JP2018076853A - Exhaust system structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust system structure capable of effectively utilizing an exhaust emission control part.SOLUTION: The exhaust system structure for an internal combustion engine includes an exhaust passage provided so that exhaust gas from the internal combustion engine flows along a linear direction, and the exhaust emission control part having an axis inclined to the linear direction for purifying the exhaust gas from the exhaust passage. The upstream side end face in the exhaust gas flowing direction of the exhaust emission control part on which the cross-sectional shape of the exhaust passage can be projected in the linear direction has the same shape as the image of the cross-sectional shape projected on the upstream side end face.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art Conventionally, there has been known an exhaust purification device that is provided in an exhaust system of an internal combustion engine and includes a catalyst that removes carbon monoxide, unburned hydrocarbons, and the like in exhaust gas discharged from the internal combustion engine. In order to effectively use the catalyst of the exhaust gas purification device, it is desired that the exhaust gas be allowed to uniformly flow into the upstream end of the catalyst.

  In Patent Document 1, a straight pipe is provided in the exhaust gas conduit, the upstream end face of the catalyst is inclined with respect to the straight pipe axis, and the exhaust gas is evenly distributed in the exhaust gas conduit to the upstream end of the catalyst. An exhaust emission control device provided with a turning means for flowing in is disclosed.

  Further, in Patent Document 2, the upstream end face of the catalyst is inclined with respect to the axis of the exhaust gas inflow pipe, and the exhaust gas flows evenly into the upstream end of the catalyst into the cone connecting the catalyst and the exhaust gas inflow pipe. An exhaust emission control device provided with a curved bulging portion is provided.

JP-T-2001-526349 JP 2004-332607 A

  However, the flow velocity distribution of the exhaust gas on the upstream end face of the catalyst described in Patent Document 1 becomes higher at the position of the central portion, the position of the turning means, and the position on the opposite side, but other than that There was a problem that the position of the catalyst was lowered and the catalyst could not be used effectively.

  Similarly, the upstream end face of the catalyst described in Patent Document 2 also has a problem that the catalyst cannot be used effectively because there are places where the exhaust gas flow velocity distribution is low.

  An object of the present disclosure is to provide an exhaust system structure capable of effectively utilizing an exhaust purification unit.

The exhaust system structure of the internal combustion engine of the present disclosure is:
An exhaust passage provided such that exhaust gas from the internal combustion engine flows along a linear direction;
An exhaust purification unit that has an axis inclined with respect to the linear direction and purifies the exhaust gas from the exhaust passage;
With
The upstream end surface in the exhaust gas flow direction in the exhaust purification unit is a surface capable of projecting the cross-sectional shape of the exhaust passage in the linear direction, and the image of the cross-sectional shape projected on the upstream end surface Have the same shape.

  According to the exhaust system structure of the internal combustion engine of the present disclosure, the exhaust purification unit can be effectively used.

Schematic showing an exhaust system according to an embodiment of the present disclosure Partial enlarged view of FIG. The figure which shows the upstream end surface of DOC concerning a comparative example

  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. 1 and 2, the X axis, the Y axis, and the Z axis are drawn. In the following description, the left-right direction in FIG. 1 is referred to as the X direction or the vehicle front-rear direction, the right direction is referred to as “+ X direction” or “vehicle front side”, and the left direction is referred to as “−X direction” or “vehicle rear side”. Further, the vertical direction in FIG. 1 is referred to as the Y direction or the vehicle vertical direction, the upward direction is referred to as “+ Y direction” or “vehicle upper side”, and the downward direction is referred to as “−Y direction” or “vehicle lower side”. Further, in FIG. 1, a direction perpendicular to the paper surface is referred to as a Z direction or a vehicle width direction, a front direction is referred to as “+ Z direction” or “vehicle right side”, and a 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 FIG. 1, the exhaust system 1 extends from 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 the turbocharger 4. An upstream exhaust passage 5, a post-treatment device 6, and a downstream exhaust passage 7. In the case of the present embodiment, the respective members are arranged on the right side of the engine 2 in the vehicle. However, the arrangement of the members with respect to the engine 2 in the vehicle width direction is not limited to the illustrated structure.

  The direction, size and shape of the exhaust gas outlet 4a of the turbocharger 4 are comprehensively determined based on the shape, size and installation location 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 (see FIG. 2)), and downstream. It has a function as a flow path that flows out from the side opening. 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 of the straight tube 8 (that is, the direction of the shaft 8a), the length, and the hollow cross-sectional shape are comprehensively 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 cross-sectional shape of the internal space defined by the inner peripheral surface of the straight tube 8 (a cross-sectional shape related to a virtual plane orthogonal to the axis 8a). In other words, 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 FIG. 1, the straight tube 8 is extended linearly in the same −X direction as the exhaust gas outlet 4 a. 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 pipe 8 are the same direction and shape as the exhaust gas outlet 4a is that the flow speed of the exhaust gas flowing into the straight pipe 8 from the turbocharger 4 is reduced by the straight pipe 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.

  A post-processing device 6 is connected to the downstream end 8 b of the straight tube 8. The details of the structure connecting the downstream end 8b of the straight tube 8 and the post-processing device 6 will be described later.

  As shown in FIG. 1, the aftertreatment device 6 includes a cylindrical case 10, an oxidation catalyst (DOC) 11 for purifying exhaust gas (corresponding to the “exhaust purification unit” of the present invention), and a diesel particulate filter. (DPF) 12 is accommodated. In FIG. 1, the inorganic mat 13 (see FIG. 2) described later for holding the DOC 11 and the like and the plate thickness of the case 10 are omitted.

  The DOC 11 and the DPF 12 are held in the case 10 by the inorganic mat 13 (see 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.

  As described above, the installation location of the post-processing device 6 is determined at the position in the −X direction of the turbocharger 4. 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 each of the axes 11a and 12a is 3 in the X direction, the Y direction, and the Z direction. It is arranged to tilt in a dimension. 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 aftertreatment device 6. The exhaust gas purified by the post-treatment device 6 is led out through the downstream exhaust passage 7. 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 a structure for connecting the downstream end portion 8b of the straight pipe 8 and the post-processing device 6 will be described with reference to FIG. 1 and FIG. FIG. 2 is a partially enlarged view of FIG. FIG. 2 shows a circle C as the shape of the exhaust gas outlet 4a seen from the direction of the axis 8a (that is, the hollow cross-sectional shape of the straight tube 8), and an ellipse E as the shape of the upstream end face 11b seen from the direction of the axis 11a. Indicates. FIG. 2 shows the flow of exhaust gas in the straight tube 8 and the DOC 11 with broken lines.

  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 shaft 11a is inclined at a predetermined angle α about the Z axis (counterclockwise) with respect to the shaft 8a in the −X direction. That is, the upstream end surface 11b of the DOC 11 is inclined at a predetermined angle (π / 2−α) around the Z axis (clockwise) with respect to the shaft 8a.

  The upstream end surface 11b of the DOC 11 is a surface that can project the hollow cross-sectional shape (here, the circle C) of the straight tube 8 in the linear direction (−X direction). The image of the hollow cross-sectional shape projected on the upstream end surface 11b of the DOC 11 is an ellipse (ellipse E ′) having a long axis that is aligned with the long axis of the ellipse E. Further, as shown in FIG. 2, the major axis end of the ellipse E ′ near the exhaust gas outlet 4 a coincides with the major axis end of the ellipse E near the exhaust gas outlet 4 a. Here, the “surface capable of projecting a hollow cross-sectional shape” refers to a surface capable of projecting the entire hollow cross-sectional shape. For example, when the surface is arranged out of the −X direction (projection direction), the surface is hollow. A surface on which only a part of the cross-sectional shape is projected is not required. In the present embodiment, the short axes of the ellipse E and the ellipse E ′ are positioned on a straight line, and the short axis ends coincide with each other, so that the ellipse E ′ is equal to the ellipse E. It is in.

  That is, in the present embodiment, the lower end of the upstream end surface 11b in the vehicle vertical direction is located at the same height as the lower end of the inner periphery of the straight pipe 8 in the vehicle vertical direction. In addition, the inclination angle of the upstream end surface 11b with respect to the shaft 8a is determined based on, for example, the size and shape of the DOC 11 and its location.

  As shown in FIG. 2, the downstream end portion 8 b of the straight tube 8 is formed along the outer peripheral edge 11 c of the upstream end surface 11 b of the ellipse E. In the present embodiment, the downstream end 8b of the straight pipe 8 is fitted to the upstream end edge 10a of the case 10 and welded, whereby the straight pipe 8 and the case 10 are sealed.

  FIG. 3 is a view showing the upstream end face 11b of the DOC 11 according to the comparative example. FIG. 3 shows an ellipse E as a shape of the upstream end face 11b, a circle C as a hollow cross-sectional shape of the straight tube 8, and a circle C ′ having a major axis of the ellipse E as a diameter.

  In the case of the comparative example in which the shape of the upstream end face 11b ′ is a circle C ′, the flow rate of the exhaust gas in the region indicated by the hatched portion in FIG. descend. Exhaust gas purification capacity in the shaded area is reduced by the amount of decrease in the exhaust gas flow rate.

  On the other hand, in this embodiment, the shape of the upstream end surface 11b is set to an ellipse E by deleting the shaded area. As shown in FIG. 2, the area of the ellipse E is an area where the exhaust gas uniformly hits the straight pipe 8 at a high flow velocity from the straight pipe 8, and the exhaust gas that hits uniformly flows into the DOC 11 uniformly. , DOC11 can be used effectively. Here, when uniform, the exhaust gas hits and flows in the upstream end face 11b according to the present embodiment is more uniform than the exhaust gas hits and flows in the upstream end face 11b ′ according to the comparative example shown in FIG. It means that.

<Effect of this embodiment>
As described above, according to the exhaust system structure of the internal combustion engine according to the present embodiment, the upstream end surface 11b of the DOC is a surface on which the hollow cross-sectional shape of the straight tube 8 can be projected in the −X direction, It has the same shape as the ellipse E as an image of the hollow cross-sectional shape projected on the end surface 11b. As a result, the upstream end face 11b (area indicated by the ellipse E) becomes an area where the exhaust gas from the straight tube 8 uniformly hits, so that the DOC 11 can be used effectively.

  Further, the upstream end surface 11 b of the DOC 11 is inclined with respect to the axis 8 a of the straight tube 8. As a result, since the exhaust gas flows directly into the DOC 11, there is no need to provide a turning means for changing the flow direction of the exhaust gas from the straight pipe 8 to the direction of the upstream end face 11b, thereby reducing the cost. it can.

  Moreover, the cross-sectional shape of DOC11 has the same shape as the upstream end surface 11b. Thereby, the exhaust gas purification capacity of the DOC 11 can be maintained within an allowable range.

  Further, the exhaust gas from the turbocharger 4 flows through the straight pipe 8 to the upstream end face 11 b of the DOC 11. As a result, the exhaust gas from the straight pipe 8 is rectified along the shaft 8a while maintaining a high flow velocity, and uniformly and directly hits the upstream end surface 11b of the DOC 11, so that the exhaust purification ability of the DOC 11 is increased. be able to. In addition, the DOC 11 can be downsized by the amount that the exhaust purification capacity of the DOC 11 is increased. Further, the cost can be reduced by the amount that the DOC 11 is miniaturized.

<Modification of this embodiment>
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, in the said embodiment, the axis | shaft 11a of DOC11 is extended in the surface orthogonal | vertical direction of the upstream end surface 11b. That is, it becomes the same shape as the cross-sectional shape of DOC11 and the upstream end surface 11b. However, the present invention is not limited to this. For example, the shaft 11a may extend in a direction inclined with respect to the direction perpendicular to the upstream end surface 11b. Since the shaft 11a of the DOC 11 extends in a direction in which the shaft 11a is inclined, the cross-sectional shape of the DOC 11 and the upstream end surface 11b are not the same shape. In this case, the shaft 11a is preferably inclined in a range where the cross-sectional area of the DOC 11 is larger than the cross-sectional area of the hollow portion of the straight tube 8 in order to maintain the exhaust processing capacity of the DOC 11 within an allowable range.

  In the above embodiment, the shaft 12a of the DPF 12 is tilted two-dimensionally at a predetermined angle β around the Z axis with respect to the shaft 11a of the DOC 11, as shown in FIG. It may be tilted three-dimensionally with respect to the shaft 11a depending on the shape and the arrangement location thereof.

  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 DOC11, another catalyst may be provided. When the present invention is applied to this configuration, the axis of the LNT is inclined at a predetermined angle with respect to the axis 8 a of the straight tube 8.

  The exhaust system structure of the internal combustion engine of the present disclosure is useful as an exhaust gas aftertreatment device that requires effective use of an 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 Shaft 8b Downstream end 10 Case 11 DOC
11a shaft 11b upstream end face 12 DPF
12a shaft 12b upstream end face

Claims (6)

An exhaust passage provided such that exhaust gas from the internal combustion engine flows along a linear direction;
An exhaust purification unit that has an axis inclined with respect to the linear direction and purifies the exhaust gas from the exhaust passage;
With
The upstream end surface in the exhaust gas flow direction in the exhaust purification unit is a surface capable of projecting the cross-sectional shape of the exhaust passage in the linear direction, and the image of the cross-sectional shape projected on the upstream end surface An exhaust system structure of an internal combustion engine having the same shape.   The exhaust system structure of the internal combustion engine according to claim 1, wherein a cross-sectional shape of the exhaust purification unit has the same shape as the upstream end surface.   The exhaust system structure of the internal combustion engine according to claim 1 or 2, wherein the exhaust passage extends from a turbocharger to a vehicle rear side.   The exhaust system structure of the internal combustion engine according to claim 1 or 2, wherein the exhaust passage extends from the turbocharger to the front side of the vehicle.   The exhaust system structure of an internal combustion engine according to any one of claims 1 to 4, wherein the exhaust passage includes a straight pipe having a straight shaft.   The exhaust system structure for an internal combustion engine according to any one of claims 1 to 5, wherein a shape of the upstream end face is an ellipse.

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