JPH06264740A - Insulated exhaust pipe for engine - Google Patents

Abstract

PURPOSE:To improve the purification efficiency by swirling exhaust gas from respective groove-like walls and uniforming the harmful component density through the process of constituting an inner pipe by circumferentially lining a plurality of spirally extended groove-like walls, in an insulated exhaust pipe for an engine. CONSTITUTION:An insulated exhaust pipe 3 is composed of an inner pipe 7 for communicating an exhaust manifold 2 with a catalytic converter 4, an outer pipe 8 for surrounding the inner pipe 7 and an insulating material 10 to be filled into a cylindrical clearance 9 formed between the inner and outer pipes 7, 8 except for both ends. Both ends of both pipes 7, 8 are respectively and closely joined with each other, and flanges 11, 12 are welded thereon. In the inner pipe 7, three lines of grooved-like walls 7a formed into an U shape in section, and whose recessed surface is turned inward are circumferentially lined, and the groove-like walls 7a are so formed into a spiral shape as to be twisted in the same direction. Thereby, exhaust gas to flow through the inner pipe 7 produces swirling flow, and its harmful component density is uniformed, so that the purification efficiency is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adiabatic exhaust pipe for an engine, and more particularly to an improvement of an inner pipe that connects an exhaust manifold of an engine to an exhaust gas purifier and an outer pipe that encloses the inner pipe.

[0002]

2. Description of the Related Art Such an adiabatic exhaust pipe is disclosed in, for example,
It is already known as disclosed in Japanese Patent Publication No. 29625.

[0003]

The adiabatic exhaust pipe keeps the exhaust gas of the engine warm and guides it to the exhaust gas purifier to remove harmful components such as HC, CO and NOx contained in the exhaust gas by oxidation or reduction. However, if the concentration of harmful components in the exhaust gas is non-uniform, a large purification load will be partially applied to the exhaust gas purifier, resulting in the inconvenience of reduction in purification efficiency and durability.

The present invention has been made in view of such circumstances, and makes the concentration of harmful components in the exhaust gas of the engine introduced into the exhaust gas purifier uniform, thereby contributing to the improvement of the purification efficiency and durability of the exhaust gas purifier. It is an object of the present invention to provide a heat-insulating exhaust pipe for an engine.

[0005]

In order to achieve the above object, the present invention is characterized in that an inner pipe is constructed by connecting a plurality of spirally extending groove walls in the circumferential direction.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 1, reference numeral 1 denotes an automobile engine, and an exhaust manifold 2 of the automobile engine is connected with a catalytic converter 4 as an exhaust gas purifier through an adiabatic exhaust pipe 3 of the present invention. Further, a silencer 6 is connected to the catalytic converter 4 via an exhaust pipe 5.

As shown in FIGS. 2 and 3, the adiabatic exhaust pipe 3
Is an inner pipe 7 that communicates the exhaust manifold 2 with the catalytic converter 4, an outer pipe 8 that encloses the inner pipe 7, and a tubular space defined between the inner and outer pipes 7, 8 except both ends. 9 and a heat insulating material 10 filled therein. Both ends of both pipes 7 and 8 are tightly fitted to each other, and flanges 11 and 12 for connecting to the exhaust manifold 2 and the catalytic converter 4 are welded to them.

The inner pipe 7 except for both ends is
It is constituted by connecting three groove-shaped walls 7a ... Having a U-shaped cross section with the concave surface facing inward in the circumferential direction, and each groove-shaped wall 7a is formed in a spiral shape twisted in the same direction.

The outer pipe 8 also has three groove-shaped walls 8a having a U-shaped cross section with the concave surface facing inward except at both ends.
It is constructed by lining up in the circumferential direction. Also in this outer pipe 8, each groove wall 8a is formed in a spiral shape twisted in the same direction, and is arranged in the same phase as the groove wall 7a of the inner pipe 7. Therefore, the space 9 between the pipes 7 and 8 is constant in each part, and the thickness of the heat insulating material 10 filling the space 9 is also constant.

Next, the operation of this embodiment will be described.

Exhaust gas from the engine 1 is exhausted from the exhaust manifold 2
Is discharged to the catalytic converter 4 through the adiabatic exhaust pipe 3.
The harmful components in the exhaust gas are removed by oxidation or reduction, and then discharged through the exhaust pipe 5 and the silencer 6 in order.

In the adiabatic exhaust pipe 3, since the three groove walls 7a forming the inner pipe 7 are twisted in a spiral shape, the exhaust gas flowing in the inner pipe 7 is discharged into the groove wall. A spiral flow is generated by being guided by the spiral concave surface of 7a, whereby the exhaust gas is agitated and the concentration of its harmful components becomes uniform. Moreover, since the inner pipe 7 heated by the heat of the exhaust gas is kept warm by the heat insulating material 10 and the outer pipe 8, the exhaust gas is introduced into the catalytic converter 4 without a large temperature drop. Therefore, in the catalytic converter 4, since the harmful components in the exhaust gas are removed over the entire area, the purification efficiency is increased, and the purification load is not locally concentrated, which improves the durability of the catalytic converter. Can also contribute.

FIG. 4 shows a second embodiment of the present invention.
The configuration is the same as that of the previous embodiment except that the outer pipe 8 is made of a pipe having a circular cross section. In the figure, the same reference numerals are given to the portions corresponding to those of the previous embodiment.

In the above embodiment, various design changes can be made without departing from the gist of the present invention. For example, the groove-shaped wall 7a of the inner pipe 7 can be changed to three or more threads. Also, Inan and outer pipe 7,
The space 9 between 8 can be made into a heat insulation space, without filling a heat insulating material there.

[0016]

As described above, according to the present invention, in an adiabatic exhaust pipe, a plurality of spirally extending groove walls are connected in the circumferential direction to form an inner pipe. Exhaust gas can be swirled by each groove-shaped wall to make the concentration of harmful components in the exhaust gas uniform. Therefore, in an exhaust gas purifier that introduces such exhaust gas, the harmful components in the exhaust gas must be removed over the entire area. Therefore, the purification efficiency is high, and the purification load is widely dispersed, which contributes to the improvement of the durability of the exhaust gas purifier.

[Brief description of drawings]

FIG. 1 is a plan view of an exhaust system of an automobile engine showing a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of an adiabatic exhaust pipe in the exhaust system.

3 is a sectional view taken along line 3-3 of FIG.

FIG. 4 is a sectional view corresponding to FIG. 3, showing a second embodiment of the present invention.

[Explanation of symbols]

 1 engine 2 exhaust manifold 3 adiabatic exhaust pipe 4 catalytic converter as an exhaust purifier 7 inner pipe 7a Groove wall 8 ... Outer pipe

Claims (1)

[Claims] 1. A heat-insulated exhaust pipe for an engine, comprising an inner pipe (7) communicating an exhaust manifold (2) of the engine (1) with an exhaust gas purifier (4) and an outer pipe (8) enclosing the inner pipe (7). An adiabatic exhaust pipe for an engine, characterized in that an inner pipe (7) is configured by connecting a plurality of spirally extending grooved walls (7a) in the circumferential direction.