Pipes and tubular conduits – Plural duct – Longitudinally extending common wall
Reexamination Certificate
2000-12-22
2003-06-10
Hook, James (Department: 3752)
Pipes and tubular conduits
Plural duct
Longitudinally extending common wall
C138S169000, C138S170000, C138S171000
Reexamination Certificate
active
06575198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a method of connecting thin metallic plate (or plates) by welding along a portion in which a single metallic plate is bent to form a joint portion for welding together or along a joint portion in which two members meet together. In particular, it relates to a method of manufacturing an exhaust pipe of two-passage construction to be used in an exhaust system of an internal combustion engine, as an example of a product manufactured by the above-described method. It also relates to an exhaust pipe of two-passage construction manufactured by the above and other methods, which is free from stress concentration due to pulsations of exhaust gases.
2. Description of Related Art
As a method of welding two relatively thin metallic plates for the purpose of manufacturing a product such as an exhaust pipe of two-passage construction which is suitable for connection to an exhaust manifold of a multi-cylinder internal combustion engine of a motor vehicle, there is known the following method in, for example, Published Unexamined Japanese Patent Application No. 192727/1997 as shown in FIG.
11
. Namely, a single piece of metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe is bent substantially into S shape (i.e., a configuration of an alphabet “S”), as seen in cross section. The product thus obtained has: a partition plate or a partition wall “a” which extends in a diametrical direction and is elongated in a longitudinal direction of the exhaust pipe; and substantially semicircular peripheral wall portions b, b on each lateral side of the partition plate (i.e., on a side at a right angle to the partition plate). In this manner, independent chambers d, d are formed between the partition plate “a” and the peripheral walls b, b for passing therethrough the exhaust gases from the engine. Diametrical end portions, as seen in cross section, of the first end and the second end of the metallic plate are respectively bent radially inward to form connecting pieces c, c which lie along the partition plate “a” in its assembled state. Radially outer sides of the connecting pieces c and the partition plate “a” are welded together from a radially out side to thereby form welding beads e, e. On both longitudinal end portions of this exhaust pipe, flanges are welded for connecting the exhaust pipe to the engine on an upstream side thereof as well as to a catalyst converter on a downstream side thereof.
The exhaust pipe of two-passage construction thus formed has, however, the following disadvantages. Namely, a welding bead e which is formed in the longitudinal direction of the exhaust pipe is likely to protrude beyond the outer circumferential surface of the exhaust pipe. It follows that, when the longitudinal end portion of this welded exhaust pipe is to be inserted into the flange for fixing it to the exhaust pipe by means of welding, or when an outer pipe which is used for covering the inner pipe for the purpose of thermal insulation is swaged (or tapered to a smaller diameter) to thereby bring the two members into close contact with each other, the protruded welding bead e is an obstacle.
As a solution, the following arrangement may be considered as shown in FIG.
12
A. The exhaust pipe of two-passage construction in this example is formed into a substantially S shape in cross section with a single piece of relatively thin metallic plate. It is made up of: a central partition plate “a” which forms, as seen in cross section, a diametrical line of the exhaust pipe and which extends in the longitudinal direction throughout the exhaust pipe; a substantially semicircular peripheral wall b which is formed on each lateral side of the central partition plate “a”; and a connecting piece c′ which is formed on each end of the metallic plate and which is bent so as to partially overlap with the partition plate “a” in close contact with each other at each diametrically outer end of the partition plate “a.” As a result, on each diametrically outer end portion of the partition plate “a”, there is provided a groove (or valley) f substantially in the shape of an alphabet V. This groove f is formed by an arched end of the thin metallic plate and that arched end of the semicircular peripheral wall b which transforms (or changes) into the central partition plate “a.” Welding is then made at this groove f by means of a welding gun (or a welding torch) g by generating an arc between the welding gun g and a bottom of the groove f in an attempt to integrally weld the central partition plate “a” and the peripheral wall b. In welding, however, electric discharging is likely to take place toward that portion of the mother material (peripheral wall b) which is closer to the welding gun g as shown by arrows g
1
, g
1
. As a result of this electric discharging, a lump h of welded metal (welding bead) is likely to be formed as shown in
FIG. 12B
in a manner not to reach deep into the groove (or the overlapped portion). A penetration bead is sometimes formed to thereby reduce the strength of the mother material. Sometimes, a penetrating hole i which breaks through the peripheral wall b is formed as shown in FIG.
12
C. If an attempt is made to enlarge the width of the groove f, the cross section of the exhaust pipe approaches the shape of a flattened one, resulting in a reduction in the area of flow of the exhaust gases.
The exhaust pipe of two-passage construction as disclosed in the above-described Published Unexamined Japanese Patent Application No. 192727/1997 has still another disadvantage as explained hereinbelow. Namely, when the exhaust gases from the multi-cylinder internal combustion engine pass through a right side passage (as shown in FIG.
11
), the central partition plate “a” tends to deflect toward the left side by the exhaust pressure as shown by dotted lines a
1
. When the exhaust gases pass through the left side passage d, the central partition plate “a” tends to deflect toward the right side by the exhaust pressure as shown by dotted lines a
2
. As a result, by the pulsation of the exhaust gases to pass through the two passages d, d, the partition plate “a” vibrates by alternately bending in opposite directions as shown by dotted lines a
1
, a
2
. This bending takes place with the following point serving as the point of bending, i.e., each welding portion between the connecting piece “c” and the partition plate “a” or a portion which lies on the radially inside thereof. Stresses are concentrated on these points of bending and fatigue occurs there if the vibrations continue.
In view of the above-described points, the present invention has an object of providing a method of connecting two elongated portions of a metallic plate by welding, a method of manufacturing an exhaust pipe of two-passage construction as an example of a product manufactured by the above-described method, as well as an exhaust pipe of two-passage construction manufactured by the above and other methods.
SUMMARY OF THE INVENTION
In order to attain the above and other objects, according to one aspect of the present invention, there is provided a method of connecting two elongated portions of a metallic plate, comprising the steps of: longitudinally disposing the two elongated portions at an angle so as to form a groove of substantially V shape in cross section having a substantially closed end and an open end; providing a target elongated along the groove, the target extending from the substantially closed end toward the open end; and generating a welding arc between the target and a welding gun disposed on a side of the open end above the target such that the substantially closed end of the two elongated portions and the target are welded together.
Preferably, the target is formed by bending that end of one of the elongated portions which lies on the substantially closed end toward the open end. The target may be arranged to lie on an inner surface of the other of the elonga
Eguchi Yoshihiko
Hosoda Fumio
Ishii Kazuo
Munemura Takeshi
Sasagase Takeshi
Armstrong Westerman & Hattori, LLP
Hook James
Kabushiki Kaisha Yutaka Giken
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