Method for manufacturing resin-molded body, resin-molded body, and louver for air conditioner

Abstract

The present invention provides a manufacturing technique of a resin molded body in which only a necessary portion has strength while enjoying the benefits of foaming molding as a whole, such as light weight and thermal insulation, and a louver for an air conditioner. In a resin molded body (10) (louver (10)), a rib (11) (first member (11)) that is non-foam molded and supports an applied load to an external member, and a main body portion (12) (second member (12)) that is foam molded and supports an applied load to the external member via the rib (11) are integrally molded.

Description

Technical Field

[0001] The embodiments of the present invention relate to foamed resin molded bodies, louvers of air conditioners, and their manufacturing techniques. Background Technology

[0002] To adjust the vertical direction of the airflow from the air conditioner, the indoor unit of the air conditioner is equipped with louvers at the air outlet. These louvers have a problem: because they guide the cool air blown out during summer cooling on one side, moisture from the cooled indoor air condenses and forms water droplets on the opposite side.

[0003] As a prior art for solving the problem of water droplet formation, the following invention is known. Specifically, a technique is disclosed that suppresses the generation of surrounding warm air turbulence by forming ribs or sub-louvers on louvers, or by adjusting their positional relationship, thereby preventing condensation on the louvers. Furthermore, a technique is disclosed that improves insulation by attaching insulating material to a portion of the louver or by making the interior of the louver hollow, thus preventing condensation.

[0004] On the other hand, resin molded parts, which are produced by pre-mixing chemical foaming agents or by mixing supercritical fluids into the cylinder to foam the resin in the cavity, have been widely used in recent years as a molding method for parts requiring lightweight and thermal insulation.

[0005] Furthermore, the following invention is known. That is, after a non-foamed portion made of non-foamed material is formed in one step, a foamed portion is formed in a second step. During the injection molding of the foamed portion, the core is retracted, causing the mold to expand and form a single piece.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 10-122641

[0009] Patent Document 2: Japanese Patent Application Publication No. 2013-040738

[0010] Patent Document 3: Japanese Patent Application Publication No. 2003-314851

[0011] Patent Document 4: Japanese Patent Application Publication No. 2016-003807

[0012] Patent Document 5: Japanese Patent Application Publication No. 2005-155437

[0013] Summary of the invention

[0014] The problem that the invention aims to solve

[0015] However, louvers not only adjust the vertical direction of the airflow by shifting their opening angle during air conditioner operation, but also close the air outlet when the unit is not running. Therefore, altering the appearance of louvers primarily to suppress or prevent water droplets risks sacrificing other required functions of the louvers, which is something to be avoided.

[0016] Furthermore, the aforementioned technique, which involves molding a non-foamed portion made of non-foamed material in one stage followed by a secondary molding of the foamed portion, and then expanding the mold during injection molding of the foamed portion to form a single integral structure, suffers from weakened bonding at its boundary regions because foamed resin is filled on the secondary side after the non-foamed portion is molded on the primary side. Therefore, it is impossible to make the entire body of components such as louvers, blower fans, and panels (requiring strength for fixed parts and lightweight drive parts) a foamed body, while simultaneously making non-foamed components such as ribs for reinforcement along the length and width directions of the body, bosses for connection with other parts, and shafts and bearings on a portion of the body for rotational displacement. In other words, in the aforementioned well-known techniques, it is impossible to simultaneously achieve both high-pressure introduction of fine and uniform air bubbles to ensure a smooth, warp-free, and non-distorted skin layer on the louver body and its thermal insulation properties, as well as the provision of non-foamed portions. Summary of the Invention

[0017] The embodiments of the present invention were made with such consideration in mind, and their purpose is to provide resin molded bodies that enjoy the benefits of foam molding as a whole, such as lightweight and thermal insulation, while only giving strength to the necessary parts, louvers for air conditioners, and the manufacturing techniques thereof.

[0018] Methods for solving problems

[0019] The method for manufacturing a resin molded article disclosed in the embodiments is characterized in that molten resin is injected into a gate opening at any position of a first cavity, and the molten resin that is filled into a second cavity that is continuous from the first cavity solidifies after foaming, and the molten resin that is filled into the first cavity solidifies before foaming.

[0020] The effects of the invention

[0021] According to embodiments of the present invention, a resin molded body, an air conditioner louver, and a manufacturing technique thereof are provided that enjoy the overall benefits of foam molding such as lightweight and thermal insulation, while only giving strength to the necessary parts. Attached Figure Description

[0022] Figure 1 This is a perspective view of the louvers (resin molded body) of an air conditioner according to an embodiment of the present invention.

[0023] Figure 2 This is a cross-sectional view of the injection molding machine and mold used in the method for manufacturing resin molded articles according to embodiments of the present invention.

[0024] Figure 3 An illustration of the injection point of molten resin that is filled into the cavity of a resin molded body.

[0025] Figure 4 An illustration of the flow path for dispensing molten resin into the cavity of a resin molded body.

[0026] Figure 5 A flowchart illustrating the steps of the method for manufacturing a resin molded article according to an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures

[0028] 10—Louvre (resin molded body); 11—Rib (Part 1); 12—Main body (Part 2); 15—Mold; 16—Fixed mold; 17—Moving mold; 20—Injection molding machine; 21—Gas cylinder; 22—Supply section; 25—Lead screw; 26—Injection section; 27—Hopper; 28—Barrel; 29—Nozzle; 30—Cavity; 31—First cavity; 32—Second cavity; 35—Gate; 36—Runner; 37—Sprue Detailed Implementation

[0029] Figure 1 This is a perspective view of the louver 10 (hereinafter referred to as "louver 10") of an air conditioner according to an embodiment of the present invention. An air conditioner (not shown) is a device that provides air conditioning air to an air-conditioned space (indoors, etc.) using a refrigeration cycle system that circulates refrigerant. In the structure of this air conditioner, the indoor unit (not shown), disposed within the air-conditioned space, is framed by a housing (not shown) that forms an intake port for drawing in air retained within the air-conditioned space and an outlet port for providing air conditioning air to the air-conditioned space.

[0030] Furthermore, inside the housing, there is a blower (not shown) that draws in stagnant air through the intake port and blows out air conditioning air through the outlet port, and a heat exchanger (not shown) disposed in the flow path from the blower to the outlet port that generates air conditioning air from the stagnant air by exchanging heat with the refrigerant. Also, at the outlet port of the housing, a louver 10 arranged along the length of the opening is rotatably supported to adjust the direction of the air conditioning airflow.

[0031] like Figure 1 As shown, the louver 10 (resin molded body 10) includes: a rib 11 (first part 11) that supports the load applied to the louver 10, and a main body 12 (second part 12) that is integrally formed with the rib 11 and defines the blowing direction of the air conditioning air.

[0032] Furthermore, the flat main body 12 is foam-molded, and the load applied by its own weight, fluid resistance, or external force is transferred to the ribs 11. Moreover, the ribs 11 are non-foam-molded, and the load transferred from the main body 12 is supported on the external components (e.g., the housing) by the ribs themselves (ribs 11).

[0033] Figure 1 In this paper, the function of rib 11 is illustrated by taking a bearing that engages with the louvered plate 10, which is a rotating support for a shaft (not shown) located on one side of the housing, as an example. However, the use of rib 11 is not limited to shafts used for rotating supports, or reinforcing members used to improve the mechanical strength of the main body 12.

[0034] In addition, the resin constituting the louver 10 can be a general thermoplastic resin used for injection molding, such as polypropylene (PP), acrylonitrile butadiene styrene copolymer resin (ABS), other general-purpose resins and engineering plastics.

[0035] The weight reduction rate Δw1 of rib 11 (first component 11) differs from the weight reduction rate Δw2 of main body 12 (second component 12), with Δw1 < Δw2. Furthermore, the boundary value for distinguishing between foamed and non-foamed molding weight reduction rates is set to 3%, with Δw1 < 3% < Δw2. That is, if the weight reduction rates Δw1 and Δw2 of both rib 11 and main body 12 are less than 3%, both are considered non-foamed molding; if the weight reduction rates Δw1 and Δw2 of both rib 11 and main body 12 exceed 3%, both are considered foamed molding. Regions with weight reduction rates lower than the set boundary value of 3% are considered non-foamed molding, while regions with weight reduction rates higher than this boundary value are considered foamed molding. Additionally, the weight reduction rate represents the ratio of the weight difference to that of a non-foamed body in an ideal state completely free of air bubbles.

[0036] However, the weight reduction rate of the louvered panel 10 (resin molded body) has a random distribution throughout the whole. Therefore, if the weight reduction rate specified by the boundary value is achieved in more than 80% of the area of ​​both the main body 12 and the ribs 11, it is considered that foamed molding and non-foamed molding can be distinguished.

[0037] The most common value for the bubble diameter distribution of the foamed body 12 is expected to be in the range of 30 to 50 μm, but at the end of the molten resin flow, the upper limit is allowed to be 75 μm or 150 μm.

[0038] By molding the louvered panel 10 (resin molded body) in this way, even when cold air (air conditioning air) is guided on one side of the foamed main body 12, heat conduction between the opposite side is suppressed, moisture condensation in the trapped air is suppressed, and water droplets are prevented. Furthermore, the mechanical strength of the bearings that rotate and support the louvered panel 10 is ensured by the non-foamed ribs 11.

[0039] Figure 2 This is a cross-sectional view of the injection molding machine 20 and the mold 15 used in the method for manufacturing a resin molded body according to an embodiment of the present invention. The injection molding machine 20 is capable of dissolving a large amount of supercritical fluid (SCF) such as nitrogen or carbon dioxide as a foaming agent into the molten resin under high pressure. Furthermore, when the molten resin is injected into the mold 15, it is rapidly depressurized within the cavity 30 of the molded louver 10 (resin molded body), causing the dissolved supercritical fluid to vaporize and generate a large number of bubbles.

[0040] In this way, the injection molding machine 20 includes: a gas cylinder 21 for providing nitrogen and carbon dioxide as raw material gases as supercritical fluids; a supply unit 22 for pressurizing the raw material gases to generate supercritical fluids using a booster pump or the like and providing them at a certain flow rate; a hopper 27 for feeding resin particles that become the raw material for the louvered plate 10 (resin molded body); a barrel 28 for heating the fed solid resin particles to turn them into molten resin; a screw 25 for rotating and stirring the molten resin in the cylindrical internal cavity of the barrel 28; an injection unit 26 for injecting supercritical fluids into the barrel 28 to dissolve them into the molten resin; and a nozzle 29 for injecting the molten resin containing the dissolved supercritical fluids into the mold 15.

[0041] The mold 15 has a split structure consisting of a fixed mold 16 connected to the nozzle 29 of the injection molding machine 20 and a movable mold 17 that is moved relative to the fixed mold 16 for mold closing or removal of the molded article. When the fixed mold 16 and the movable mold 17 are closed, a closed space, i.e., a cavity 30, is formed, which is shaped to match the louver 10 (resin molded body). Furthermore, the fixed mold 16 includes: a sprue 35 through which molten resin injected from the nozzle 29 passes; a runner 36 that branches the molten resin passing through the sprue 35 and distributes it to the cavity 30; and a unidirectional gate 37 provided at the top of each runner 36, which is narrowed and opens to increase the inflow velocity of the molten resin into the cavity 30.

[0042] Figure 3 This is an explanatory diagram showing the injection point (connection point of gate 37) for the molten resin filling the cavity 30 of the resin molded body. Additionally, Figure 3 A louvered plate 10 (resin molded body) with the same shape as the cavity 30 was also drawn. Figure 4An explanatory diagram of the flow channel 36 for distributing molten resin to the cavity 30 of the resin molded body.

[0043] Here, let the short side dimension D (D1, D2, D3) of the cross section of the first cavity 31 orthogonal to the direction of molten resin injection be defined. In this case, the fixed mold 16 ( Figure 2 The lengths L (L1, L2, L3) of the flow channels 36 (361, 362, 363) are set to have a relationship of 200×D<L. By having this relationship, in the case of ribs 11 (first component 11) and main body 12 (second component 12) with a weight reduction rate of Δw1<3%<Δw2, it is possible to reduce the weight reduction rate Δw1 of ribs 11 to increase strength, while simultaneously increasing the weight reduction rate Δw2 of main body 12 to improve lightweighting and thermal insulation. Furthermore, when the length of the short side of this cross-section varies depending on the cross-sectional position of the first cavity 31, the short side dimension D of the cross-section at the position of maximum size can be used.

[0044] based on Figure 5 The flowchart illustrates the steps of the method for manufacturing a resin molded body according to an embodiment of the present invention. In this method, for manufacturing a resin molded body 10 with ribs 11 provided on a flat body 12, molten resin is injected into a unidirectional gate 37 that opens at any position (including the point of connection with the body 12) in the first cavity 31 forming the ribs 11 (first component 11) (S11). The molten resin is then filled into a second cavity 32 continuous from the first cavity 31, foams, and solidifies, foam-molding the body 12 (second component 12) (S12). Furthermore, in the first cavity 31, the ribs 11 are non-foam-molded in stages before foaming (S13, end).

[0045] In the initial stage, most of the molten resin injected into the first cavity 31 does not remain in the first cavity 31, but is instead filled into the second cavity 32. The molten resin flowing into the second cavity 32, which has a larger volume than the first cavity 31, is rapidly depressurized and begins to foam, continuously filling the second cavity 32 as its volume increases. Then, the foamed molten resin filled into the second cavity 32 is cooled and solidified in the mold, forming the foamed main body 12.

[0046] After the foamed molten resin in the second cavity 32 has been filled, the molten resin remaining in the first cavity 31 does not foam under high pressure and is cooled and solidified in the mold, forming non-foamed ribs 11 in stages. Furthermore, although the example of using a supercritical fluid as a foaming agent for the louver 10 (resin molded body) was given in the above description, there are no particular limitations on the foaming agent, and chemical foaming agents can also be used. Moreover, while the embodiment described the resin molded body 10 as a louver for an air conditioner, it is not limited to this. For example, it can also be used for resin molded bodies with fixed parts requiring strength and drive parts requiring lightweight, such as fans for blowers or panels.

[0047] According to at least one embodiment of the resin molded body described above, the foamed main body (second part) and the staged non-foamed ribs (first part) are integrally molded, eliminating the need for screws or the like to join the two, thus increasing the strength (bonding force). Furthermore, the overall benefits of foam molding, such as lightweight and thermal insulation, are enjoyed, while only the necessary parts can be made strong.

[0048] While several embodiments of the present invention have been described above, these embodiments are merely illustrative and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the invention as described in the claims and their equivalents.

Claims

1. A method for manufacturing a resin molded article, wherein, Molten resin is injected through multiple gates that open at the locations of multiple first cavities. In the initial stage, after injection into the multiple first-type cavities, most of the molten resin does not remain but is filled into second-type cavities that are continuous with the multiple first-type cavities and have a larger volume. The molten resin filled into the second-type cavities solidifies after foaming. In the stage where the molten resin in the second cavity is completely filled, the molten resin that was filled into the first cavity solidifies before foaming. The main body of the resin molded body is foamed and molded in the second cavity mentioned above. The ribs or bosses provided on the main body are non-foamed in the first cavity.

2. The method for manufacturing a resin molded article as described in claim 1, wherein, The aforementioned molten resin is a material mixed with supercritical fluid.

3. A method for manufacturing a resin molded article, wherein, Molten resin is injected through multiple gates that open at the locations of multiple first cavities. In the initial stage, after injection into the multiple first-type cavities, most of the molten resin does not remain but is filled into second-type cavities that are continuous with the multiple first-type cavities and have a larger volume. The molten resin filled into the second-type cavities solidifies after foaming. In the stage where the molten resin in the second cavity is completely filled, the molten resin that was filled into the first cavity solidifies before foaming. The short side dimension D of the cross section of the first cavity orthogonal to the injection direction of the molten resin and the length L of the runner connected to the corresponding gate are set to have a relationship of 200×D<L.

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