JP2017141742A - Connecting method of exhaust pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the intrusion of a weld sputter into an exhaust pipe and a catalyst case when welding the exhaust pipe and the catalyst case.SOLUTION: In an assembling process, an upstream-side end part 23 of a catalyst case 21 is inserted into an internal peripheral side of a downstream-side end part 11 of an exhaust pipe 10, and the catalyst case and the exhaust pipe are brought into an assembled state. After that, the exhaust pipe 10 and the catalyst case 21 are sent into a press process while maintaining the assembled state. In the press process, a metal mold member 30 is arranged so that a salient part 32 is oriented to the exhaust part 10 side and the catalyst case 21 side at the outside of radial directions of the downstream-side end part 11 of the exhaust pipe 10 and the upstream-side end part 23 of the catalyst case 21 which are in the assembled state. Then, by moving the metal mold member 30 to the inside of the radial direction, a protrusion 12 protruding toward an internal peripheral side from an external peripheral side is formed at the downstream-side end part 11 of the exhaust pipe 10. After the press process, a downstream side rather than the protrusion 12 at the downstream-side end part 11 of the exhaust pipe 10 and an external peripheral face of the catalyst case 21 are welded to each other while maintaining the assembled state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an exhaust pipe connection method.

  Patent Document 1 describes an exhaust system in which an exhaust pipe through which exhaust from an engine flows and an exhaust purification catalyst unit for purifying exhaust are connected. The exhaust purification catalyst portion in the exhaust device described in Patent Document 1 has a tubular catalyst case, and the purification catalyst is accommodated therein. The exhaust pipe and the catalyst case of the exhaust purification catalyst unit are connected. Patent Document 1 describes that the exhaust pipe and the catalyst case of the exhaust purification catalyst section are connected by welding. Specifically, in the connection method described in Patent Document 1, the end of the catalyst case in the exhaust purification catalyst unit is inserted into the inner peripheral side of the end of the exhaust pipe, and in this state, the end of the exhaust pipe and the catalyst The outer peripheral surface of the case is welded.

JP 2011-256785 A

  In the exhaust pipe connecting method as described in Patent Document 1, the end of the catalyst case is installed in consideration of ease of assembly when the end of the catalyst case is inserted into the inner peripheral side of the end of the exhaust pipe. Generally, a predetermined gap (for example, about 0.5 mm) is secured between the outer peripheral surface and the inner peripheral surface of the end portion of the exhaust pipe. However, when such a gap is generated, welding spatter (fine particles) enters the inside of the catalyst case and the exhaust pipe through the gap when welding the end of the catalyst case and the end of the exhaust pipe. There is. The welding spatter that has entered the inside of the catalyst case or the exhaust pipe may interfere with the flow of exhaust gas in the exhaust purification catalyst section, or may cause malfunction of other devices (for example, EGR valve) mounted inside the exhaust pipe. It can be. Therefore, it is required to connect the exhaust pipe and the catalyst case so that welding spatter does not enter as much as possible.

  In order to solve the above-mentioned problems, the present invention provides an exhaust pipe connection method in which an exhaust pipe through which exhaust from an engine flows and a tubular catalyst case containing a purification catalyst are connected by welding. An assembly step of inserting an end portion of the catalyst case into an inner peripheral side of the portion to make an assembled state, and an end portion of the exhaust pipe from the outer peripheral side with respect to the exhaust pipe and the catalyst case in the assembled state A pressing step of pressing to form a convex portion protruding toward the outer peripheral surface side of the catalyst case, and the pressing step at the end of the exhaust pipe with respect to the exhaust pipe and the catalyst case in the assembled state A welding step of welding a tip end side of the projected portion to the outer peripheral surface of the catalyst case.

  According to said structure, the convex part which protrudes in the outer peripheral surface side of a catalyst case is formed in the edge part of an exhaust pipe in the step of a welding process. The gap between the inner peripheral surface at the end of the exhaust pipe and the outer peripheral surface at the end of the catalyst case is reduced by the protrusion length of the convex portion. Therefore, it is possible to suppress welding spatter from entering the exhaust pipe or the catalyst case in the welding process. On the other hand, at the stage of the assembling process, no convex portion is formed at the end of the exhaust pipe, and it corresponds as a gap between the inner peripheral surface at the end of the exhaust pipe and the outer peripheral surface at the end of the catalyst case. The gap is secured. Therefore, it can also suppress that the assembly | attachment property in an assembly | attachment process deteriorates.

Sectional drawing of an exhaust pipe and a catalyst case. The enlarged view of the connection part of an exhaust pipe and a catalyst case. (A)-(c) is explanatory drawing which shows the method of connecting an exhaust pipe and a catalyst case. In (b), the right drawing is a cross-sectional view taken along the line 3b-3b of the left drawing, and in (c), the right drawing is a cross-sectional view taken along the line 3c-3c of the left drawing.

  Hereinafter, an embodiment relating to an exhaust pipe connection method will be described with reference to FIGS. 1 and 2, the exhaust from the engine is assumed to circulate from the left side to the right side in the figure, and the left side in the figure is the upstream side and the right side in the figure is the downstream side.

First, a connection structure between the exhaust pipe and the catalyst case will be described.
As shown in FIG. 1, the exhaust pipe 10 has a circular tubular shape as a whole. As shown in FIG. 2, the downstream end portion 11 that is a part of the downstream side of the exhaust pipe 10 has an inner diameter R1a larger than an upstream inner diameter R1b. As shown in FIG. 1, a catalyst case 21 of the exhaust purification catalyst unit 20 is inserted on the inner peripheral side of the downstream end portion 11 in the exhaust pipe 10.

  The catalyst case 21 has a circular tube shape as a whole. In the catalyst case 21, a purification catalyst 25 is accommodated in the central portion 22 in the axial direction. 1 and 2 show the purification catalyst 25 in a simplified manner.

  As shown in FIG. 2, the outer diameter R <b> 2 a of the upstream end 23, which is a part of the upstream side of the catalyst case 21, is smaller than the outer diameter R <b> 2 b of the central portion 22 in the catalyst case 21. Further, the outer diameter R2a of the upstream end 23 of the catalyst case 21 is smaller than the inner diameter R1a of the downstream end 11 of the exhaust pipe 10. The difference between the outer diameter R2a of the upstream end 23 of the catalyst case 21 and the inner diameter R1a of the downstream end 11 of the exhaust pipe 10 is, for example, about several hundred μm to several mm.

  An upstream end 23 of the catalyst case 21 is inserted on the inner peripheral side of the downstream end 11 in the exhaust pipe 10. Therefore, a gap S corresponding to the difference between the inner diameter R1a and the outer diameter R2a is generated between the inner peripheral surface of the downstream end 11 in the exhaust pipe 10 and the outer peripheral surface of the upstream end 23 in the catalyst case 21. ing. Specifically, when the central axis of the downstream end 11 in the exhaust pipe 10 coincides with the central axis of the upstream end 23 in the catalyst case 21, the inner circumference of the downstream end 11 in the exhaust pipe 10. The distance between the surface and the outer peripheral surface of the upstream end 23 in the catalyst case 21 is one half of the difference between the inner diameter R1a and the outer diameter R2a.

  As shown in FIG. 1, the outer diameter of the downstream end 24, which is a part of the downstream side of the catalyst case 21, is smaller than the outer diameter of the central portion 22 in the catalyst case 21. In this embodiment, the downstream end 24 of the catalyst case 21 has the same dimensional configuration as the upstream end 23. The downstream end 24 of the catalyst case 21 is connected to another circular tubular member (not shown).

  As shown in FIG. 2, the downstream end portion 11 of the exhaust pipe 10 is provided with a convex portion 12 that protrudes from the outer peripheral side toward the inner peripheral side. The convex part 12 is provided over the circumferential direction whole region (360 degree whole region) in the downstream end part 11. The protrusion length of the convex portion 12 is set to one half of the difference between the outer diameter R2a of the upstream end portion 23 of the catalyst case 21 and the inner diameter R1a of the downstream end portion 11 of the exhaust pipe 10. Therefore, the top portion (the most radially inner portion) of the convex portion 12 is in contact with the outer peripheral surface of the upstream end portion 23 in the catalyst case 21.

  The downstream end 11 of the exhaust pipe 10 is welded to the outer peripheral surface of the catalyst case 21. Specifically, the downstream side of the convex portion 12 at the downstream end portion 11 of the exhaust pipe 10 and the outer peripheral surface of the catalyst case 21 are welded. As a result, the weld bead 15 is provided over the entire circumferential direction so as to block between the opening edge 11a of the downstream end 11 of the catalyst case 21 and the outer peripheral surface of the catalyst case 21.

Next, a connection method between the exhaust pipe and the catalyst case will be described together with the effects.
In connecting the exhaust pipe 10 and the catalyst case 21, first, the exhaust pipe 10 and the catalyst case 21 are subjected to an assembly process. In the assembling step, as shown in FIG. 3A, the upstream end 23 of the catalyst case 21 is inserted into the inner peripheral side of the downstream end 11 of the exhaust pipe 10, and these are put into an assembled state. At the time of this assembling step, the above-described convex portion 12 is not formed at the downstream end portion 11 of the exhaust pipe 10. Further, the inner diameter R 1 a of the downstream end 11 of the exhaust pipe 10 is larger than the outer diameter R 2 a of the upstream end 23 of the catalyst case 21. Therefore, even if the central axis of the downstream end portion 11 of the exhaust pipe 10 and the central axis of the catalyst case 21 do not completely coincide with each other, the upstream side of the catalyst case 21 is located on the inner peripheral side of the downstream end portion 11 of the exhaust pipe 10. A side end 23 can be inserted. That is, assemblability when the upstream end 23 of the catalyst case 21 is inserted into the inner peripheral side of the downstream end 11 of the exhaust pipe 10, appropriate assemblability according to the difference between the inner diameter R1a and the outer diameter R2a. Is secured.

  After the assembly process, the exhaust pipe 10 and the catalyst case 21 are subjected to the pressing process while maintaining the assembled state. In this pressing process, three mold members 30 are used as shown in FIG. Each mold member 30 has a long shape extending in an arc shape as a whole. Each mold member 30 extends over a range of 120 ° when the virtual center point of the arc is used as a reference. Each mold member 30 has a base 31 that has a quadrangular shape when viewed in cross section along the radial direction of the arc, and a ridge 32 that extends from the inner peripheral surface 31a of the base 31 toward the inner side of the arc. And. The curvature radius of the inner peripheral surface 31 a in the base 31 is substantially the same as the curvature radius of the outer peripheral surface of the downstream end 11 in the exhaust pipe 10. The protrusion 32 is provided over the entire longitudinal direction of the base 31. The protruding length of the protrusion 32 is one half of the difference between the inner diameter R1a of the downstream end 11 in the exhaust pipe 10 and the outer diameter R2a of the upstream end 23 in the catalyst case 21. 3B and 3C, the exhaust pipe 10 and the catalyst case 21 are shown as cross-sectional views, and the mold members 30 are shown as side views.

  As shown in FIG. 3 (b), in the pressing step, the protrusion 32 is formed on the exhaust pipe 10 on the radially outer side of the downstream end 11 of the assembled exhaust pipe 10 and the upstream end 23 of the catalyst case 21. And the metal mold | die member 30 is arrange | positioned so that it may face the catalyst case 21 side. Further, three mold members 30 are arranged at equal intervals in the circumferential direction, that is, at positions shifted by 120 °. Then, as shown in FIGS. 3B and 3C, each mold member 30 is moved inward in the radial direction.

  As shown in FIG. 3C, when each mold member 30 moves radially inward, the protruding portion 32 of each mold member 30 has an outer peripheral surface of the downstream end portion 11 in the exhaust pipe 10. Abut. And the protrusion part 32 of each metal mold | die member 30 deform | transforms a part of downstream end part 11 in the exhaust pipe 10 to radial inside. As a result, a convex portion 12 that protrudes from the outer peripheral side toward the inner peripheral side is formed at the downstream end portion 11 of the exhaust pipe 10.

  Here, each mold member 30 extends over a range of 120 °, and as shown in FIG. 3C, when the end portions of adjacent mold members 30 move to a position where they abut, It will be in the state where the one mold member 30 was connected over 360 degrees. Therefore, the convex part 12 is formed in the downstream end part 11 of the exhaust pipe 10 over the whole circumferential direction.

  Further, in a state where the ends of the adjacent mold members 30 are in contact with each other, the mold members 30 interfere with each other and cannot move further inward in the radial direction. In each mold member 30, the curvature of the inner peripheral surface 31 a of the base portion 31 is substantially equal to the curvature of the outer peripheral surface of the downstream end portion 11 in the exhaust pipe 10. Therefore, even if each mold member 30 moves radially inward to a state where the end portions thereof are in contact with each other, the inner peripheral surface 31a of the base portion 31 of each mold member 30 remains at the downstream end of the exhaust pipe 10. The portion 11 is not pressed radially inward with an excessively strong force. As a result, the entire downstream end 11 of the exhaust pipe 10 is prevented from being deformed radially inward.

  In addition, the protruding length of the protrusion 32 in each mold member 30 is two minutes of the difference between the inner diameter R1a of the downstream end 11 in the exhaust pipe 10 and the outer diameter R2a of the upstream end 23 in the catalyst case 21. It is 1. Therefore, the protruding length of the convex portion 12 formed at the downstream end portion 11 in the exhaust pipe 10 is also a half of the difference between the inner diameter R1a and the outer diameter R2a. Therefore, even if the central axis of the downstream end 11 of the exhaust pipe 10 and the central axis of the catalyst case 21 do not coincide with each other in the assembly process, the downstream end 11 of the exhaust pipe 10 in the pressing process. In the process of forming the convex portion 12, the top portion of the convex portion 12 in the exhaust pipe 10 comes into contact with the catalyst case 21, and the catalyst case 21 is pushed out toward the central axis. Therefore, in this embodiment, the top part of the convex part 12 of the downstream end part 11 in the exhaust pipe 10 contacts the outer peripheral surface of the upstream end part 23 in the catalyst case 21 over the entire circumferential direction. The central axis of the upstream end 23 of the catalyst case 21 is positioned on the central axis of the downstream end 11 of the exhaust pipe 10 by the top of the convex portion 12 of the downstream end 11 of the exhaust pipe 10. become.

  When the above pressing process is completed, the exhaust pipe 10 and the catalyst case 21 are subjected to a welding process. In this welding step, as shown in FIG. 3C, the downstream side of the convex portion 12 at the downstream end portion 11 of the exhaust pipe 10 and the outer peripheral surface of the catalyst case 21 are welded. Examples of the type of welding include MIG welding. In addition, in FIG.3 (c), the location welded in a welding process is illustrated with the broken line virtually as a location where the weld bead 15 is formed.

  Here, when the downstream end portion 11 of the exhaust pipe 10 and the outer peripheral surface of the catalyst case 21 are welded, welding spatter (fine particles) is generated. The generated weld spatter may enter the gap S between the inner peripheral surface of the downstream end 11 in the exhaust pipe 10 and the outer peripheral surface of the upstream end 23 in the catalyst case 21. In the present embodiment, at the time of the welding process, the convex portion 12 is already formed on the downstream end portion 11 in the exhaust pipe 10, and the top of the convex portion 12 is the outer peripheral surface of the upstream end portion 23 in the catalyst case 21. Abut. Therefore, as shown in FIG. 2, the portion where the weld bead 15 is formed and the inside of the exhaust pipe 10 and the inside of the catalyst case 21 are blocked by the convex portion 12 of the exhaust pipe 10. There is no communication. Therefore, even if welding spatter is generated in the welding process, the welding spatter is prevented from entering the exhaust pipe 10 or the catalyst case 21 through the gap S.

The above embodiment can be modified as follows.
The series of techniques related to the pressing step and the welding step in the above embodiment may be applied to a method for connecting the downstream end 24 of the catalyst case 21 and the tubular member connected to the downstream end 24.

  The shapes of the exhaust pipe 10 and the catalyst case 21 are not limited to those exemplified above. For example, the inner diameter and outer diameter of the exhaust pipe 10 and the catalyst case 21 may be formed constant in the axial direction. That is, the technique of the above embodiment can be applied as long as the end of the catalyst case 21 can be inserted into the inner peripheral side of the end of the exhaust pipe 10. Further, the downstream end 11 of the exhaust pipe 10 and the upstream end 23 of the catalyst case 21 do not necessarily have to be tubular. For example, a cross-sectional elliptical shape or a polygonal shape may be used. If the shape of the downstream end 11 of the exhaust pipe 10 is changed, the shape of the mold member 30 used in the pressing process may be changed accordingly.

  -The convex part 12 of the downstream end part 11 in the exhaust pipe 10 does not necessarily need to be formed in the whole circumferential direction. Even when the convex portion 12 is not formed in the entire circumferential direction, at least a portion where the convex portion 12 is formed and its periphery, welding spatter is generated inside the exhaust pipe 10 and inside the catalyst case 21 during the welding process. It is possible to suppress entry.

  -The protrusion length of the convex part 12 is not restricted to the protrusion length illustrated by the said embodiment. For example, the protruding length of the convex portion 12 may be shorter than one half of the difference between the outer diameter R2a of the upstream end portion 23 of the catalyst case 21 and the inner diameter R1a of the downstream end portion 11 of the exhaust pipe 10. . In this case, a gap is generated between a part of the convex portion 12 and the outer peripheral surface of the upstream end 23 in the catalyst case 21 in the circumferential direction. However, the gap is less than the gap between the inner peripheral surface of the downstream end 11 in the exhaust pipe 10 and the outer peripheral surface of the upstream end 23 in the catalyst case 21 when the convex portion 12 is not formed. small. Therefore, even in the case of this modified example, it is possible to suppress welding spatter from entering the inside of the exhaust pipe 10 or the inside of the catalyst case 21 in the welding process as compared with the case where the convex portion 12 is not provided.

  The protrusion length of the convex portion 12 is slightly longer than one half of the difference between the outer diameter R2a of the upstream end portion 23 of the catalyst case 21 and the inner diameter R1a of the downstream end portion 11 of the exhaust pipe 10. Is also possible. In the case of this modified example, the upstream end portion 23 of the catalyst case 21 is pushed radially inward by the convex portion 12 of the exhaust pipe 10 and deformed during the pressing process.

  -Another process may exist between an assembly process and a press process. However, it is necessary that the exhaust pipe 10 and the catalyst case 21 are in an assembled state during the pressing process.

  Similarly, other processes may exist between the pressing process and the welding process. Also in this modified example, it is necessary that the exhaust pipe 10 and the catalyst case 21 be in an assembled state during the welding process.

  The number of mold members 30 used in the pressing process can be changed as appropriate. For example, four mold members 30 extending over a range of 90 ° may be used. Further, depending on the outer diameter and shape of the exhaust pipe 10 and the catalyst case 21, the pressing process may be performed with the two mold members 30.

  -The mode of welding in a welding process is not ask | required. For example, arc welding other than MIG welding or laser welding may be used. That is, as long as the welding mode can cause welding spatter during welding, the series of techniques of the above-described embodiment and modification examples can be applied to any welding mode.

  DESCRIPTION OF SYMBOLS 10 ... Exhaust pipe, 11 ... Downstream end part, 12 ... Convex part, 15 ... Weld bead, 20 ... Exhaust purification catalyst part, 21 ... Catalyst case, 22 ... Center part, 23 ... Upstream end part, 24 ... Downstream side End part, 25 ... purification catalyst, 30 ... mold member, 31 ... base part, 31a ... inner peripheral surface, 32 ... ridge part.

Claims (1)

An exhaust pipe connection method for connecting an exhaust pipe through which exhaust from an engine circulates and a tubular catalyst case containing a purification catalyst by welding,
An assembling step for inserting the end of the catalyst case into the inner peripheral side of the end of the exhaust pipe to put it in an assembled state;
A pressing step of pressing the end of the exhaust pipe from the outer peripheral side to form a convex portion protruding toward the outer peripheral surface of the catalyst case with respect to the exhaust pipe and the catalyst case in the assembled state;
A welding step of welding the tip side of the exhaust pipe with respect to the assembled exhaust pipe and the catalyst case to the outer peripheral surface of the catalyst case with respect to the convex portion formed in the pressing step at the end portion of the exhaust pipe. An exhaust pipe connection method comprising the steps of:

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