JP2002213241A - Terminal exhaust pipe and its machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive terminal exhaust pipe by establishing a method of manufacturing the pipe efficiently at a low cost. SOLUTION: In this terminal exhaust pipe, the terminal of the pipe forms an increased diameter pipe part which forms a double pipe bent inward generally through the entire area thereof. A method of machining the exhaust pipe 10 comprises a pipe diameter increasing step for forming the increased diameter part 1c by expanding the end part of the pipe, a step for decreasing the diameter of the pipe at the tip of the increased diameter part, a step for cutting the pipe at the tip of the decreased diameter part, and a step for forming the pipe by folding inward the increased diameter pipe part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal exhaust pipe through which exhaust gas of an engine of a vehicle or the like is discharged into the atmosphere, and a method of processing the same.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional example of a terminal exhaust pipe 1 arranged at a site where exhaust gas of an engine of a vehicle or the like is discharged into the atmosphere. When the exhaust gas after silencing by the muffler 2 is finally discharged into the atmosphere, the exhaust gas passes through the terminal exhaust pipe 1.
At the final end of the exhaust pipe main body 1a, a pipe expansion member 3 having a diameter larger than that of the separate exhaust pipe main body 1a is attached to the final end of the exhaust pipe main body 1a by a welded portion P in consideration of danger prevention and appearance. The expansion member 3 is formed such that the inner diameter of the base end portion is equal to or larger than the outer diameter of the exhaust pipe main body 1a to be extrapolated, and the space between the expansion member 3 and the large diameter expansion member 3 is tapered. As the terminal exhaust pipe, such a structure, a type in which another component externally inserted into the exhaust pipe main body is attached by band tightening, fixing with a bolt and nut, and the like were generally used.

[0003] In the manufacture of the terminal exhaust pipe, the conventional structure in which a separate expansion member is integrated with the exhaust pipe main body requires operations such as welding and caulking, and requires a large number of parts. Some products have disadvantages such as requiring a surface treatment such as plating in a later step.

[0004]

Accordingly, the present inventor has studied a low-cost and high-efficiency manufacturing method of a terminal exhaust pipe in which exhaust gas of an engine is discharged into the atmosphere, and has aimed to provide an inexpensive method.

[0005]

As a result of examining the above-mentioned problems, a terminal exhaust pipe is formed in which the end of the pipe forms an expanded part and an inner folded double pipe is formed over substantially the entire area of the expanded part. . Here, the expanded portion has a continuous pipe, and that the pipe is continuous means that the expanded portion at the final end is the same as the exhaust pipe main body and is not a separate member. The phrase “substantially over the entire area of the expanded portion” refers to a state in which the double pipe exists from the final end to almost reach the tapered portion.

[0006] The manufacturing method of such a terminal exhaust pipe is as follows.
The method includes a pipe expanding step of expanding an end of a pipe to form a pipe expanding section, a step of contracting a pipe expanding end, a step of cutting a tip of a contracting section, and a step of forming an internal folded portion of the expanded section. The expansion is so-called bulge processing, and employs a press of a type in which a core is pressed into the pipe or a general-purpose hydraulic processing method. As for the tube contraction step at the tip of the tube portion, it is preferable to use a press using a mold having a contracted tube shape or general-purpose hydraulic forming. The inside of the expanded tube is preferably formed by press-fitting the front end of the punch into the contracted tube.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in the order of steps with reference to the drawings. First, a part of the pipe is expanded as shown in FIG. The pipe here is the exhaust pipe body 1a
The expanded portion 1c is formed in a continuous state through the tapered portion 1b at one end thereof. The degree of expansion can be freely designed according to design specifications within the pipe expansion allowance. As shown in FIG. 2, an outer mold 5 composed of a small-diameter hole portion 5a, a tapered portion 5b, and a large-diameter hole portion 5c into which the raw tube 4 can be inserted is formed in this expanded tube portion 1c.
The raw material tube 4 is disposed therein, and has a small-diameter portion 6a, a tapered portion 6b, and a large-diameter portion 6c, which have substantially the same shape as the inner mold of the outer mold 5 and have a smaller diameter by the thickness of the formed exhaust pipe. Is press-fitted.

[0008] Next, the distal end of the expanded portion is contracted. This step is press molding using a female mold 7 having the shape of a contracted tube as shown in FIG. The distal end of the expanded portion is pressed to forcibly contract the tube. Then, as seen in FIG.
The distal end of the constricted portion is cut (arrow C) to prepare the distal end of the constricted portion as shown in FIG.

In the step of forming the expanded portion 1c inwardly, a punch 8 is used as shown in FIG. The tip 8a of the punch 8 is provided on the contracted tube portion 1d above the expanded tube portion 1c held by the outer die 5.
And press-fit. FIG. 6 is a sectional view of the completed terminal exhaust pipe 10. The final end forms an expanded portion 1c in a state where the pipe is continued as it is via a tapered portion 1b at one end of the exhaust pipe main body 1a, and a folded pipe portion is formed inside substantially the entire area of the expanded portion 1c.
1e forms a double tube formed. If there is a risk of adversely affecting the use performance by remaining after the contracted tube portion in contact with the punch becomes a product, the step of removing the contracted tube portion of the vent hole in the tube may be increased, As shown in FIG. 8, it may be turned outward. The pipe wall surfaces of the double pipe can be brought into close contact with each other.

[0010]

According to the present invention, a low-cost and high-efficiency manufacturing method that does not require the surface treatment of the terminal exhaust pipe or another member is established, and the terminal exhaust pipe can be provided at low cost. By pressing the punch tip into the constricted tube part and press-fitting it into the formation of the folded tube part inside the pipe, it is more reliable than the method of simply press-fitting from the pipe end and causing buckling at the bent part The terminal exhaust pipe bent inside at the designed position is obtained, and the yield is good. Further, since the terminal exhaust pipe has a double structure, a surface finish for preventing terminal corrosion is not required. The strength and appearance of the terminal are also good.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a terminal exhaust pipe manufacturing process of the present invention.

FIG. 2 is a cross-sectional view of a molding apparatus showing a state in which a raw material tube is placed in an outer mold and a core is press-fitted.

FIG. 3 is a cross-sectional view of a forming apparatus showing a state of a contraction tube.

FIG. 4 is a side view of a main part of a terminal exhaust pipe manufacturing process in which the distal end of the constricted pipe is cut.

FIG. 5 is a side view of a main part of a terminal exhaust pipe manufacturing process.

FIG. 6 is a sectional view of a main part of a terminal exhaust pipe manufacturing process.

FIG. 7 is a cross-sectional view of the forming apparatus showing a state of the folding forming step.

FIG. 8 is a sectional view of a main part showing an example of a terminal exhaust pipe of a product.

FIG. 9 is a plan view showing an arrangement of a conventional terminal exhaust pipe.

[Explanation of symbols]

 1a Exhaust pipe main body 1b Taper section 1c Expanding section 1d Contracting section 1e Turned pipe section 2 Muffler 3 Expanding member 4 Raw tube 5 Outer die 6 Core 7 Molding die 8 Punch 10 Terminal exhaust pipe of the present invention

Claims (3)

[Claims] 1. A terminal exhaust pipe in which a terminal of a pipe forms an expanded part, and an inner folded double pipe is formed over substantially the entire area of the expanded part. 2. A pipe expanding step of expanding an end of a pipe to form a pipe expanding section, a step of contracting a front end of the pipe expanding section, a step of cutting a distal end of the tube reducing section, and a step of forming an inside of the expanded section inwardly. Processing method of terminal exhaust pipe. 3. The method for processing a terminal exhaust pipe according to claim 2, wherein the inside of the expanded pipe section is formed by press-fitting the compressed pipe section by abutting a tip end of a punch.