JP2006009793A - Exhaust pipe structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust pipe structure capable of diffusing flow of exhaust gas flowing into a catalyst converter from each exhaust pipe. <P>SOLUTION: This exhaust pipe structure is provided with an exhaust manifold 5 composed of a plurality of exhaust pipes P connected with an exhaust port of the internal combustion engine, the catalyst converter 9 for purifying exhaust gas, and a swirl stream generator 8 provided between the exhaust manifold 5 and the catalyst converter 9. The swirl stream generator 8 is provided with a flow-in part 8b provided on the downstream side of a collection part 8a for collecting downstream terminal parts of the plurality of exhaust pipes P, a swirl stream generation part 8c provided on the downstream side of the flow-in part 8b to convert flow of exhaust gas into swirl stream, and a flow-out part 8f connected with the downstream side of the swirl stream generation part 8c and communicating with the catalyst converter 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust pipe structure of an internal combustion engine.

Conventionally, exhaust gas discharged from the exhaust port of a multi-cylinder engine can be purified by a single catalytic converter by connecting the downstream end portion of an exhaust manifold composed of a plurality of exhaust pipes to a swirl flow generating portion (mixing chamber). (For example, refer to Patent Document 1).
In such an exhaust gas exhaust pipe structure, a swirling flow generating section for generating a swirling flow of the exhaust gas is provided between the exhaust manifold and the catalytic converter.
JP 2003-193829 (paragraph 0013, FIG. 1)

However, the swirl flow generating portion described in Patent Document 1 has an elliptical shape that is flat in the horizontal direction, and the exhaust pipe of the exhaust manifold is connected to the outer peripheral surface and the outer peripheral surface of the elliptical shape from each direction. Directly connected by welding means.
Each of the conventional exhaust pipes is separated and connected to a plurality of locations of the swirl flow generation unit, and the exhaust gas flowing from each exhaust pipe is united in the swirl flow generation unit. It has come to join. For this reason, the structure of the swirling flow generator is complicated, and the exhaust gases flowing from the respective exhaust pipes to the swirling flow generating section interfere with each other, so that the ventilation resistance is large and the power loss of the internal combustion engine is caused. It was.

  In the exhaust manifold as described in Patent Document 1, since the distance from the swirl flow generating portion, which is a collection portion of each exhaust pipe, to the catalytic converter is short, the exhaust gas that flows from the exhaust pipe and merges is diffused. However, it was flowing into the catalytic converter as it was. Then, the exhaust gas that has flowed into the catalytic converter from the swirling flow generating portion hits the catalyst in a biased state, and the flow velocity distribution is in a non-uniform state, so that there is a problem that the purification performance cannot be sufficiently exhibited.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is an exhaust pipe structure capable of diffusing the flow of exhaust gas flowing from each exhaust pipe to the catalytic converter. Is to provide.

  In order to solve the above-mentioned problem, the exhaust pipe structure according to claim 1 includes an exhaust manifold including a plurality of exhaust pipes connected to an exhaust port of an internal combustion engine, a catalytic converter for purifying exhaust gas, and the exhaust. An exhaust pipe structure provided with a swirling flow generator interposed between a manifold and the catalytic converter, wherein the swirling flow generator is formed of a collecting portion in which downstream end portions of the plurality of exhaust pipes are gathered. An inflow portion provided on the downstream side, a swirl flow generation portion provided on the downstream side of the inflow portion for converting the flow of the exhaust gas into a swirl flow, and connected to the downstream side of the swirl flow generation portion And an outflow portion communicating with the catalytic converter.

  According to the first aspect of the present invention, the swirling flow generator has a collecting portion in which the downstream end portions of the plurality of exhaust pipes are gathered, and an inlet of the swirling flow generator is provided downstream of the gathering portion. Therefore, the exhaust gas that has flowed through the plurality of exhaust pipes merges into one, and then flows into the downstream swirl flow generation unit. For this reason, since the exhaust pipe can be extended long in the downstream direction, it is not necessary to press work like a conventional exhaust pipe, and it is possible to use a general steel pipe, and from each exhaust pipe Interference of exhaust gas that has flowed can be reduced. Further, the exhaust gas flowing into the swirling flow generator from each exhaust pipe is converted into a swirling flow by the swirling flow generating unit and becomes uniform, does not interfere with each other, and has a non-uniform state where the flow velocity is biased. In a diffused state, the gas flows into the catalytic converter from the outflow portion that is the outlet of the swirling flow generator. Thus, since the flow of the exhaust gas is rectified, the purification performance by the catalytic converter is improved and the exhaust gas is purified well.

The exhaust pipe structure according to claim 2 is the exhaust pipe structure according to claim 1, wherein the inflow portion is provided in an outer peripheral portion at a position eccentric from a central portion of the swirl flow generation portion, The swirling flow generating portion is defined as a, where the inflow portion has an inner diameter a, and the swirling flow generation portion has an inner diameter b.
b ≧ 2a
It is characterized by becoming.

  According to the second aspect of the present invention, since the inflow portion is provided in the outer peripheral portion at a position eccentric from the central portion of the swirling flow generating portion for swirling the exhaust gas, the inflow portion is collected from each exhaust pipe. The exhaust gas flows in a direction tangential to the outer peripheral portion of the swirl flow generating portion, and flows so as to be swirled and diffused from the outer peripheral portion of the swirl flow generating portion toward the central portion. Further, the exhaust gas in the swirling flow generating section can adjust the strength of the swirling flow by appropriately changing the ratio of the inner diameter b of the swirling flow generating section and the inner diameter a of the inflow section. (Cyclone) can be generated. And when flowing from the outflow part to the catalytic converter, the exhaust gas is distributed substantially evenly over the entire cross section of the catalytic converter, so that the flow is uniform and does not pass to a specific part in the catalytic converter. In addition to improving the purification efficiency, it is possible to prevent a part of the catalyst from being biased and exposed to high temperatures. As a result, a part of the catalytic converter is prevented from being intensively deteriorated, so that the lifetime can be extended.

The exhaust pipe structure according to claim 3 is the exhaust pipe structure according to claim 1 or 2, wherein the outflow portion has an inner diameter of the inflow portion, and an inner diameter of the swirl flow generation portion, b. , Where c is the inner diameter of the narrowest part of the outflow part,
a ≦ c ≦ b
It is characterized by becoming.

According to the third aspect of the present invention, the inner diameter c of the narrowest portion of the outflow portion is larger than the inner diameter a of the inflow portion and smaller than the inner diameter b of the swirl flow generating portion. As a result, the exhaust gas in the swirl flow generating portion flows while smoothly swirling with reduced ventilation resistance, and the exhaust gas flowing from each exhaust pipe flows along the inner wall of the outflow portion, The flow can be made uniform and flowed to the catalytic converter, and the catalytic converter can efficiently purify the flow.
For example, when the oxygen concentration detection sensor is provided on the inner wall of the outflow part, the restriction on the attachment position is eliminated and the degree of freedom of attachment is improved as compared with the case where the oxygen concentration detection sensor is provided in the swirl flow generation part. At the same time, the flow of the exhaust gas is stabilized, and the detection accuracy of the oxygen concentration detection sensor is improved.

  The exhaust pipe structure according to claim 4 is the exhaust pipe structure according to any one of claims 1 to 3, wherein the outflow portion has a base end portion of the outflow portion that generates the swirling flow. It is provided on the center line of the part.

  According to the fourth aspect of the present invention, the base end portion of the outflow portion is provided on the center line of the swirling flow generating portion, so that the exhaust gas in the swirling flow generating portion is directed from the outer peripheral portion toward the central portion. It is uniformly diffused while swirling so as to smoothly vortex, and flows from the outflow portion at the center of the swirling flow generating portion to the catalytic converter.

  The exhaust pipe structure according to claim 5 is the exhaust pipe structure according to claim 1, wherein the swirling flow generating portion has a center line of the swirling flow generating portion with respect to a center line of the inflow portion. The guide wall portion is arranged so as to be shifted and has a wall surface in the swirl flow generating portion for restricting the flow direction of the exhaust gas.

  According to the fifth aspect of the present invention, the swirling flow generating section is arranged such that the center line of the swirling flow generating section is shifted with respect to the center line of the inflow section. Since it flows into the swirl flow generation part from the outer peripheral part shifted from the center part of the part, swirl flow is likely to occur. Further, the wall surface in the swirling flow generating portion has a guide wall portion that regulates the flow direction of the exhaust gas, so that the exhaust gas flowing from the inflow portion into the swirling flow generating portion collides with the guide wall portion and turns downstream. It is guided to strengthen the flow to flow in the direction. As a result, the exhaust gas flow component flowing in the downstream direction in the outflow portion and the exhaust gas flow component flowing while swirling in the outflow portion are combined in a well-balanced manner, so that the flow resistance can be rectified and the airflow resistance can be reduced. .

  The exhaust pipe structure according to claim 6 is the exhaust pipe structure according to claim 1 or claim 5, wherein the swirl flow generating portion expands in diameter from the inflow portion toward the outflow portion, and is twisted. It is characterized by being formed in the state.

  According to the sixth aspect of the present invention, the swirling flow generating portion is formed in a state in which the diameter is increased from the inflow portion toward the outflow portion and twisted in a substantially spiral shape, so Exhaust gas from each exhaust pipe that flows to is guided along its enlarged diameter and twisted shape, and flows uniformly as a spiral flow that spreads while turning. As a result, when the exhaust gas flowing from each exhaust pipe flows from the inflow portion to the outflow portion, a swirling flow is generated in the same manner and rectified to flow to the catalytic converter.

  The exhaust pipe structure according to claim 7 is the exhaust pipe structure according to claim 1, wherein the outflow portion is formed to be inclined from the swirl flow generation portion toward the catalytic converter. Features.

  According to the seventh aspect of the present invention, the outflow portion is inclined from the swirl flow generation portion toward the catalytic converter, so that the exhaust gas flows spirally in the downstream direction.

  The exhaust pipe structure according to claim 8 is the exhaust pipe structure according to claim 1, wherein an oxygen concentration detection sensor is provided at a position near the swirl flow generation unit or the swirl flow generation unit of the outflow unit. Is provided.

  According to the present invention as set forth in claim 8, the exhaust gas flowing from each exhaust pipe is similarly applied to the inner wall at a position near the swirling flow generating portion or the swirling flow generating portion of the outflow portion. It flows along the way. For this reason, the oxygen concentration detection sensor is provided at a position close to the swirl flow generation part or the swirl flow generation part of the outflow part. Since the flowing exhaust gas flows uniformly, the average oxygen concentration can be accurately detected without depending on the attachment position. Therefore, the degree of freedom of the attachment position of the oxygen concentration detection sensor is great.

  According to the exhaust pipe structure of the present invention, it becomes possible to diffuse the flow of exhaust gas flowing from each exhaust pipe to the catalytic converter, improving the purification efficiency and preventing the deterioration of the catalytic converter and extending the life. Can be long.

<< First Embodiment >>
First, the exhaust pipe structure according to the first embodiment of the present invention will be described in detail with reference to FIGS.
The type and type of the internal combustion engine to which the exhaust pipe structure according to the present invention is applied are not particularly limited. Hereinafter, as an example, an exhaust pipe structure connected to four exhaust ports of an in-line four-cylinder gasoline engine. Will be explained. Further, in the exhaust pipe structure according to the present invention, the vertical and horizontal directions are arbitrary because they change depending on the direction in which the exhaust manifold or the like is installed, but an outflow part connected to the swirl flow generating part of the collecting pipe is installed. The following description will be given with the front direction (see FIG. 2) as the front direction.
FIG. 1 is a perspective view showing an exhaust pipe structure according to the first embodiment of the present invention.

<Exhaust manifold>
As shown in FIG. 1, the exhaust manifold 5 is for sending combustion gas burned in a combustion chamber (not shown) of an internal combustion engine to a catalytic converter 9 via a collecting pipe 8 to be described later. The exhaust manifold 5 includes, for example, four first to fourth exhaust pipes 1 to 4 (hereinafter referred to as first to fourth exhaust pipes 1 to 4) connected to exhaust ports (not shown) of a four-cylinder internal combustion engine. 4 is collectively referred to as “exhaust pipe P”). The exhaust manifold 5 is provided with a flange portion 6 connected to the upstream end portion of the exhaust pipe P on the upstream side, and a collective portion 8a in which the downstream end portions of the exhaust pipe P are assembled and integrated on the downstream side. It has been.

<Exhaust pipe>
The exhaust pipe P is composed of a plurality of stainless steel pipes, steel pipes, and the like, and mounting ports (not shown) and first to fourth exhaust pipes 1 to 4 are installed in the flange portion 6 by the number of cylinders of the internal combustion engine. The exhaust pipe P is formed in a smooth curved shape so that the exhaust gas does not cause a power loss of the engine (not shown) due to the flow velocity resistance in the pipe. Each exhaust pipe P has, for example, an upstream opening end portion that is welded laterally to the flange portion 6 and concentrated so that the central portion converges, and directly below the downstream end portion from the central portion. The end portions on the downstream side are welded to the upper surface of the collecting portion 8 a of the collecting pipe 8. For this reason, since the exhaust pipe P can extend long in the downstream direction, it is also possible to use a general steel pipe.

<Collecting pipe (swirl flow generator)>
As shown in FIG. 1, the collecting pipe 8 collects the exhaust pipe P at the collecting portion 8a, and converts the flow of the exhaust gas united at the inflow portion 8b into a swirling flow at the swirling flow generating portion 8c. It is a pipe that diffuses and flows to the catalytic converter 9, and is formed of stainless steel, steel, cast iron, or the like. The collecting pipe 8 is communicated between the collecting portion 8a of the exhaust manifold 5 and the catalytic converter 9. The collecting pipe 8 includes a collecting portion 8a in which the downstream end portions of the plurality of exhaust pipes P are gathered, and an inflow portion 8b that is provided on the downstream side of the collecting portion 8a to join and take in exhaust gas. The swirl flow generating portion 8c for swirling the exhaust gas and the outflow portion 8f for sending the exhaust gas connected to the catalytic converter 9 are provided in this order, and are integrally formed by welding means or the like, respectively. .
The collecting pipe 8 corresponds to the swirling flow generator described in the claims.

<Meeting part>
The collecting portion 8a is formed at the downstream end portion so that the exhaust gas flowing through the four (plural) exhaust pipes P becomes one, and is formed in, for example, a substantially cylindrical shape. The upstream side of the collecting portion 8a is a disc-shaped member in which the tip end portion of each exhaust pipe P is welded and a through hole (not shown) communicating with each exhaust pipe P is formed. Is provided. The downstream side of the collecting portion 8a is formed of a cylindrical member having a short length continuously provided from the outer peripheral portion of the disk-shaped member to the lower side, and to the exhaust gas collecting tube 8 on the downstream side thereof. An inflow portion 8b serving as an inlet is connected.

<Inflow section>
FIG. 2 is a view showing the exhaust pipe structure according to the first embodiment of the present invention, and is a front view having a partial cross section showing the collecting pipe.
As shown in FIG. 2, the inflow portion 8b is a portion that is connected to the collecting portion 8a and joins the exhaust gas flowing from the exhaust pipes P, and is eccentric from the central portion O of the swirl flow generating portion 8c. It is provided on the outer peripheral portion 8d at the position. The inflow portion 8b is formed in a substantially conical shape so that the diameter on the collecting portion 8a side is large, the diameter on the swirling flow generating portion 8c side is small, and the diameter increases toward the upstream side. The inflow portion 8b is disposed, for example, at an eccentric position obliquely upward from the central portion O, and the exhaust gas flowing from the exhaust pipe P enters the swirl flow generating portion 8c from the tangential direction at the left center of the outer peripheral portion 8d. It is arranged so as to smoothly flow in a vortex from the outside of the swirling flow generating portion 8c toward the center portion O side. The inflow portion 8b is formed so that the downstream side from the central portion of each exhaust pipe P flows straight toward the inflow portion 8b, so that interference of the exhaust gas flowing from each exhaust pipe P is reduced. It can be done. Moreover, the inflow part 8b may be either the upper left side or the upper right side of the swirl flow generation part 8c.

<Swirl flow generator>
The swirling flow generating portion 8c is provided on the downstream side of the inflow portion 8b, and converts the flow of the exhaust gas from each exhaust pipe P into a swirling flow so as to rectify it uniformly. The swirling flow generating portion 8c is formed of a hollow having a substantially disk shape, and the inflow portion 8b is integrally formed by welding means from the left side of the outer peripheral portion 8d to the upper side, and the swirling flow generating portion 8c A base end portion 8e of the outflow portion 8f is integrally formed and communicated with the center portion O (on the center line) by welding means. That is, as shown in FIG. 2, the swirling flow generating portion 8c causes the exhaust gas from each exhaust pipe P to flow from the upper side to the lower side and into the outer peripheral portion 8d on the left side of the swirling flow generating portion 8c. It is formed so as to turn and flow from the central portion O on the front side to the outflow portion 8f while changing its direction by approximately 90 degrees.

As shown in FIG. 2, the swirling flow generating portion 8c has an inner diameter of the inflow portion 8b as a and an inner diameter of the swirling flow generating portion 8c as b.
b ≧ 2a
The inner diameter b of the swirl flow generating portion 8c is formed larger than the inner diameter a of the inflow portion 8b.
That is, since the inflow portion 8b is disposed at a position eccentric from the central portion O of the swirling flow generating portion 8c, the inner diameter b of the swirling flow generating portion 8c is at least twice as large as the inner diameter a of the inflow portion 8b. Is formed.

<Outflow part>
The outflow part 8f is for sending the exhaust gas swirled by the swirl flow generating part 8c to the catalytic converter 9 while diffusing, and is formed in a substantially conical shape whose diameter is increased in the direction of the catalytic converter 9. The outflow portion 8f is provided from the central portion O of the swirling flow generating portion 8c toward the downstream side, forms an outlet of the collecting pipe 8, and communicates with the catalytic converter 9.
As shown in FIGS. 4 (a) and 4 (b), the outflow portion 8f has an upstream base end portion 8e having a substantially conical shape in the horizontal direction from the front central portion of the swirl flow generating portion 8c. It is formed with an enlarged diameter, and is connected to the catalytic converter 9 in a state where the downstream end is bent obliquely downward.
In addition, as shown in FIG.4 (b), the location near the swirl | flow flow generation part 8c of the outflow part 8f has left | separated slightly from the base end part 8e in order to make it flow while rotating exhaust gas smoothly. It is formed in a curved shape so that the position is the inner diameter c of the narrowest portion of the outflow portion 8f. That is, as shown in FIG. 1, the outflow portion 8f is formed such that the exhaust gas flowing into the outflow portion 8f from the swirling flow generating portion 8c diffuses while spiraling and flows to the catalytic converter 9. Yes.

As shown in FIG. 2, the outflow portion 8f has an inner diameter of the inflow portion 8b, a as an inner diameter of the swirling flow generation portion 8c, and c as an inner diameter of the narrowest portion of the outflow portion 8f (see FIG. 4B). ),
a ≦ c ≦ b
It is formed to become.
That is, the inner diameter c of the thinnest portion of the outflow portion 8f is formed to be not less than the inner diameter a of the inflow portion 8b and not more than the inner diameter b of the swirling flow generating portion 8c.
As shown in FIG. 2, in the present embodiment, the inner diameter of the inflow portion 8b is a.
a = b / 2−c / 2
Are formed in substantially the same length.

Then, as shown in FIGS. 4A and 4B, for example, the oxygen concentration is detected at a position close to the swirl flow generating portion 8c of the outflow portion 8f (the portion where the inner diameter c of the outflow portion 8f is the narrowest). An O ₂ sensor S is installed. This O ₂ sensor S detects the concentration of oxygen in exhaust gas flowing from an engine cylinder (not shown), and sends the detected signal to an engine control unit that controls the air-fuel ratio. Connected.
The O ₂ sensor S may be provided in the swirl flow generation unit 8c. The O ₂ sensor S corresponds to the oxygen concentration detection sensor described in the claims.

<Catalytic converter>
The catalytic converter 9 is a device that purifies exhaust gas that will eventually be released into the atmosphere by passing through the catalytic converter 9 and removes harmful components contained in the exhaust gas. A catalyst 9a is provided inside. The catalytic converter 9 is composed of, for example, a monolith type three-way catalytic converter, and a muffler (not shown) is installed on the downstream side of the catalytic converter 9.
The catalytic converter 9 may be other as long as it has an exhaust gas detoxifying effect.

<Operation of First Embodiment>
Next, the operation of the exhaust pipe structure according to the first embodiment of the present invention will be described with reference to FIGS.
FIG. 3 is a main part perspective view showing the exhaust pipe structure according to the first embodiment of the present invention, and is an explanatory view showing the trajectory of the exhaust gas flowing from the first exhaust pipe. 4A and 4B are diagrams showing an exhaust pipe structure according to the first embodiment of the present invention. FIG. 4A is an explanatory diagram showing a locus of exhaust gas flowing from the first exhaust pipe, and FIG. This is the left side of the unit. 5A and 5B are drawings showing an exhaust pipe structure according to the first embodiment of the present invention, in which FIG. 5A is a perspective view, and FIG. 5B is a first exhaust at a cross-section along line BB in FIG. Flow velocity distribution diagram of exhaust gas flowing from the pipe, (c) Flow velocity distribution diagram of exhaust gas flowing from the second exhaust pipe, (d) Flow velocity of exhaust gas flowing from the third exhaust pipe The distribution diagram (e) is a flow velocity distribution diagram of the exhaust gas flowing from the fourth exhaust pipe.

  When an internal combustion engine (not shown) operates, exhaust gas flows from each exhaust port (not shown) to the first to fourth exhaust pipes 1 to 4 shown in FIG. The first to fourth exhaust pipes 1 to 4 are connected together by a collecting portion 8a of the collecting pipe 8, and an inflow portion 8b is installed below the collecting portion 8a.

Thus, the exhaust gas that has passed through the first to fourth exhaust pipes 1 to 4 passes through the inflow portion 8b at the upper left end of the collecting pipe 8 as in the first exhaust pipe 1 shown in FIG. Descend. The exhaust gas flows from the inflow portion 8b to the left center of the outer peripheral portion 8d of the swirling flow generating portion 8c, is guided to the inner wall of the collecting pipe 8, and enters the swirling flow generating portion 8c while swirling.
The exhaust gas that has entered the swirl flow generation unit 8c is guided by the inner wall of the swirl flow generation unit 8c and swirls in a vortex, and the exhaust gas from each exhaust pipe P is similarly swirled. And flows into the outflow part 8f.
As shown in FIGS. 4A and 4B, the exhaust gas in the outflow portion 8f is diffused along the inner wall of the outflow portion 8f because the outflow portion 8f has a substantially conical shape. It flows into the catalyst 9a of the catalytic converter 9.

  Then, the exhaust gas in the catalytic converter 9 has a substantially uniform flow of exhaust gas in each exhaust pipe P as shown in FIGS. 5B to 5E, as compared with the conventional exhaust pipe structure. The exhaust gas flow velocity is constant, and the number of lines is small, and the central portion is rectified at a low speed. Exhaust gases from the first to fourth exhaust pipes 1 to 4 are swirled by the swirling flow generation unit 8c, so that the lowest speed portion of the catalytic converter 9 is as shown in FIGS. It appears in a circle at the approximate center, and the fastest part appears on the outer peripheral side.

<Effect of the first embodiment>
Thus, in the exhaust pipe structure according to the first embodiment of the present invention, exhaust gas is concentrated on a specific portion of the catalyst 9a by installing the collective pipe 8 between the collective portion 8a and the catalytic converter 9. The phenomenon of the gas passing disappears, and the exhaust gas enters the entire section of the catalytic converter 9 in a substantially uniform manner. Moreover, even if it flows in from any of the four exhaust pipes 1-4, it becomes a substantially equivalent flow. For this reason, the deviation of the exhaust gas in the catalytic converter 9 is eliminated, the purification efficiency of the catalyst 9a can be improved, and there is an effect of preventing the shortening of the life due to the deterioration of the catalyst 9a.

<< Second Embodiment >>
Next, an exhaust pipe structure according to a second embodiment of the present invention will be described with reference to FIGS. 6 (a) and 6 (b). In addition, the same thing as the said 1st Embodiment attaches | subjects the same code | symbol, and abbreviate | omits the description. FIG. 6 is a drawing showing an exhaust pipe structure according to a second embodiment of the present invention, where (a) is a perspective view, (b) is a rear view, and (c) is a left side view.

<Collecting pipe (swirl flow generator)>
In the second embodiment of the present invention, the collecting pipe 8 of the first embodiment provided between the exhaust manifold 5 and the catalytic converter 9 is modified.
The collecting pipe (swirl flow generator) 10 shown in FIGS. 6A to 6C converts the exhaust gas from the exhaust pipe P connected to the collecting portion 10a into a swirling flow and diffuses it. Is. The collecting pipe 10 includes the collecting portion 10a, an inflow portion 10b provided to be inclined to the downstream side of the collecting portion 10a, a guide wall portion 10c formed at a corner of the bottom surface of the inflow portion 10b, A swirl flow generating unit 10e for swirling gas and an outflow unit 10g for sending exhaust gas are configured.

<Meeting part>
The collecting portion 10a is a portion for connecting the exhaust pipes P to one to take in exhaust gas, and has a diameter that is increased in a substantially conical shape toward the upstream side. An inflow portion 10b is connected in a diagonally lower right direction on the downstream side of the collective portion 10a.

<Inflow section>
The inflow portion 10b is formed on a downstream side of the collecting portion 10a and is inclined toward the downstream direction, and is a pipe for guiding the swirling flow (cyclone) to be easily generated effectively in the swirling flow generating portion 10e. is there. The inflow portion 10b is guided so that the exhaust gas from each exhaust pipe P flowing from the collecting portion 10a flows obliquely in the downstream direction and flows toward a guide wall portion 10c described later. The swirl flow generator 10e is guided and flows so as to be efficiently converted into a swirl flow.

<Guide wall>
The guide wall portion 10c is a surface that regulates the direction in which the exhaust gas flows in a direction in which a swirl flow is generated (a direction in which the exhaust gas swirls in a spiral manner in the passage). The guide wall portion 10c is formed of, for example, an oblique surface formed at the corner of the inner wall on the bottom surface side of the inflow portion 10b in the swirling flow generating portion 10e, and exhaust gas flowing into the swirling flow generating portion 10e is discharged to the outflow portion 10g. It is a guide which guides to flow while turning to the side. The guide wall 10c is formed, for example, by forming a part of the curved inner wall of the swirl flow generator 10e in a substantially flat shape. What is necessary is just to form the magnitude | size of this guide wall part 10c suitably according to the flow volume of the flowing exhaust gas.
The guide wall portion 10c is an extension of the center line O1-O1 of the inflow portion 10b in order to guide the exhaust gas flowing into the swirl flow generation portion 10e from the inflow portion 10b to the outflow portion 10g so as to flow easily. It is desirable to install in the vicinity. In addition, the guide wall portion 10c is not limited to a flat surface, and may be a curved surface having a smaller curvature than other portions and smoothly connected to the surroundings.

<Swirl flow generator>
The swirling flow generating portion 10e is a portion where a guide wall portion 10c is formed on the inner wall and there is a circular space for swirling exhaust gas. The swirling flow generating portion 10e has a circular shape in which the center line O2-O2 of the swirling flow generating portion 10e is shifted by a length L with respect to the center line O1-O1 of the inflow portion 10b connected to the collecting portion 10a. . Here, the circular form means a circular shape, an elliptical shape, or an oval shape, and a substantially circular shape.
As shown in FIGS. 6A, 6B, and 6C, the swirling flow generating portion 10e is expanded in a substantially conical shape from the inflow portion 10b toward the outflow portion 10g, and the center line O1. -O1 and the center line O2-O2 are formed in a twisted state (substantially spiral), which is inconsistent with the flow direction of the exhaust gas.
Incidentally, as shown in FIG. 6 (c), the inside peripheral portion 10f of the swirl flow generation section 10e, O ₂ sensor S for detecting the concentration of oxygen is installed. The oxygen concentration detected by the O ₂ sensor S is transmitted to the engine control unit and used for air-fuel ratio control.

<Outflow part>
As shown in FIGS. 6 (b) and 6 (c), the outflow portion 10g expands in a substantially conical shape from the swirling flow generating portion 10e obliquely downward, and is continuously connected to the catalytic converter 9 to exhaust gas. It is a part for sending out while turning.
As shown in FIG. 6C, the outflow portion 10g is formed to be inclined downward at an angle θ1 with respect to the center line O1-O1 of the inflow portion 10b in a side view.
The angle θ1 is an inclination angle of the center line O3-O3 of the outflow portion 10g with respect to the center line O1-O1 of the inflow portion 10b.
θ1 <90 °
It is. The angle θ1 is preferably
30 ° <θ1 <60 °
It is.
For this reason, the swirling flow generating unit 10e has an inlet direction of the inflow portion 10b that is the inlet of the swirling flow generating portion 10e and an outlet direction of the outflow portion 10g that is the outlet of the swirling flow generating portion 10e, The exhaust gas outlet in the pipe 10 is not on the central axis (center line O1-O1) of the inlet.
Further, as shown in FIG. 6 (c), the swirl flow generating portion 10e is formed in a state where the entire diameter is substantially enlarged with respect to the flow direction of the exhaust gas, the inner diameter of the inflow portion 10b is small, and the outflow portion. The inner diameter of 10 g is formed large.

<Operation of Second Embodiment>
Next, with reference to FIGS. 6A to 6C, the operation of the exhaust pipe structure according to the second embodiment of the present invention will be described.
When the internal combustion engine (not shown) operates, the exhaust gas flows from the respective exhaust ports (not shown) to the first to fourth exhaust pipes 1 to 4 shown in FIGS. The exhaust gas that has passed through the first to fourth exhaust pipes 1 to 4 flows into the collecting portion 10a of the collecting pipe 10 and merges into one at the inflow portion 10b.

As shown in FIG. 6 (b), the exhaust gas that has joined at the inflow portion 10b is guided by the inflow portion 10b and is swirled toward the outer peripheral portion 10f on the lower side of the swirl flow generating portion 10e that is obliquely downward. Flows so as to easily occur, collides with the guide wall 10c, and the flow in the downstream direction is strengthened.
As shown in FIG. 6 (c), the exhaust gas that has collided with the guide wall 10c swirls in the swirl flow generation unit 10e along the guide wall 10c, thereby generating a swirl flow. The exhaust gas in the swirling flow generating portion 10e is expanded in a substantially conical shape from the inner wall of the circular swirling flow generating portion 10e to the outflow portion 10g and twisted in a substantially helical shape. And is diffused so as to swirl while being swung while being guided by a swirling flow generating portion 10e that is shifted by a length L in the left-right direction and inclined downward at an angle θ1. Gas flows into the outflow part 10g through substantially the same path. The exhaust gas in the outflow portion 10g is diffused along the inner wall surface of the outflow portion 10g and purified by flowing into the catalytic converter 9 because the outflow portion 10g has a substantially conical shape.

On the other hand, in the O ₂ sensor S, the exhaust gas of each exhaust pipe P flowing in the outer peripheral portion 10f flows uniformly along the inner wall. The average oxygen concentration in the exhaust gas can be accurately detected. Since the O ₂ sensor S can detect the oxygen concentration of the exhaust gas from each exhaust pipe P in a well-balanced manner, the engine control unit can control the air / fuel ratio satisfactorily. Further, the O ₂ sensor S is free from the restriction of the attachment position, and the degree of freedom of the attachment position is increased.

<Effects of Second Embodiment>
Thus, the exhaust pipe structure according to the second embodiment of the present invention is similar to the first embodiment described above, because the collecting pipe 10 is installed between the collecting portion 10a and the catalytic converter 9. The exhaust gas flow is rectified substantially uniformly over the entire cross section of the catalytic converter 9 and enters. For this reason, the uneven flow of the exhaust gas in the catalytic converter 9 is eliminated, and the purification efficiency can be improved.

  The present invention is not limited to the first and second embodiments, and various modifications and changes can be made within the scope of the technical idea, and the present invention includes these modifications and changes. It goes without saying that Hereinafter, the modification is demonstrated.

≪First modification≫
7A and 7B are drawings showing a first modification of the exhaust pipe structure according to the embodiment of the present invention, wherein FIG. 7A is a left side view and FIG. 7B is a perspective view.
For example, as shown in FIG. 7A, the outflow portion 8f1 includes a base end portion 8e of the outflow portion 8f1 provided on the center portion O (on the center line) of the swirling flow generation portion 8c and the inflow portion 8b. The angle θ2 formed by the center line O1-O1 and the center line O3-O3 of the outflow portion 8f1 may be 45 ° to 135 °. Thus, the outflow portion 8f1 is formed to be inclined from the swirling flow generating portion 8c toward the catalytic converter 9, so that the exhaust gas flows while swirling in the swirling flow generating portion 8c in a substantially spiral shape. become.

≪Second modification≫
FIG. 8 is a drawing showing a second modification of the exhaust pipe structure according to the embodiment of the present invention, where (a) is a left side view and (b) is a perspective view.
Further, as shown in FIG. 8A, the outflow portion 8f2 has a cylindrical shape in which the diameter of the entire outflow portion 8f2 is substantially the same as that of the swirling flow generation portion 8c, as shown in FIG. 8B. Further, it may be formed obliquely downward. Even if formed in this way, the exhaust gas flows while swirling in the spiral flow generating portion 8c in a substantially spiral shape.

  Note that the shapes of the outflow portions 8f, 8f1, 8f2 and the exhaust pipe P may be changed as appropriate according to the arrangement state of components provided around the outflow portions 8f, 8f1, 8f2.

1 is a perspective view showing an exhaust pipe structure according to a first embodiment of the present invention. It is drawing which shows the exhaust pipe structure which concerns on 1st Embodiment of this invention, and is a front view which has a partial cross section which shows a collection pipe. It is a principal part perspective view which shows the exhaust pipe structure which concerns on 1st Embodiment of this invention, and is explanatory drawing which shows the locus | trajectory of the exhaust gas which flowed from the 1st exhaust pipe. It is a figure which shows the exhaust pipe structure which concerns on 1st Embodiment of this invention, (a) is explanatory drawing which shows the locus | trajectory of the exhaust gas which flowed from the 1st exhaust pipe, (b) is a principal part left side surface. is there. It is drawing which shows the exhaust pipe structure which concerns on 1st Embodiment of this invention, (a) is a perspective view, (b) flows from the 1st exhaust pipe in the BB line cross-section part of Fig.5 (a). (C) is a flow velocity distribution diagram of the exhaust gas flowing from the second exhaust pipe, (d) is a flow velocity distribution diagram of the exhaust gas flowing from the third exhaust pipe, e) is a flow velocity distribution diagram of the exhaust gas flowing from the fourth exhaust pipe. It is drawing which shows the exhaust pipe structure which concerns on 2nd Embodiment of this invention, (a) is a perspective view, (b) is a rear view, (c) is a left view. It is drawing which shows the 1st modification of the exhaust pipe structure which concerns on embodiment of this invention, (a) is a left view, (b) is a perspective view. It is drawing which shows the 2nd modification of the exhaust pipe structure which concerns on embodiment of this invention, (a) is a left view, (b) is a perspective view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st exhaust pipe 2 2nd exhaust pipe 3 3rd exhaust pipe 4 4th exhaust pipe 5 Exhaust manifold 8, 10 Collecting pipe (swirl flow generator)
8a, 10a Aggregation part 8b, 10b Inflow part 8c, 10e Swirling flow generation part 8d, 10f Outer peripheral part 8f, 8f1, 8f2, 10g Outflow part 9 Catalytic converter 10c Guide wall part O Center part O1, O2, O3 Center line P Exhaust Pipe S O ₂ sensor (oxygen concentration detection sensor)

Claims (8)

An exhaust manifold comprising a plurality of exhaust pipes connected to an exhaust port of an internal combustion engine, a catalytic converter for purifying exhaust gas, and a swirling flow generator interposed between the exhaust manifold and the catalytic converter Exhaust pipe structure,
The swirl flow generator is provided with an inflow portion provided on a downstream side of a collecting portion in which downstream end portions of the plurality of exhaust pipes are gathered;
A swirl flow generator provided on the downstream side of the inflow portion for converting the flow of the exhaust gas into a swirl flow;
An exhaust pipe structure comprising: an outlet portion connected to the downstream side of the swirl flow generating portion and communicating with the catalytic converter. The inflow portion is provided in an outer peripheral portion at a position eccentric from a central portion of the swirl flow generating portion,
The swirl flow generation unit is defined as a, where the inflow portion has an inner diameter a, and the swirl flow generation portion has an inner diameter b.
b ≧ 2a
The exhaust pipe structure according to claim 1, wherein The outflow part has an inner diameter of the inflow part a, an inner diameter of the swirl flow generation part b, and an inner diameter of the narrowest part of the outflow part c,
a ≦ c ≦ b
The exhaust pipe structure according to claim 1 or 2, wherein: The exhaust pipe structure according to any one of claims 1 to 3, wherein the outflow portion has a base end portion of the outflow portion provided on a center line of the swirl flow generation portion. The swirl flow generation unit is arranged such that the center line of the swirl flow generation unit is shifted with respect to the center line of the inflow portion,
2. The exhaust pipe structure according to claim 1, wherein a guide wall portion that regulates a flow direction of the exhaust gas is provided on a wall surface in the swirl flow generating portion. 6. The exhaust pipe structure according to claim 1, wherein the swirl flow generating portion is formed in a twisted state with a diameter increasing from the inflow portion toward the outflow portion. The exhaust pipe structure according to claim 1, wherein the outflow portion is formed to be inclined from the swirl flow generation portion toward the catalytic converter. 2. The exhaust pipe structure according to claim 1, wherein an oxygen concentration detection sensor is provided at a position near the swirl flow generation unit or the swirl flow generation unit of the outflow unit.

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