Method for manufacturing a resin molded body

Abstract

To provide a technique for manufacturing a resin molded body that gives strength only in necessary parts while enjoying the benefits of foam molding such as weight reduction and heat insulation as a whole, and a louver of an air conditioner.SOLUTION: In a resin molded body 10 (a louver 10), a rib 11 (a first member 11) which is non-foam molded and in which an applied load is externally supported, and a main body part 12 (a second member 12) which is foam molded and in which an applied load is externally supported via the rib 11, are integrally molded.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a manufacturing technique for a foamed resin molding. of the body

Background Art

[0002] In an indoor unit of an air conditioner, a louver is provided at an air outlet in order to adjust the vertical direction of the conditioned air blown out. This louver has a problem that, by guiding the cold air blown out during cooling in summer on one side thereof, moisture of the indoor air cooled on the opposite side is condensed to generate water droplets.

[0003] As prior art for solving the problem of generating such water droplets, the following inventions are known. That is, a technique is disclosed in which ribs or sub-louvers are formed on the louver or the positional relationship thereof is devised to suppress the generation of ambient warm air turbulence and prevent the occurrence of dew condensation on the louver. Further, a technique is disclosed in which heat insulation properties are improved and dew condensation is prevented by attaching a heat insulating material to a part of the louver or making the inside of the louver hollow.

[0004] On the other hand, in recent years, a resin molded body in which resin is foamed in a cavity by previously mixing a chemical foaming agent or mixing a supercritical state fluid into a cylinder has been widely adopted as a molding method for members that require weight reduction and heat insulation properties.

[0005] And the following invention is known. That is, a non-foamed portion made of a non-foamed material is first molded, and then a foamed portion is secondarily molded, and when the foamed portion is injection molded, the mold is core backed and expanded to be integrally molded.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, the louver not only displaces the opening angle by adjusting the vertical direction of the conditioned air during the operation of the air conditioner, but also functions to close the air outlet during non-operation. For this reason, modifying the external shape of the louver mainly for suppressing or preventing water droplet generation may sacrifice other functions required for the louver, which is something to be avoided.

[0008] Also, in the above-described technique of performing secondary molding of the foamed portion after primary molding of the non-foamed portion made of non-foamed material and expanding the mold during injection molding of the foamed portion to integrally mold it, since the non-foamed portion is molded on the primary side and then the foamed resin is filled on the secondary side, the bonding strength at the boundary portion becomes weak. For this reason, it is impossible to make non-foamed the ribs provided for reinforcement along the longitudinal direction or width direction of the main body having a fixed portion requiring strength such as a louver, a fan for a blower, and a panel and a driving portion requiring weight reduction, bosses provided for fastening to other parts, shafts, bearings, etc. provided in a part of the main body for rotational displacement. In other words, it is impossible with the above-described known techniques to make both the louver main body have a smooth skin layer without warping or twisting and further have heat insulation properties by introducing fine and uniform air bubbles at high pressure and providing non-foamed portions.

[0009] Embodiments of the present invention have been made in consideration of such circumstances, and an object thereof is to provide a resin molded body that enjoys the benefits of foam molding such as weight reduction and heat insulation as a whole, while having strength only in necessary parts, a louver of an air conditioner, and manufacturing techniques therefor.

Means for Solving the Problems

[0010] In the manufacturing method of the resin molded body shown in the embodiment, molten resin is injected from a gate that opens at any position in the first cavity, and after the molten resin filled in the second cavity continuous from the first cavity foams and solidifies, the molten resin filled in the first cavity solidifies before foaming. and, in the second cavity, the main body portion of the resin molded body is foam-molded, and in the first cavity, ribs or bosses provided on the main body portion are non-foam-molded It is characterized by this.

Effects of the Invention

[0011] According to the embodiments of the present invention, a resin molded body that enjoys the benefits of foam molding such as weight reduction and heat insulation as a whole, while having strength only in necessary parts, a louver of an air conditioner, and manufacturing techniques therefor are provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0013] FIG. 1 is a perspective view of a louver 10 (hereinafter simply referred to as "louver 10") of an air conditioner according to an embodiment of the present invention. The air conditioner (not shown) uses a refrigeration cycle that circulates refrigerant to supply conditioned air to an air-conditioned space (such as a room). Among the components of this air conditioner, an indoor unit (not shown) disposed in the air-conditioned space has a casing (not shown) in which a suction port for sucking stagnant air in the air-conditioned space and a blowout port for supplying conditioned air to the air-conditioned space are formed, and its framework is formed by this casing.

[0014] And inside this casing, a blower (not shown) that sucks stagnant air from the suction port and blows out conditioned air from the blowout port, and a heat exchanger (not shown) that is disposed in the flow path from this fan to the blowout port and exchanges heat with the refrigerant to generate conditioned air from the stagnant air are accommodated. And at the blowout port of this casing, a louver 10 arranged along the longitudinal direction of the opening is rotatably supported so as to adjust the blowing direction of the conditioned air.

[0015] As shown in FIG. 1, the louver 10 (resin molded body 10) includes a rib 11 (first member 11) that supports the load applied to the louver 10, and a main body portion 12 (second member 12) that is integrally molded with the rib 11 and defines the blowing direction of the conditioned air.

[0016] And the flat main body portion 12 is foam-molded, and the load applied by its own weight, fluid resistance, external force, etc. is transmitted to the rib 11. And this rib 11 is non-foam-molded, and supports the load transmitted from the main body portion 12 to the outside (for example, the casing) through itself (rib 11).

[0017] In FIG. 1, an example of the function of the rib 11 is a bearing that engages with a shaft body (not shown) provided on the casing side to rotatably support the louver 10. Note that the application of the rib 11 is not limited, and in addition, a shaft body for rotatable support, a reinforcing material for improving the mechanical strength of the main body portion 12, etc. can also be mentioned.

[0018] Note that the resin constituting the louver 10 is generally a thermoplastic resin suitable for injection molding, such as polypropylene (PP), acrylonitrile-butadiene-styrene copolymer resin (ABS), other general-purpose resins, and engineering plastics.

[0019] Here, the weight reduction rate Δw1 of the rib 11 (first member 11) and the weight reduction rate Δw2 of the main body 12 (second member 12) are relatively different, and have a relationship of Δw1 < Δw2. Also, the boundary value of the weight reduction rate for distinguishing between foam molding and non-foam molding is set at 3%, and has a relationship of Δw1 < 3% < Δw2. That is, if the weight reduction rates Δw1 and Δw2 of both the rib 11 and the main body 12 are less than 3%, both are regarded as non-foam molding, and if the weight reduction rates Δw1 and Δw2 of both the rib 11 and the main body 12 exceed 3%, both are regarded as foam molding. And the region with a weight reduction rate lower than the set boundary value of 3% is regarded as non-foam molding, and the region with a weight reduction rate higher than this boundary value is regarded as foam molding. Here, the weight reduction rate indicates the ratio of the difference to the weight of a non-foamed body in an ideal state where no bubbles are contained at all.

[0020] By the way, the weight reduction rate of the louver 10 (resin molded body) has a sparse distribution overall. For this reason, if the weight reduction rate defined by the boundary value is achieved in 80% or more of each of the main body 12 and the rib 11, it is regarded that the distinction between foam molding and non-foam molding can be made.

[0021] It is desirable that the mode value of the bubble diameter distribution of the main body 12 formed by foam molding is in the range of 30 to 50 μm, but it is also acceptable that this upper limit becomes 75 μm or 150 μm at the flow end portion of the molten resin.

[0022] By molding the louver 10 (resin molded body) in this way, even when guiding cold air (air-conditioning air) on one side of the main body 12 formed by foam molding, heat conduction with the opposite side is suppressed, condensation of moisture in the stagnant air is suppressed, and generation of water droplets is prevented. Furthermore, the mechanical strength of the bearing that rotatably supports the louver 10 is ensured by the non-foam molded rib 11.

[0023] Figure 2 is a cross-sectional view of an injection molding machine 20 and a mold 15 applied to a method for manufacturing a resin molded body according to an embodiment of the present invention. This injection molding machine 20 can dissolve a large amount of supercritical fluid (SCF: Supercritical Fluid) such as nitrogen or carbon dioxide as a foaming agent into molten resin at high pressure. When the molten resin is injected into the mold 15, the pressure is rapidly reduced in the cavity 30 that forms the louver 10 (resin molded body), and the dissolved supercritical fluid vaporizes to generate a large amount of bubbles.

[0024] As described above, the injection molding machine 20 includes a cylinder 21 that supplies nitrogen or carbon dioxide, which is a raw material gas for the supercritical fluid, a supply unit 22 that pressurizes this raw material gas with a booster pump or the like to generate a supercritical fluid and supplies it at a constant flow rate, a hopper 27 that inputs resin pellets that are the raw materials for the louver 10 (resin molded body), a barrel 28 that heats the input solid resin pellets to form molten resin, a screw 25 that rotates in the cylindrical internal cavity of the barrel 28 to knead the molten resin, an injection unit 26 that injects the supercritical fluid into the barrel 28 and dissolves it in the molten resin, and a nozzle 29 that injects the molten resin in which the supercritical fluid is dissolved into the mold 15.

[0025] The mold 15 has a split structure composed of a fixed mold 16 connected to the nozzle 29 of the injection molding machine 20 and a moving mold 17 that moves relative to the fixed mold 16 to perform mold clamping and removal of the molded product. In a state where these fixed mold 16 and moving mold 17 are clamped, a cavity 30, which is a sealed space that matches the shape of the louver 10 (resin molded body), is formed. The fixed mold 16 is provided with a sprue 35 that allows the molten resin injected from the nozzle 29 to pass through, a runner 36 that branches the molten resin that has passed through the sprue 35 and distributes it to the cavity 30, and a gate 37 provided at the tip of each runner 36 that narrows its diameter to increase the inflow rate of the molten resin into the cavity 30 from one direction.

[0026] FIG. 3 is an explanatory diagram of the injection position (connection position of gate 37) of the molten resin filled in cavity 30 of the resin molded body. Note that FIG. 3 also shows a louver 10 (resin molded body) having the same shape as this cavity 30. FIG. 4 is an explanatory diagram of runner 36 that distributes the molten resin to cavity 30 of the resin molded body.

[0027] Here, let the short side dimension D (D1, D2, D3) of the cross section of the first cavity 31 perpendicular to the injection direction of the molten resin. In this case, the respective lengths L (L1, L2, L3) of runners 36 (361, 362, 363) provided in the fixed mold 16 (FIG. 2) are set to have a relationship of 200×D < L. By having such a relationship, in rib 11 (first member 11) and main body portion 12 (second member 12) having a relationship of Δw1 < 3% < Δw2 for the weight reduction rate, the weight reduction rate Δw1 of rib 11 can be further reduced to increase the strength, and at the same time, the weight reduction rate Δw2 of main body portion 12 can be further increased to improve the weight reduction and heat insulation properties. Note that when the length of this cross-sectional short side varies depending on the cross-sectional position of the first cavity 31, the short side dimension D of the position cross section taking the maximum value is adopted.

[0028] Based on the flowchart of FIG. 5, the steps of the manufacturing method of the resin molded body according to the embodiment of the present invention will be described. Thus, in the manufacturing method of the resin molded body 10 in which rib 11 is provided on the flat main body portion 12, the molten resin is injected from a gate 37 in one direction opening at any position (including the connection portion with the main body portion 12) of the first cavity 31 in which rib 11 (first member 11) is formed (S11). Then, the molten resin is filled into the second cavity 32 continuous from the first cavity 31, foams, and then solidifies to foam-mold the main body portion 12 (second member 12) (S12). Further, in the first cavity 31, the filled molten resin solidifies before foaming, and rib 11 is stepwise non-foam molded (S13, END).

[0029] In the initial stage, most of the molten resin injected into the first cavity 31 is filled into the second cavity 32 without staying in the first cavity 31. The molten resin flowing into the second cavity 32, which has a larger volume compared to the first cavity 31, is rapidly depressurized and starts to foam, filling the second cavity 32 while increasing its volume. Then, the foam of the molten resin filled in the second cavity 32 is cooled and solidified in the mold to form a foam-molded body to form the main body portion 12.

[0030] When the filling of the foam of the molten resin in the second cavity 32 is completed, the molten resin staying in the first cavity 31 is cooled and solidified in the mold without foaming while under high pressure, and gradually forms the non-foam-molded rib 11. In the above description, the louver 10 (resin molded body) shows an example using a supercritical fluid as a foaming agent, but the foaming agent is not particularly limited, and a chemical foaming agent can also be used. Also, as the resin molded body 10, the louver of an air conditioner has been described in the embodiment, but it is not limited thereto. For example, it can also be applied to a resin molded body having a fixed portion that requires strength such as a fan for a blower and a driving portion that requires weight reduction, like a panel.

[0031] According to the resin molded body of at least one of the embodiments described above, the foam-molded main body portion (second member) and the rib (first member) that is gradually non-foam-molded are integrally molded, eliminating the need for screws or the like to connect the two, and further increasing the strength (bonding force). And while enjoying the benefits of foam molding such as weight reduction and heat insulation as a whole, it is possible to provide strength only to the necessary parts.

[0032] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Description of Symbols

[0033] 10…Louver (resin molded body), 11…Rib (first member), 12…Main body (second member), 15…Mold, 16…Fixed mold, 17…Movable mold, 20…Injection molding machine, 21…Cylinder, 22…Supply unit, 25…Screw, 26…Injection part, 27…Hopper, 28…Barrel, 29…Nozzle, 30…Cavity, 31…First cavity, 32…Second cavity, 35…Spoil, 36…Runner, 37…Gate.

Claims

1. Melted resin is injected from a gate that opens at any position in the first cavity, the melted resin filled in the second cavity continuous from the first cavity foams and then solidifies, the melted resin filled in the first cavity solidifies before foaming, a main body portion of a resin molded body is foam-molded in the second cavity, A method for manufacturing a resin molded body, wherein ribs or bosses provided on the main body portion are non-foam-molded in the first cavity.

2. Melted resin is injected from a gate that opens at any position in the first cavity, the melted resin filled in the second cavity continuous from the first cavity foams and then solidifies, the melted resin filled in the first cavity solidifies before foaming, A method for manufacturing a resin molded body, wherein the short side dimension D of the cross section of the first cavity perpendicular to the injection direction of the melted resin and the length L of the runner connected to the gate are set to have a relationship of 200×D<L.

3. In the method for manufacturing a resin molded body according to Claim 1 or Claim 2, the melted resin is a resin mixed with a supercritical fluid. A method for manufacturing a resin molded body.

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