JP2010144710A - Connection structure for hollow double-pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide connection structure for a hollow double-pipe capable of restricting lowering of the temperature of exhaust gas to the minimum in a connection part of the hollow double-pipe. <P>SOLUTION: This connection structure 10 for a hollow double-pipe is formed by connecting two double-pipes respectively formed of an inner pipe and an outer pipe, in which the exhaust gas flows. The connection structure 10 for a hollow double-pipe includes an enlarged pipe part 23 formed by enlarging an end of a first inner pipe 21, which is arranged on a downstream side of the connection part 40, toward an upstream side of the exhaust gas to form into a conical shape, and an end edge part continued to the enlarged pipe part 23 is brought into inner-contact with the inside of the first outer pipe 22 so as to form a first double-pipe 20. In an end of a second double-pipe 30 on the connection part side, a second inner pipe 31 is protruded from a second outer pipe 32. In the connection part 40, an end of the second inner pipe 31 is arranged close to the enlarged pipe part 23, and an end of the first outer pipe 22 and an end of the second outer pipe 32 abut on each other, and the abutment parts are welded to each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hollow double pipe connection structure, and more particularly to a hollow double pipe connection structure used as an exhaust pipe for circulating exhaust gas from an internal combustion engine.

  In order to prevent the release of HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) contained in the exhaust gas discharged from the internal combustion engine into the atmosphere, a catalyst is used to purify them. There is provided an exhaust purification device using Since the catalyst exhibits its catalytic function by being maintained at a temperature equal to or higher than the activation temperature, the activation of the catalyst can be promoted by maintaining the exhaust gas at a high temperature and passing through the catalyst. Can be improved.

  In order to maintain the temperature of the exhaust gas at a high temperature, for example, an exhaust pipe having a double pipe structure comprising an inner pipe in which exhaust flows inside and an outer pipe having air and gas outside the inner pipe. Has been developed.

  However, because the double pipe structure exhaust pipe is bent, the inner pipe and the outer pipe of the double pipe structure are displaced, so it cannot be bent multiple times, and the exhaust pipe is divided as necessary. By connecting, an exhaust pipe having a desired length and shape is formed.

  As the structure of the connecting portion, for example, in Patent Document 1 below, in an exhaust system for an internal combustion engine having a double pipe exhaust pipe composed of an outer pipe 01 and an inner pipe 03 as shown in FIG. A structure is described in which a connection is made by welding a connecting portion 05 in which the ends of the outer pipe (outer tube) 01 are overlapped in the middle.

  FIG. 3 shows the structure of the connection portion of a conventional hollow double tube. As shown in FIG. 3, in the connection portion of the conventional hollow double tube, the upstream double tube 130 has a hollow double tube structure, but the end portion of the downstream double tube 120 The pipe 121 and the outer pipe 122 were integrally formed and connected by welding at a butt connection portion 140.

JP-A-9-189216

  However, in the exhaust device described in Patent Document 1, as shown in FIG. 4, since the exhaust gas and the outside air are in contact with each other only at the outer pipe (outer pipe) at the connection portion 05, the temperature of the exhaust gas is low. Easily taken away.

  In the connection of the conventional hollow double pipe structure shown in FIG. 3, the hollow double pipe is formed at the connection portion 140 where the inner pipe 121 and the outer pipe 122 of the downstream double pipe 120 are integrally formed. There is a part that does not have a tube structure, and the temperature of the exhaust gas is deprived due to heat dissipation or exhaust gas convection at this part, so the temperature drops and the processing efficiency to purify the exhaust gas is sufficient It was not obtained.

  This invention is made | formed in view of such a situation, and provides the connection structure of the hollow double tube which can suppress the fall of the temperature of exhaust gas to the minimum in the connection part of a hollow double tube.

In order to achieve the above object, the present invention provides a hollow double pipe connection structure formed by connecting a double pipe consisting of an inner pipe and an outer pipe through which exhaust gas from an internal combustion engine flows. A first double pipe provided on the downstream side of the exhaust gas, a second double pipe provided on the upstream side of the exhaust gas, and a connecting portion for connecting the first double pipe and the second double pipe. And
Having an expanded tube portion in which an end portion of the first inner tube which is an inner tube of the first double tube disposed on the downstream side of the connecting portion is expanded conically toward the upstream side of the exhaust gas; The first double pipe is formed by inscribed the inner edge of the first outer pipe, which is the outer pipe of the first double pipe, with the end edge portion following the expanded pipe section, and the second double pipe is connected. The end portion on the part side is formed by projecting a second inner pipe that is an inner pipe of the second double pipe from a second outer pipe that is an outer pipe of the second double pipe. 2. A hollow characterized in that the end of the inner tube is brought close to the expanded tube portion, the end of the first outer tube and the end of the second outer tube are in contact, and the corresponding contact is welded. Provide double pipe connection structure.

According to this invention, the second inner pipe of the upstream second double pipe is connected so as to be close to the expanded portion of the first double pipe on the downstream side. A space can be formed between the inner tube and the first inner tube and the first outer tube which are integrally formed in contact with each other.
Therefore, a double structure can be formed in the connecting portion, and there is no overlapping portion, a heat retention effect of the exhaust gas can be expected, and a decrease in temperature can be minimized. As a result, the exhaust gas maintained at a high temperature can be circulated through the catalyst, so that the exhaust gas purification efficiency can be improved.

  In the present invention, it is preferable that the first inner pipe and the second inner pipe of the connection portion are connected with a gap so that they do not come into contact with each other when they are heated by the exhaust gas flow and thermally expanded. Good.

  According to such a configuration, even if the double tube expands due to thermal expansion, the second inner tube does not come into contact with the expanded portion of the first inner tube. And a double pipe structure capable of circulating the exhaust gas maintained at a high temperature can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the connection structure of the hollow double tube which can suppress the fall of the temperature of exhaust gas to the minimum in the connection part of a hollow double tube can be provided.

  FIG. 1 is a view for explaining a connection structure of a hollow double tube according to the present invention, FIG. 1 (a) is a cross-sectional view of a connection portion after welding, and FIG. 1 (b) is a view before welding. It is sectional drawing of the edge part of a double tube. As shown in FIG. 1, the hollow double pipe connection structure 10 of the present invention has an exhaust gas that passes in the direction of arrow A and a first double pipe 20 provided on the downstream side of the exhaust gas, and an upstream side. The second double pipe 30 is provided.

  The double pipe is a hollow double pipe composed of a first inner pipe 21 which is an inner pipe and a first outer pipe 22 which is an outer pipe for heat insulation, heat insulation, etc. of the exhaust gas, The second double tube 30 is a hollow double tube comprising a second inner tube 31 that is an inner tube and a second outer tube 32 that is an outer tube. And, gas such as exhaust gas circulates in the gap formed between each inner pipe and outer pipe, and an air layer is formed, thereby preventing heat dissipation of the exhaust gas and preventing temperature drop of the exhaust gas And maintain the temperature.

  The end of the first double pipe 20 on the second double pipe 30 side has a pipe expanding section 23 in which the end of the first inner pipe 21 is expanded conically toward the upstream side of the exhaust gas, An end edge portion following the expanded tube portion 23 is inscribed inside the first outer tube 22. On the other hand, the end of the second double pipe 30 on the first double pipe 20 side is formed by projecting the second inner pipe 31 toward the first double pipe 20 from the second outer pipe 32.

  Then, the second inner tube 31 of the second double tube 30 enters the expanded portion 23 of the first double tube 20, and the first outer tube 22 and the second outer tube 32 are welded and connected at the contact portion 41. ing. The welding method in the contact portion 41 is not particularly limited, and the contact portion 41 is welded and connected in a circumferential shape.

  At this time, the length of the second inner tube 32 is adjusted so that the second inner tube 31 is close to the first inner tube 21 of the expanded portion 23 of the first double tube 20. By adopting such a configuration, a space can be formed by the second inner pipe 31 and the expanded pipe portion 23 of the first double pipe 20, so that the connection section 40 can also have a double pipe structure. it can. Therefore, it is possible to prevent the temperature of the exhaust gas from decreasing.

The length of the portion of the second double pipe 30 protruding from the second outer pipe 32 of the second inner pipe 31 is such that the first double pipe 20 and the second double pipe 30 are welded. When the exhaust gas is circulated and the exhaust gas is circulated, the tip of the second inner pipe 31 does not come into contact with the expanded portion 23 of the first inner pipe 30 even when the temperature is increased by the exhaust gas flow and thermal expansion occurs. And it is preferable to be close to the pipe expansion part 23.
As shown in FIG. 1, a ring-shaped wire mesh 44 is interposed between the second inner tube 31 and the second outer tube 32, and the outer peripheral surface of the wire mesh 44 and the inner peripheral surface of the second outer tube 32. Is welded, and the inner peripheral surface of the wire mesh 44 and the outer peripheral surface of the second inner tube 31 are slidable, and the tip of the second inner tube 31 is moved to the first inner tube according to the temperature change. It is supported so as to be able to expand and contract so as to be close to or away from 30 expanded portions 23.

  Even when the temperature is increased by the exhaust gas flow and the thermal expansion occurs, the tip of the second inner pipe 31 is prevented from coming into contact with the expanded portion 23 of the first inner pipe 30. In this case, the generation of abnormal noise and vibration due to contact and the problem of generation of tensile stress in the axial direction in the welded portion do not occur, and a hollow double tube structure can be reliably obtained.

In FIG. 2, the example used for the bus vehicle 50 is shown as a specific example using the hollow double pipe structure 10 of this invention. FIG. 2 is a plan view showing the arrangement of the large bus around the rear engine.
The exhaust gas exhausted from the diesel engine 60 passes through the exhaust pipe 80 having the hollow double pipe connection structure 10 of the present invention, is purified by the exhaust purification device 70, and is exhausted from the exhaust port 85 to the atmosphere. It is configured.

The exhaust purification device 70 includes a diesel particulate filter (DPF) that collects PM (particulate matter) discharged from the diesel engine 60, and a catalyst is disposed on the upstream side or the downstream side of the DPF. Exhaust gas components such as HC (hydrocarbon), CO (carbon monoxide) and NO _x (nitrogen oxide) are purified.

As shown in FIG. 2, the exhaust pipe 80 is connected to the exhaust purification device 70, and the exhaust pipe 80 is bent at several places in order to exhaust the exhaust gas in the rearward direction of the bus vehicle 50. However, since the exhaust pipe 80 has a hollow double pipe structure, the bending causes a deviation between the inner pipe and the outer pipe of the hollow double pipe structure, and this deviation becomes large when the number of bent portions increases. Therefore, when bending at a plurality of places, it is formed by connecting a plurality of double tubes.
In particular, when the vehicle is a large vehicle such as the bus vehicle 50, the exhaust purification device 70 is disposed away from the diesel engine 60, and therefore the length of the exhaust pipe 80 that guides the exhaust gas of the exhaust purification device 70 is long. Since it becomes long, the connection structure of the hollow double pipe of the present invention is effective in activating the catalyst in the exhaust purification device 70.

  In FIG. 2, the exhaust pipe 80 is configured using two double pipes. However, the same applies to a case where the distance to the exhaust purification device 70 is long and three or more double pipes are used. It can be connected in the configuration.

According to the present invention, since the temperature reduction of the exhaust gas can be minimized at the connection portion of the hollow double tube, the hollow double tube constituting the exhaust passage provided with the exhaust gas aftertreatment device of the diesel engine Suitable for connection structure.

It is a figure explaining the connection structure of the hollow double tube of this invention, (a) is sectional drawing after a connection, (b) is sectional drawing before a connection. It is the schematic which used the connection structure of the hollow double pipe of this invention for the exhaust pipe of a vehicle. It is explanatory drawing of a prior art. It is explanatory drawing of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hollow double pipe connection structure 20 1st double pipe 21 1st inner pipe 22 1st outer pipe 23 Expanded part 30 2nd double pipe 31 2nd inner pipe 32 2nd outer pipe 40 Connection part 41 Contact part 50 bus vehicle 60 diesel engine 70 exhaust purification device 80 exhaust pipe

Claims (2)

In the connection structure of the hollow double pipe formed by connecting the double pipe consisting of the inner pipe and the outer pipe through which the exhaust gas from the internal combustion engine circulates,
A first double pipe provided on the downstream side of the exhaust gas, a second double pipe provided on the upstream side of the exhaust gas, and a connecting portion for connecting the first double pipe and the second double pipe. Have
Having an expanded tube portion in which an end portion of the first inner tube which is an inner tube of the first double tube disposed on the downstream side of the connecting portion is expanded conically toward the upstream side of the exhaust gas; The first double pipe is formed by inscribed the inner edge of the first outer pipe, which is the outer pipe of the first double pipe, with the end edge portion following the expanded pipe section;
The end of the second double pipe on the connection part side is formed by a second inner pipe that is an inner pipe of the second double pipe protruding from a second outer pipe that is an outer pipe of the second double pipe. The connecting portion brings the end portion of the second inner tube close to the expanded portion, and the end portion of the first outer tube and the end portion of the second outer tube abut, Hollow double pipe connection structure characterized by welding.   The said 1st inner pipe and the said 2nd inner pipe of the said connection part exist in the clearance gap which does not contact, when it heats up by an exhaust gas flow and thermally expands, It is characterized by the above-mentioned. The hollow double pipe connection structure described.

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