JP2002106339A - Inner pipe connecting method for double-pipe exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner pipe connecting method for a double-pipe exhaust manifold capable of lowering the cost by reducing the machining process. SOLUTION: The connecting end part in one first inner pipe 31 constituting an inner pipe is formed cylindrical, and the inside diameter of the connecting end part in the other second inner pipe 32 is substantially equal to the outside diameter of the first inner pipe 31. Axial slits s and s are formed at least in one portion in the circumferential direction of the connecting end part, and fixed pieces 32c and 32d are respectively extended outward substantially parallel at designated spaces from both side edge parts of the slits s and s. With the cylindrical connecting end part of the first inner pipe 31 inserted in the connecting end part of the second inner pipe, both fixed pieces 32c and 32d of the second inner pipe 32 are pressed and welded by spot welding, thereby connecting the first inner pipe 31 and the second inner pipe 32 to each other tightly without play in the state of expanding and contracting in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an outer tube and an inner tube arranged inside the outer tube while keeping a space between the outer tube and the inner tube. The present invention relates to a method for connecting an inner pipe of a double pipe exhaust manifold constituted by at least two first inner pipes and second inner pipes which are connected to each other so as to be extendable.

[0002]

2. Description of the Related Art Generally, an exhaust manifold is
In order to further enhance the purification performance of the car, the catalyst provided in the exhaust system is warmed up more quickly by using the exhaust gas, and the outer pipe for heat insulation is used to cover the outer circumference of the inner pipe and the outer circumference to exhibit the purification function earlier. In addition to the double pipe structure of the inner pipe, the inner pipe is moved in the axial direction in order to provide the inner pipe with the function of absorbing the thermal expansion difference generated based on the temperature difference and the thermal expansion coefficient difference between the inner pipe and outer pipe. It is composed of two members, a first inner tube and a second inner tube, which are connected to each other so as to be able to expand and contract.

[0003] As a method of connecting the inner pipe in this type of conventional double pipe exhaust manifold, for example, as shown in FIG. 5, a first inner pipe 1 formed in a cylindrical shape is used.
By attaching one of the connection ends of the first and second inner tubes 102 to the outside of the other connection end, they are connected to each other so as to be able to expand and contract in the axial direction.

[0004]

However, in the conventional method of connecting the inner pipes of the double pipe exhaust manifold, as described above, the connection ends of both the inner pipes are both formed in a cylindrical shape. Therefore, there were the following problems. That is, the connection portion of the inner pipe is intended to have a function of absorbing a thermal expansion difference based on a temperature difference or the like as described above, and the connection portion cannot be fixed by welding or the like. In order to prevent the generation of chattering noise due to the vibration of the vehicle and to secure the function of holding the inner pipes together, set the connection end of both inner pipes to the size of the press-in tolerance and press-fit them. It is necessary to caulk the connection end of the inner pipe to be the outer side so that the connection end of the inner pipe to be in the inner side is in close contact with the outer peripheral surface. .

An object of the present invention is to provide a method for connecting an inner pipe of a double-pipe exhaust manifold which can reduce costs by reducing the number of steps.

[0006]

According to the first aspect of the present invention, an outer tube and an inner peripheral surface of the outer tube are formed by an inner tube disposed inside the outer tube with a space therebetween. A method for connecting an inner pipe of a double pipe exhaust manifold comprising at least two members, a first inner pipe and a second inner pipe, wherein the inner pipe is connected to the middle pipe so as to be able to expand and contract in the axial direction. The inner diameter of the connection end of one of the second inner pipes constituting the inner pipe is formed to be substantially the same as the outer diameter of the other first inner pipe, and at least one circumferential direction of the connection end is provided in the axial direction. Along the slits are formed, and fixing pieces are respectively extended outwardly from both side edges of the slit substantially in parallel at a predetermined interval from each other, and a cylindrical connection end of the first inner pipe is formed in a second direction. While being inserted into the connection end of the second inner pipe, the second inner pipe is By contacting the fixing piece press-welding, and to be connected to the first inner tube and a second inner tube axially stretchable state.

According to a second aspect of the present invention, in the method for connecting an inner pipe of a double-pipe exhaust manifold according to the first aspect, both the fixing pieces of the second inner pipe are pressure-welded by spot welding.

[0008]

According to the first aspect of the present invention, as described above, the second end of the second inner tube is inserted into the second end of the second inner tube while the connection end of the first inner tube is inserted into the second end of the second inner tube. By pressing and welding the fixing pieces, each of which extends outward in a substantially parallel manner with both side edges of the slit in the inner pipe having a predetermined distance from each other, the connection end of the first inner pipe is formed by the pressing force. The connection end of the second inner pipe is swaged with an appropriate force against the outer peripheral surface of the portion, and the two fixing pieces are fixed by welding. Thereby, the first inner pipe and the second inner pipe are connected to each other in a state in which the first inner pipe and the second inner pipe can be extended and contracted in the axial direction without any backlash. Therefore, unlike the conventional example, it is not necessary to set and process the connection end portions of both inner tubes to the size of the press-in tolerance, so that rough dimension setting is possible, and a slit is formed at the connection end portion of the second inner tube. By being formed, the mounting operation of the first inner pipe can be easily performed, and further, the pressurizing operation and the welding operation for caulking can be performed simultaneously, thereby reducing the number of operation steps. This has the effect of reducing costs by reducing the number of steps.

According to the second aspect of the present invention, as described above,
Since the two fixed pieces in the second inner pipe are pressure-welded by spot welding, it is not necessary to use a pressing means separately from the welding means, and therefore, it is possible to reduce the equipment cost. The effect is obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for connecting an inner pipe of a double pipe exhaust manifold according to an embodiment of the present invention corresponds to the first and second aspects of the present invention. First, a configuration of a double pipe exhaust manifold to which a method for connecting an inner pipe of a double pipe exhaust manifold according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall view showing an exhaust system of an engine to which a method of connecting an inner pipe of a double pipe exhaust manifold according to an embodiment of the present invention is applied. FIG. 2 is an enlarged sectional view of a main part of FIG. 1, and FIG. FIG. 3 is an enlarged vertical sectional view taken along line III-III in FIG. 2, in which 1 is a 6-cylinder V-type engine,
2 is a catalyst, 3 is an inner pipe, 4 is an outer pipe, and 5 is an exhaust pipe.

That is, as shown in FIG. 1, the double-pipe exhaust manifold to which the embodiment of the present invention is applied includes the catalyst 2 provided in the exhaust system for further improving the purification performance of the vehicle. As shown in FIGS. 2 and 3, in order to use the exhaust gas from the cylinder V-type engine 1 to warm up more quickly and to exert the purification function earlier, the inner pipes 3 and the outer periphery of the inner pipes 3 are used. The outer pipe 4 has a double-pipe structure with the outer pipe 4 that keeps the exhaust gas passing through the inner pipes 3 by covering the outer circumference thereof and keeping the gap from the surface, and thermally insulating the air with an air layer. Each inner pipe 3 is made to be able to expand and contract with each other in the axial direction in order to provide each inner pipe 3 with a function of absorbing a thermal expansion difference generated based on a temperature difference and a thermal expansion coefficient difference between the inner pipe 3 and the outer pipe 4. It is composed of two members, a first inner tube 31 and a second inner tube 32, which are connected.

Returning to FIG. 1, and more specifically, this double-pipe exhaust manifold is provided on each of both sides of a 6-cylinder V-type engine 1 having two cylinder banks, and each of the double-pipe exhaust manifolds is ,
Three internal pipes 3 are provided in accordance with the number of cylinders, respectively, and these three internal pipes 3 are integrated into one at the downstream side and connected to the catalyst 2 via the exhaust pipe 5.

As shown in FIG. 3, each of the inner pipes 3 has a first inner pipe 31 connected to the engine 1 and is formed into a cylindrical shape, while a second inner pipe 31 is integrated into the downstream side. Reference numeral 32 denotes a press which is divided into two parts in the vertical direction, and is formed in a middle shape.
That is, as shown in FIG. 4B, the second inner pipe 32 has semicircular cross-section main bodies 32a and 32b along the upper and lower outer peripheral surfaces of the connection end of the first inner pipe 31, respectively. Fixing pieces 32c and 32d are provided to extend substantially in parallel from both side edges outwardly with a predetermined vertical interval t therebetween.

The second inner pipe 32 is mounted on the outer periphery of the connection end of the first inner pipe 31 such that the inner diameter of the connection end is substantially the same as the outer diameter of the first inner pipe 31. In the state, a predetermined interval t is formed between the fixing pieces 32c and 32d, respectively, and the upper and lower cross-section semi-circular main bodies 32a, 32a,
The dimensions are set so that slits s, s, corresponding to the crimping allowance, are formed between both side edges of 32b.

Next, a method of connecting the inner pipe in the double pipe exhaust manifold will be described with reference to FIG. Since the double-pipe exhaust manifold according to the embodiment of the present invention is configured as described above, first, as shown in FIG. 4A, the connection end of the first inner pipe 31 formed in a cylindrical shape. Is inserted into the connection end of the second inner tube 32, as shown in FIG.
When the inner surfaces of the first and second inner pipes a and 32b are in contact with the outer periphery of the connection end of the first inner pipe, a predetermined interval t is formed between the two fixing pieces 32c and 32d, and the upper and lower cross-sectional semi-circular main bodies 32 are formed.
Slits s, s corresponding to swaging margins are formed between both side edges of a, 32b.

Then, in this state, as shown in FIG. 4C, the two fixed pieces 32c and 32d are spot-welded by spot welding between the fixed pieces 32c and 32d at the positions indicated by arrows, so that the first inner part is formed by the pressing force. With respect to the outer peripheral surface of the connection end of the pipe 31, the upper and lower cross-sectional semi-circular main bodies 32 of the second inner pipe 32
a, 32b are caulked with a moderate force, and both fixing pieces 32c,
32d is welded and fixed, whereby the first
The inner tube 31 and the second inner tube 32 are connected to each other in a state in which the inner tube 31 and the second inner tube 32 can be extended and contracted in the axial direction without any backlash.

Therefore, the two inner tubes 31, 32 are different from the prior art.
It is not necessary to set and process the connection end portion to the size of the press-fit tolerance, so that rough dimension setting is possible.
Slits s, s are formed at the connection end of
The mounting work of the inner tube 31 can be easily performed.
Since the pressurizing work and the welding work for caulking can be performed simultaneously, the number of working steps is reduced, and the effect of reducing costs by reducing the number of steps is obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and even if there is a design change or the like within a range not departing from the gist of the present invention, Included in the present invention.

For example, in the embodiment of the invention, the two fixed pieces 32c and 32d are press-welded by spot welding between the two fixed pieces 32c and 32d.
The fixing pieces 32c and 32d may be welded and fixed by ordinary welding with the c and 32d pressed and held.

In the embodiment of the present invention, the first inner pipe 3
Although the example in which the connection end of 1 is formed in a cylindrical shape is taken as an example, similarly to the connection end of the second inner tube 32, a press in which the fixing pieces on both sides are welded and fixed is also formed in a middle shape. It can also be used.

In the embodiment of the present invention, the slit s
Although the fixing pieces 32c and 32d are formed on both sides, only one of them may be used.

[Brief description of the drawings]

FIG. 1 is an overall view showing an exhaust system of an engine to which a method for connecting an inner pipe of a double pipe exhaust manifold according to an embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part of FIG. 1 showing a method of connecting an inner pipe of the double pipe exhaust manifold according to the embodiment of the present invention.

FIG. 3 is an enlarged vertical sectional view taken along the line III-III of FIG. 2 showing a method of connecting the inner pipe of the double pipe exhaust manifold according to the embodiment of the present invention.

FIG. 4 is a process explanatory view showing a method of connecting an inner pipe of a double pipe exhaust manifold according to the embodiment of the present invention.

FIG. 5 is a plan view showing a method of connecting an inner pipe of a conventional double pipe exhaust manifold.

[Explanation of symbols]

 1 6-cylinder V-type engine 2 Catalyst 3 Inner tube 31 First inner tube 32 Second inner tube 32a Cross-section semi-circular main body 32b Cross-section semi-circular main body 32c Fixed piece 32d Fixed piece 4 Outer pipe 5 Exhaust pipe s Slit t Predetermined interval

Claims (2)

[Claims] 1. An outer tube and an inner peripheral surface of the outer tube are constituted by an inner tube arranged inside with a space therebetween, and the inner tubes are connected to each other so as to be able to expand and contract in the axial direction along the way. A method for connecting an inner pipe of a double pipe exhaust manifold constituted by at least two members, a first inner pipe and a second inner pipe, wherein an inner diameter of a connection end of one of the second inner pipes constituting the inner pipe is A slit is formed substantially at the same outer diameter as the other first inner pipe, and a slit is formed along the axial direction at at least one circumferential position of the connection end, and a predetermined interval is formed from both side edges of the slit. The fixing pieces are respectively extended outward in a substantially parallel manner in a state where the second inner pipe is inserted into the connection end of the second inner pipe. The first inner pipe and the second inner pipe are axially welded by pressure welding the two fixed pieces of the pipe. Double pipe inner pipe connecting method of the exhaust manifold, characterized in that it has to be connected to a telescopic state. 2. The method for connecting an inner pipe of a double-pipe exhaust manifold according to claim 1, wherein both fixed pieces of the second inner pipe are pressure-welded by spot welding.