Method for manufacturing exterior case for hot water unit

Abstract

To provide a manufacturing method of an outer case for a hot water unit, capable of preventing cracks from easily occurring due to pressing to be used in pressing with a deeper drawing than before.SOLUTION: A manufacturing method of an outer case for a hot water unit has a printing process of providing a printing layer 4 on a flat metal plate 30, and a pressing process of pressing the metal plate 30 after this printing process. The pressing step is a process for forming the metal plate 30 as a component of an outer case used for housing a hot water device for hot water generation or hot water storage inside. The pressing process is performed in a state where the metal plate 30 is heated.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a manufacturing method for manufacturing an outer case for a hot water unit used to house hot water equipment for generating or storing hot water in a hot water unit such as a water heater or a cogeneration system. [Background technology]

[0002] The present applicant has previously proposed the exterior cases described in Patent Documents 1 and 2 as specific examples of exterior cases for hot water units. The exterior cases for hot water units described in these documents are manufactured by pressing a metal plate such as a colored steel plate. However, before the pressing, the metal plate is subjected to inkjet printing to provide an inkjet printed layer. The inkjet printed layer represents, for example, characters, symbols, figures, patterns, etc. According to this configuration, it is possible to display a desired pattern on the surface of the exterior case, thereby improving the design.

[0003] However, the above-mentioned conventional techniques still have room for improvement, as described below.

[0004] That is, the press working of the metal plate is performed in a state where the printed layer (inkjet printed layer) is provided on the metal plate. Therefore, when the press working is performed, for example, by drawing to elongate a part of the metal plate, if the printed layer has better ductility than the metal plate, the range in which the drawing can be performed is determined by the ductility of the metal plate, and when the metal plate is drawn deeply, even if the printed layer has a ductility margin, the metal plate does not have a ductility margin, and cracks may occur. In this case, the characteristics of the printed layer are not fully utilized. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-60508 A [Patent Document 2] JP 2019-60509 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention was conceived under the circumstances described above, and has as its object to provide a manufacturing method for an exterior case for a hot water unit which prevents cracks from easily occurring due to press processing and is capable of handling press processing with deeper drawing than conventional methods. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following technical solutions.

[0008] The manufacturing method of an exterior case for a hot water unit provided by the present invention includes a printing step of providing a printing layer on a flat metal plate, and a pressing step of performing a press process on the metal plate after the printing step, the pressing step being a step for forming the metal plate into a component part of an exterior case used to house a hot water device for generating or storing hot water, the pressing step being carried out in a state where the metal plate is heated. In the printing step, the printing layer is provided using a printing ink containing a thermosetting resin, and in the pressing step, the printing layer is thermally cured using heat for heating the metal plate. It is characterized by the following. Preferably, said printing process is an inkjet printing process.

[0009] According to this configuration, the metal plate is heated and the pressing process is carried out in a state where the ductility of the metal plate is improved, so that it is possible to appropriately perform press processing that draws the metal plate deeper than in the past in order to take advantage of the good ductility of the printed layer. Furthermore, such a configuration is rational because the printed layer can be thermally cured (dried and solidified) using the heat generated during heating to improve the ductility of the metal plate.

[0010] In the present invention, preferably, the outer case comprises an outer case body having at least one side formed as an opening, and a cover body attached to the outer case body so as to cover the opening, and the components of the outer case are the outer case body or the cover body.

[0013] In the present invention, preferably, in the printing step, a printing ink containing an ultraviolet-curable resin in addition to the thermosetting resin is used as the printing ink, and in the process of providing the printing layer on the metal plate, the printing layer is cured by exposure to ultraviolet light.

[0014] According to this configuration, the printed layer can be preliminarily cured using the ultraviolet curing resin until the thermosetting resin in the printed layer is thermally cured, and the printed layer can be appropriately protected. In addition, as printing proceeds, it is possible to provide a new printed layer in contact with the printed layer cured by ultraviolet irradiation or to the side of the printed layer, and the occurrence of the so-called print bleeding phenomenon can be suppressed.

[0017] In the present invention, preferably, the pressing process includes a process of applying drawing to the metal plate, and in the printing process, the thickness of the printing layer in a portion of the planned drawing area where the thickness of the metal plate is thinner than other portions is made thinner than the thickness of the printing layer in the other portions.

[0018] According to this configuration, the following effects can be obtained. That is, when an inkjet printing process is performed before drawing a metal plate, if the thickness of the inkjet printed layer in the area to be drawn is large and uniform, there is a risk that cracks will occur in the inkjet printed layer in the portion of the metal plate where the amount of drawing is large (the portion of the drawn portion where the plate thickness is thinner than other portions) when drawing is performed. In contrast, the above configuration makes it possible to appropriately avoid such a risk.

[0019] Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1A is a side view showing an example of a hot water unit equipped with an outer case manufactured by a manufacturing method according to the present invention, FIG. 1B is an exploded oblique view of the outer case shown in FIG. 1A, and FIG. 1C is a cross-sectional view taken along the line Ic-Ic of FIG. [Diagram 2] 2 is a front cross-sectional view of a main part of a cover body of an exterior case shown in FIG. 1, and corresponds to a front cross-sectional view of a portion indicated by reference symbol II in FIG. 1(b). [Diagram 3] 1. (a) to (c) are explanatory views showing an example of a manufacturing method according to the present invention, and correspond to a series of work steps in the method for manufacturing the cover body shown in FIG. [Figure 4] FIG. 4A is a schematic perspective view showing an example of an inkjet printer used in the inkjet printing process, and FIG. 4B is a view taken along an arrow IVb in FIG. [Diagram 5] FIG. 2 is a schematic cross-sectional view showing a main part of an example of a pressing device used in a pressing process. [Figure 6] 6 is a schematic cross-sectional view of a main part of the press apparatus shown in FIG. 5 in an operating state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0022] For ease of understanding, prior to describing the manufacturing method of this embodiment, the configurations of an exterior case C for a hot water unit manufactured by the manufacturing method of this embodiment and a hot water unit U including the same will be described.

[0023] 1, the hot water unit U is configured as a hot water supply device, and has a configuration in which a hot water device 1 for generating hot water is housed in an exterior case C. The hot water device 1 includes a heat exchanger 10 through which hot water flows, a burner 11 for heating the hot water in the heat exchanger 10, and a fan 12 for supplying combustion air to the burner 11.

[0024] The exterior case C includes a rectangular box-shaped case body 2 having an opening 20 on the front side, and a cover body 3 (front cover body) that covers the opening 20. The cover body 3 is detachably attached to the front part of the case body 2 by using a screw body 9, such as a screw, and the screw insertion holes 31, 21 through which the screw body 9 passes.

[0025] In this embodiment, an inkjet printed layer 4 (a printed layer 4a shown by a halftone dot pattern and a printed layer 4b showing the letters "ABC") is provided on the cover body 3, and the manufacturing method of the present invention is applied. The inkjet printed layer 4 is a specific example of the printed layer of the present invention. The case body 2 does not have an inkjet printed layer, and the manufacturing method of the present invention is not applied to it. Therefore, hereinafter, the configuration of the cover body 3 and the manufacturing method thereof will be mainly described, and the description of the case body 2 will be omitted or simplified. However, it goes without saying that the manufacturing method of the present invention can be applied to the manufacturing of the case body 2.

[0026] The cover body 3 is made of a color steel plate 30 (corresponding to an example of a metal plate in the present invention) and has a substantially rectangular panel shape when viewed from the front. The cover body 3 includes an outer peripheral flange portion 32 and a bulging portion 33 that is surrounded by the outer peripheral flange portion 32 and bulges forward (toward the front side of the outer case C) from the outer peripheral flange portion 32. The outer peripheral flange portion 32 is a portion for abutting against the flange portion 22 on the front portion of the case main body 2. The bulging portion 33 has a standing peripheral wall portion 33a that stands forward from the outer peripheral flange portion 32, and a substantially flat front portion 33b that is connected to the tip of the standing peripheral wall portion 33a. The front portion 33b is provided with a plurality of air intake ports 34 that allow outside air to flow into the outer case C, and an exhaust port 35 that exhausts exhaust gas that has completed heat recovery by the heat exchanger 10 to the outside of the outer case C.

[0027] As shown in the partially enlarged cross-sectional views of FIG. 1(c) and FIG. 3, the color steel sheet 30 is composed of a plated steel sheet 30a, a white-based (including white) front-side paint layer 30b laminated on the outer surface of the plated steel sheet 30a, and a back surface of the plated steel sheet 30a. The cover body 3 has a multi-layer structure with a paint layer 30c on the back side as a service coat. The cover body 3 has a paint layer 30b located on the front side, and an inkjet printed layer 4 provided on this paint layer 30b.

[0028] The inkjet printed layer 4 (4a) is, for example, a solid printed layer, and is provided over a wide area of ​​the surface of the cover body 3. The inkjet printed layer 4 (4b) is, for example, a printed layer showing characters such as the logo of the manufacturer of the hot water unit U. In the drawings, it is conveniently shown as "ABC", but is not limited to this. The inkjet printed layer 4 is a coating film provided by using an inkjet printer 8, as described below. As the ink for inkjet printing, a water-based pigment ink or a solvent-based pigment ink can be used, but in this embodiment, an ink containing both an ultraviolet curing resin and a thermosetting resin is used.

[0029] Next, an example of a method for manufacturing the cover body 3 will be described.

[0030] First, as shown in Fig. 3(a), a flat color steel sheet 30 is prepared as a raw material for the cover body 3. The configuration of the color steel sheet 30 is as described above.

[0031] Next, as shown in Fig. 3(b), an inkjet printing process is carried out to provide an inkjet printed layer 4 on the surface of the paint layer 30b of the color steel plate 30. This inkjet printing process is carried out, for example, by using an inkjet printer 8 as shown in Fig. 4. The inkjet printer 8 is arranged so that a print head 80 can be moved in mutually orthogonal x and y directions above a mounting table 81 that supports the color steel plate 30. The print head 80 is equipped with a plurality of inkjet nozzles 82 that spray droplets of inkjet paint of a predetermined color toward the color steel plate 30, and a pair of ultraviolet light sources 83 (83a, 83b).

[0032] In the inkjet printing process, when inkjet printing is performed while moving the print head 80 in the x1 direction of FIG. 4(b) as the main scanning direction, the ultraviolet light source 83a on the rear side of the main scanning direction is turned on to irradiate ultraviolet light to the area immediately after inkjet printing. Since the inkjet printing layer 40 contains ultraviolet curing resin, it is possible to quickly cure the inkjet printing layer 40 (to a degree that does not cause bleeding, etc.) by irradiating ultraviolet light as described above. When such curing process is completed, inkjet printing is performed again. By repeating such inkjet printing and curing process by ultraviolet irradiation, it is possible to overcoat a plurality of inkjet printing layers 40 and give the inkjet printing layer 4 an appropriate thickness. When inkjet printing is performed in the opposite direction to the x1 direction, the ultraviolet light source 83b is turned on instead of the ultraviolet light source 83a to obtain the same effect as described above.

[0033] When the inkjet printed layer 4 (4a) is provided, the thickness ta of the corner 33a' of the peripheral wall 33a of the color steel plate 30 is made thinner than the thickness tb of the other parts, as shown in Fig. 2. The corner 33a' corresponds to an example of "a part of the region to be subjected to drawing where the thickness of the metal plate is thinner than the other parts" according to the present invention.

[0034] After the inkjet printing on the color steel plate 30 is completed, the color steel plate 30 is subjected to drawing as a press process to form the outer circumferential flange portion 32 and the bulge portion 33 as shown in Fig. 3(c). In addition, hole punching press process to form the air intake port 34, the exhaust port 35, etc., and trimming process to remove excess portions of the outer circumferential flange portion 32 are also performed. In this way, the cover body 3 described above can be manufactured.

[0035] The press working as the drawing process is performed in a state where the color steel sheet 30 and the inkjet printing layer 4 are heated to about 120°C, which is the thermal curing temperature of the inkjet printing layer 4. More specifically, the press working is performed using a press device 5 as shown in FIG. 5. The press dies 5a, 5b (upper die 5a, lower die 5b) of the press device 5 have built-in heaters 50a, 50b capable of heating the press dies 5a, 5b to a desired temperature. In addition, hole-shaped water passages 51a, 51b for passing water for cooling the press dies 5a, 5b, water supply pipes 52a, 52b connected to the water passages 51a, 51b, and drainage pipes 53a, 53b are also provided.

[0036] When the press processing of the color steel plate 30 is performed using the press device 5 described above, it is preferable to heat (preheat) the color steel plate 30 to a temperature close to 120°C using an appropriate heating device. Meanwhile, the press dies 5a and 5b are heated to about 120°C. In this state, the color steel plate 30 is set in the press device 5, and the color steel plate 30 is pressed using the press dies 5a and 5b as shown in FIG. 6. After that, the press dies 5a and 5b are opened vertically, but the press dies 5a and 5b and the pressed color steel plate 30 are thermally expanded, and it may be difficult to remove the color steel plate 30 from the press device 5. In response to this, if water is supplied to the water passages 51a and 51b to cool the press dies 5a and 5b, it becomes easier to remove the color steel plate 30.

[0037] In the above-mentioned pressing process, the color steel plate 30 is heated and pressed in a state where its ductility is improved, so that the drawing dimension of the color steel plate 30 can be increased while preventing cracks from occurring at the drawing points. In addition, during the pressing process, the inkjet printing layer 4 is also heated and the thermosetting resin in the inkjet printing layer 4 is thermally cured, so that the inkjet printing layer 4 is further cured in addition to the ultraviolet curing described above, and can be made sturdy. The thermal curing process of the inkjet printing layer 4 is rational because it is performed using the heat for increasing the temperature of the color steel plate 30 during the pressing process.

[0038] Furthermore, unlike this embodiment, for example, if press working is performed in a state where the inkjet printed layer 4 has been sufficiently thermally cured and the ductility of the inkjet printed layer 4 has decreased, there is a risk of cracks occurring in the inkjet printed layer 4. In contrast, according to this embodiment, the thermal curing of the inkjet printed layer 4 can be completed approximately simultaneously with the end of the press working, so it is possible to eliminate such a risk.

[0039] 2, the corner 33a' of the upright peripheral wall 33a of the bulge 33 provided on the cover body 3 is elongated by drawing to a greater extent than the other portions. In contrast, the thickness ta of the portion of the inkjet printed layer 4 corresponding to the corner 33a' is made thinner than the thickness tb of the other portions, making it less likely to crack. Therefore, it is possible to minimize the risk of cracks occurring in the inkjet printed layer 4 due to the drawing.

[0040] The cover body 3 has an inkjet printed layer 4, and the presence of this inkjet printed layer 4 makes it possible to give the entire exterior case C an excellent design and a good appearance. Furthermore, inkjet printing makes it possible to perform printing in various forms with high precision, quickly, and inexpensively.

[0041] The present invention is not limited to the above-described embodiment. The specific configuration of each step of the manufacturing method of the exterior case for a hot water unit according to the present invention can be freely changed in various ways within the intended scope of the present invention.

[0042] In the present invention ,mark The printing step may be performed by other printing methods instead of inkjet printing. The printed layer may represent any of characters, symbols, figures, and patterns, and may be, for example, a simple solid coating. It may also be a clear layer that does not contain a pigment.

[0043] In the above embodiment, the press molds 5a, 5b are heated by the heaters 50a, 50b of the press device 5, and in addition to the color steel sheet 30 being heated by this heat, the color steel sheet 30 is preheated before being set in the press device 5, so that it is possible to prevent the color steel sheet 30 from being insufficiently heated. However, this is not limited to this, and for example, the color steel sheet 30 may be heated only by the heaters 50a, 50b of the press device 5, or the press device 5 may not be provided with the heaters 50a, 50b, and the color steel sheet 30 may be heated only by an appropriate heating means before being set in the press device 5. Various means can be used as a heating means for the color steel sheet 30 (metal sheet).

[0044] The hot water unit of the present invention may be configured as a hot water storage tank unit in which a hot water storage device such as a hot water storage tank is housed in an exterior case, instead of a hot water generating device such as a hot water heater housed in an exterior case. Therefore, the exterior case is not limited to a combination of a case body with a front opening and a cover body that closes the front opening. A metal plate is used as the material for the exterior case, and it is possible to use a metal plate other than a commercially available color steel plate as this metal plate. [Explanation of symbols]

[0045] U Hot water unit C. Outer case 1 Hot water equipment 2 Case body 3 Cover body 30 Color steel plate (metal plate) 4 Inkjet printing layer

Claims

1. A printing process for providing a printing layer on a flat metal plate; After the printing step, a pressing step is performed on the metal plate. It has The pressing step is a step for forming the metal plate into a component part of an exterior case used to house a hot water device for generating hot water or storing hot water, The pressing step is carried out in a state where the metal plate is heated, In the printing step, the printing layer is provided using a printing ink containing a thermosetting resin, A method for manufacturing an exterior case for a hot water unit, comprising: heat for heating the metal plate in the pressing step being utilized to thermally harden the printed layer.

2. A method for manufacturing an exterior case for a hot water unit according to claim 1, comprising the steps of: The outer case includes an outer case body having at least one surface formed as an opening, and a cover body attached to the outer case body so as to cover the opening, A method for manufacturing an exterior case for a hot water unit, wherein the component part of the exterior case is the exterior case main body or the cover body.

3. A method for manufacturing an exterior case for a hot water unit according to claim 1 or 2, comprising the steps of: In the printing step, a printing ink containing an ultraviolet curable resin in addition to the thermosetting resin is used as the printing ink, A method for manufacturing an exterior case for a hot water unit, comprising the steps of: curing the printed layer by exposure to ultraviolet light during the process of providing the printed layer on the metal plate.

4. A method for manufacturing an exterior case for a hot water unit according to any one of claims 1 to 3, comprising the steps of: The pressing step includes a step of performing drawing on the metal plate, A method for manufacturing an exterior case for a hot water unit, in which, in the printing process, the thickness of the printed layer in the planned drawing area where the thickness of the metal plate is thinner than other parts is made thinner than the thickness of the printed layer in the other parts.

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