Patent Description:
<CIT>, <CIT>, <CIT>, <CIT>, and <CIT> disclose mufflers. A conventional method disclosed in <CIT> is often used as a method for automatically installing the sound-absorbing material in the vehicle muffler having the above structure. In this method, glass fiber serving as the sound-absorbing material is blown into a space between inner and outer pipes constituting the inner-outer double pipe of the above-mentioned muffler using a nozzle supplied with compressed air, and, at the same time, air inside the inner pipe having many sound-absorbing holes formed thereon is sucked using a fan to facilitate the blowing of the glass fiber.

However, the above-mentioned conventional method requires large-scale equipment including the nozzle and the fan for blowing of the fiber and piping for the nozzle and the fan. Also, the conventional method requires a long time from start to completion of the blowing of the fiber, which disadvantageously increases a takt time of a manufacturing line.

In view of the above, the present invention has been made to solve the above problems, and an object thereof is to provide a half body manufacturing method and a vehicle muffler manufacturing method that can simply and promptly install a sound-absorbing material between pipes of an inner-outer double pipe of a vehicle muffler.

In order to achieve the above object, a first aspect of the present invention is a method according to claim <NUM>.

According to the first aspect, it is possible to efficiently manufacture the porous half bodies constituting the tubular body serving as the sound-absorbing material.

In a second aspect, the nonwoven fabric (<NUM>) is obtained by: opening strands (<NUM>) of the inorganic fibers (<NUM>); and loosely knitting the opened strands longitudinally and laterally and subjecting the knitted strands to needle processing.

According to the second aspect, sound absorption is efficiently performed due to small spaces formed by the opened strands. In addition, since the strands are loosely knitted longitudinally and laterally and subjected to needle processing, the strength of the formed tubular body can be sufficiently maintained.

In a third aspect of the present invention, basalt fiber (<NUM>) or glass fiber is used as the inorganic fiber.

According to the third aspect, sufficient resistance to high-temperature exhaust gas and exhaust gas components can be exhibited.

A fourth aspect of the present invention is a method according to claim <NUM>.

In the fourth aspect, the pair of half bodies made of the nonwoven fabric are attached in an abutting state to the outer periphery of the inner pipe so as to cover the inner pipe to obtain the tubular body serving as the sound-absorbing material, and the tubular body is covered with the outer pipe. Thus, it is possible to adjust to an inner pipe and an outer pipe that have not a parallel tubular shape, but an odd tubular shape. Further, compared to the conventional method that blows fiber for sound absorption into a space between the inner pipe and the outer pipe, large-scale equipment is not required, and the takt time of the manufacturing line can be largely reduced. In particular, since the inorganic fiber in the filament form is used, it is possible to endure high back pressure of exhaust gas.

The above reference signs in parentheses indicate the correspondence relationship with concrete means described in embodiments described below for reference.

As described above, according to the vehicle muffler manufacturing method of the present invention, it is possible to simply and promptly install the sound-absorbing material between the pipes of the inner-outer double pipe of the vehicle muffler.

In a manufacturing method of a first exemplary embodiment, for example, a basalt fiber <NUM> (<FIG>) which is a filament of <NUM>µmϕ to <NUM>µmϕ is used as an inorganic fiber. A strand <NUM> which is a bundle of, for example, <NUM> to <NUM> basalt fibers <NUM> is opened using, for example, air (<FIG>). Then, the opened strands <NUM> are loosely knitted and stacked respectively as warp and woof and subjected to needle processing to obtain a nonwoven fabric <NUM> having a rectangular mat shape as illustrated in <FIG>.

An inorganic binder <NUM> is applied to one surface 2a of the nonwoven fabric <NUM> obtained in this manner (<FIG>). And as illustrated in <FIG>, the nonwoven fabric <NUM> is wrapped around a core metal <NUM> with the surface 2a applied with the binder <NUM> located on an inner peripheral side. In this state, the inner peripheral surface 2a of the nonwoven fabric <NUM> is hardened with the binder <NUM>. Then, as illustrated in <FIG>, a rotary roller <NUM> supplied with the same binder <NUM> described above is brought into contact with an outer peripheral surface to infiltrate the binder <NUM> into the entire outer periphery of the nonwoven fabric <NUM> wrapped around the core metal <NUM> and the inside of the nonwoven fabric <NUM>.

Then, the nonwoven fabric <NUM> wrapped around the core metal <NUM> and infiltrated with the binder <NUM> is left inside a heating furnace heated to, for example, <NUM> for <NUM> to <NUM> hours to solidify the whole thereof. Then, the nonwoven fabric <NUM> is removed from the core metal <NUM> (<FIG>) to obtain a tubular body <NUM> for sound absorption as illustrated in <FIG>. In this state, an outer diameter of the tubular body <NUM> is slightly smaller than an inner diameter of an outer pipe <NUM> (<FIG>) of an inner-outer double pipe (described later), and an inner diameter of the tubular body <NUM> is slightly larger than an outer diameter of an inner pipe <NUM> of the double pipe. Note that although <FIG> is a perspective view illustrating the tubular body <NUM> as if the tubular body <NUM> is a conical tube, the tubular body <NUM> is actually a parallel cylindrical body. The tubular body <NUM> does not necessarily have to be a cylindrical body and may be, for example, an elliptical tube or a rectangular tube.

Then, the tubular body <NUM> formed in this manner is inserted between the pipes of the double pipe constituting the vehicle muffler, which is illustrated in <FIG>. The double pipe includes the outer pipe <NUM> which has a larger diameter and is held in a vertical position by holding means (not illustrated), and the inner pipe <NUM> which has a smaller diameter and has a plurality of sound-absorbing holes (not illustrated) formed thereon, and the inner pipe <NUM> is located on the center of the outer pipe <NUM>. An end plate <NUM> is welded to one end of the outer pipe <NUM> so as to close an opening on the one end. One end <NUM> (the lower end in the drawing) of the inner pipe <NUM> penetrates the center of the end plate <NUM> so that the inner pipe <NUM> is supported inside the outer pipe <NUM>.

The other end <NUM> (the upper end in the drawing) of the outer pipe <NUM> is open. As indicated by an arrow in <FIG>, the tubular body <NUM> is inserted and installed, from above, into a space S between the inner pipe <NUM> located on the center of the opening and the outer pipe <NUM> so as to serve as a sound-absorbing material. After the tubular body <NUM> is installed, another end plate (not illustrated) is welded to the opening of the outer pipe <NUM> to close the opening on the other end <NUM> with the other end <NUM> of the inner pipe <NUM> penetrating the center of the end plate to obtain the vehicle muffler.

As described above, according to the manufacturing method of the present invention, the tubular body for sound absorption is inserted and installed between the inner pipe and the outer pipe with a single motion. Thus, compared to the conventional method that blows fiber for sound absorption, large-scale equipment is not required, and the takt time of the manufacturing line can be largely reduced.

In the first embodiment, the method for manufacturing the vehicle muffler including the outer pipe which is the simple parallel tubular body has been described. On the other hand, in the present embodiment, an example of a method for manufacturing a vehicle muffler including an outer pipe which is an odd-shaped tubular body will be described below.

<FIG> is a perspective view of the vehicle muffler in the present embodiment. <FIG> is a sectional view of the vehicle muffler in the present embodiment. As illustrated in <FIG>, an inner pipe <NUM> of the vehicle muffler has a plurality of sound-absorbing holes <NUM> formed on the outer periphery thereof and has a parallel cylindrical shape. On the other hand, an outer pipe <NUM> of the vehicle muffler is an odd-shaped tubular body having a box shape, and the inner pipe <NUM> penetrates the outer pipe <NUM>. The outer pipe <NUM> includes a pair of half tubular bodies <NUM> and <NUM> each of which is formed by bending into a predetermined shape, specifically, into an open container shape. The half tubular bodies <NUM> and <NUM> abut against each other with the inner pipe <NUM> interposed between open edges of the half tubular bodies <NUM> and <NUM>. Further, a tubular body <NUM> (<FIG>, described below) serving as a sound-absorbing material is installed inside a space between the inner pipe <NUM> and the outer pipe <NUM> constituting an inner-outer double pipe. Note that the inner pipe <NUM> does not necessarily have to have the parallel cylindrical shape.

The tubular body <NUM> includes a half body <NUM> installed inside the half tubular body <NUM> of the outer pipe <NUM> and a half body <NUM> installed inside the half tubular body <NUM> of the outer pipe <NUM>. The half body <NUM> and the half body <NUM> abut against each other to constitute the tubular body <NUM> having a tubular shape. As illustrated in <FIG>, a recessed part <NUM> having a substantially semicircular cross section along the outer periphery of the inner pipe <NUM> is formed on the center of an abutment surface of the half body <NUM>, and a recessed part <NUM> having a substantially semicircular cross section along the outer periphery of the inner pipe <NUM> is formed on the center of an abutment surface of the half body <NUM>. Also, an outer peripheral surface of the half body <NUM> is formed in a shape extending along an inner peripheral surface of the half tubular body <NUM> of the outer pipe <NUM>, and an outer peripheral surface of the half body <NUM> is formed in a shape extending along an inner peripheral surface of the half tubular body <NUM> of the outer pipe <NUM>.

The tubular body <NUM> serving as the sound-absorbing material is attached to the outer periphery of the inner pipe <NUM> so as to cover the inner pipe <NUM> by making the half bodies <NUM> and <NUM> like these abut against each other with the inner pipe <NUM> located in the recessed parts <NUM> and <NUM> of the half bodies <NUM> and <NUM> (<FIG>). Then, the tubular body <NUM> integrated with the inner pipe <NUM> is installed inside the half tubular body <NUM> constituting the outer pipe <NUM>, and the half tubular body <NUM> constituting the outer pipe <NUM> is put thereon from above so as to abut against the open edge of the half tubular body <NUM> to complete the vehicle muffler (<FIG>).

The above-mentioned half body <NUM> of the tubular body <NUM> is manufactured in the following manner. Note that a method for manufacturing the half body <NUM> is also similar to the method for manufacturing the half body <NUM>. A binder is applied to one surface of a nonwoven fabric 2A which is similar to the one manufactured by the method described in the first embodiment (refer to <FIG>). As illustrated in <FIG>, the nonwoven fabric 2A is horizontally installed, with the surface applied with the binder facing upward, along an inner peripheral surface of a container-shaped jig <NUM> which is open and has the same cross section as the half tubular body <NUM> of the outer pipe <NUM> (<FIG>) so as to hang down in a recessed shape. Then, as illustrated in <FIG>, a plurality of other nonwoven fabrics 2B each of which is similar to the nonwoven fabric 2A are rolled up into a tubular shape and inserted into a recessed space formed by the nonwoven fabric 2A.

Then, as illustrated in <FIG>, both side edges <NUM> and <NUM> of the nonwoven fabric 2A are folded inward so as to wrap the plurality of nonwoven fabrics 2B (<FIG>), and a lid-shaped jig <NUM> is put thereon to close the container-shaped jig <NUM> so as to cover the nonwoven fabric 2A (<FIG>). Note that the lid-shaped jig <NUM> includes a projection <NUM> which is formed by bending the center thereof and projects downward in a semicircular shape. The projection <NUM> pushes the folded side edges <NUM> and <NUM> of the nonwoven fabric 2A downward. At the same time, the inside nonwoven fabrics 2B rolled up in a tubular shape become slightly compressed. In this state, the container-shaped jig <NUM> closed with the lid-shaped jig <NUM> is put into a heating furnace, heated at, for example, <NUM> for <NUM> to <NUM> hours to solidify the nonwoven fabric 2A, and then taken out from the heating furnace to obtain the half body <NUM> described above (<FIG>).

Note that, for example, glass fiber can be used as the inorganic fiber instead of the basalt fiber described above.

Further, the nonwoven fabric formed by knitting strands longitudinally and laterally does not necessarily have to be used. A nonwoven fabric formed by aligning and stacking strands in the same direction or a nonwoven fabric formed by alternately stacking, longitudinally and laterally, strands aligned in the same direction and the like may be used.

Claim 1:
A half body manufacturing method for manufacturing each of a pair of half bodies (<NUM>, <NUM>), the pair of half bodies (<NUM>, <NUM>) being attached, in an abutting state, to an outer periphery of an inner pipe (<NUM>) of an inner-outer double pipe constituting a vehicle muffler so as to cover the inner pipe (<NUM>), to constitute a tubular body (<NUM>) serving as a sound-absorbing material, the method comprising:
horizontally installing one nonwoven fabric (2A) made of inorganic fibers (<NUM>) each being in a filament form, the one nonwoven fabric (2A) having one surface applied with a binder (<NUM>), in a recessed shape along an inner periphery of a container-shaped jig (<NUM>), the container-shaped jig (<NUM>) being open;
rolling up a plurality of other nonwoven fabrics (2B) made of inorganic fibers (<NUM>) each being in a filament form, inserting the other nonwoven fabrics (2B) into a recessed space formed by the one nonwoven fabric (2A), and wrapping the other nonwoven fabrics (2B) with the one nonwoven fabric (2A); and
then closing the container-shaped jig (<NUM>) and heating the container-shaped jig (<NUM>) to a predetermined temperature.