exhaust gas flows into the third EGR passage 53 from the inner pipe 3 a through the opening 30. It is supposed to do.

  Therefore, according to the exhaust gas purification apparatus according to the second embodiment of the present invention, there are substantially the same advantages as those of the first embodiment described above, and the inner pipe 3a and the third EGR passage 53 are connected upstream of the catalyst 4. By communicating, exhaust gas with high pressure can be recirculated to the intake manifold 2 via the EGR passage 5. For this reason, for example, there is an advantage that exhaust gas can be reliably recirculated to the intake manifold 2 even when the engine 1 includes a supercharger and the pressure in the intake manifold 2 is high.

Further, since the high temperature exhaust gas before passing through the catalyst 4 flows into the third EGR passage 53, the temperature of the EGR gas becomes higher than that in the first embodiment, and the temperature increase effect and the heat retention effect of the inner pipe 3a are further enhanced. There is an advantage that can be.
(3) Others The exhaust gas recirculation system of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, a double tube structure in which the outer tube 3b partially covers the inner tube 3a instead of the entire circumference may be employed. Further, the second EGR passage 52 may be formed outside the cylinder head 1a without being formed in the cylinder head 1a. Furthermore, the intake manifold and the first EGR passage 51 may be configured separately or may be configured integrally. Further, as the exhaust purification catalyst 4, other catalysts such as a lean NOx catalyst and an HC trap catalyst may be provided instead of the above three-way catalyst, or a filter for capturing PM in the exhaust may be provided. .

It is a mimetic diagram showing the whole exhaust gas recirculation system composition concerning a 1st embodiment of the present invention. It is a schematic diagram which shows the whole structure of the exhaust gas recirculation system which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows an example of the conventional EGR apparatus.

Explanation of symbols

1 engine (internal combustion engine)
1a Cylinder head 1b Exhaust port 2 Intake manifold (intake passage)
3 Exhaust manifold (exhaust passage)
3a Inner pipe 3b Outer pipe 4 Catalyst (Exhaust gas purification catalyst)
5 EGR passage (exhaust gas recirculation passage)
6 EGR valve 7 EGR device (exhaust gas recirculation device)
21 1st opening 22 2nd opening 30 Communication hole 51 1st EGR passage (2nd passage)
52 2nd EGR passage (first passage)
53 3rd EGR passage

Claims (4)

An exhaust port formed in the cylinder head of the internal combustion engine;
An exhaust manifold having a double-pipe structure connected to the exhaust port, comprising an inner tube and an outer tube provided at a position spaced from the outer surface of the inner tube;
A communication hole formed in the inner pipe;
An exhaust gas, comprising an exhaust gas recirculation device that recirculates a part of the exhaust gas to the intake passage of the internal combustion engine via a space between the inner pipe and the outer pipe located upstream of the communication hole Reflux system. The exhaust gas recirculation device is configured so that the cylinder head faces the intake passage from a first opening formed on an outer surface of the cylinder head located between the inner tube and the outer tube connected to a side surface of the cylinder head. The exhaust gas recirculation system according to claim 1, further comprising a first passage formed therein. The first passage has a second opening formed on the outer surface of the cylinder head opposite to the outer surface of the cylinder head in which the first opening is formed, and connects the second opening and the intake passage. The exhaust gas recirculation system according to claim 2, further comprising a second passage. A catalyst that is disposed in the inner pipe and purifies exhaust gas passing through the inner pipe; the outer pipe is extended to at least a position where the catalyst is interposed; and the communication hole is provided downstream of the catalyst. The exhaust gas recirculation system according to claim 1, wherein the exhaust gas recirculation system is formed in the inner pipe located.

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