Power plants – Internal combustion engine with treatment or handling of... – Common receiver having inlets from plural cylinder
Reexamination Certificate
2000-01-24
2001-03-27
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Common receiver having inlets from plural cylinder
C060S313000, C285S125100, C285S405000
Reexamination Certificate
active
06205778
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust pipe assembly for a multi-cylinder internal combustion engine, in which exhaust pipes to be connected to a head of the engine are made of steel pipes.
2. Description of the Related Art
The structure of an exhaust pipe assembly in which steel pipes are used in making exhaust pipes is shown in, e.g., Japanese Published Unexamined Utility Model Registration Application No. 1819/1993, as illustrated in
FIGS. 6A through 6C
. In
FIG. 6A
, reference alphabet “a” denotes a flange which is connected to a cylinder head of an internal combustion engine, reference alphabets b denote exhaust pipes which are made of steel pipes, alphabet c denotes a collecting case (or an assembly casing), and alphabet d denotes a flange which is connected to an exhaust gas purifier. Downstream ends of the exhaust pipes b are shaped into sectors (or fan shapes) b
1
as shown in FIG.
6
B. The V-shaped portions (i.e., the portions formed by two radii) of the respective fan-shaped portions b
1
are welded together and are converged such that a series of arched portions substantially form a circle. The subassembly thus obtained is fitted into the collecting case c, and the subassembly and the collecting case are welded together. In
FIG. 6C
, a welded portion W
1
shows a cross-shaped welding performed along the V-shaped portions. A welded potion W
2
shows a welding performed between the arched portions and the collecting case.
In these welded portions, the cross-shaped welded portion W
1
must be welded along the entire length of the V-shaped portions so that the exhaust gases do not leak under pressure. In the welded portion W
2
, attention must be paid so that gases do not leak under pressure through clearances e which are formed on outer corners of the arched portions. This kind of welding work is not easy to perform and is low in workability (or welding efficiency). In addition, there is a disadvantage in that welding defects, if any, cannot be easily located and repaired. Furthermore, in this example, since the above-described V-shaped portions are assembled on a back-to-back relationship in as many as at four portions, heat is accumulated to thereby raise the temperature therein. As a result, the temperature difference between the V-shaped portions and the outer arched portions becomes so large as to cause cracks. In order to minimize the possibility of occurrence of cracking, a high-quality and heat-resistant material must be used in the exhaust pipes b.
FIGS. 7A and 7B
show another example of the conventional exhaust pipe assembly, in which an intermediate flange f is interposed between the exhaust pipes b and the collecting case c. The intermediate flange f is made by forming holes f
1
for receiving therein respective exhaust pipes b. The respective exhaust pipes b are then inserted into the holes f
1
and are welded to the flange f at welding portions W
3
. This intermediate flange f is thereafter welded to the collecting case c at a welding portion W
4
. In this example, the intermediate flange f must be provided, as shown in
FIG. 7B
, with an allowance (or a required length) t
1
for inserting the pipe as well as an allowance t
2
for welding. Therefore, the thickness T of the intermediate flange f becomes large and the heat is accumulated therein, with the result that the intermediate flange f is likely to be subject to a damage by the heat. To minimize this kind of disadvantage, a thicker and highly heat-resistant material must be used, resulting in a lager weight. In addition, if the distance
1
between the holes f
1
, f
1
for inserting the exhaust pipes b is made smaller in an attempt to minimize the weight of the intermediate flange f, the strength of a metallic mold for use in punching the intermediate flange f becomes so low that the punching of the holes can no longer be performed. As a solution to this problem, the holes f
1
, f
1
for inserting the pipes b must be made by an expensive way of working in the form of cutting. Even if these holes are formed by cutting work, the intermediate flange f is likely to cause cracks at welding beads due to thermal strains by welding, if the distance
1
is minimized.
The present invention has an object of providing an exhaust pipe assembly for a multi-cylinder internal combustion engine in which the members for assembling the plurality of exhaust pipes together can be made in a material which is less likely to accumulate heat and which is small in weight and less expensive.
SUMMARY OF THE INVENTION
In order to attain the above and other objects, the present invention is an exhaust pipe assembly for a multi-cylinder internal combustion engine comprising: a plurality of exhaust pipes made of steel, upstream ends thereof being connected to a flange provided for connection to a cylinder head; a collecting case to which downstream ends of the exhaust pipes are connected; and a coupling flange interposed between the exhaust pipes and the collecting case, the coupling flange being made of a thin steel plate, wherein the coupling flange comprises upward burred portions which are circular in shape and into which respective downstream ends of the exhaust pipes are separately inserted for welding with the burred portions, and a downward bent portion whose peripheral edge portion is fitted onto an upper outside end portion of the collecting case for welding with the bent portion.
According to this arrangement, the exhaust pipes, the coupling flange itself and the fitting portion can be formed light in weight. Therefore, the heat does not accumulate in these members, and they can be prevented from reaching an elevated temperature. It is thus not necessary to use an expensive and highly heat-resistant material to make the exhaust assembly. In addition, by providing the coupling flange with the burred portions and the bent portion, the area of dissipating the heat in the coupling flange increases to thereby improve the cooling characteristics. Still furthermore, the above-described arrangement of the exhaust pipe assembly facilitates the fitting and the welding of each of the portions, and the rigidity of the coupling flange increases. Due to this increased rigidity, the radiating sounds or noises from the coupling flange can be reduced. Furthermore, since the welding portions are circular and simple in shape, the welding work can be performed easily and the leak of exhaust gases under pressure can be easily detected.
Preferably, the burred portions are provided at a distance from one another. According to this arrangement, each of the burred portions is formed separately from, or independent of, one another at a distance therebetween. Therefore, the heat dissipating area becomes large and the cooling characteristics can be improved. As a result, heat is not accumulated in the coupling flange and, consequently, the concentration of thermal stresses in the coupling flange can be avoided.
Preferably, steel materials used in the exhaust pipes, in the coupling flange and in the collecting case have similar thicknesses. According to this arrangement, since the plate thicknesses of each of the members are close to one another, the thermal stresses hardly occur and, thus, the cracking at the welding bead can be prevented.
REFERENCES:
patent: 3470690 (1969-10-01), Thompson
patent: 3507301 (1970-04-01), Larson
patent: 4373329 (1983-02-01), Martini
patent: 4656830 (1987-04-01), Ohno et al.
patent: 5887428 (1999-03-01), Garisto
patent: 6009706 (2000-01-01), Haneda
patent: 6038855 (2000-03-01), Markström et al.
patent: 6082103 (2000-07-01), Sugiura et al.
patent: 5-1819 (1993-01-01), None
Akaba Manabu
Furuhashi Kazuhiro
Matsuzawa Hideo
Armstong, Westerman, Hattori, McLeland & Naughton
Denion Thomas
Kabushiki Kaisha Yutaka Giken
Tran Binh
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