JP2007211663A - Exhaust gas catalyst device and multi-cylinder internal combustion engine equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain good exhaust efficiency by controlling increase of resistance in an introduction passage, and make even exhaust gas flow at the inlet end area of the catalyst converter of an exhaust catalyst device. <P>SOLUTION: An introduction passage 41 for guiding exhaust gas from an outlet 6b of the collective exhaust port of a cylinder head 2 into the inlet end area 10a of a catalyst converter 10 is provided in an exhaust catalyst device A of a multi-cylinder internal combustion engine E. The introduction passage 41 comprises: an area 42 upstream the point of exhaust gas flowing into the passage 41; a curved part 44 where exhaust gas becomes curved streams; and an area 43 downstream the point of discharging the curved exhaust gas streams into an inlet end area 10a. A swelling part 45 is provided in the curved part 44. The swelling part 45 swells outwardly beyond the curve relative to an imaginary arc connecting the upstream area 42 with the downstream area 43. Part of the exhaust gas flow becomes a deflected flow after flowing along the wall surface of the swelling part 45, and the deflected flow is discharged from the swelling part 45 inwardly beyond the curve and toward the inlet end area 10a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust catalyst device as an exhaust gas purification device that purifies exhaust gas generated in a combustion device such as an internal combustion engine, and a multi-cylinder internal combustion engine equipped with the exhaust catalyst device. The present invention relates to a passage structure for leading to a catalytic converter as an exhaust gas purification member.

In an exhaust catalyst device as an exhaust gas purification device that purifies exhaust gas, for example, like a direct exhaust catalyst device of an internal combustion engine, a passage that leads exhaust gas to a catalytic converter for exhaust gas purification has a predetermined angle on the layout, For example, it may be bent at a substantially right angle. On the other hand, it is desirable from the viewpoint of purification performance and durability of the catalytic converter that the state of the flow of the exhaust gas flowing into the catalytic converter is as uniform as possible without being locally biased at the input end face of the catalytic converter. For this reason, in the exhaust catalyst device provided with the bent introduction passage, various techniques for making the flow of the exhaust gas flowing into the catalytic converter uniform are known (for example, refer to Patent Documents 1 and 2).
JP 2003-49640 A JP 2005-240711 A

  By the way, in order to make the flow of exhaust gas uniform at the inlet end of the catalytic converter, an insertion member such as a rectifying plate is provided in the introduction passage, passage resistance increases, exhaust efficiency decreases, and cost increases. Become. In addition, providing a protrusion for deflecting the flow on the wall surface of the introduction passage similarly increases the passage resistance, leading to a reduction in exhaust efficiency.

  The present invention has been made in view of such circumstances, and the invention according to claims 1 to 4 suppresses an increase in passage resistance in the introduction passage and maintains good exhaust efficiency while purifying exhaust. An object of the present invention is to make the flow of exhaust gas uniform at the inlet end face of a catalytic converter as an exhaust purification member of an exhaust catalyst device as a device. The invention according to claim 2 achieves the above object in a multi-cylinder internal combustion engine in which a collective exhaust port is formed in a cylinder head, and the invention according to claim 4 is further generated in an exhaust catalyst device. The purpose is to reduce noise.

  The invention according to claim 1 is an exhaust catalyst device provided with a catalytic converter for purifying exhaust gas and an introduction passage for introducing exhaust gas to an inlet end face of the catalytic converter, wherein the introduction passage is configured to receive exhaust gas. An upstream portion having a passage inlet, a bent portion in which exhaust gas from the passage inlet becomes a bent flow, and a downstream portion having a passage outlet for causing the flow of the exhaust gas after being bent to flow toward the inlet end face In the exhaust catalyst device configured, the bent portion is bent outwardly from a virtual arc connecting the most downstream portion of the outer peripheral portion of the upstream portion and the most upstream portion of the outer peripheral portion of the downstream portion in a side view. A bulging portion that bulges out, and a part of the exhaust gas of the bent portion flows along the wall surface of the bulging portion, whereby the inflow direction of the exhaust gas at the passage inlet in a side view The deflection flow is reversed with respect to Countercurrent is an exhaust catalyzer flowing out of the bulging portion directed bending inwardly and said inlet end face.

  According to this, since the exhaust gas is bent at the bent portion of the introduction passage, the flow of the exhaust gas at the inlet end surface of the catalytic converter is biased toward the outer portion of the inlet end surface (hereinafter referred to as “non-uniform flow state”). The flow at the outer part of the bent part, which is the main cause of the occurrence of the above, becomes a deflected flow by the bulging part toward the inner part at the inlet end face, so that the exhaust at the inner part of the inlet end face of the catalytic converter While the gas flow increases, the flow toward the outer portion of the inlet end surface decreases. Further, since the deflected flow is generated by the bulging portion, unlike the protruding wall that protrudes inwardly to generate the deflected flow, the passage resistance is not increased to generate the deflected flow, and the introduction passage Since the passage area is increased by an amount corresponding to the bulging portion, an increase in passage resistance in the introduction passage is suppressed. Furthermore, since the bulging portion is provided at the bent portion, exhaust gas tends to flow into the bulging portion as compared with the case where the bulging portion is provided on the side of the linear passage, so that directivity is strong. A deflected flow can be generated.

  The invention according to claim 2 is connected to a cylinder head in which a collective exhaust port in which exhaust gases from a plurality of combustion chambers arranged in the arrangement direction gather and formed immediately downstream of the outlet of the collective exhaust port. A multi-cylinder internal combustion engine including a direct type exhaust catalyst device for purifying exhaust gas, wherein the exhaust catalyst device includes a catalytic converter for purifying exhaust gas and an introduction passage for guiding exhaust gas to an inlet end face of the catalytic converter. And the introduction passage has an upstream portion having a passage inlet through which exhaust gas flows, a bent portion where the exhaust gas from the passage inlet becomes a bent flow, and the flow of the exhaust gas after being bent flows into the inlet In the exhaust catalyst device comprising a downstream portion having a passage outlet that flows out toward the end surface, the bent portion includes, in a side view, the most downstream portion of the outer peripheral portion of the upstream portion and the outer peripheral portion of the downstream portion. Top of A bulging portion that bulges outward from a virtual arc connecting to the portion is provided, and a part of the exhaust gas of the bending portion flows along the wall surface of the bulging portion, thereby This is a multi-cylinder internal combustion engine in which the deflected flow is reversed with respect to the inflow direction of the exhaust gas as viewed from the side, and the deflected flow flows inwardly from the bulging portion toward the inlet end surface.

  According to this, in the multi-cylinder internal combustion engine including the cylinder head in which the collective exhaust port is formed, the same operation as that of the first aspect of the invention is performed.

  According to a third aspect of the present invention, in the multi-cylinder internal combustion engine according to the second aspect, both wall surfaces of the bulges in the arrangement direction are in the exhaust gas flow direction when viewed from the central axis direction of the catalytic converter. It is tapered and is substantially parallel to the inflow direction of the exhaust gas from the combustion chamber of the specific cylinder at the passage inlet.

  According to this, since the main flow of the exhaust gas from the specific cylinder flows into the bulging portion without being deflected by the wall surface of the bulging portion, the exhaust gas smoothly flows into the bulging portion, and the smooth Since the flow gathers at the bulging portion formed in a taper, a relatively strong deflection flow can be generated at the bulging portion.

  According to a fourth aspect of the present invention, there is provided the exhaust catalyst device according to the first aspect or the multi-cylinder internal combustion engine according to the second or third aspect, wherein the bulging portion has the passage in the inflow direction of exhaust gas at the passage inlet. Provided at a position facing the inlet, the bulging portion is a gentle wall surface and smoothly continues to the upstream portion.

  According to this, since the exhaust gas flowing into the introduction passage hardly bends and flows into the bulging portion in a substantially straight line, a relatively strong deflection flow can be generated, and the swelled with the upstream portion. Part smoothly flows along the gentle wall surface, so that the exhaust gas flows into the bulging part while gently bending as compared with the case where it is bent largely because there is no bulging part. And the sound generated by hitting the wall surface of the bulging portion is reduced.

  In the specification or claims, the term “plan view” means viewing from the central axis direction or the direction orthogonal to the inlet end surface of the catalytic converter as the exhaust purification member, and “side view” This means viewing in a plan view or from a direction perpendicular to the symmetry plane described later, and “bending outward” and “bending inward” are directions away from the bending center that is the center of the virtual arc and directions approaching the bending center. The “outside” and “inside” in a member, passage, flow, etc. mean a portion far from the bending center and a portion near the bending center in the member, passage, flow, etc., respectively.

  According to invention of Claim 1, the following effect is show | played. That is, the flow of exhaust gas in the inner portion of the inlet end surface is increased by the deflected flow generated by the bulging portion, so that the flow of exhaust gas at the inlet end surface is made uniform. For this reason, the purification rate of the catalytic converter is improved, the local deterioration of the catalytic converter due to the non-uniform flow state is prevented, and the durability of the catalytic converter is improved. In addition, since the effect of the passage resistance in the introduction passage is suppressed, an increase in the back pressure in the exhaust passage is suppressed, and good exhaust efficiency can be ensured. Further, since the bulging portion is provided at the bent portion, a highly directional deflected flow can be generated, and a deflected flow effective for making the exhaust gas flow uniform at the inlet end surface can be generated. .

  According to the invention described in claim 2, in the multi-cylinder internal combustion engine including the cylinder head in which the collective exhaust port is formed, the same effect as that of the invention described in claim 1 is exerted.

  According to invention of Claim 3, in addition to the effect of the invention of the cited claim, there exist the following effects. That is, since the exhaust gas smoothly flows into the bulging portion, an increase in passage resistance due to the bulging portion is suppressed, and the non-uniform flow state is effectively corrected by the relatively strong deflection flow, and the inlet end face The flow at is made uniform, and the bulging portion is reduced in size by being tapered.

  According to invention of Claim 4, in addition to the effect of the invention of the cited claim, there exists the following effect. That is, the relatively strong deflected flow effectively corrects the non-uniform flow state, makes the flow at the inlet end surface uniform, and reduces the noise generated by the exhaust gas hitting the wall surface of the introduction passage. In addition, noise generated in the member that forms the introduction passage, and thus in the exhaust catalyst device provided with the introduction passage, is reduced.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Referring to FIGS. 1 and 2, an exhaust catalyst device A as an exhaust purification device to which the present invention is applied is a series 4 as a combustion device, for example, a water-cooled multi-cylinder internal combustion engine having a predetermined number of cylinders of two or more. A cylinder four-stroke internal combustion engine E is provided. The internal combustion engine E includes an engine body including a cylinder block 1 in which four first to fourth cylinders arranged in the arrangement direction are integrally formed, and a cylinder head 2 coupled to an upper end portion of the cylinder block 1. Prepare.
In this specification, the up-down direction and the front-rear direction are directions shown in FIG. 1, and the up-down direction is a direction parallel to the central axis of the catalytic converter 10 described later.

  The cylinder head 2 has an intake port 3 having combustion chambers C1 to C4 positioned facing pistons slidably fitted in the cylinders and a pair of intake ports 3a that open to the combustion chambers C1 to C4. Is formed for each cylinder, and further includes an individual exhaust port 5 having a pair of exhaust ports 5a that open to the respective combustion chambers C1 to C4, and one collecting portion in which the exhaust gas from each exhaust port 5 gathers. As a result, a collective exhaust port 4 is formed. In the internal combustion engine E, four combustion chambers C1 to C4 are arranged in a line in the arrangement direction corresponding to the four cylinders, respectively. Further, the cylinder head 2 includes, for each of the combustion chambers C1 to C4, a pair of intake valves and a pair of exhaust valves (both not shown) that open and close the intake port 3a and the exhaust port 5a, respectively, There is also provided an overhead camshaft type valve gear having a camshaft that opens and closes the exhaust valve at a predetermined timing in synchronization with the rotation of the crankshaft of the internal combustion engine E.

  Then, in the intake device connected to the intake side wall 2i of the cylinder head 2 where the inlet of each intake port 3 opens, the mixture formed by the intake air whose flow rate is controlled by the throttle valve and the fuel supplied from the fuel injection valve The air flows into the combustion chambers C1 to C4 through the intake ports 3 when the intake valves are opened, and is ignited by ignition plugs (not shown) provided in the cylinder head 2 in the combustion chambers C1 to C4. And burn. The piston, which is driven by the pressure of the generated combustion gas and reciprocates, drives the crankshaft through a connecting rod. Further, the combustion gas flows into the exhaust port 5 as the exhaust gas when the exhaust valve is opened, and further flows out from the outlet 6b through the collective port 6 and out of the collective exhaust port 4. Exhaust gas flowing out from the collective exhaust port 4 is circulated through a direct exhaust catalyst device A connected to the exhaust side wall 2e of the cylinder head 2, and further, an underfloor exhaust catalyst device (not shown) for purification. And then discharged outside the internal combustion engine E.

  The exhaust catalyst device A includes a catalytic converter 10 as an exhaust purification member for purifying exhaust gas, a storage case 11 as a main body for holding and storing the catalytic converter 10, and exhaust gas from an exhaust port 5 as a catalytic converter. An introduction cone 21 as an introduction part that forms an introduction passage 41 leading to 10 and exhaust gas purified by passing through the catalytic converter 10 are led to an exhaust pipe connected to a device disposed downstream of the exhaust catalyst device A. A lead-out cone 31 as a lead-out portion that forms the lead-out passage 34 is provided. The introduction cone 21 is connected to the cylinder head 2 via the flange 7 (see also FIGS. 3A and 3B) at the upstream end 22 and to the storage case 11 at the downstream end 23. On the other hand, the lead-out cone 31 is connected to the storage case 11 at the upstream end 32 and is connected to the exhaust pipe at the downstream end 33. Therefore, the exhaust catalyst device A is provided with the introduction passage 41, the catalytic converter 10, and the outlet passage 34.

  A cylindrical catalytic converter 10 having a central axis Lc (see also FIGS. 5 and 6), in this case, a cylindrical catalytic converter 10 includes a carrier having a honeycomb structure in which a large number of cells are formed, and platinum and rhodium carried on the carrier. It is comprised with catalyst materials, such as. The catalytic converter 10 has an inlet end face 10a through which exhaust gas flows from the introduction passage 41, and an outlet end face 10b through which exhaust gas purified by the catalytic converter 10 flows out to the outlet passage 34.

An introduction passage 41 connected to the outlet 6b of the collective exhaust port 4 and leading exhaust gas immediately downstream of the collective port 6 to the inlet end surface 10a of the catalytic converter 10 has an upstream portion 42 having a passage inlet 42a into which exhaust gas flows. And the bent portion 44 in which the flow of the exhaust gas flowing in from the passage inlet 42a having a shape matching the outlet 6b becomes a bent flow, and the exhaust after being bent at the bent portion 44 between the bent portion 44 and the inlet end face 10b. And a downstream portion 43 having a passage outlet 43b through which gas flows out toward the inlet end face 10a. The upstream portion 42 extends substantially in a straight line substantially parallel to the inlet end face 10a, and the downstream portion 43 extends in a substantially straight line in a direction substantially perpendicular to the inlet end surface 10a. Further, the downstream portion 43 whose passage area increases toward the downstream has a passage cross section having a central axis substantially coincident with the central axis Lc.
The bending angle between the inflow direction of the exhaust gas at the passage inlet 42a of the introduction passage 41 and the outflow direction of the exhaust gas at the passage outlet 43b of the introduction passage 41 is substantially perpendicular. Therefore, in the introduction passage 41 or the introduction cone 21, the exhaust gas flows while being bent at a substantially right angle by the bent portion 44.

  3 and 4, the introduction cone 21 has an upstream end 22 extending substantially parallel to the inlet end face 10a, a direction extending substantially perpendicular to the inlet end face 10a, and a conical shape toward the inlet end face 10a. A downstream end portion 23 having a diameter that is larger than the downstream end portion 23 and an intermediate portion 24 that is bent at a substantially right angle between the downstream end portion 23 and the upstream end portion 22. The upstream end 22 has a passage inlet 42a that is oblong and elongated in the arrangement direction corresponding to the outlet 6b, and a passage section that is oblong and elongated in the arrangement direction like the passage inlet 42a. An upstream portion 42 is formed.

  The upstream end portion 22 is disposed at the central portion in the arrangement direction with respect to all the combustion chambers C1 to C4 arranged in a row corresponding to the position of the outlet 6b in the cylinder head 2 (see FIG. 2). . For this reason, the exhaust gas from the combustion chamber C1 of the first cylinder and the combustion chamber C2 of the second cylinder is different from the exhaust gas from the combustion chamber C4 of the fourth cylinder and the combustion chamber C3 of the third cylinder, respectively. It flows into the upstream portion 42 in a form symmetric with respect to H. Here, the center plane H is a plane that bisects the four combustion chambers C1 to C4 in the arrangement direction as viewed from the cylinder axis direction.

  The downstream end portion 23 forms a circular passage outlet 43b having a shape corresponding to the inlet end surface 10a, and a downstream portion 43 having a circular passage section. An oxygen concentration sensor 8 as an air-fuel ratio sensor that detects an air-fuel ratio by detecting an exhaust component is attached to the upstream end portion 22. The oxygen concentration sensor 8 is inserted into the upstream portion 42 through the insertion hole K of the upstream end portion 22 so that the detection portion 8a is located at the central portion in the arrangement direction in the upstream portion 42.

  In addition, the bent portion 44 includes, as viewed from the side, the most downstream portion 42b1 of the outer peripheral portion (outer peripheral portion) of the upstream portion 42 and the most upstream portion 43a1 of the outer peripheral portion of the downstream portion 43 around the bent center B. A bulging portion 45 is provided that bulges outward from the bending with respect to a virtual arc R (see FIG. 3B). The bulging portion 45 is formed by a bulging forming portion 25 which is a part of the intermediate portion 24, the bulging forming portion 25 is in the intermediate portion 24, and the bulging portion 45 is in the shape of a knob in the bent portion 44, respectively. And it bulges out in an arc shape in a side view.

  The bulging portion 45 is an upstream portion in the inflow directions D2 and D3 (see also FIG. 2) of the exhaust gas from the combustion chambers C2 and C3 of the second and third cylinders, which are specific cylinders, at the passage inlet 42a. 42 or a position opposite to the passage entrance 42a, and smoothly continues to the upstream portion 42 along the wall surface 24s of the bent portion 44 having a gently curved surface or inclined surface, and also has a sharp corner on the downstream portion 43. Smoothly and continuously. Further, the wall surface 25s of the bulging portion 45 (that is, the inner surface of the bulging forming portion 25) is a smooth concave curved surface or flat surface having no sharp corners. The bulging portion 45 that constitutes a part of the introduction passage 41 is a concave space that is formed in the outer peripheral portion of the bending portion 44 so as to be bent outwardly. 44 passage areas increase.

  Referring to FIG. 1, FIG. 3 and FIG. 4, the introduction cone 21 is composed of first and second halves 21a and 21b formed by pressing a metal plate material. It is divided substantially along the center line of the passage 41. The first and second halves 21a and 21b are fitted together by their fitting portions 21a1 and 21b1, and then joined by welding or the like. The first half 21a has an upper part of the upstream end part 22, a part extending from the upper part of the intermediate part 24 to the rear part, and a rear part of the downstream end part 23, and the second half 21b is a lower part of the upstream end part 22 and an intermediate part. A portion extending from the lower part to the front part of the part 24 and a front part of the downstream end part 23 are provided. For this reason, since the first half body 21a having the bulging portion 25 that forms the bulging portion 45, which is a means for equalizing the flow of exhaust gas at the inlet end face 10a, is manufactured by pressing, the cost is reduced. Is done.

  When the bulging portion 45 is divided into two substantially equal to the upstream portion 45a and the downstream portion 45b, the upstream portion 45a is provided at a position facing the passage inlet 42a in the inflow directions D2 and D3, and the downstream portion 45b is In the inflow directions D2 and D3, they are located directly upstream of the downstream portion 43 without facing the passage inlet 42a and closer to the catalytic converter 10 than the passage inlet 42a in the central axis Lc direction. Therefore, the exhaust gas maintaining the flow direction at the passage inlet 42a flows into the upstream portion 45a. The exhaust gas flowing into the collecting port 6 and the passage inlet 42a differs in the mainstream inflow direction corresponding to each of the combustion chambers C1 to C4. In this embodiment, as shown in FIG. The main flows F2, F3 of the exhaust gas from the plurality of combustion chambers C2, C3 that are between the combustion chambers C1, C4 at both ends in the direction flow in a straight line through the collecting port 6 and the passage inlet 42a, It reaches the upstream portion 45a. The shape of the exhaust port 5 may be formed so that the exhaust gas from all the combustion chambers C1 to C4 flows in a straight line through the collecting port 6 and the passage inlet 42a and reaches the upstream portion.

  Further, in the portion forming the downstream portion 45b in the wall surface 25s, the shelf portion 25s3 is a wall surface in which the normal of the wall surface is directed in the direction opposite to the inlet end surface 10a in the central axis direction on the plane including the central axis Lc. Is a partial conical shape which is a part of a substantially conical shape whose diameter increases toward the upstream side of the exhaust gas. As a result, when the exhaust gas that becomes the bent flow is swiveled around the central axis Lc, the swivel is maintained also in the shelf portion 25s3. Then, the depth W of the shelf 25s3 or the degree of bulging of the bulging portion 45 decreases as the distance from a symmetry plane Hc described later in the circumferential direction about the central axis Lc decreases (see FIGS. 3C and 4). ). Further, the tangent line M (see FIG. 5A) in the vicinity of the upstream portion of the downstream portion 43 of the shelf portion 25s3 on the plane including the central axis Lc is the center N (the inlet end surface 10a and the center) at the inlet end surface 10a. Intersects with the inlet end face 10a at a position farther from the bulging portion 45 than the center N).

  The bulging portion 45 is formed substantially symmetrically with a plane including the central axis Lc of the catalytic converter 10 as a symmetry plane Hc (in this embodiment, coincides with the center plane H), and the passage inlet 42a and the upstream portion 42 are also formed. A shape having the symmetry plane Hc is formed. Then, as shown in FIG. 3C, both the wall surfaces 25s1, 25s2 of the bulging portion 45 in the arrangement direction or the direction orthogonal to the symmetry plane Hc and the bent portions 44 respectively connected to the both wall surfaces 25s1, 25s2 are provided. Both wall surfaces 24s1, 24s2, and both wall surfaces 22s1, 22s2 of upstream portion 42 (or passage walls of bulge forming portion 25, intermediate portion 24, and upstream end portion 22) are in the direction of the central axis of catalytic converter 10 (hereinafter, (Referred to as “plan view”), it is tapered in the flow direction of the exhaust gas and substantially parallel to the inflow directions D2 and D3 of the exhaust gas from the two combustion chambers C2 and C3 (see also FIG. 2). ).

  Furthermore, the bulging portion 45 bulges outward from the most upstream portion 43a of the downstream portion 43 that is substantially concentric with the inlet end face 10a in the radial direction about the central axis Lc. The degree of bulging of the bulging portion 45 is such that, in a side view, the bulging amount P of the largest bulging portion is in the range of about 1/3 to about 1/2 of the passage diameter of the passage section of the most upstream portion 43a. is there.

Next, operations and effects of the embodiment configured as described above will be described.
2 and 5, the main flow F2, F3 of the exhaust gas from the combustion chambers C2, 3 close to the symmetry plane Hc in the arrangement direction is the same direction as the outflow direction from the exhaust port 5, the inflow direction D2. , D3 flows into the passage inlet 42a and flows in a straight line through the upstream portion 42 substantially parallel to the wall surfaces 22s1, 22s2. The exhaust gases from the combustion chambers C1 to C4 flow into the upstream portion 42 or the bent portion 44 and the bulging portion 45 facing the passage inlet 42a in the inflow direction at the passage inlet 42a, or with respect to the symmetry plane Hc. Since the air flows into the bent portion 44 and the bulging portion 45 at a small inclination angle, the flow tends to cause a non-uniform state of the flow at the inlet end surface 10a of the catalytic converter 10.

  Part of the exhaust gas at the bent portion 44 flows straight into the bulging portion 45 along the wall surfaces 24s1, 24s2 and the wall surfaces 25s1, 25s2, and in the bulging portion 45, the bulging portion 45 Of the exhaust gas at the passage inlet 42a is reversed with respect to the inflow directions F2a and F3a (see FIG. 5A) in a side view, that is, the inflow direction F2a. , F3a has a velocity component in the opposite direction. The deflected flow Fa is directed from the upstream of the most upstream portion 43a of the downstream portion 43 toward the bent inner side and the inlet end surface 10a. More specifically, the tangent M of the shelf portion 25s3 of the wall surface 25s is the inlet end surface. The center N of 10a or a position farther from the bulging portion 45 than the center N crosses the inlet end face 10a, and flows out toward the center N or a bent inward portion from the center N in a plane including the center axis Lc. To do.

  As described above, the bent portion 44 of the introduction passage 41 in the exhaust catalyst device A of the internal combustion engine E including the cylinder head 2 in which the collective exhaust port 4 is formed has the outermost peripheral portion of the upstream portion 42 in a side view. Since the bulging portion 45 bulging outward from the virtual arc R connecting the downstream portion 42b1 and the most upstream portion 43a1 of the outer peripheral portion of the downstream portion 43 is provided, the bent portion 44 of the introduction passage 41 has the exhaust gas. Therefore, the flow of the exhaust gas at the inlet end face 10a is biased toward the outer portion of the inlet end face 10a (that is, the non-uniform flow state). However, since the bulging portion 45 becomes a deflection flow Fa toward the inner portion at the inlet end surface 10a, the flow of exhaust gas at the inner portion of the inlet end surface 10a is larger than that of the introduction passage 41 without the bulging portion 45. On the other hand, the flow toward the outer portion of the inlet end face 10a is reduced.

Further, since the deflection flow Fa is generated by the bulging portion 45, unlike the protruding wall that protrudes inwardly to generate the deflection flow, the passage resistance does not increase in order to generate the deflection flow Fa. Since the passage area of the introduction passage 41 is increased by the bulging portion 45, an increase in passage resistance in the introduction passage 41 is suppressed. Furthermore, since the bulging portion 45 is provided in the bent portion 44, the exhaust gas easily flows into the bulging portion 45 as compared with the case where a portion bulging to the side of the linear passage is provided. A highly directional deflected flow Fa can be generated.
As a result, the flow of exhaust gas in the inner portion of the inlet end face 10a is increased by the deflected flow Fa generated by the bulging portion 45, and the flow of exhaust gas on the inlet end face 10a is made uniform. For this reason, the purification rate of the catalytic converter 10 is improved, the local deterioration of the catalytic converter 10 due to the non-uniform flow state is prevented, and the durability of the catalytic converter 10 is improved. In addition, since the effect of the passage resistance in the introduction passage 41 is suppressed, an increase in the back pressure in the exhaust passage is suppressed, and good exhaust efficiency can be ensured. Further, since the bulging portion 45 is provided in the bent portion 44, a highly directional deflected flow Fa can be generated, and the deflected flow Fa effective for uniforming the flow of exhaust gas at the inlet end face 10a can be generated. Can be generated.

  Further, both wall surfaces 25s1, 25s2 of the bulging portions 45 in the arrangement direction are tapered in the flow direction of the exhaust gas in a plan view, and exhaust from the combustion chambers C2, C3 of the second and third cylinders. By being substantially parallel to the inflow directions D2 and D3 of the gas at the passage inlet 42a, the main flows F2 and F3 of the exhaust gas from the combustion chambers C2 and C3 are caused by the wall surfaces 22s1 and 22s2 of the upstream portion 42 and the bent portions 44, respectively. Almost no deflection is caused by the wall surfaces 24 s 1 and 24 s 2, and the air flows into the bulging portion 45. Further, the bulging portion 45 is hardly deflected by the wall surfaces 25 s 1 and 25 s 2. For this reason, the exhaust gas smoothly flows into the bulging portion 45 and the smooth flow gathers at the bulging portion 45 formed in a taper, so that the bulging portion 45 generates a relatively strong flow deflection flow Fa. Can be made. As a result, since the exhaust gas smoothly flows into the bulging portion 45, an increase in passage resistance due to the bulging portion 45 is suppressed, and the nonuniform flow state is effectively corrected by the relatively strong deflection flow Fa. Thus, the flow at the inlet end face 10a is made uniform, and the bulging portion 45 is reduced in size by being tapered.

  The bulging portion 45 is provided at a position facing the passage inlet 42a in the inflow directions F2 and F3 of the exhaust gas from the combustion chambers C2 and C3 at the passage inlet 42a, and the bulging portion 45 has a gentle wall surface 24s. Therefore, the exhaust gas flowing from the combustion chambers C2 and C3 into the introduction passage 41 hardly bends and flows into the bulging portion 45 in a substantially straight line, so that it is relatively strong. Since the deflection flow Fa can be generated, and the upstream portion 42 and the bulging portion 45 are smoothly continuous along the wall surface 24s formed of a gently curved surface or an inclined surface, there is no bulging portion 45. Compared with the case where the gas is greatly bent, the gas flows into the bulging portion 45 while being bent gently, so that the sound generated when the exhaust gas hits the wall surfaces 24s, 25s of the bulging portion 44 and the bulging portion 45 is reduced. As a result, the non-uniform flow state is effectively corrected by the relatively strong deflected flow Fa, the flow at the inlet end surface 10a is made uniform, and the exhaust gas strikes the wall surfaces 24s and 25s of the introduction passage 41. Since the generated sound is reduced, the noise generated in the exhaust catalyst device A provided with the introduction passage 41 and thus the exhaust passage device 41 provided with the introduction passage 41 is reduced.

  Referring to FIGS. 2 and 6, the main flows F1 and F4 of the exhaust gas from the combustion chambers C1 and C4 farther from the symmetry plane Hc in the arrangement direction than the combustion chambers C2 and C3 flow out from the exhaust port 5, respectively. Inflow directions D1 and D4, which are the same as the directions, flow into the passage inlet 42a in a straight line, and are deflected by the wall surfaces 22s2 and 22s1 of the upstream portion 42 or the wall surfaces 24s2 and 24s1 of the bent portion 44 and from the combustion chambers C1 to C4 A flow having a stronger swirl component than the exhaust gas flows through the bent portion 44.

  A part of the exhaust gas in the bent portion 44 flows into the bulging portion 45 in a state having a strong swirling component, and becomes a deflected flow Fb that is swung in the bulging portion 45 and reversed to the bent inward. This deflection flow Fb is a flow having a weak directivity and a small flow velocity compared to the deflection flow Fa generated by the exhaust gas from the combustion chambers C2 and C3.

  For this reason, since the effect of the swirl component is large in the most upstream portion 43a of the downstream portion 43, the flow of the exhaust gas in the downstream portion 43 expanding in a conical shape is larger than that from the combustion chambers C2 and C3. The flow is more uniform. Then, the deflection flow Fb and the swirl flow are combined, and the flow of the exhaust gas at the inlet end surface 10a of the catalytic converter 10 is made uniform.

Hereinafter, an embodiment in which a part of the configuration of the above-described embodiment is changed will be described with respect to the changed configuration.
The introduction cone 21 may be integrally formed with the cylinder head 2 in which the collective exhaust port 4 is formed.
The internal combustion engine E may include an exhaust manifold that is attached to the cylinder head 2 and collects exhaust gas from each of the combustion chambers C1 to C4 without forming the collective exhaust port 4 in the cylinder head 2. In this case, the introduction cone 21 is connected to the exhaust collecting portion of the exhaust manifold. Further, the introduction cone 21 may be integrally formed with the exhaust manifold.
The bending angle of the flow of the exhaust gas in the introduction passage 41 by the bending portion 44 (the angle formed by the flow direction at the passage inlet 42a and the flow direction at the passage outlet 43b in a side view) is substantially a right angle in the above embodiment. However, it may be acute or obtuse.
Further, the wall surface 25s of the bulging portion 45 may be formed as a concave surface by a large number of planes within a range in which the pressure loss does not increase much compared to the embodiment.
The exhaust purification device may include an exhaust purification member that does not use a catalyst substance.
The internal combustion engine E may be a V-type internal combustion engine including a single cylinder or a plurality of cylinders arranged in series, or may be a single-cylinder internal combustion engine. Further, the exhaust catalyst device A may be provided in a combustion device other than the internal combustion engine.
Although the internal combustion engine E is used for a vehicle in the embodiment, it may be used for a ship propulsion device such as an outboard motor having a crankshaft oriented in the vertical direction.

1 is a view of a main part in a side view of a multi-cylinder internal combustion engine provided with an exhaust catalyst device to which the present invention is applied, and schematically shows an engine body. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. It is a figure of the introduction cone of the exhaust-catalyst apparatus of FIG. 1, (A) is a IIIa arrow directional view of FIG. 1, (B) is a b arrow directional view (figure in a side view) of (A), (C) is a c arrow view of (B), (D) is a d arrow view of (B). It is the IV-IV sectional view taken on the line of FIG. FIG. 2 is a schematic diagram showing a flow of exhaust gas from combustion chambers of second and third cylinders in an introduction passage obtained by simulation in the exhaust catalyst device of FIG. 1. (A) shows the flow in the section taken along the line Va-Va in FIG. 3 (C), and (B) shows the flow separately from the combustion chambers of the second and third cylinders in the section taken along the line Vb-Vb in FIG. . It is a schematic diagram which shows the flow of the exhaust gas from the combustion chamber of a 1st, 4th cylinder in the introduction channel | path obtained by the simulation similar to FIG. FIG. 5A is a diagram corresponding to FIG. 5A, and FIG. 5B is a diagram corresponding to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 2 ... Cylinder head, 3 ... Intake port, 4 ... Collective exhaust port, 5 ... Exhaust port, 6 ... Collective port, 7 ... Flange, 8 ... Oxygen concentration sensor, 10 ... Catalytic converter, 10a ... Inlet End face, 11: storage case, 21 ... introduction cone, 22 ... upstream end, 23 ... downstream end, 24 ... middle part, 25 ... bulge forming part, 31 ... outlet cone, 32 ... upstream end, 33 ... downstream End part, 34 ... Derivation passage, 41 ... Introduction passage, 42 ... Upstream part, 42a ... Passage inlet, 43 ... Downstream part, 44 ... Bending part, 45 ... Swelling part, 45s ... Wall surface,
E: Internal combustion engine, A: Exhaust catalyst device, C1 to C4: Combustion chamber, Lc: Center axis, H ... Center plane, Hc: Symmetric plane, K ... Insertion hole, B ... Bending center, R ... Virtual arc, D1 D4 ... Inflow direction, W ... Depth, N ... Center, F1-F4 ... Mainstream, M ... Tangent, P ... Swelling amount.

Claims (4)

An exhaust catalyst device provided with a catalytic converter for purifying exhaust gas and an introduction passage for introducing exhaust gas to an inlet end face of the catalytic converter, wherein the introduction passage has an upstream portion having a passage inlet through which exhaust gas flows. In the exhaust catalyst device comprising a bent portion in which the exhaust gas from the passage inlet becomes a bent flow, and a downstream portion having a passage outlet for flowing the flow of the exhaust gas after bending toward the inlet end surface,
The bent portion has a bulging portion that bulges outward from the virtual arc connecting the most downstream portion of the outer peripheral portion of the upstream portion and the most upstream portion of the outer peripheral portion of the downstream portion in a side view. A part of the exhaust gas at the bent portion flows along the wall surface of the bulging portion, thereby forming a deflected flow that is reversed with respect to the inflow direction of the exhaust gas at the passage entrance in a side view. The exhaust catalyst device according to claim 1, wherein the deflected flow flows out of the bulging portion in a bent inward direction toward the inlet end surface. A cylinder head formed with a collective exhaust port in which exhaust gases from a plurality of combustion chambers arranged in the arrangement direction gather, and a direct type that is connected directly downstream of the outlet of the collective exhaust port to purify exhaust gas A multi-cylinder internal combustion engine including an exhaust catalyst device, wherein the exhaust catalyst device is provided with a catalytic converter for purifying exhaust gas and an introduction passage for guiding exhaust gas to an inlet end face of the catalytic converter, and the introduction passage Are an upstream portion having a passage inlet into which exhaust gas flows, a bent portion in which the exhaust gas from the passage inlet becomes a bent flow, and a passage outlet for causing the flow of the bent exhaust gas to flow out toward the inlet end surface. In the exhaust catalyst device comprising a downstream portion having
The bent portion is provided with a bulging portion that bulges outward from the virtual arc connecting the most downstream portion of the outer peripheral portion of the upstream portion and the most upstream portion of the outer peripheral portion of the downstream portion in a side view. A part of the exhaust gas in the bent portion flows along the wall surface of the bulging portion, thereby becoming a deflected flow reversed with respect to the inflow direction in a side view of the exhaust gas at the passage entrance, The multi-cylinder internal combustion engine characterized in that the deflected flow flows out of the bulging portion while being bent inward and directed toward the inlet end face.   Both wall surfaces of the bulging portions in the arrangement direction are tapered in the flow direction of the exhaust gas when viewed from the central axis direction of the catalytic converter, and the exhaust gas from the combustion chamber of a specific cylinder The multi-cylinder internal combustion engine according to claim 2, wherein the multi-cylinder internal combustion engine is substantially parallel to an inflow direction at the passage entrance. The bulging portion is provided at a position facing the passage inlet in the exhaust gas inflow direction at the passage inlet, and the bulging portion smoothly continues to the upstream portion with a gentle wall surface. The exhaust catalyst device according to claim 1 or the multi-cylinder internal combustion engine according to claim 2 or 3.

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