Exhaust pipe for internal combustion engine

Abstract

To provide an exhaust pipe for an internal combustion engine that can suppress deterioration in output power.SOLUTION: An exhaust pipe for an internal combustion engine is connected to an internal combustion engine. The exhaust pipe includes: a first part; a second part positioned downstream of the first part and provided with a catalyst; and a third part positioned downstream of the first part and upstream of the second part and having an inner diameter that is smaller than the first part and the second part. The third part includes an inner wall including a projection projecting on an outer side from an inner side of the exhaust pipe.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an exhaust pipe for an internal combustion engine. [Background technology]

[0002] Exhaust gas generated by an internal combustion engine is discharged through an exhaust pipe. A catalyst for purifying the exhaust gas is provided in the exhaust pipe. By providing a narrowed portion with a smaller cross-sectional area than other portions in the exhaust pipe, the exhaust gas is diffused and the purification performance of the catalyst is improved (for example, Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-17261 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the presence of the constriction increases the pressure loss of the exhaust, which may result in a decrease in the output of the internal combustion engine. Therefore, an object of the present invention is to provide an exhaust pipe for an internal combustion engine that is capable of suppressing the decrease in output. [Means for solving the problem]

[0005] The above object can be achieved by an exhaust pipe of an internal combustion engine, the exhaust pipe comprising a first portion, a second portion located downstream of the first portion and provided with a catalyst, and a third portion located downstream of the first portion and upstream of the second portion and having an inner diameter smaller than the first portion and the second portion, wherein the inner wall of the third portion has a protrusion protruding from the inside to the outside of the exhaust pipe. Effect of the Invention

[0006] It is possible to provide an exhaust pipe for an internal combustion engine that is capable of suppressing a decrease in output. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram illustrating an exhaust pipe according to an embodiment. [Diagram 2] 2(a) and 2(b) are cross-sectional views illustrating an exhaust pipe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the exhaust pipe of the internal combustion engine of the present embodiment will be described with reference to the drawings. However, in the drawings, the dimensions, ratios, etc. of each part may not be illustrated to be completely consistent with the actual ones. Also, in some drawings, some details may be omitted.

[0009] FIG. 1 is a schematic diagram illustrating an exhaust pipe 14 according to an embodiment. An internal combustion engine 10 is, for example, a four-cylinder engine. An intake pipe 12 and an exhaust pipe 14 are connected to the four cylinders of the internal combustion engine 10. Air flows through the intake pipe 12 and is supplied to the cylinders of the internal combustion engine 10. A throttle valve 13 is provided in the intake pipe 12. The larger the opening of the throttle valve 13, the greater the amount of air supplied to the internal combustion engine 10. The smaller the opening, the less the amount of air supplied.

[0010] Each of the four cylinders of the internal combustion engine 10 is provided with a spark plug 16 and a fuel injection valve 18. The fuel injection valve 18 directly injects fuel into the inside of the cylinder. In the cylinder, the fuel and air form a mixture. The spark plug 16 ignites the mixture, causing it to burn. Exhaust gas after combustion passes through an exhaust pipe 14 and is discharged to the outside of the vehicle. A catalyst 15 is provided in the exhaust pipe 14. The catalyst 15 is, for example, a three-way catalyst, and purifies nitrogen oxides (NOx), carbon monoxide (CO), and the like in the exhaust.

[0011] The exhaust pipe 14 has four sections 20, a section 21, a chamber 22 (first section), a throttle section 24 (third section), and a section 26 (second section). The four sections 20 are connected to the cylinders of the internal combustion engine 10, merge into one, and are connected to the section 21. The chamber 22 is located downstream of the section 21. The throttle section 24 is located downstream of the chamber 22. In FIG. 1, a protruding section, which will be described later, is omitted. The section 26 is located downstream of the throttle section 24. The section 26 has a support for the catalyst 15, and the catalyst 15 is provided in the section 26.

[0012] Exhaust gas is introduced into the catalyst 15, and the heat of the exhaust gas warms up the catalyst 15. The warm-up raises the temperature of the catalyst 15, and improves the exhaust gas purification performance of the catalyst 15. To warm up the catalyst 15, the flow rate of the exhaust gas is controlled so that the exhaust gas is introduced into the catalyst 15.

[0013] 2(a) and 2(b) are cross-sectional views illustrating an example of the exhaust pipe 14. FIG. 2(b) illustrates a cross section taken along line AA in FIG. 2(a). The X-axis direction is the direction in which the exhaust gas flows. The +Z-axis direction is the upward direction. The -Z-axis direction is the downward direction, in which gravity acts. In FIG. 2(b), the constriction portion 24 is illustrated by a solid line. The portion 26 is illustrated by a dotted line.

[0014] As shown in Figures 2(a) and 2(b), the inner diameter of portion 26 of exhaust pipe 14 is R1. The inner diameter of constricted portion 24 is R2. Diameter R2 of constricted portion 24 is smaller than diameter R1 of portion 26. The inner diameter of chamber 22 is larger than diameter R2 of constricted portion 24 and may be equal to diameter R1 of portion 26, larger than diameter R1, or smaller than diameter R1. That is, constricted portion 24 is located between chamber 22 and portion 26 and is narrower than these two portions.

[0015] The constriction portion 24 has a protrusion 30 and a protrusion 32. As shown in FIG. 2(b), the protrusions 30 and 32 protrude from the inside to the outside of the exhaust pipe 14. The protrusion 30 is a portion of the inner wall of the constriction portion 24 that protrudes in the -Z direction. The protrusion 32 is a portion of the inner wall that protrudes in the +Z direction. The protrusions 30 and 32 face each other. An inner diameter R3 between the protrusions 30 and 32 is larger than an inner diameter R2 at a position not including the protrusions. The inner diameter R3 may be equal to or different from, for example, the diameter R1 of the portion 26. In FIG. 2(a), the protrusions 30 and 32 are indicated by dashed lines. As shown in FIG. 2(a), the protrusions 30 and 32 extend from the chamber 22 to the portion 26 in the X-axis direction.

[0016] The catalyst 15 is warmed up by introducing exhaust gas into it, thereby improving the exhaust purification performance. The exhaust gas flows through sections 20 and 21 of the exhaust pipe 14 and enters the chamber 22. In the chamber 22, which is wider than the section 21, the exhaust gas is separated and the flow speed decreases. Because the throttling section 24 is narrower than the chamber 22, the exhaust gases interfere with each other and the flow speed decreases. By reducing the flow speed, the catalyst 15 is more likely to receive heat from the exhaust gas and is warmed up. On the other hand, because the throttling section 24 is narrow, it is difficult for the exhaust gas to flow, and pressure loss (pressure loss) may occur. If the pressure loss increases, the output of the internal combustion engine 10 decreases.

[0017] According to this embodiment, the throttle section 24 is located downstream of the chamber 22 and upstream of the portion 26. The throttle section 24 is provided with the protruding portions 30 and 32. Even if the flow rate of the exhaust gas decreases, the exhaust gas passes through the protruding portions 30 and 32, flows into the portion 26, and is introduced into the catalyst 15. Since the protruding portions 30 and 32 function as exhaust passages, the pressure loss is unlikely to increase. A decrease in the output of the internal combustion engine 10 can be suppressed.

[0018] When the flow rate of exhaust gas decreases, the amount of exhaust gas introduced into the catalyst 15 also decreases, making it difficult for the catalyst 15 to warm up. According to this embodiment, the exhaust gas flows through the protruding portions 30 and 32 and is introduced into the catalyst 15. Since the catalyst 15 is warmed up, the deterioration of the purification performance can be suppressed.

[0019] Condensation may occur from moisture contained in the exhaust air. Accumulation of condensation water may cause corrosion of the exhaust pipe 14. Since the inner wall of the constriction portion 24 is raised higher than the inner wall of the chamber 22, condensation water is likely to accumulate in the chamber 22. According to this embodiment, the condensation water flows through the protrusion 30 and is discharged to the outside of the chamber 22. Corrosion caused by condensation water is suppressed.

[0020] The number of protrusions may be one or more. In order to allow condensed water to flow out, it is preferable that one protrusion 30 faces the -Z direction.

[0021] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0022] 10 Internal combustion engine 12 Intake pipe 13 Throttle valve 14 Exhaust pipe 15 Catalyst 16 Spark plug 18 Fuel Injection Valve 20, 21, 26 parts 22 Chamber 24 Squeezing section 30, 32 protrusion

Claims

[Claim 1] An exhaust pipe connected to an internal combustion engine, The exhaust pipe includes a first portion and a second portion located downstream of the first portion and provided with a catalyst; a third portion located downstream of the first portion and upstream of the second portion, the third portion having an inner diameter smaller than the first portion and the second portion; An exhaust pipe for an internal combustion engine, wherein the inner wall of the third portion has a protruding portion that protrudes from the inside of the exhaust pipe to the outside.

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