JP2019060523A - Foamed duct and method of molding the same - Google Patents

Abstract

To provide a foamed duct having an excellent fitting property to prevent the occurrence of air leakage, and also to provide a method of manufacturing such a foamed duct.SOLUTION: A foamed duct is formed by blow-molding a foamed resin. At least an opening end thereof has a nearly circular shape, and an outer peripheral surface near a parting line in the vicinity of the opening end is made to be a flat surface. The flat surface comprises a flat surface which corresponds to a first tangent line having a contact with the parting line and a flat surface which corresponds to a second tangent line having a position apart from the parting line as a contact. The expansion ratio of the foamed resin is 2 to 4, and the average wall thickness is 2 mm to 6 mm. For molding, the cross-sectional shape of each metal mold is made to be semicircular, and the portion near each fitting face corresponding to the parting line is made to be a cross-section straight surface.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a foam duct used for air conditioning ducts and the like of automobiles, and further relates to a method of molding the same.

  For example, as a manufacturing method of the duct for motor vehicles for ventilating the air from an air-conditioner, the blow method which clamps and shape | molds foaming molten resin with a split mold is adopted widely. In blow molding, various types of ducts can be easily molded, and it is possible to mass-produce ducts of complex shapes.

  Moreover, in the above-mentioned ducts, two or more ducts are connected to construct a pipe. By connecting the ducts, it is possible to cope with various piping configurations.

  For example, in Patent Document 1, as a connection structure of a duct, a duct having an air flow inlet formed at one end, a reinforcing member provided inside the insertion hole and holding the shape of the air inlet, and air circulation A duct connection structure is disclosed, which comprises a separate member having a receptacle for use in connection with the duct and the separate member by inserting the insertion port into the receptacle. The connecting structure of ducts described in Patent Document 1 focuses on providing a seal.

JP, 2006-38322, A

  By the way, in the blow molding of the foam duct, the foam resin is extruded at the parting line, and as a result, a thick portion may be formed in the vicinity of the parting line. FIG. 7 shows a thick portion 102 formed in the vicinity of the parting line PL in the foam duct 101 having a circular cross section.

  When the foam duct 101 is formed by blow molding, a parison P is supplied between a pair of molds 111 and 112 as shown in FIG. 7A, and as shown in FIGS. 7B and 7C. The mold is clamped and air is blown into the parison to shape it. During shaping, a parison P is sandwiched between the opposing surfaces 111a and 112a of the molds 111 and 112 and pinched off. At this time, the sandwiched parison (molten resin) is crushed and extruded. Become. As a result, as shown in FIG. 7D, the thick portion 102 is formed of the resin extruded toward the inside of the molds 111 and 112.

  When the thick portion 102 as described above is formed, the inner surface shape of the foam duct 101 does not have the original circular shape, and there is a problem that a fitting failure occurs when combining with another duct or attaching a register. is there.

  In order to eliminate such a disadvantage, for example, as shown in FIG. 8, it is conceivable to provide a protrusion so as to project the parting line PL to the outside, and in this case, the parting line As a result of the groove portion 103 being formed on the inner surface of the duct along the PL, there arises a disadvantage that an air leak occurs from here.

  The present invention has been proposed in view of such conventional circumstances, and it is possible to easily fit and mount a register, other ducts, etc., and there is no occurrence of air leakage, such as fitting. It is an object of the present invention to provide a good foam duct of the present invention, and further to provide a method for forming the same.

  In order to achieve the above object, the foam duct of the present invention is a foam duct obtained by blow molding a foam resin, wherein at least the open end is substantially circular, and at least near the open end and near the parting line. The outer peripheral surface of is made flat.

  Further, the method of molding a foam duct according to the present invention is a method of molding a foam duct in which a foamed molten resin is sandwiched between a pair of molds and blow-molded, and the cross-sectional shape of the molds is substantially semicircular. The present invention is characterized in that the vicinity of the abutting surfaces corresponding to the parting lines is a flat surface having a linear cross section.

  For example, in a cylindrical foam duct, when at least the outer peripheral surface in the vicinity of the parting line is a flat surface, the inward extrusion of the molten resin is alleviated, and it is difficult to form a thick portion. Further, since the parting line is not retracted, no groove is formed on the inner surface of the duct.

  According to the present invention, it is possible to provide a foam duct which is excellent in fit, can be fitted and mounted easily on a register, other ducts and the like, and does not cause air leakage.

It is a schematic perspective view which shows an example of a foam duct. It is a figure which shows an example of the cross-sectional shape of a foaming duct. It is a figure which expands and shows the parting line vicinity of the foaming duct of FIG. It is a figure explaining the cross-sectional shape of the foaming duct shown to FIG. It is a figure which shows typically the other example of the cross-sectional shape of a foaming duct. It is a figure which shows an example of the metal mold | die which shape | molds a foam duct. (A) shows a parison supply state, (B) shows a mold clamping start state, (C) shows a mold clamping state, and (D) shows a thick part It is a figure which shows the cross-sectional shape of the foam duct in which was formed. It is a figure which shows the other example of the cross-sectional shape of the conventional foam duct, and shows the cross-sectional shape of the foam duct in which the groove part was formed in the inner surface.

  Hereinafter, embodiments of a foam duct to which the present invention is applied and a method for molding the same will be described in detail with reference to the drawings.

  The foam duct of the present embodiment is, for example, a foam duct having a circular cross section, and is a lightweight automobile duct for circulating the warm and warm air supplied from the air conditioner unit to a desired portion. FIG. 1 shows one example of the foam duct 1, and the register fitting portions 3, 3 are formed to branch from the main flow path portion 2. In the case of this embodiment, although both the main flow path 2 and the register fitting portion 3 are formed in a cylindrical shape, the present invention is applicable if the opening portion of the register fitting portion 3 is circular. And the other parts need not be cylindrical. Further, as described above, the present invention is applied when the opening of the register fitting portion 3, 3 is circular, but the circular in this case is not limited to a perfect circular shape, for example, an elliptical shape etc. Also included.

  The foam duct 1 is molded, for example, by clamping a thermoplastic resin mixed with a foaming agent with a split mold and blow molding. Examples of the thermoplastic resin to be used include polypropylene-based resins and the like, and a blend resin in which 1 to 20% by mass of a polyolefin-based polymer and 5 to 40% by mass of a hydrogenated styrene-based thermoplastic elastomer are mixed. Etc. can also be used.

  Blowing agents include physical blowing agents, chemical blowing agents and mixtures thereof. As physical foaming agents, inorganic physical foaming agents such as air, carbon dioxide gas, nitrogen gas, water and the like, organic physical foaming agents such as butane, pentane, hexane, dichloromethane, dichloroethane and the like, and their supercritical fluids Can be applied. As a supercritical fluid, it is preferable to use carbon dioxide, nitrogen, etc., and if it is nitrogen, its critical temperature is -149.1 ° C, its critical pressure is 3.4 MPa or more, and if it is carbon dioxide, its critical temperature is 31 ° C, its critical pressure It can produce by setting it as 7.4 Mpa or more.

  The expansion ratio of the foam duct formed by blow molding is arbitrary, and is configured by a closed cell structure (a closed cell rate is 70% or more) having a plurality of cell cells. The present invention is effective in forming a foam duct having a high expansion ratio and a certain thickness. From such a viewpoint, the expansion ratio is 2 to 4 times, preferably 2.5 times or more (for example, 2.8 times) The effect is high when the thickness is 2 mm to 6 mm, preferably 3 mm or more (for example, 4 mm). The average cell diameter of the cells in the thickness direction is, for example, less than 300 μm, preferably less than 100 μm.

  In the foam duct 1 formed by blow molding the foam resin as described above, the resin is pushed out to the inner surface in the vicinity of the parting line, and a thick portion with a large thickness is formed in the vicinity of the parting line Ru. When the thick portion is formed, the inner surface shape of the foam duct is changed, which causes a fitting failure. Alternatively, in order to eliminate this, a projection is provided so that the parting line protrudes outward, and when the parting line is retracted from the circular inner wall surface, a groove is formed on the inner surface of the duct along the parting line. Air leaks from here.

  So, in the foaming duct 1 of this embodiment, this is eliminated by forming a flat surface part in the outer peripheral surface of the parting line vicinity vicinity at least opening part vicinity of the register | resistor fitting parts 3 and 3. FIG.

  For example, as shown in FIG. 2 and FIG. 3, as the form of the vicinity of the parting line in the vicinity of the opening of the register fitting portion 3, the inner surface shape remains circular and only the outer surface is a flat surface (linear portion) It is possible to do.

  2 and 3. In this example, the basic shape of the cross section of the resistor fitting portion 3 remains circular, and the shape is expanded linearly in the vicinity of the parting line PL in this example. There is. It is FIG. 4 which demonstrated this in detail.

  That is, in the present embodiment, in the cross-sectional shape of the circular resistor fitting portion 3, a tangent with the parting line PL as a contact (a tangent S1 with the point A as a contact in the figure) and a point separated from the parting line PL. A tangent line having a contact point (a tangent line S2 having a point B as a contact point in the drawing) is drawn, and an area (a broken line area in the figure) surrounded by the tangent line S1 and the tangent line S2 is enlarged. Therefore, the register fitting portion 3 has a flat surface 31 corresponding to the tangent S1 and a flat surface 32 corresponding to the tangent S2 on the outer surface in the vicinity of the parting line PL, and these flat surfaces are linear Department will be composed.

  By making the cross-sectional shape as shown in FIG. 2 to FIG. 4, the resin capacity is enlarged at the parting line PL. Specifically, the shaded area in FIG. 4 is enlarged. In the enlarged region, the extrusion of the resin in the vicinity of the parting line PL is absorbed, and the formation of the thick portion is suppressed.

  However, in the above embodiment, if the dimension of the flat surface 31 corresponding to the tangent line S1 is too large and too large, the shape of the foam duct 1 will be largely changed. It is preferable to For example, when the radius R of the foam duct 1 is 50 mm, the dimension L1 of the flat surface 31 from the parting line PL is preferably about 10 mm. The ratio (L1 / R) of the radius R to the dimension L1 is preferably 0.05 to 0.4, and more preferably 0.1 to 0.3.

  The shape near the parting line is not limited to this, and various modifications are possible.

  FIG. 5 shows another example of the cross-sectional shape in the vicinity of the opening of the resistor fitting portion 3. In the foam duct 1 of the present embodiment, the resistor fitting portion 3 is formed in a cylindrical shape, and the cross-sectional shape in the vicinity of the opening is circular. In this example, a part of such a circular cross-sectional shape is changed so that the thick portion and the groove portion are not formed.

  Specifically, in the register fitting portion 3 having a circular cross-sectional shape, a portion near the parting line PL is a linear portion. In the case of the present embodiment, as shown in FIG. 5, the portion in the vicinity of the parting line PL has a straight shape (a linear shape in which both the inner surface and the outer surface are linear flat surfaces). The straight portion 33 is formed on both sides of the parting line PL, and is formed on any of the two parting lines PL.

  The length L2 from the parting line PL of the straight portion 33 can be set arbitrarily, but if the length L is too large, the shape will largely change from a circular cross section, which is not preferable. Therefore, the length L is preferably about 3 mm to 20 mm (e.g., 10 mm).

  When the straight portion 33 is formed at least in the vicinity of the opening of the resistor fitting portion 3, the resin extruded at the parting line PL maintains the inner surface shape without forming the thick portion. Therefore, fitting of a register etc. can be performed easily. Further, by forming the straight portion 33, no groove is formed in the vicinity of the parting line PL, and there is no concern such as air leakage.

  The above-described foam duct 1 is formed by sandwiching a foamed molten resin with a pair of molds having semicircular cavities and blow molding. At this time, for example, in order to form the foam duct 1 whose cross-sectional shape is shown in FIGS. 2 to 4, as shown in FIG. 6, corresponding to the flat surfaces 31 and 32 near the parting line PL shown in FIG. A part of the arcs of the respective molds 11 and 12 (portions near the mating surfaces of each other) may be linear. If flat surfaces 11a and 12a corresponding to the flat surface 31 and flat surfaces 11b and 12b corresponding to the flat surface 32 are formed in the respective molds 11 and 12, molding in the shape shown in FIG. 4 is possible. .

  In the foam duct of the present embodiment, since the linear portion is formed along the parting line, the extrusion of the resin to the inner surface side is alleviated, and the thick portion projecting to the inner wall is not formed. . As a result, fitting with a register, another duct, etc. can be performed easily. In addition, since no gap or the like is formed when fitting, air leakage does not occur.

  Although the embodiments to which the present invention is applied have been described above, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. It is possible.

DESCRIPTION OF SYMBOLS 1 Foaming duct 2 Main flow path part 3 Register fitting part 11,12 Mold 31, 32 Flat surface 33 Straight part PL Parting line A, B Contact S1 1st tangent S2 2nd tangent

Claims (5)

A foam duct in which a foam resin is blow molded,
A foam duct characterized in that at least the open end is substantially circular and the outer peripheral surface near the parting line is flat at least near the open end.   The flat surface is composed of a flat surface corresponding to a first tangent line having a parting line as a contact point and a flat surface corresponding to a second tangent line having a position spaced from the parting line as a contact point, and substantially circular The foam duct according to claim 1, wherein the area surrounded by the tangents is expanded in the cross-sectional shape of (1).   The foaming duct according to claim 1 or 2, wherein a foaming ratio of the foamed resin is 2 to 4 and an average thickness is 2 mm to 6 mm. A forming method of a foam duct in which a foamed molten resin is sandwiched between a pair of molds and blow molded,
A method of forming a foam duct, wherein the cross-sectional shape of the mold is substantially semicircular, and the vicinity of the abutting surfaces corresponding to the parting lines is a flat surface having a linear cross section.   The flat surface having a linear cross-section has a flat surface corresponding to a first tangent line having a parting line as a contact, and a flat surface corresponding to a second tangent line having a position separated from the parting line as a contact A method of molding a foam duct according to claim 4, characterized in that

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