JP7280502B2 - Duct manufacturing method - Google Patents

Description

The present invention relates to a duct and its manufacturing method.

Patent Literature 1 discloses a duct having a first wall made of unfoamed resin and a second wall made of foamed resin.

JP 2011-131776 A

In Patent Literature 1, a duct is formed by welding two shaped bodies formed by shaping an unfoamed resin sheet and a foamed resin sheet in a mold. As a result, the weight is reduced while maintaining the strength of the parts that require strength.

In Patent Document 1, an accumulator is used to form a foamed resin sheet for one molding each time molding is performed. It is technically extremely difficult to increase Therefore, the foaming ratio of the second wall portion of the obtained duct is at most about 5 times.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a duct manufacturing method capable of manufacturing a duct that is excellent in mechanical strength and lightweight.

According to the present invention, a method for manufacturing a duct using first and second molds comprises a mounting step, a resin sheet placement step, a shaping step, and a mold closing step, wherein the mounting step includes: A first shaped body formed by pre-shaping a first resin sheet is attached to the first mold, and in the resin sheet disposing step, a molten second shaped body formed by extruding the molten resin from a T die The resin sheet is arranged between the first and second molds, and in the shaping step, the second resin sheet is shaped using the second mold to form a second shaped body, and the mold closing step A method is provided in which the first and second shaped bodies are welded together by closing the first and second molds.

According to the present invention, a duct is formed by welding together a first shaped body formed by shaping a first resin sheet in advance and a second shaped body formed by shaping a second resin sheet in a molten state. It is characterized by manufacturing Since the first shaped body can be formed using a foamed resin sheet with a very high expansion ratio, the method of the present invention enables the manufacture of a lightweight duct. Also, the second molded body can be formed using a non-foamed resin sheet or a resin sheet having a lower expansion ratio than the first resin sheet. Therefore, it is possible to obtain a duct with excellent mechanical strength.

Various embodiments of the present invention are illustrated below. The embodiments shown below can be combined with each other.
Preferably, in the method described above, the first shaped body is shaped using a pre-shaping die, and the pre-shaping die has a convex shape corresponding to the inner surface of the duct. is.
Preferably, in the method described above, the first shaped body has an expansion ratio of 7 times or more.
Preferably, the duct has a tubular portion, and the tubular portion is configured by welding a first wall portion and a second wall portion to each other. The duct has a wall with an expansion ratio of 1 to 6 times.
Preferably, a duct as described above, wherein the inner surface of the first wall has a smaller surface roughness than the outer surface of the first wall.

1 is a perspective view of a duct 1 of one embodiment of the invention; FIG. FIG. 2A is a cross-sectional view for explaining the shaping method of the first shaped body 21, FIG. 2C shows the state after the first shaped body 21 is formed by shaping the first resin sheet 31 with the mold 2, and FIG. 2C shows the state after the first shaped body 21 is removed from the mold 2. FIG. 1 shows an example of a molding machine 10 that can be used to manufacture the duct 1 of one embodiment of the present invention. FIG. 4 is a cross-sectional view of the vicinity of the molds 41 and 42 in FIG. 5 is a cross-sectional view showing a state after the first shaped body 21 is attached to the mold 41 from the state of FIG. 4 and the second resin sheet 32 is arranged between the molds 41 and 42. FIG. 6 is a cross-sectional view showing a state after forming a second shaped body 22 by shaping the second resin sheet 32 with a mold 42 from the state of FIG. 5. FIG. FIG. 7 is a cross-sectional view showing a state after closing molds 41 and 42 from the state of FIG. 6 to form a structure 33; 4 is a perspective view of the structure 33 after removal from the molds 41, 42 and removal of the burrs 34; FIG.

Embodiments of the present invention will be described below. Various features shown in the embodiments shown below can be combined with each other. In addition, the invention is established independently for each characteristic item.

1. Structure of Duct 1 As shown in FIG. 1, a duct 1 according to one embodiment of the present invention is a vehicle duct that is arranged on an instrument panel or ceiling of a vehicle, and includes a cylindrical portion 1a, a flange portion 1b, and a protruding portion 1c. Prepare.

The cylindrical portion 1a is a cylindrical portion that constitutes the air passage of the duct 1. As shown in FIG. The cylindrical portion 1a is configured by welding a first wall portion 11 and a second wall portion 12 to each other. A flange portion 1b is provided at the welded portion between the first wall portion 11 and the second wall portion 12 to increase the welding strength of the first and second wall portions 11 and 12 . The flange portion 1b can be omitted. The projecting portion 1c is a portion projecting from the flange portion 1b (the cylinder portion 1a if the flange portion 1b is not provided). Various marks are provided on the projecting portion 1c, and an uneven shape (so-called welding bead) 1d used when the duct 1 is welded to another member is provided. The projecting portion 1c can be omitted.

The expansion ratio of the first wall portion 11 is preferably 7 times or more, for example, 7 to 20 times, specifically, for example, 7, 8, 9, 10, 15, 20 times. It may be in a range between any two of the numerical values given. The expansion ratio of the second wall portion 12 is preferably 1 to 6 times. 4.5, 5, 5.5, 6, and may range between any two of the numbers exemplified herein. A foaming ratio of 1 means that the second wall portion 12 is not foamed. When the expansion ratio of the first wall portion 11 is 7 times or more and the expansion ratio of the second wall portion 12 is 1 to 6 times, the mechanical strength and lightness are excellent.

Preferably, the inner surface 11a of the first wall portion 11 has a smaller surface roughness than the outer surface 11b of the first wall portion 11 . If the surface roughness of the inner surface 11a is small, the blowing resistance is reduced. When the surface roughness of the outer surface 11b is large, the adhesiveness and the ability to retain condensed water are improved. In addition, in this specification, "surface roughness" means arithmetic mean height Ra specified by JIS B 0601-2001.

The duct 1 comprises a first shaped body 21 (see FIG. 2) formed by shaping a first resin sheet 31 in advance and a second shaped body 21 formed by shaping a second resin sheet 32 in a molten state. It is formed by welding features 22 (see FIGS. 5-6).

A method for shaping the first shaped body 21 and a method for manufacturing the duct 1 will be described in detail below.

2. Shaping Method of First Shaped Body 21 As shown in FIG. 2 , the first shaped body 21 can be formed by shaping the first resin sheet 31 using the preliminary shaping die 2 .

The first resin sheet 31 is preferably a foamed resin sheet, and its expansion ratio is preferably 7 times or more, for example, 7 to 20 times, specifically for example, 7, 8, 9, 10, 15, 20 times, and may be in the range between any two of the values exemplified here.

The first resin sheet 31 is preferably unwound from a roll of resin sheets. A resin sheet roll can be formed, for example, by winding a resin sheet formed by extruding a molten resin through a T-die into a roll after cooling.

When forming a foamed resin sheet using an accumulator as in Patent Document 1, it is necessary to operate the sheet forming apparatus intermittently. In this case, it is necessary to set the temperature of the molten resin higher in order to prevent the molten resin from solidifying. Prone. In addition, in the intermittent operation, it is difficult to stabilize the state of the sheet, so it is difficult to increase the foaming ratio of the foamed resin sheet.

On the other hand, when forming a roll of a foamed resin sheet, the molten resin is continuously extruded from a T-die and the foamed resin sheet formed is continuously wound. and the state of the foamed resin sheet is stabilized, the foaming ratio of the foamed resin sheet can be easily increased.

In the method of the present embodiment, the first resin sheet 31 softened by heating is arranged to face the mold 2 as shown in FIG. 2A, and the mold 2 is used as shown in FIG. 2B. The first shaped body 21 is formed by shaping. The first resin sheet 31 can be heated using a heater or the like. Examples of shaping methods include vacuum molding and blow molding.

The mold 2 preferably has a convex shape 2 a corresponding to the inner surface of the duct 1 . Thereby, the first shaped body 21 is shaped into a shape along the convex shape 2a. In this case, as shown in FIG. 2C, the shape of the inner surface 21a of the first molded body 21 (the surface that becomes the inner surface 11a of the first wall portion 11) is defined by the mold 2. The dimensional accuracy of the inner surface 21a is improved, making it easier to insert another member into the end of the duct 1 and connect it.

When the first resin sheet 31 is a foamed resin sheet and shaped using the mold 2 having the convex shape 2a, the surface roughness of the inner surface 21a is smaller than the surface roughness of the outer surface 21b of the first shaped body 21. Become. Since the inner surface 21a is formed by pressing the first resin sheet 31 against the convex shape 2a, a smooth skin layer is formed in the vicinity of the inner surface 21a, whereas the outer surface 21b which is not pressed against the mold 2 is formed. This is because a skin layer is not formed in the The outer surface 21b becomes a bubble breaking surface and has a large surface roughness. Moreover, when the mold 2 has the convex shape 2a, it becomes possible to use a slide core, and the degree of freedom in shape transfer is improved.

The first shaped body 21 includes a body portion 21c that forms the first wall portion 11 and a flange portion 21d that protrudes from the end of the body portion 21c. The flange portion 21d is welded to a flange portion 22d (see FIG. 6) of the second shaped body 22, which will be described later, so that the first and second shaped bodies 21 and 22 can be firmly welded. Since the first and second molded bodies 21 and 22 can be welded without the flanges 21d and 22d, the flanges 21d and 22d may be omitted if unnecessary.

3. Configuration of Forming Machine 10 A forming machine 10 that can be used to manufacture the duct 1 according to one embodiment of the present invention will be described with reference to FIG. The molding machine 10 includes a hopper 4 , an extruder 13 , an accumulator 17 , a T-die 18 , and first and second molds 41 and 42 . The extruder 13 and the accumulator 17 are connected via a connecting pipe 25 . The accumulator 17 and the T-die 18 are connected via a connecting pipe 27 .
Each configuration will be described in detail below.

<Hopper 4, Extruder 13>
The hopper 4 is used to charge the raw material resin 3 into the cylinder 13 a of the extruder 13 . Although the form of the raw material resin 3 is not particularly limited, it is usually in the form of pellets. The raw material resin 3 is, for example, a thermoplastic resin such as polyolefin. The raw material resin 3 is put into the cylinder 13a from the hopper 4, and then heated in the cylinder 13a to be melted into a molten resin. In addition, it is conveyed toward the tip of the cylinder 13a by the rotation of the screw arranged in the cylinder 13a.

<Accumulator 17, T die 18>
The molten resin 3 a is extruded from the resin extrusion port of the cylinder 13 a and injected into the accumulator 17 through the connecting pipe 25 . The accumulator 17 has a cylinder 17a and a piston 17b slidable inside the cylinder 17a, and the molten resin can be stored in the cylinder 17a. By moving the piston 17b after a predetermined amount of the molten resin 3a is stored in the cylinder 17a, the molten resin 3a is extruded through the slit provided in the T-die 18 through the connecting pipe 27, and the molten second resin is A sheet 32 is formed.

The second resin sheet 32 may be a non-foamed resin sheet or a foamed resin sheet. When forming a foamed resin sheet, a chemical foaming agent is introduced from the hopper 4 together with the raw resin 3, or an injector is provided in the extruder 13, and a physical foaming agent (eg, nitrogen or carbon dioxide) is injected through the injector. be able to. The expansion ratio of the second resin sheet 32 is preferably 1 to 6 times, specifically, for example, 1, 1.1, 1.5, 2, 2.5, 3, 3.5, 4, 4. .5, 5, 5.5, 6, and may be in the range between any two of the numbers exemplified herein.

<Molds 41, 42>
The second resin sheet 32 is guided between the molds 41 and 42 . As shown in FIG. 4, the molds 41 and 42 have cavities 41a and 42a, and pinch-off portions 41b and 42b are provided to surround the cavities 41a and 42a. The cavities 41a, 42a are configured to take the shape of the structure 33 (see FIG. 8) when the molds 41, 42 are closed.

The cavity 41a includes a recess 41a1 that accommodates the body portion 21c of the first shaped body 21 and a recess 41a2 that accommodates the flange portion 21d. The recessed portion 41a2 is so deep that the flange portion 21d protrudes from the recessed portion 41a2 (that is, the length of the recessed portion 41a2 in the depth direction is shorter than the length of the flange portion 21d in the thickness direction).

The cavity 42a includes a concave portion 42a1 for forming the main body portion 22c of the second shaped body 22 and a concave portion 42a2 for forming the flange portion 22d (see FIGS. 4 and 6). The recess 42a2 has a depth such that the second resin sheet 32 protrudes from the recess 42a2 (that is, the length of the recess 42a2 in the depth direction is shorter than the length in the thickness direction of the second resin sheet 32). ).

3. Duct Manufacturing Method The manufacturing method of the duct 1 according to one embodiment of the present invention includes a mounting step, a resin sheet forming step, a shaping step, a mold closing step, and a post-processing step.

<Mounting process>
In the mounting step, as shown in FIGS. 4 and 5, the first molded body 21 is mounted on the first mold 41 with the molds 41 and 42 opened. The first shaped body 21 can be mounted in the cavity 41 a of the first mold 41 . For example, the first shaped body 21 can be attached to the first mold 41 by vacuum-sucking the first shaped body 21 through a vacuum suction hole (not shown) provided in the first mold 41 . The first shaped body 21 has already been cooled at the time of the mounting step.

<Resin sheet placement process>
In the resin sheet arranging step, as shown in FIG. 5, a molten second resin sheet 32 formed by extruding the molten resin 3a from the T-die 18 is arranged between the molds 41 and 42 .

<Shaping process>
In the shaping step, as shown in FIGS. 5 and 6, a second mold 42 is used to shape the second resin sheet 32 to form the second shaped bodies 22 . A vacuum suction hole (not shown) is provided in the second mold 42 , and the second resin sheet 32 is vacuum-sucked by the second mold 42 to shape the second resin sheet 32 . As a result, the second molded body 22 having the body portion 22c and the flange portion 22d is formed.

<Mold closing process>
In the mold closing process, as shown in FIGS. 6 and 7, the molds 41 and 42 are closed. As a result, the first and second formed bodies 21 and 22 are welded together. At this time, the flange portions 21d and 22d are compressed by the molds 41 and 42 and welded firmly. The outer sides of the pinch-off portions 41b and 42b become burrs 34, and a structure 33 shown in FIG. 8 is formed in the space formed by the cavities 41a and 42a.

Air may be blown into the structure 33 while the molds 41 and 42 are closed. When forming a duct using a foamed resin sheet in a molten state as in Patent Document 1, if air is blown in before the foamed resin sheet is sufficiently cooled, the bubbles will be crushed and the expansion ratio will decrease. There is fear. On the other hand, since the first shaped body 21 of the present embodiment is in a sufficiently cooled state, air bubbles in the first shaped body 21 are hardly or not crushed at all even if air is blown into the first shaped body 21 . Therefore, it is possible to blow air at a high pressure, and the shape transferability of the second shaping body 22 is improved.

When the structure 33 is sufficiently cooled, the molds 41 and 42 are opened, the structure 33 is removed from the molds 41 and 42, and the burrs 34 are removed to obtain the structure 33 shown in FIG.

The duct 1 having the structure shown in FIG. 1 is obtained by cutting off the bag portions 33a at both ends of the structure 33 from the state shown in FIG.

Reference Signs List 1: Duct 1a: Cylindrical portion 1b: Flange portion 1c: Protruding portion 1d: Concavo-convex shape 2: Preforming mold 2a: Convex shape 3: Raw material resin 3a: Molten resin 4: Hopper 10: Molding machine 11: First wall Portion 11a: inner surface 11b: outer surface 12: second wall portion 13: extruder 13a: cylinder 17: accumulator 17a: cylinder 17b: piston 18: T die 21: first shaped body 21a: inner surface 21b: outer surface 21c: main body portion 21d : Flange portion 22 : Second shaped body 22c : Body portion 22d : Flange portion 25 : Connecting pipe 27 : Connecting pipe 31 : First resin sheet 32 : Second resin sheet 33 : Structure 33a : Bag portion 34 : Flash 41 : First mold 41a : Cavity 41a1 : Recess 41a2 : Recess 41b : Pinch-off portion 42 : Second mold 42a : Cavity 42a1 : Recess 42a2 : Recess 42b : Pinch-off

Claims (1)

A method for manufacturing a duct using first and second molds,
Equipped with a mounting process, a resin sheet placement process, a shaping process, and a mold closing process,
In the mounting step, a first molded body formed by pre-shaping a first resin sheet is mounted on a first mold,
In the resin sheet arranging step, a molten second resin sheet formed by extruding a molten resin from a T-die is arranged between the first and second molds,
In the shaping step, a second shaped body is formed by shaping the second resin sheet using a second mold,
In the mold closing step, the first shaped body and the second shaped body are welded to each other by closing the first and second molds ,
The first shaped body is formed by shaping a first resin sheet, which is a foamed resin sheet having an expansion ratio of 7 times or more, using a pre-shaping mold having a convex shape corresponding to the inner surface of the duct. ,
The duct comprises a first wall composed of a first shaped body and a second wall composed of a second shaped body,
The expansion ratio of the first wall portion is 7 times or more, and the expansion ratio of the second wall portion is 1 to 6 times,
The method , wherein the inner surface of the first wall has a surface roughness less than the outer surface of the first wall .

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