JP2018076854A - Exhaust system structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system structure for an internal combustion engine capable of effectively utilizing a downstream side exhaust emission control part for purifying exhaust gas after passing though an upstream side exhaust emission control part.SOLUTION: The exhaust system structure for the internal combustion engine includes a first exhaust emission control part for purifying exhaust gas from the internal combustion engine, and a second exhaust emission control part provided on the downstream side of the first exhaust emission control part. The first axis line of the first exhaust emission control part is inclined to the second axis line of the second exhaust emission control part. When the cross section of the first exhaust emission control part is projected in the direction of the first axis line, the shape of an image projected on the upstream side end face of the second exhaust emission control part is the same as the shape of the upstream side end face of the second exhaust emission control part.SELECTED DRAWING: Figure 2

Description

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

  Conventionally, a catalyst that is provided in an exhaust system of an internal combustion engine and removes carbon monoxide and unburned hydrocarbons in exhaust gas discharged from the internal combustion engine, and a filter that removes particulate matter in the exhaust gas. An exhaust emission control device is known.

  Patent Document 1 discloses an exhaust purification device in which a filter (second exhaust purification unit) is provided on the downstream side of a catalyst (first exhaust purification unit). In the exhaust emission control device described in Patent Document 1, the catalyst and the filter are arranged in a straight line so that their center axes coincide with each other, and the diameter of the filter is made larger than the diameter of the catalyst. By doing so, the area of the upstream end face of the filter is increased and the dust collection capability is improved.

JP 2014-105664 A

  By the way, in order to effectively use the exhaust gas purification unit (catalyst, filter, etc.) of the exhaust gas purification device, it is desired that the exhaust gas flow evenly into the exhaust gas purification unit.

  However, the exhaust gas purification device described in Patent Document 1 has a problem that exhaust gas hardly flows near the outer periphery of the upstream end face of the filter, and the filter cannot be effectively used.

  An object of the present invention is to provide an exhaust system structure of an internal combustion engine that can effectively utilize a second exhaust purification unit that purifies exhaust gas after passing through the first exhaust purification unit.

  An exhaust system structure of an internal combustion engine according to the present invention includes a first exhaust purification unit that purifies exhaust gas from the internal combustion engine, and a second exhaust purification unit that is provided downstream of the first exhaust purification unit. A first axis of the first exhaust purification unit is inclined with respect to a second axis of the second exhaust purification unit, and a cross-section of the first exhaust purification unit is When projected in the axial direction of 1, the shape of the image projected on the upstream end face of the second exhaust purification unit is the same as the shape of the upstream end face of the second exhaust purification unit.

  According to the exhaust system structure of the internal combustion engine of the present invention, the exhaust gas after passing through the first exhaust purification unit can be made to uniformly flow into the second exhaust purification unit, and the second exhaust purification unit is effectively used. It can be used for.

Schematic showing an exhaust system according to an embodiment of the present invention. Partial enlarged view of FIG. Schematic diagram showing the first modification Schematic diagram showing a second modification Schematic diagram showing a third modification

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, embodiment described below is an example and this invention is not limited by this embodiment.

  FIG. 1 is a schematic view showing an exhaust system according to the present invention. FIG. 2 is a partially enlarged view of FIG. 1 and 2, the X axis, the Y axis, and the Z axis are drawn. In the following description, the left-right direction in FIGS. 1 and 2 is referred to as the X direction or the vehicle front-rear direction, the right direction is “+ X direction” or “vehicle front side”, and the left direction is “−X direction” or “vehicle rear side”. That's it. 1 and 2 is referred to as a Y direction or a vehicle vertical direction, an upward direction is referred to as a “+ Y direction” or “vehicle upper side”, and a downward direction is referred to as a “−Y direction” or “vehicle lower side”. 1 and 2, the direction perpendicular to the paper surface is referred to as the Z direction or the vehicle width direction, the front direction is referred to as "+ Z direction" or "vehicle right side", and the back direction is referred to as "-Z direction" or "vehicle left side". . Further, the upstream side and the downstream side in the flow direction of the exhaust gas flowing through the exhaust passage are simply referred to as “upstream side” and “downstream side”.

  As shown in FIGS. 1 and 2, the exhaust system 1 includes an exhaust manifold 3 provided on the right side of the vehicle of the engine 2, a turbocharger 4 connected to a collecting portion of the exhaust manifold 3, and a turbocharger. 4, an upstream exhaust passage 5 extending from 4, an aftertreatment device 6, and a downstream exhaust passage 7. In the case of the present embodiment, the above-described members are arranged on the right side of the engine 2 in the vehicle. However, the arrangement of the above members with respect to the engine 2 in the vehicle width direction is not limited to the illustrated structure.

  The direction (opening direction), size, and shape of the exhaust gas outlet 4a of the turbocharger 4 are comprehensively determined based on the shape, size, installation location, and the like of the aftertreatment device 6. Here, the direction of the exhaust gas outlet 4a is the -X direction. The shape of the exhaust gas outlet 4a is a general circular shape. The installation location of the post-processing device 6 is set at a position in the −X direction of the turbocharger 4.

  The upstream exhaust passage 5 is configured by an internal space of a hollow tubular straight tube 8. The straight pipe 8 causes the exhaust gas flowing into the internal space from the upstream opening to flow linearly along the extending direction of the straight pipe 8 (that is, the direction of the axis 8a) and flows out from the downstream opening. It has a function as a flow path. In the case of this configuration example, the shaft 8 a corresponds to the central axis of the straight tube 8.

  The upstream end of the straight tube 8 is connected to the exhaust gas outlet 4a. On the other hand, the downstream end of the straight pipe 8 is fixed to the upstream end of a case 10 (described later) of the post-processing device 6. The extending direction (that is, the direction of the shaft 8a), the length, and the hollow cross-sectional shape of the straight tube 8 are comprehensive based on the direction of the exhaust gas outlet 4a, the position of the DOC 11 (described later) in the aftertreatment device 6, and the like. Determined.

  Note that the hollow cross-sectional shape of the straight tube 8 refers to a transverse cross-section of the internal space defined by the inner peripheral surface of the straight tube 8 (cross-sectional shape related to a virtual plane orthogonal to the axis 8a). In other words, the outer shape (the shape of the outer peripheral edge) of the hollow cross-sectional shape of the straight tube 8 matches the cross-sectional shape of the inner peripheral surface of the straight tube 8 with respect to a virtual plane orthogonal to the axis 8a.

  The extending direction of the straight tube 8 is tilted three-dimensionally based on, for example, the position of the DOC 11. Here, in order to make the explanation easy to understand, as shown in FIGS. 1 and 2, the straight tube 8 is extended linearly in the same −X direction as the exhaust gas outlet 4a. Moreover, the hollow cross-sectional shape of the straight tube 8 is the same circular shape as the shape of the exhaust gas outlet 4a.

  The reason why the extending direction and the hollow cross-sectional shape of the straight tube 8 are the same direction and shape as the exhaust gas outlet 4a is that the flow rate of the exhaust gas flowing into the straight tube 8 from the turbocharger 4 is reduced by the straight tube 8 as much as possible. It is for making it flow out to DOC11, maintaining it in a high state without doing. Further, the length of the straight pipe 8 is preferably as short as possible in order to prevent heat dissipation between the turbocharger 4 and the DOC 11 and to suppress a decrease in the flow rate of the exhaust gas.

  As described above, the upstream end of the post-processing device 6 is connected to the downstream end of the straight tube 8. The post-processing device 6 includes a tubular case 10, a DOC 11 for purifying exhaust gas (corresponding to the “first exhaust purification unit” of the present invention), and a diesel particulate filter (DPF) 12 (of the present invention). "Corresponding to the" second exhaust purification unit ") is accommodated.

  The case 10 includes an upstream first case portion 14 and a downstream second case portion 15. The DOC 11 is accommodated in the first case portion 14. The 1st case part 14 makes | forms the tubular shape centering on the axis | shaft 11a (after-mentioned) of DOC11. Further, the DPF 12 is accommodated in the second case portion 15. The second case portion 15 has a tubular shape centering on a shaft 12a (described later) of the DPF 12. As shown in FIG. 2, the second case portion 15 is bent with respect to the first case portion 14. A detailed positional relationship between the DOC 11 and the DPF 12 will be described later.

  DOC11 and DPF12 are hold | maintained at the 1st case part 14 and the 2nd case part 15 with the inorganic mat 13 (refer FIG. 2). The DOC 11 is formed in a column shape having an axis 11a. In the present embodiment, the shaft 11a corresponds to the central axis of the DOC 11. The shaft 11a extends in the direction perpendicular to the upstream end surface 11b of the DOC 11. That is, the cross-sectional shape of the DOC 11 (the cross-sectional shape related to the virtual plane orthogonal to the axis 11a) is the same shape as the upstream end surface 11b.

  Similarly, the DPF 12 is formed in a column shape having a shaft 12a. In this embodiment, the shaft 12a corresponds to the central axis of the DPF 12. The shaft 12a extends in the direction perpendicular to the upstream end surface 12b of the DPF 12. That is, the cross-sectional shape of the DPF 12 (the cross-sectional shape related to the virtual plane orthogonal to the axis 12a) is the same shape as the upstream end surface 12b.

  The installation place of the post-processing device 6 is set at the position in the −X direction of the turbocharger 4 as described above. Here, the DOC 11 and the DPF 12 are not arranged linearly in the −X direction in order to effectively use the installation location, but the axes 11a and 12a are arranged with respect to the X direction, the Y direction, and the Z direction. It is arranged so as to be tilted three-dimensionally. Details of the inclinations of the axes 11a and 12a will be described later.

  In DOC11, for example, platinum, iridium oxide or cobalt oxide as an oxidation catalyst is supported on alumina as a carrier. The DOC 11 has a function of oxidizing unburned gases such as hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas. Note that the basic structure and function of the DOC 11 are the same as those of conventionally known DOCs, and thus detailed description thereof is omitted.

  The DPF 12 arranges a number of cells forming a grid-like exhaust flow path partitioned by porous ceramic partition walls along the flow direction of the exhaust gas, and alternately seals the upstream and downstream sides of these cells. It is configured to stop. The DPF 12 has a function of collecting particulate matter (PM) contained in the exhaust gas. Since the basic structure and function of the DPF 12 are the same as those of conventionally known DPFs, detailed description thereof is omitted.

  A downstream exhaust passage 7 is connected to the downstream end of the post-processing device 6. The exhaust gas purified by the post-processing device 6 passes through the downstream exhaust passage 7 and is led out to the outside. The downstream side of the downstream side exhaust passage 7 extends linearly in the −X direction, and the exhaust gas is led out from the rear end of the downstream side exhaust passage 7 toward the rear of the vehicle.

  Next, details of the structure of the post-processing device 6 will be described. In FIG. 2, the flow of the exhaust gas passing through the DOC 11 and the DPF 12 is indicated by a broken line. Further, FIG. 2 shows a circle P as the shape of the exhaust gas outlet 4a viewed from the direction of the shaft 8a (that is, the hollow cross-sectional shape of the straight tube 8).

  FIG. 2 shows an ellipse Q as the outer shape of the upstream end face 11b of the DOC 11 as viewed from the direction of the axis 11a. As described above, the shape of the upstream end surface 11b of the DOC 11 is the same shape as the cross-sectional shape of the DOC 11. Therefore, the ellipse Q has shown the cross-sectional shape of DOC11.

  Further, FIG. 2 shows an ellipse R as an outer shape of the upstream end face 12b of the DPF 12 as viewed from the direction of the axis 12a. As described above, the shape of the upstream end surface 12b of the DPF 12 is the same as the cross-sectional shape of the DPF 12. Therefore, the ellipse R indicates the cross-sectional shape of the DPF 12.

  The direction of the axis 8a of the straight tube 8 is the -X direction as described above. The axis 11a of the DOC 11 is tilted three-dimensionally with respect to the axis 8a in the -X direction. Here, for easy understanding, as shown in FIG. 2, the axis 11a is tilted by α around the Z axis (counterclockwise) with respect to the axis 8a in the −X direction. That is, the upstream end face 11b of the DOC 11 is inclined by (π / 2−α) around the Z axis (clockwise) with respect to the axis 8a.

  Further, in the present embodiment, the ellipse Q that is the shape of the upstream end surface 11b of the DOC 11 is the upstream end surface of the DOC 11 when the hollow cross-sectional shape (here, circle P) of the straight tube 8 is projected in the −X direction. The shape of the image projected on 11b is the same.

  The shaft 12a of the DPF 12 is tilted three-dimensionally with respect to the shaft 11a. Here, for easy understanding, as shown in FIG. 2, the shaft 12a is tilted by β around the Z axis (counterclockwise) with respect to the shaft 11a. That is, the upstream end surface 12b of the DPF 12 is inclined by (π / 2−β) around the Z axis (clockwise) with respect to the shaft 11a.

  Further, the ellipse R, which is the shape of the upstream end face 12b of the DPF 12, is an image projected on the upstream end face 11b of the DPF 12 when the cross-sectional shape of the DOC 11 (here, the ellipse Q) is projected in the direction of the axis 11a. The shape is the same.

<Effect of this embodiment>
As described above, according to the exhaust system structure of the internal combustion engine according to the present embodiment, the shape of the upstream end surface 12b of the DPF 12 is the upstream end surface when the cross-sectional shape of the DOC 11 is projected in the direction of the axis 11a. The shape of the image projected onto 12b is the same. As a result, the exhaust gas from the DOC 11 flows evenly into the upstream end surface 12b of the DPF 12, including the region near the outer periphery. Therefore, the DPF 12 can be used effectively.

  Moreover, according to the exhaust system structure of the internal combustion engine according to the present embodiment, the DPF 12 can be used effectively, and thus the purification ability of the DPF 12 can be increased. Further, the DPF 12 can be downsized by the amount that the purification ability of the DPF 12 is increased. Further, the exhaust system structure can be saved in space and the cost can be reduced by the size of the DPF 12.

  Further, according to the exhaust system structure of the internal combustion engine according to the present embodiment, the upstream end surface 12b of the DPF 12 is inclined with respect to the shaft 11a of the DOC 11. As a result, the exhaust gas that flows linearly through the DOC 11 flows evenly into the upstream end surface 12b of the DPF 12, so that the flow direction of the exhaust gas from the DOC 11 is changed to the direction of the upstream end surface 12b of the DPF 12. The DPF 12 can be effectively used without providing any means.

  Furthermore, in the present embodiment, the shape of the upstream end surface 11b of the DOC 11 is the same as the shape of the image projected on the upstream end surface 11b when the hollow cross-sectional shape of the straight tube 8 is projected in the direction of the axis 8a. is there. Thereby, the high-speed exhaust gas which flowed out from the exhaust-gas outlet 4a of the turbocharger 4 can be made to flow uniformly into the upstream end surface 11b of the DOC11. Therefore, the exhaust gas flowing out from the DOC 11 also has a high flow rate and a uniform flow. According to the present embodiment, the exhaust gas having a high flow velocity and flowing uniformly from the DOC 11 can be uniformly introduced into the upstream end face 12 b of the DPF 12.

  Thereby, the purification | cleaning capability of DPF12 can further be raised. Further, the DPF 12 can be further downsized by the amount that the purification capability of the DPF 12 is increased. Further, the exhaust system structure can be further reduced in space and the cost can be reduced by the size of the DPF 12.

<Modification 1>
In the above-described embodiment, the cross-sectional shape of the DOC 11 and the cross-sectional shape of the DPF 12 are both elliptical, but the present invention is not limited to this. For example, as shown in FIG. 3, the cross-sectional shape of the DOC 11 may be a circle, and the cross-sectional shape of the DPF 12 may be an ellipse.

<Modification 2>
As for the cross-sectional shape of the DOC 11 and the cross-sectional shape of the DPF 12, as shown in FIG. 4, the cross-sectional shape of the DOC 11 may be an ellipse, and the cross-sectional shape of the DPF 12 may be a circle.

<Modification 3>
Further, regarding the cross-sectional shape of the DOC 11 and the cross-sectional shape of the DPF 12, as shown in FIG. 5, the extending direction of the elliptical long axis may be inclined with respect to the plane including the shaft 11a and the shaft 12a. .

<Other variations>
In the above embodiment, the straight tube 8 is extended to the rear side of the vehicle. However, the present invention is not limited to this, and is extended to the front side of the vehicle, for example, depending on the installation location of the post-processing device 6. May be.

  Moreover, although the said embodiment demonstrated what provided DOC11 in the upstream of DPF12, it is not limited to this. Various catalysts for purifying exhaust gas such as a lean NOx trap catalyst (LNT) and a selective catalytic reduction catalyst (SCR) as other catalysts may be provided on the upstream side of the DPF 12, in addition to the DOC 11. Thus, another catalyst may be provided. When the present invention is applied to this configuration, the upstream end face of the LNT is inclined at a predetermined angle with respect to the axis 8a of the straight tube 8.

  In the above embodiment, the shaft 11a of the DOC 11 extends in a direction perpendicular to the upstream end surface 11b of the DOC 11, and the cross-sectional shape of the DOC 11 is the same as the shape of the upstream end surface 11b. It is not limited to. You may make it incline the upstream end surface 11b with respect to the cross section of DOC11.

  In the above embodiment, the shaft 12a of the DPF 12 extends in a direction perpendicular to the upstream end surface 12b of the DPF 12, and the cross-sectional shape of the DPF 12 is the same as the shape of the upstream end surface 12b. It is not limited to. The upstream end face 12b may be inclined with respect to the transverse section of the DPF 12.

  The exhaust system structure of the internal combustion engine of the present invention is useful as an exhaust gas aftertreatment device that requires effective use of the exhaust purification unit.

DESCRIPTION OF SYMBOLS 1 Exhaust system 2 Engine 3 Exhaust manifold 4 Turbocharger 4a Exhaust gas outlet 5 Upstream exhaust passage 6 Post-processing device 7 Downstream exhaust passage 8 Straight pipe 8a, 11a, 12a Shaft 10 Case 11 DOC
11b, 12b Upstream end face 12 DPF
13 Inorganic mat 14 First case part 15 Second case part

Claims (4)

A first exhaust gas purification unit that purifies exhaust gas from the internal combustion engine; and a second exhaust gas purification unit that is provided downstream of the first exhaust gas purification unit;
A first axis of the first exhaust purification unit is inclined with respect to a second axis of the second exhaust purification unit;
When a cross section of the first exhaust purification unit is projected in the first axial direction, the shape of the image projected on the upstream end face of the second exhaust purification unit is the second exhaust purification unit. The shape of the upstream end face of
The exhaust system structure of an internal combustion engine. The cross-sectional shape of the second exhaust purification unit is the same as the shape of the upstream end surface of the second exhaust purification unit.
The exhaust system structure of the internal combustion engine according to claim 1. The cross-sectional shape of the first exhaust purification unit and the shape of the upstream end face of the second exhaust purification unit are elliptical.
The exhaust system structure of the internal combustion engine according to claim 1 or 2. The extending direction of the major axis of the ellipse is inclined with respect to a plane including the axis of the first exhaust purification unit and the axis of the second exhaust purification unit.
An exhaust system structure for an internal combustion engine according to claim 3.

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