JP2021038701A - Exhaust passage - Google Patents

Abstract

To provide an exhaust passage having a high agitation effect while suppressing pressure loss.SOLUTION: An exhaust passage 10 includes: an exhaust pipe 11; and a projection part 20 which is provided continuously to a partial range in a circumferential direction of the inner surface of the exhaust pipe 11 and has a tapered part inclined in the extending direction of the exhaust pipe 11, and the cross sectional area of which is decreased as it approaches the downstream side of the exhaust pipe. Exhaust gas passes through the tapered part of the projection part 20 when the gas flows from upstream to downstream, but gas inside the tapered part is pushed to the outside of the tapered part as it approaches downstream and thereby air flow is generated because the cross sectional area of the tapered part becomes smaller as it approaches the downstream side. The air flows are continuously generated in all the range of the tapered part to become a swirl flow, the agitation of the exhaust gas progresses further in the whole of the inside of the exhaust pipe 11, and thereby accuracy in measurement by a sensor is improved. Also, an opening part is relatively large even at the tapered part and the swirl flow spreads over the whole of the inside of the exhaust pipe 11, so that increase in pressure loss can be suppressed.SELECTED DRAWING: Figure 2

Description

The present invention relates to an exhaust passage.

The exhaust pipe of the internal combustion engine is provided with a sensor for detecting the oxygen concentration in the exhaust gas. In the operation control of the internal combustion engine, for example, the intake air amount and the fuel injection amount are adjusted according to the detected oxygen concentration, and the air-fuel ratio is controlled.
The exhaust gas emitted from each cylinder flows into one exhaust pipe via the exhaust manifold. Since the flow of exhaust gas has high directivity in the downstream direction and tends to be biased in the cross section of the exhaust pipe, it is being considered to provide a mechanism for stirring before reaching the sensor.

Patent Document 1 discloses a dispersion plate in which two plates are combined as a dispersion plate for dispersing an exhaust flow.
Patent Document 2 discloses an airfoil-shaped fin composed of a plurality of blades as an exhaust gas stirring unit arranged between an exhaust gas sensor and an exhaust gas purification unit.
Further, Patent Document 3 discloses that a protrusion having a hole is provided between the first exhaust pipe and the second exhaust pipe. According to Patent Document 3, it is described that when the exhaust gas passes near the protrusion, it becomes a turbulent flow and the exhaust gas is diffused.

Japanese Unexamined Patent Publication No. 2016-79962 JP-A-2015-55227 Japanese Unexamined Patent Publication No. 2014-12609

Since the dispersion plates and the like of Patent Documents 1 to 3 have a small aperture ratio, there is a problem that the pressure loss tends to be large. Further, since the dispersion plates and the like of Patent Documents 1 and 2 use a plurality of plates, they are disadvantageous in terms of manufacturing cost and reliability. Further, in the protrusion of Patent Document 3, depending on the arrangement of the hole and the sensor, the flow rate per gas to the sensor may decrease and the responsiveness of the sensor may deteriorate.

The present invention solves such a problem and provides an exhaust passage having a high stirring effect while suppressing a pressure loss.

The exhaust passage according to this embodiment is
Exhaust pipe and
It is provided with a protruding portion that is continuously provided on the inner surface of the exhaust pipe and a part of the circumferential direction, and has a tapered portion that is inclined in the extending direction of the exhaust pipe and the cross-sectional area becomes smaller toward the downstream side of the exhaust pipe. It is characterized by that.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an exhaust passage having a high stirring effect while suppressing a pressure loss.

It is a schematic perspective view which shows an example of the exhaust passage which concerns on this embodiment. It is a schematic perspective view for demonstrating the mechanism that the exhaust gas is agitated by the protrusion. It is a figure which shows the distribution of the exhaust gas flow rate. It is a graph which shows the relationship between the pressure loss due to the difference in the central angle of the protrusion, and the mixing effect. It is (A) front view, (B) top view, (C) side view which shows an example of the protrusion. It is a schematic perspective view of the protrusion shown in the example of FIG. It is a perspective view which shows another example of the protrusion. It is a perspective view which shows another example of the protrusion. It is a schematic perspective view which shows another example of an exhaust passage.

Hereinafter, the present invention will be described through the embodiments, but the invention according to the claims is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings have been simplified as appropriate. In the present specification, the X-axis is taken in the downstream direction in the axial direction (extending direction) of the exhaust pipe, and the plane perpendicular to the X-axis is referred to as the YZ plane (also simply referred to as a cross section).

The exhaust passage 10 shown in the example of FIG. 1 is an exhaust passage preferably used for an internal combustion engine, and includes an exhaust pipe 11 (11A, 11B) and a protruding portion 20. As shown in FIGS. 5 and 6, the protruding portion 20 may have at least a tapered portion 22 inclined in the extending direction of the exhaust pipe, and may have an inscribed portion 21 inscribed in the exhaust pipe 11. The tapered portion 22 has a shape in which the cross-sectional area becomes smaller toward the downstream side of the exhaust pipe 11. Here, the cross section of the tapered portion means an arc-shaped cross section perpendicular to the axis of the exhaust pipe, and the cross-sectional area of the tapered portion is a line connecting the arc, the end point of the arc, and the center of the exhaust pipe. The area of the fan shape that is composed. Further, the central angle of the sector is θ (see FIG. 5 (A)). The exhaust passage of the present embodiment has a high stirring effect while suppressing pressure loss. This will be described with reference to FIG.

FIG. 2 is a schematic perspective view for explaining a mechanism in which the exhaust gas is agitated by the protruding portion. (A) and (B) in FIG. 2 schematically show an XY cross section of the exhaust gas passing through the exhaust passage, respectively.
As shown in the example of FIG. 2, the exhaust gas passes through the tapered portion 22 of the protruding portion 20 when flowing from the upstream to the downstream (FIG. 2 (A)). Since the tapered portion 22 has a structure in which the cross-sectional area becomes smaller toward the downstream side, the gas in the tapered portion 22 is pushed out of the tapered portion as it goes downstream, and the air flow indicated by the arrow is generated. This airflow is continuously generated over the entire tapered portion 22 to form a swirling flow, and the exhaust gas is agitated throughout the pipe even after passing through the protruding portion (FIG. 2B). As a result, the surface uniformity of the exhaust gas is improved, and the measurement accuracy by the sensor is improved. Further, the exhaust passage of the present embodiment has a relatively large opening even in the tapered portion, and the swirling flow described above spreads throughout the pipe, so that an increase in pressure loss can be suppressed.
FIG. 3 is a diagram showing the difference in the distribution of the exhaust gas flow rate depending on the presence or absence of the protrusion. As shown in FIG. 3, in the exhaust passage of the present embodiment having a protruding portion, the surface uniformity of the exhaust gas flow rate is improved. In particular, it is preferable that the cross-sectional area of the protruding portion is 50% or less of the cross-sectional area of the exhaust pipe from the viewpoint of excellent effect of suppressing pressure loss.

5 and 6 are schematic showing an example of a protruding portion. As shown in the examples of FIGS. 5 and 6, the protruding portion 20 has a tapered portion 22 whose cross-sectional area becomes smaller toward the downstream side. The shape of the tapered portion 22 is not particularly limited as long as the cross-sectional area becomes smaller toward the downstream side. For example, it may be a linear shape as in the examples of FIGS. 6 and 7, and a curved line as shown in FIG. It may be (semi-circular type or parabolic type). Further, the tip of the tapered portion may have a linear shape up to the tip as shown in the example of FIG. 7, or may have a trapezoidal shape such that the tip is cut and closed as shown in FIG. Often, it may be open as in the example of FIG. Any shape has a high stirring effect while suppressing pressure loss. The protruding portion 20 may have an inscribed portion 21 for connecting to the exhaust pipe 11.

Next, the relationship between the central angle θ and the stirring effect in the front view (FIG. 5 (A)) when the protruding portion is viewed in the X-axis direction will be described. FIG. 4 is a graph showing the relationship between the pressure loss due to the difference in the central angle of the protruding portion and the mixing effect.
As shown in FIG. 4, as the central angle θ becomes larger, the mixing effect is improved, but the pressure loss tends to increase. When the central angle θ exceeds 180 degrees, the increase in pressure loss becomes remarkable with respect to the improvement of the mixing effect. On the other hand, if the central angle is less than 90 degrees, a sufficient mixing effect may not be obtained. In the present embodiment, it is particularly preferable that the central angle θ is in the range of 90 to 180 degrees from the viewpoint of the balance between the mixing effect and the suppression of the pressure loss.

In the present embodiment, the method of providing the protruding portion 20 in the exhaust pipe 11 is not particularly limited. For example, as in the example of FIG. 1, the protruding portion 20 may be provided between the exhaust pipe 11A on the upstream side and the exhaust pipe 11B on the downstream side by using a connector 23 provided with the protruding portion 20. .. Further, the protruding portion 20 may be welded to the exhaust pipe 11.

Further, as shown in the example of FIG. 9, the exhaust pipe 11 may have a sensor mounting portion 31 for mounting the sensor 30 on the downstream side of the protruding portion 20. The shape of the sensor mounting portion 31 may be appropriately adjusted according to the sensor 30. The sensor 30 is preferably a sensor capable of measuring the oxygen concentration in the exhaust pipe, and examples thereof include an A / F sensor and an O ₂ sensor.

As described above, the exhaust passage of the present embodiment has a high stirring effect while suppressing pressure loss, and can be suitably used as, for example, an exhaust passage of an internal combustion engine. Since the protruding portion used in the present embodiment has a relatively simple structure with one piece, it is highly reliable and the manufacturing cost can be suppressed.

10 Exhaust passage, 11 (11A, 11B) Exhaust pipe, 20 Protruding part, 21 Inscribed part, 22 Tapered part, 23 Connector, 30 Sensor, 31 Sensor mounting part.

Claims (1)

Exhaust pipe and
It is provided with a protruding portion that is continuously provided on the inner surface of the exhaust pipe and a part of the circumferential direction, and has a tapered portion that is inclined in the extending direction of the exhaust pipe and the cross-sectional area becomes smaller toward the downstream side of the exhaust pipe. ,
Exhaust passage.