JP2020012396A - Exhaust structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent air flowing into an engine room from hitting a catalytic converter and cooling the catalytic converter as the vehicle travels. A catalytic converter that purifies exhaust gas is connected to a downstream end of an exhaust manifold 31. An insulator 60 is provided so as to surround the exhaust manifold 31 and the catalytic converter from the outside, and the internal combustion engine side of the insulator 60 is open. The exhaust manifold 31 includes a tubular portion 32 through which exhaust gas flows. A flange 33 projects outward from the end of the tubular portion 32 on the exhaust port side. Further, the exhaust manifold 31 includes first fins 35 and second fins 36 that project outward from the flange 33 when viewed from the axial direction at the opening on the exhaust port side of the tubular portion 32. .. [Selection diagram] Fig. 4

Description

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

  The exhaust manifold of Patent Literature 1 includes a plurality of branch pipes connected to an exhaust port of an internal combustion engine, and a merging pipe in which the plurality of branch pipes are integrated. A catalytic converter for purifying exhaust gas is attached downstream of the exhaust manifold (merging pipe). Exhaust gas discharged from each exhaust port of the internal combustion engine flows further downstream through each branch pipe, merging pipe, and catalytic converter.

JP-A-2017-115681

  In the exhaust structure as disclosed in Patent Document 1, in order for the catalytic converter to purify exhaust gas, the temperature of the catalyst inside the catalytic converter needs to be raised to an activation temperature or higher. However, for example, when the vehicle is running, air flowing into the engine room along with the running of the vehicle hits the catalytic converter to cool the catalytic converter, which may hinder the temperature rise of the catalytic converter.

  In order to solve the above-mentioned problems, the present invention provides an exhaust manifold connected to an exhaust port of an internal combustion engine, through which exhaust gas flows, and an exhaust manifold connected to a downstream end of the exhaust manifold, and the exhaust gas is heated to an activation temperature or higher. An exhaust structure including a catalytic converter to be purified, and an insulator surrounding the exhaust manifold and the catalytic converter from outside, wherein the internal combustion engine side of the insulator is open, and the exhaust manifold has a tubular shape into which exhaust gas flows. Part, the tubular portion protrudes outward from the end on the exhaust port side, the flange connected to the exhaust port, when viewed from the axial direction at the opening on the exhaust port side of the tubular portion. And fins projecting outward from the flange.

  In the above configuration, since the internal combustion engine side of the insulator is open, the air that has flowed into the engine room as the vehicle travels can flow into the insulator from the internal combustion engine side of the insulator. In this regard, in the above configuration, the fins of the exhaust manifold protrude outward, and a part of the open portion of the insulator is closed by the fins. Therefore, it is possible to suppress the air from flowing into the insulator, and also to prevent the temperature rise of the catalytic converter from being hindered due to the air flowing into the insulator.

FIG. 1 is a plan view of an internal combustion engine and an exhaust structure applied to the internal combustion engine. FIG. 2 is a plan view of an exhaust manifold and a catalytic converter. FIG. 2 is a plan view of the exhaust manifold and the catalytic converter viewed from the internal combustion engine side. FIG. 2 is a plan view of the exhaust structure viewed from the internal combustion engine side.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the internal combustion engine 10 includes a cylinder block 11 in which a cylindrical cylinder 12 is partitioned. The cylinder 12 is open on the upper surface of the cylinder block 11. Although the cylinder 12 is divided into a plurality of sections, FIG. 1 shows only one cylinder 12. A crankcase 13 is fixed to a lower end of the cylinder block 11. The crankcase 13 sandwiches and supports the crankshaft 14 together with the cylinder block 11. An oil pan 15 for storing oil for lubricating various parts of the internal combustion engine 10 is fixed to a lower end of the crankcase 13. The crankcase 13 and the oil pan 15 may be collectively referred to as an “oil pan”.

  A cylinder head 21 is fixed to an upper end of the cylinder block 11. On the lower surface of the cylinder head 21, a concave portion 22 having a circular shape in plan view is depressed upward. The recess 22 is arranged to face the cylinder 12 in the cylinder block 11. An intake port 23 for introducing intake air into the cylinder 12 is defined in the cylinder head 21. One side of the intake port 23 is open to the recess 22, and the other side of the intake port 23 is open to the side surface (the left side surface in FIG. 1) of the cylinder head 21. A plurality of intake ports 23 are provided corresponding to the number of cylinders 12. FIG. 1 shows only one intake port 23.

  An exhaust port 24 for exhausting the exhaust from the cylinder 12 is defined in the cylinder head 21. One side of the exhaust port 24 is branched into a plurality of portions corresponding to the number of the cylinders 12, and each of the branched passages is opened to the recess 22. On the other side of the exhaust port 24, the branched passages are gathered and gathered into one passage, and the gathered passage is opened on the side surface (the right side surface in FIG. 1) of the cylinder head 21. FIG. 1 shows only one of the branched passages in the exhaust port 24. A head cover 25 that covers the internal space of the cylinder head 21 from above is attached to the upper surface of the cylinder head 21.

  As shown in FIG. 2, an exhaust manifold 31 is connected to an opening of the exhaust port 24 on the side surface of the cylinder head 21. The tubular portion 32 of the exhaust manifold 31 has a substantially elliptical tubular shape, and is curved so that the downstream side of the exhaust (the side opposite to the exhaust port 24) is directed downward. A plate-like flange 33 projects outward from an end of the tubular portion 32 on the exhaust upstream side (exhaust port 24 side).

  As shown in FIG. 3, the plan view shape of the flange 33 is a substantially square shape (a substantially trapezoidal shape). At four corners of the rectangular shape of the flange 33, bolt holes H1 penetrate in the thickness direction of the flange 33. Both bolts are fixed in a state where the flange 33 of the exhaust manifold 31 is in contact with the side surface of the cylinder head 21 by a bolt (not shown) inserted into the bolt hole H1.

  As shown in FIG. 2, a catalytic converter 40 is connected to a downstream end of the exhaust manifold 31. The catalytic converter 40 can be roughly divided into an upstream part 41, a middle part 42, and a downstream part 43 in order from the upstream side. The upstream portion 41 of the catalytic converter 40 has a circular tubular shape whose diameter increases toward the downstream side. The diameter at the upstream end of the upstream portion 41 is substantially the same as the diameter at the downstream end of the exhaust manifold 31. The downstream end of the upstream portion 41 is connected to a tubular middle flow portion 42. The diameter of the middle part 42 is substantially the same as the diameter of the downstream end of the upstream part 41. Further, the diameter of the midstream portion 42 is substantially constant over the entire axial direction. A three-way catalyst for purifying nitrogen oxides and sulfur oxides contained in the exhaust gas is accommodated inside the middle flow section 42. The three-way catalyst exhibits a purification ability for nitrogen oxides and sulfur oxides when the temperature is raised to an activation temperature (for example, 500 to 700 degrees) or higher. The downstream end of the midstream portion 42 is connected to a tubular downstream portion 43 whose diameter decreases toward the downstream side. The diameter at the upstream end of the downstream part 43 is the same as the diameter of the middle part 42. A part of the downstream side of the downstream part 43 is formed in a tubular shape having a constant diameter, and another exhaust pipe (not shown) is connected to this part.

  As shown in FIG. 3, a tubular exhaust gas recirculation pipe 51 is connected to a downstream portion 43 of the catalytic converter 40. The exhaust gas recirculation pipe 51 is routed to the internal combustion engine 10 side. In this embodiment, the exhaust gas recirculation pipe 51 is arranged so as to extend alongside the exhaust manifold 31 and the catalytic converter 40. A plate-like flange 52 projects outward from an end of the exhaust gas recirculation pipe 51 on the downstream side (the side opposite to the downstream portion 43). The planar shape of the flange 52 is substantially elliptical. At both ends in the major diameter direction of the flange 52, bolt holes H5 penetrate in the thickness direction of the flange 52. The flange 52 of the exhaust gas recirculation pipe 51 is connected to another pipe (not shown) by a bolt (not shown) inserted into the bolt hole H5. The exhaust gas recirculation pipe 51 is connected to the intake passage of the internal combustion engine 10 via another pipe. In FIG. 2, the exhaust gas recirculation pipe 51 is shown by a two-dot chain line.

  A plate-shaped bracket 53 extends from the surface of the flange 52 on the side opposite to the other pipe (in FIG. 3, on the rear side of the paper). The bracket 53 extends obliquely downward on the upstream side (downstream side of the catalytic converter 40) of the exhaust gas recirculation pipe 51. The plan view shape of the bracket 53 is substantially square. A bolt hole H6 penetrates a tip portion of the bracket 53 in the thickness direction of the bracket 53.

  As shown in FIGS. 2 and 3, a plate-like first fin 35 is formed from the surface of the flange 33 of the exhaust manifold 31 opposite to the internal combustion engine 10 (the right side in FIG. 2, the back side in FIG. 3). Extending. The first fin 35 extends from a portion of the flange 33 below the opening on the exhaust port 24 side in the tubular portion 32. The first fin 35 extends obliquely downward on the downstream side of the tubular portion 32 as a whole. As shown in FIG. 3, the first fin 35 is located below the outer edge of the flange 33 when viewed from the axial direction of the opening of the tubular portion 32 on the exhaust port 24 side (the thickness direction in FIG. 3). Has been reached. That is, the first fins 35 project beyond the flange 33.

  As shown in FIG. 3, when the width of the first fin 35 in the direction perpendicular to the extending direction is defined as the width, the width of the first fin 35 becomes shorter toward the distal end. At the tip of the first fin 35 in the extending direction, a bolt hole H2 penetrates in the thickness direction of the first fin 35.

  As shown in FIGS. 2 and 3, a plate-like second fin 36 extends from a surface of the flange 33 of the exhaust manifold 31 on the side opposite to the internal combustion engine 10. The second fins 36 extend from a portion of the flange 33 closer to the exhaust gas recirculation pipe 51 than the opening of the tubular portion 32 on the exhaust port 24 side (the front side in FIG. 2 and the right side in FIG. 3). The second fins 36 as a whole extend obliquely so as to rise from the flange 33 and approach the exhaust gas recirculation pipe 51 closer to the distal end. As shown in FIG. 3, the second fin 36 extends from the outer edge of the flange 33 to the exhaust gas recirculation pipe 51 side when viewed from the axial direction of the opening of the tubular portion 32 on the exhaust port 24 side. That is, the second fins 36 extend beyond the flange 33.

  The second fin 36 has a triangular shape in which the width becomes narrower toward the distal end as a whole. A part of the tip of the second fin 36 is bent so that the tip of the second fin 36 faces the exhaust gas recirculation pipe 51 side. At the tip of the second fin 36 in the extending direction, a bolt hole H3 penetrates in the thickness direction of the second fin 36.

  As shown in FIG. 4, the exhaust manifold 31, the catalytic converter 40, and the exhaust gas recirculation pipe 51 are surrounded by a resin insulator 60 from the outside. The insulator 60 has a cylindrical shape as a whole, and the exhaust manifold 31, the catalytic converter 40, and the exhaust gas recirculation pipe 51 are housed inside the cylindrical shape. As described above, since the insulator 60 has a cylindrical shape, the side of the insulator 60 that is one side in the axial direction of the insulator 60 is open.

  The insulator 60 includes an upper insulator 61 constituting an upper portion of the insulator 60 and a lower insulator 62 constituting a lower portion. Each of the upper insulator 61 and the lower insulator 62 has a shape curved to one side in a sectional view. The upper insulator 61 and the lower insulator 62 are disposed so as to face each other such that the curved concave sides face each other, so that the insulator 60 as a whole has a cylindrical shape.

  The upper insulator 61 is fixed to the exhaust manifold 31 by a bolt (not shown) inserted into the bolt hole H3 of the second fin 36 in the exhaust manifold 31. Although not shown, the upper insulator 61 is also fixed to the catalytic converter 40 via bolts, brackets, and the like.

  The lower insulator 62 is fixed to the exhaust manifold 31 by a bolt (not shown) inserted into the bolt hole H2 of the first fin 35 in the exhaust manifold 31. Further, the lower insulator 62 is fixed to the exhaust gas recirculation pipe 51 by a bolt (not shown) inserted into a bolt hole H6 of the bracket 53 of the exhaust gas recirculation pipe 51. Although not shown, the lower insulator 62 is also fixed to the catalytic converter 40 via a bolt, a bracket, or the like.

The operation and effect of the present embodiment will be described.
It is assumed that the internal combustion engine 10 configured as described above is mounted on a vehicle such that the intake port 23 is located on the vehicle front side and the exhaust port 24 is located on the vehicle front side. In this case, when the vehicle travels forward, air flowing into the engine room of the vehicle flows from the intake port 23 side of the internal combustion engine 10 to the exhaust port 24 side. Then, a part of the air flowing so as to flow toward the exhaust port 24 tends to flow into the insulator 60 via the opening of the insulator 60 on the internal combustion engine 10 side. If a large amount of air flows into the insulator 60, the catalytic converter 40 housed inside the insulator 60 is cooled by the flowed air. In particular, immediately after the start of the internal combustion engine 10, the catalytic converter 40 should be activated as early as possible so that the exhaust gas purifying ability can be exhibited. When a large amount of air flows into the insulator 60 under the condition immediately after the start of the internal combustion engine 10, the temperature rise of the catalytic converter 40 is prevented, and the time until the catalytic converter 40 is activated is prolonged. I will.

  In the above-described embodiment, in the exhaust manifold 31, the first fin 35 and the second fin 36 project beyond the flange 33. Therefore, a part of the opening of the insulator 60 on the side of the internal combustion engine 10 is closed by the first fin 35 and the second fin 36. Therefore, even if air tries to flow in from the opening of the insulator 60 on the side of the internal combustion engine 10, the flow is obstructed by the first fin 35 and the second fin 36. And it can suppress that air reaches the downstream of the 1st fin 35 and the 2nd fin 36 inside the insulator 60, ie, the catalyst converter 40 side. As a result, for example, immediately after the start of the internal combustion engine 10, it is also possible to prevent the temperature rise of the catalytic converter 40 from being hindered due to the air flowing into the insulator 60.

  By the way, since high-temperature exhaust gas flows into the tubular portion 32 of the exhaust manifold 31, when the internal combustion engine 10 is driven, the temperature of the exhaust manifold 31 can be considerably high. On the other hand, when the internal combustion engine 10 is not operating, the temperature of the exhaust manifold 31 decreases to a temperature corresponding to the outside air temperature. When such a temperature change occurs repeatedly in the exhaust manifold 31, the bolts inserted into the bolt holes H1 of the flange 33 may be loosened.

  In this regard, in the above-described embodiment, since the air that is going to flow into the insulator 60 is blocked by the first fin 35 and the second fin 36, the first fin 35 and the second fin 36 have a relatively large amount of air. Air will hit. That is, the first fin 35 and the second fin 36 are cooled by the air flowing into the insulator 60, and the flange 33 is also cooled accordingly. That is, the first fin 35 and the second fin 36 also function as “cooling fins” for cooling the flange 33. By cooling the flange 33 efficiently, the flange 33 can be prevented from being heated to an excessively high temperature, and the width of the temperature change occurring in the flange 33 can be reduced.

  In addition, a bolt hole H2 is provided at the tip of the first fin 35 of the embodiment, and a bolt hole H3 is provided at the tip of the second fin 36. That is, the first fin 35 and the second fin 36 also function as “brackets” for fixing the insulator 60. Therefore, for example, compared to the case where each fin and a “bracket” for fixing the insulator 60 are separately provided, it is possible to contribute to the simplification and downsizing of the exhaust structure 30.

This embodiment can be implemented with the following modifications. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-The structure of the internal combustion engine 10 in the said embodiment is an illustration to the last, and can be changed suitably. For example, in the above embodiment, the exhaust port 24 merges into one collective passage on the downstream side inside the cylinder head 21, but the exhaust ports 24 do not merge, and May be open. In this case, the exhaust manifold 31 may include a number of branch pipes corresponding to the number of openings of the exhaust port 24, and a merging pipe connected downstream of each of the branch pipes and merging with the branch pipe. Even with such a structure of the exhaust manifold 31, if the fins extending beyond the flange extending from the upstream end of the branch pipe are employed, the same effects as in the above embodiment can be obtained.

  The exhaust gas recirculation pipe 51 is not essential in the exhaust structure 30. If the vehicle is not equipped with an exhaust gas recirculation device (EGR device) that returns exhaust gas to the intake side, the exhaust gas recirculation pipe 51 will not exist. Even in such a case, if the insulator 60 surrounds the exhaust manifold 31 and the catalytic converter 40 from the outside, the structure of the first fin 35 and the second fin 36 of the above embodiment can be applied.

  -The direction of the internal combustion engine 10 when mounted on a vehicle is not limited to the example of the above embodiment. For example, the internal combustion engine 10 may be mounted on the vehicle such that the intake port 23 of the internal combustion engine 10 faces one side in the vehicle width direction and the exhaust port 24 of the internal combustion engine 10 faces the other side in the vehicle width direction. Regardless of the orientation of the internal combustion engine 10, if the internal combustion engine 10 of the insulator 60 is open, air can flow into the insulator 60 from the open location. And the second fin 36 are effective.

  In the exhaust manifold 31, one of the first fin 35 and the second fin 36 may be omitted. If at least one fin projects beyond the flange 33, air can be prevented from flowing into the catalytic converter 40 inside the insulator 60 as compared with a case where such a fin does not exist.

  In the exhaust manifold 31, instead of or in addition to the first fins 35 and the second fins 36, other fins that extend beyond the flange 33 may be provided. Depending on the overall shape of the internal combustion engine 10 and the arrangement of devices around the internal combustion engine 10, some of the openings of the insulator 60 may be located where air can easily flow in and some may be difficult. In consideration of such circumstances, for example, if fins are provided at least at locations where air easily flows, it is possible to effectively suppress air from flowing into the insulator 60.

  In the exhaust manifold 31, fins may extend from the tubular portion 32. If the fins extending from the tubular portion 32 project beyond the flange 33, the fins can prevent air from flowing downstream (toward the catalytic converter 40) from the tubular portion 32.

  -The bolt hole H3 in the first fin 35 may be omitted. When the bolt hole H3 is omitted, a structure for fixing the insulator 60 may be provided in a portion other than the first fin 35 in the exhaust manifold 31, the catalytic converter 40, and other devices existing around the internal combustion engine 10. In this regard, the same applies to the bolt hole H6 of the second fin 36.

The insulator 60 may be formed by combining three or more members into a cylindrical shape, or may be formed by a single cylindrical member.
-The shape of the insulator 60 is not limited to a cylindrical shape as in the above embodiment. For example, the insulator 60 may be composed of only the upper insulator 61 or may be composed of only the lower insulator 62. Even in these cases, the configuration of the first fin 35 and the second fin 36 of the above embodiment can be applied as long as the internal combustion engine 10 side of the insulator 60 is open.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder block, 12 ... Cylinder, 13 ... Crankcase, 14 ... Crankshaft, 15 ... Oil pan, 21 ... Cylinder head, 22 ... Concave part, 23 ... Intake port, 24 ... Exhaust port, 25 ... Head cover, 30 exhaust structure, 31 exhaust manifold, 32 tubular part, 33 flange, 35 first fin, 36 second fin, 40 catalytic converter, 41 upstream part, 42 middle part, 43 part Downstream part, 51 ... Exhaust gas recirculation pipe, 52 ... Flange, 53 ... Bracket, 60 ... Insulator, 61 ... Upper insulator, 62 ... Lower insulator, H1 ... Bolt hole, H2 ... Bolt hole, H3 ... Bolt hole, H5 ... Bolt Hole, H6 ... bolt hole.

Claims (1)

An exhaust manifold that is connected to an exhaust port of the internal combustion engine and into which exhaust gas flows;
A catalytic converter connected to the downstream end of the exhaust manifold and purifying the exhaust by raising the temperature to an activation temperature or higher;
And an insulator surrounding the exhaust manifold and the catalytic converter from outside.
The internal combustion engine side of the insulator is open,
The exhaust manifold,
A tubular portion into which exhaust gas flows,
A flange that protrudes outward from an end on the exhaust port side of the tubular portion and is connected to the exhaust port,
A fin projecting outward from the flange when viewed from the axial direction of the opening on the exhaust port side of the tubular portion.