JPH0379171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method of connecting a box body and an inner pipe of a resonant silencer made of synthetic resin by blow molding.

``Prior art'' Resonant silencers are used to reduce noise at a certain frequency in automobile engines and stationary engines, and consist of a box, an inner tube inserted into the box and a small hole drilled therein. It becomes. The amount of noise attenuation is controlled by the volume of the cavity formed by the inner tube and the box, the total area of the plurality of small holes drilled in the inner tube, the thickness of the inner tube, etc.

As a conventional example, patent application No. 58-204451 filed by the same applicant
No. 4 in the specification (Japanese Unexamined Patent Publication No. 60-95120)
The manufacturing method of the synthetic resin resonance type muffler A (hereinafter abbreviated as muffler A) shown in the figure is explained, and its outline will be described below.

The muffler A has a box body B formed on the outside of an inner tube D having a plurality of small holes d and a thickness t, and a cavity C formed by the inner tube D and the box body B. Then, an inner tube D having a plurality of small holes d and a thickness t is created using, for example, a synthetic resin injection molding machine, and a box body B is molded on the outside of the inner tube D using a blow molding machine 10 shown in FIG. 5 as a schematic diagram. be done. [Numbers of conventional examples are shown in parentheses] That is, a slide core 4 having an air flow passage 5 communicating with a small hole d of the inner tube D is inserted into the inside of the inner tube D that has been heated to an appropriate temperature, A pipe-shaped parison (pipe-shaped semi-fluid extruded resin) 20 is suspended for a predetermined length from the crosshead 1 on the outside of the inner pipe D, and the slide core 4 is lifted up by a rod 11 of an air cylinder 9, for example, to the inner pipe D. is pressed against the crosshead 1 to make both ends of the inner tube D airtight, and then the molding molds 12 and 16 of the box body B are clamped, and the small hole d of the inner tube D is closed.
Compressed air is injected into the air flow path 5 from the inside to expand the parison 20 into the shape of the molds 12 and 16 under equal pressure to form a box B. Then, when the molds 12, 16 are cooled with a cooling device (not shown) and opened, the cut portions 14, 15, 18, 19 of the molds 12, 16 are opened.
The parison 20 is then separated to form the muffler A shown in FIG. 4.

"Problems to be Solved by the Invention" However, the surface of the inner pipe D connected by the above method and the connection part S of the box body B, as shown by the solid circle frame in FIG. The inner tube D is welded using the heat of the parison 20, but if the inner tube D has a large wall thickness or the material has a high melting point, it may appear that they are completely joined, but in reality it is only the surface. However, even if the connecting parts S are simply welded together, the connection part S becomes peeled off during use, resulting in a reduction in the silencing function.

``Object of the Invention'' In order to eliminate the above-mentioned drawbacks, it is an object of the present invention to improve the welding strength of the connection between the inner tube and the box body.

"Structure of the Invention" An annular groove is provided on the outer periphery of both sides of a small hole drilled in the inner pipe of a resonance type muffler, and a plurality of annular thin-walled protrusions are formed on the annular groove and the outer periphery of the inner pipe in the vicinity of the annular groove. is inserted into a blow molding machine, and the box body is welded to the annular thin-walled ridge portion by blow molding. At this time, the thickness of the end of the box body is increased, and the annular thin-walled protrusion is taken into the inside and welded to the outer periphery of the inner tube.

"Example" Hereinafter, an example of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory partial view of the inner tube 21 according to the present invention, showing both sides of the small hole 22 (the figure shows only one side).
An annular groove 23 is provided on the outer periphery, and a plurality of annular thin-walled protrusions 24 are formed on the annular groove 23 and the outer periphery of the inner tube 21 in the vicinity thereof. And for convenience, the fifth
To explain using the blow molding machine 10 shown in the figure, the above-mentioned inner tube 21 is heated to an appropriate temperature and inserted into the guide tube 4' of the slide core 4. There is a slight gap between the inner diameter of the inner tube 21 and the outer diameter of the guide tube 4', and the small hole 22 of the inner tube 21 and the annular groove 6 of the guide tube 4' are at almost the same position. . Then, the parison 20 is suspended from the passage 2 of the crosshead 1 to the outside of the inner tube 21, and the rod 11 of the slide core 4 is raised by the operation of the air cylinder 9. 3 and the lower pressing portion 8 of the slide core 4 to maintain airtightness. When the parison 20 hangs down to a predetermined length, the molds 12 and 16 for forming the box 28 shown in FIG. 2 are automatically clamped. When the mold clamping is completed, the compressed air in the air flow path 5 passes through the T-shaped flow path 7, the annular groove 6, and the small hole 22 of the inner tube 21 to move the parison 20 toward the empty chambers 13 and 17 of the molds 12 and 16. Press to expand parison 20 with even pressure. At that time, the inner tube 21 and the parison 20 are heated, and the joint portion, that is, the annular groove 23 of the inner tube 21 and the annular thin-walled protrusion 24 formed in the vicinity thereof are melted, and the parison is also formed in the annular groove 23. 20 flows in and welds. Then, with a cooling device (not shown), the mold 12,
When the mold is opened after cooling 16, the cut parts 14, 15, 1
When the parison 20 is separated at 8 and 19 and the slide core 4 is lowered, a box body 2 is formed outside the inner tube 21 having a thickness 27 and having a small hole 22 as shown in FIG.
8 and a cavity 29 between the inner tube 21 and the box body 28.
A resonant silencer 30 is molded.

Furthermore, the connecting portion 26 indicated by the dot-dash line circle frame in FIG.
Figure 3 shows an enlarged view of. The figure shows an annular groove 23 formed in an inner tube 21 and an annular thin-walled protrusion 2.
4 is a partial sectional view for explaining the relationship between the end portion 25 of the box body and the end portion 25 of the box body 28 when the box body 28 is molded by clamping the molds 12 and 16. An enlarged portion 25a is formed in which the enlarged portion 25a is enlarged in the axial direction. The annular thin protrusion 24 is incorporated into the end portion 25 and the enlarged portion 25a, and the end portion 25 is welded to the annular groove.

[Function and effect of the invention]

As described above, in order to mold a resonant silencer using a blow molding machine, the inner tube is first formed with an annular groove and an annular thin-walled protrusion using a synthetic resin injection molding machine, and then the inner tube is Insert into the blow molding machine,
The heat of the parison, which forms the box body, causes the annular thin-walled protrusion and the end of the box body to become integrated, and the end of the box body is also welded to the annular groove. Since it is expanded to form an enlarged part and the annular thin-walled protrusion is incorporated, the area of the joint can be increased even if the box body is thin, and the joint has perfect sealing properties. Moreover, the bonding strength is high, and the bonded portion does not peel off during use, making it possible to maintain the initial sound-deadening function.

[Brief explanation of drawings]

FIG. 1 is an explanatory partial view of the inner tube according to the present invention;
FIG. 2 is a longitudinal sectional view of the product of the present invention, FIG. 3 is an enlarged sectional view of the main part thereof, FIG. 4 is a longitudinal sectional view of the conventional product, and FIG. 5 is a schematic diagram of a blow molding machine. 1...Crosshead, 4...Slide core, 5
... Air flow path, 12, 16 ... Mold, 20 ...
Parison, 21, D... Inner tube, 22, d... Small hole, 23... Annular groove, 24... Annular thin wall protrusion, 2
5... End of box body, 28, B... Box body, 30, A
...Resonant silencer.

Claims (1)

[Claims] 1. In a method for connecting a box body and an inner tube of a resonance type muffler, in which a synthetic resin box body is welded to the outside of a synthetic resin inner tube that is open at both ends and has a small hole, the inner tube An annular groove is provided on the outer periphery of both sides of the small hole, a plurality of annular thin-walled protrusions are formed on the annular groove and the outer periphery of the inner tube in the vicinity thereof, and an air flow path communicating with the small hole is provided inside the inner tube. Insert the slide core of the blow molding machine, hang a pipe-shaped parison from the crosshead to the outside of the inner tube for a predetermined length, raise the slide core, press the upper end of the inner tube against the crosshead, and press both ends of the inner tube. After making it airtight, the mold for forming the box is clamped, and compressed air is injected from the inside of the inner tube through the air flow passage to form the box, and at the same time, the thickness of the end of the box is reduced. A box for a resonant silencer made of synthetic resin, characterized in that the inner tube is expanded in the axial direction to form an expanded portion, the annular thin-walled protrusion is taken into the expanded portion, and the end portion is welded to the outer periphery of the inner tube. How to connect the body and internal tubes.