Exterior case for hot water unit

Provided is an exterior case for a hot water unit which can be produced in a simple operational process with high productivity and with low costs without environmental pollution even if a complex pattern or the like is formed, in which the overall design properties are favorable. There is provided an exterior case used for accommodating a hot water device for hot water production or hot water storage therein, and an ink jet printing layer representing at least one of letters, symbols, figures, and patterns is provided on a paint layer of a metal plate constituting the exterior case.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Japan Applications No. 2017-183446 and No. 2017-228109, respectively filed on Sep. 25, 2017 and Nov. 28, 2017. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to a hot water unit in which a hot water device for hot water production or hot water storage, for example, a water heater and a cogeneration system, is accommodated in an exterior case and an exterior case thereof.

Description of Related Art

As specific examples of a hot water unit configured as a water heater, for example, there are hot water devices which are configured to perform hot water heating using combustion gas generated by a burner and which are accommodated in an exterior case (for example, refer to Patent Document 1 (Japanese Laid-open No. 2012-32029), Patent Document 2 (Japanese Laid-open No. H11-294867), and Patent Document 3 (Japanese Laid-open No. 2014-40950)). Such exterior cases for a hot water unit are generally produced by pressing a colored steel plate having a monochromatic surface.

In such a hot water unit, various types of device related information such as a manufacturer name, a distributor name, a model, and a manufacture date are displayed on the exterior case. In this case, in the related art, a method in which a label on which device related information is printed is prepared and the label is attached to the exterior case is used.

However, according to the related art, attaching a label is troublesome, and it cannot be said that the productivity is favorable. When there are many types of labels, there is a risk that an operator may make a mistake regarding an attachment position. In addition, there is a risk that bubbles may enter between the label and the exterior case or a part of the label may peel off, and the appearance may deteriorate. The entire label may peel off and be lost.

In order to address the above circumstances, it may be conceived that device related information is displayed by, for example, printing using a transfer system. According to such a method, it is possible to eliminate circumstances occurring when the label is attached. Moreover, the above printing cannot be said to be favorable in terms of workability, and there is room for improvement in terms of better productivity. In addition, in the case of device related information including small letters and many letters and device related information with complicated figures such as an electrical wiring diagram, it is difficult to display the information legibly or clearly (for example, refer to Patent Document 4 (Japanese Laid-open No. H10-296906), Patent Document 5 (Japanese Patent No. 5893878)).

On the other hand, in such a hot water unit, in addition to displaying letters or symbols representing, for example, a manufacturer name, a type or capabilities of the hot water unit, on the exterior case, it may be required to make a large area of a front surface of the exterior case in a predetermined color different from the background color of the front surface of the colored steel plate. In this case, in the related art, after component parts (an exterior case main body and a cover body) of the exterior case are formed by press molding, the component parts are painted by a spray system. A solvent paint or a powder paint may be used as the paint.

However, in the above related art, as will be described below, there is room for improvement.

That is, when a painting method using the spray system of the related art is used, in addition to troublesome masking processing on an uncoated part and paint color matching, a paint spraying operation using a spray gun (air gun) is also troublesome and expert skills are also required. Therefore, the workability and productivity are poor. In addition, since paint is also sprayed onto a masking part, there is much waste of paint. Therefore, production costs of the exterior case and production costs of the hot water unit are high.

Such circumstances become significant when patterns to be painted are more complicated and the number of colors increases, and it is difficult to express fine patterns. Further, when a solvent paint or a powder paint as a spray paint is used, the environmental load is large, and it is difficult to maintain a favorable state of an operation environment and appropriately perform a paint disposal process.

Here, in the related art, a painting method using a transfer system may be appropriately used. However, according to the painting method using this system, a transfer plate is necessary and high costs are incurred. In addition, it is unsuitable for painting a large area.

SUMMARY

An exterior case for a hot water unit provided according to a first aspect of the disclosure is an exterior case for a hot water unit used for accommodating a hot water device for hot water production or hot water storage therein, wherein the exterior case is formed using a metal plate, and a paint layer is provided on at least one of an outer surface and an inner surface of the metal plate, and wherein an ink jet printing layer that is laminated and provided on the paint layer and represents at least one of letters, symbols, figures, and patterns is provided.

Here, the ink jet printing layer is a print layer formed by spraying ink droplets in the form of fine liquid droplets onto a painting target area using an ink jet printer.

Other features and contents of the disclosure will become more apparent based on the following description of embodiments of the disclosure with reference to the appended drawings.

DESCRIPTION OF THE EMBODIMENTS

The embodiments of the disclosure provide an exterior case for a hot water unit which can be produced in a simple operational process with high productivity and with low costs without environmental pollution even if a complex pattern or the like is formed, in which the overall design properties are favorable, and in which device related information can be easily and appropriately displayed, and a hot water unit including the same.

The embodiments of the disclosure provide the following technical aspects.

In such a configuration, the following can be obtained.

That is, since the ink jet printing layer is additionally provided on the paint layer provided on at least one of an outer surface and an inner surface of the metal plate constituting the exterior case, it is possible to appropriately represent desired letters, symbols, figures, and patterns. As the metal plate on which the paint layer is provided, for example, a colored steel plate can be used without change. On the other hand, the ink jet printing layer can be easily provided using an ink jet printer, and unlike painting using the spray system of the related art, masking processing on the exterior case and paint color matching are not performed and expert skills are not required. In addition, unlike painting using the transfer system of the related art, a transfer plate is not used and it is easy to paint a large area. Therefore, it is possible to improve workability of painting and increase productivity for the exterior case. In addition, since the ink jet printing layer can be provided only at a desired part, it is possible to eliminate or reduce waste of the ink paint. As a result, it is possible to reduce production costs of the exterior case and production costs of the hot water unit.

In addition, according to the ink jet printing layer, since it is possible to finely represent patterns with complex shapes or patterns in which many colors are used, it is more suitable for improving an external appearance of the hot water unit. In addition, compared with the related art, it is possible to reduce the environmental load and easily realize a favorable state of the operation environment.

In the exterior case for a hot water unit according to one or some exemplary embodiments of the disclosure, on the ink jet printing layer, device related information of the hot water unit is displayed.

In such a configuration, the following can be obtained.

First, since device related information is displayed using the ink jet printing layer, it is possible to eliminate a need to attach a label for displaying device related information to the exterior case. Therefore, it is possible to appropriately eliminate circumstances occurring when a label attachment operation is used, that is, circumstances such as a complicated label attaching operation, a poor appearance due to bubbles that have entered under the label or peeling off of a part of the label, or loss due to peeling off of the label.

Second, the ink jet printing layer can be easily provided using an ink jet printer. For example, unlike a painting method using a transfer system, paint color matching and a transfer plate are not performed. In addition, it is easy to paint a large area. Therefore, it is possible to improve workability of painting, increase productivity for the exterior case, and reduce production costs of the exterior case.

Third, according to ink jet printing, it is possible to represent small letters and complicated figures finely and legibly. In addition, since the ink jet printing layer is provided on the paint layer, letters displayed on the ink jet printing layer can be made clear and it is possible to improve an appearance of the exterior case.

In one or some exemplary embodiments, on the ink jet printing layer, a decoration pattern is additionally displayed in addition to the device related information.

Such a configuration is more suitable for improving the appearance of the exterior case. In addition, compared with a case in which a decoration pattern is provided using, for example, a painting method using a transfer system or a spray system, results such as improved productivity and low production costs can be obtained.

In one or some exemplary embodiments, as the metal plate part, an exterior case main body of which at least one surface has an opening and a cover body that is attached to the exterior case main body so that it blocks the opening are provided, and the ink jet printing layer is provided on at least one of the exterior case main body and the cover body.

In one or some exemplary embodiments, as the ink jet printing layer, an ink jet printing layer which is provided on a front part of the cover body and on which at least one of a manufacturer name, a distributor name, a model, a manufacture date, and instructions for use of the hot water unit is displayed as the device related information is provided.

In one or some exemplary embodiments, as the ink jet printing layer, an ink jet printing layer on which at least one of an electrical wiring diagram and a piping diagram of the hot water unit and other diagrams for explaining installation of parts is displayed as the device related information is provided.

The exterior case for a hot water unit according to one or some exemplary embodiments of the disclosure has a drawn part, and within the drawn part, in a part in which a plate thickness of the metal plate is thinner than other parts, a thickness of the ink jet printing layer is thinner than other parts.

In such a configuration, the following can be obtained.

That is, after the ink jet printing layer is provided on the exterior case, when the drawn part is provided, if the thickness of the entire ink jet printing layer of the drawn part is large and uniform, there is a risk of the ink jet printing layer peeling off at a part (within the drawn part, a part in which a plate thickness is thinner than other parts) in which an amount of the metal plate drawn is large. On the other hand, according to the above configuration, it is possible to appropriately avoid such risks.

In the exterior case for a hot water unit according to one or some exemplary embodiments of the disclosure, a burring hole having a burring part protruding from the drawn part is provided, and in the burring part, an ink jet printing layer connected to an ink jet printing layer provided on a part surrounding the burring hole is provided.

In such a configuration, it is possible to paint the part surrounding the burring hole and the burring part in colors or patterns connected continuously, and it is possible to make an external appearance of the part favorable. Unlike the above configuration, when the ink jet printing layer is provided, for example, only on the part surrounding the burring hole, and no ink jet printing layer is provided on the burring part, there is a risk that the burring part may appear as an unnatural part from the outside. However, according to the above configuration, it is possible to eliminate such circumstances.

In one or some exemplary embodiments, at least a part of component parts of the exterior case for a hot water unit according to the disclosure are press working articles. A marker for positioning when the component parts are pressed is provided in the ink jet printing layer.

In such a configuration, when the component parts of the exterior case are formed by pressing, it is possible to perform press processing using a marker for positioning represented on the ink jet printing layer as a reference. Therefore, it is possible to accurately position letters and patterns represented on the ink jet printing layer and a processed part subjected to press processing so that they do not deviate greatly from each other.

In one or some exemplary embodiments, the ink jet printing layer contains a UV curable resin.

In such a configuration, it is possible to quickly cure the ink jet printing layer by emitting ultraviolet rays. Therefore, for example, during ink jet printing, it is possible for ink jet printing to proceed while ultraviolet rays are emitted to the ink jet printing layer and the ink jet printing layer is cured. When a new ink jet printing layer having a different color is provided in an area adjacent to the uncured ink jet printing layer, there is a risk of occurrence of bleeding. However, when ink jet printing proceeds while the ink jet printing layer is cured by emitting ultraviolet rays as described above, it is possible to prevent the above bleeding from occurring.

In one or some exemplary embodiments, the ink jet printing layer contains a thermosetting resin.

In such a configuration, after the ink jet printing is completed, when the ink jet printing layer is heated and the thermosetting resin is cured, it is possible to increase the strength of the ink jet printing layer and impart excellent weather resistance.

Exemplary embodiments of the disclosure will be described below in detail with reference to the drawings.

A hot water unit U shown inFIG. 1is a water heater, and has a configuration in which a hot water device1for hot water production is accommodated in an exterior case C. The hot water device1includes a heat exchanger10through which hot water flows, a burner11configured to heat hot water in the heat exchanger10, and a fan12configured to supply combustion air to the burner11.

The exterior case C includes a rectangular box-shaped exterior case main body2having an opening20on its front surface and a cover body3(front cover body) for blocking the opening20. The cover body3is detachably attached to a front part of the exterior case main body2using a screw body9, for example, a screw, and screw insertion holes31and21into which the screw body9is inserted.

In the present embodiment, an ink jet printing layer4(in the drawing, part marked with a dot pattern or a wavy line pattern) is provided on the cover body3, but it is not provided on the exterior case main body2. Therefore, hereinafter, a configuration of the cover body3will be described in detail and the exterior case main body2will not be described. However, as will be described below, of course, an ink jet printing layer may be provided on the exterior case main body2.

The cover body3has a configuration in which the ink jet printing layer4(4ato4g) is provided on a press-molded colored steel plate30(corresponding to an example of a metal plate on which a paint layer is provided) to be described below. However, when the cover body3in the present embodiment is produced, as will be described below, after the ink jet printing layer4is provided on the colored steel plate30, press processing is performed.

The cover body3has a substantially rectangular panel shape in a front view and includes an outer peripheral flange part32and a bulging part33that is surrounded by the outer peripheral flange part32and bulges forward (to the front side of the exterior case C) from the outer peripheral flange part32. The outer peripheral flange part32is a part which abuts a substantially rectangular frame-like flange part22provided on the front part of the exterior case main body2. As shown inFIG. 3(a), a folded part32ais connected to an outer edge part thereof by hemming processing.

The bulging part33of the cover body3occupies most of the cover body3, and an air supply port34and an exhaust port35are provided in the bulging part33(refer toFIG. 2). The air supply port34is a part that enables outside air to flow into the exterior case C. The exhaust port35is a part for discharging exhaust gas from which heat recovery by the heat exchanger10has been completed to the outside of the exterior case C, and as shown inFIG. 3(c), is formed as a burring hole in which a tubular burring part35ais connected to its peripheral edge part. Similarly to the exhaust port35, the air supply port34can be formed as a burring hole.

As will be described below, the ink jet printing layer4is a coating layer provided by using an ink jet printer8. As an ink for ink jet printing, a water-based pigment ink or a solvent-based pigment ink can be used. However, in the present embodiment, an ink containing a UV curable resin, and a thermosetting resin is used.

As the ink jet printing layer4provided on a front surface of the cover body3, for example, the ink jet printing layers4ato4drepresenting a predetermined pattern D1such as a penguin and the ink jet printing layer4erepresenting characters D2(in the drawing, “AABBCC” as an example) of a manufacturer, a model, or a trademark of the hot water unit U are provided. In addition, on four corners of the cover body3, an ink jet printing layer4frepresenting a positioning mark D3during press processing to be described below is provided. In the drawing, the positioning mark D3is shown in a (+) shape, but the disclosure is not limited thereto. In addition, the positioning mark D3may be provided on a back surface of the cover body3in place of or in addition to the front surface of the cover body3.

As shown inFIG. 4, on the back surface of the cover body3, the ink jet printing layer4grepresenting an electrical wiring diagram D4of the hot water device1is further provided. In place of or in addition to the electrical wiring diagram D4, a configuration showing a piping diagram of the hot water device1can be used. Although illustration is omitted, on the back surface of the cover body3, separately from the electrical wiring diagram D4and the piping diagram, a configuration further including an ink jet printing layer representing a description of a specification of the hot water unit U, notes, etc. can be used.

As shown inFIG. 6, the colored steel plate30as a raw material of the cover body3has a multi-layer structure including a plated steel plate30a, a white-type (including white) front side paint layer30blaminated on a front surface of the plated steel plate30a, and a back side paint layer30cas a service coat laminated on a back surface of the plated steel plate30a. The ink jet printing layers4ato4erepresent the pattern D1such as the above penguin figure and the characters D2in a color different from that of the white series front paint layer30b. A white part inFIG. 2(a)is a part of the front paint layer30bof the colored steel plate30on which ink jet printing is not applied.

Basically, the entire ink jet printing layer4ais formed in the same color and the same thickness. However, as shown inFIG. 3(d), a thickness ta of a corner33a′ of a peripheral wall33a(a wall raised forward from the outer peripheral flange part33) of the bulging part33is thinner than a thickness tb of other parts of the peripheral wall33aand a thickness of a part other than the peripheral wall33a. The bulging part33is formed in a drawing process, and the peripheral wall33acorresponds to an example of a drawn part in the disclosure. However, in this drawing process, an extending amount at the corner33a′ of the peripheral wall33abecomes the largest (the corner33a′ corresponds to an example of “a part whose plate thickness is thinner than other parts in the drawn part” in the disclosure). In connection with this, if the thickness ta of the ink jet printing layer4aat the corner33a′ is set to be smaller, as will be described below, a separation prevention effect of the ink jet printing layer4acan be obtained. Here, when an amount of the entire peripheral wall33adrawn (an extending amount) is increased in order to increase an amount of bulging of the bulging part33, the thickness tb of a part other than the corner33a′ of the peripheral wall33may be formed to be thinner than a thickness of other parts of the ink jet printing layer4a.

While the ink jet printing layer4bis provided on a part surrounding the exhaust port35, as described with reference toFIG. 3(c), the exhaust port35is formed as a burring hole having the burring part35a. On the other hand, a part of the ink jet printing layer4bis also provided on an inner surface of the burring part35a. Accordingly, a part surrounding the exhaust port35and an inner surface of the burring part35acan be formed in the same color, and it is possible to improve the appearance of the exhaust port35and parts surrounding thereof.

The ink jet printing layer4eis provided on a front surface of a step pushing part36(refer toFIG. 2(b)andFIG. 3(b)) three-dimensionally representing the characters D2. More specifically, the step pushing part36is a part in which the characters D2are three-dimensionally shaped when a part of the colored steel plate30is partially extruded by press processing, and the ink jet printing layer4eis provided on a front part of the step pushing part36. As the step pushing part36, there are a front side convex form in which a part of the colored steel plate30is extruded to the front side of the cover body3and a front side concave form in which a part of the colored steel plate30is extruded to the rear side of the cover body3, but either of them may be used.

The above cover body3can be produced by the following processes.

First, as shown inFIG. 5(a), as a raw material of the cover body3, the flat colored steel plate30described with reference toFIG. 6is prepared. Next, ink jet printing is performed on the colored steel plate30(strictly, on the paint layers30band30cof the colored steel plate30), and thus, as shown inFIG. 5(b), the ink jet printing layer4is provided. The ink jet printing is performed, for example, using the ink jet printer8shown inFIG. 7(a). In the ink jet printer8, a print head80is freely movable in x and y directions that are orthogonal to each other on the side above a mounting table81on which the colored steel plate30is mounted and supported. As shown inFIG. 7(b), the print head80includes a plurality of ink jet nozzles82through which an ink jet paint in a predetermined color is made into fine droplets and sprayed toward the colored steel plate30. This point is the same as that known in the related art, but in the present embodiment, a pair of UV light sources83(83aand83b) are further provided.

For example, when ink jet printing is performed while the print head80is moved in an x1 direction inFIG. 7(b)as a main scanning direction, the UV light source83aon the rear side in the main scanning direction is caused to emit light, and ultraviolet rays are emitted to an area immediately after ink jet printing is performed. Since a UV curable resin is contained in the ink jet printing layer4, it is possible to rapidly cure (curing to a degree that bleeding to be described below does not occur) the ink jet printing layer4by emitting ultraviolet rays described above. Therefore, it is possible to prevent circumstances such as occurrence of bleeding due to mixing of uncured ink jet printing layers4with different colors. When ink jet printing proceeds in a direction opposite to the above x1 direction, the UV light source83bis caused to emit light in place of the UV light source83a, and thus the same actions as described above are obtained.

Here, when the ink jet printing layer4ais provided, the thickness to of a part scheduled to become the corner33a′ of the peripheral wall33awithin the colored steel plate30shown inFIG. 3(d)is set to be thinner than the thickness tb of other parts.

After the above ink jet printing on both front and back surfaces of the colored steel plate30is completed, as shown inFIG. 5(c), the colored steel plate30is heated, the ink jet printing layer4is dried, and a thermosetting resin contained in the ink jet printing layer4is cured. This heating is performed using, for example, a heating furnace. According to such processing, it is possible to increase the strength of the ink jet printing layer4and impart excellent weather resistance. In addition, it is possible to provide durability in subsequent press processing.

Next, drawing processing as press processing is performed on the above colored steel plate30, and as shown inFIG. 5(d), the outer peripheral flange part32and the bulging part33are formed. Then, as shown inFIG. 5(e), a press process in which the air supply port34, the exhaust port35, the step pushing part36, and the like are formed, a trimming process in which extra parts of the outer peripheral flange part32are removed, a subsequent hemming process, and the like are performed. Accordingly, it is possible to produce the above cover body3. In the above operational process, it is possible to perform positioning of the colored steel plate30accurately using the positioning mark D3as a reference. In addition, an operation of forming the exhaust port35is performed using, for example, a punch7aand a die7bas shown inFIG. 8. However, since the ink jet printing layer4bis provided not only on a part surrounding a part in which the exhaust port35is scheduled to be formed but also on a part in which the exhaust port35is to be formed continuously, as shown inFIG. 3(c), a configuration in which the ink jet printing layer4bis provided continuously from the part surrounding the exhaust port35to the burring part35acan be appropriately realized.

Next, operations of the exterior case C including the above cover body3and the hot water unit U will be described.

First, since the pattern D1such as a penguin is represented on the front part of the cover body3, for example, compared with the cover body3whose front surface is formed in a single color with no pattern, it is possible to make the hot water unit U have excellent design properties. Since an inner surface of the burring part35aof the exhaust port35is coated in continuity with a part surrounding the exhaust port35, an external appearance is more favorable than a case in which an inside of the burring part35ais formed in a color different from that of the part surrounding the burring part35a. In addition, at the corner33a′ of the peripheral wall33a, a part of the colored steel plate30extends greatly according to the drawing process. However, since the thickness to of the ink jet printing layer4at the part is made thinner than the thickness tb of other parts, it is possible to prevent a risk of the ink jet printing layer4being easily separated according to the above drawing process.

On the back surface of the cover body3, since the electrical wiring diagram D4or the piping diagram is represented on the ink jet printing layer4g, it is useful for maintenance work and the like. For example, in a method of attaching a sheet on which an electrical wiring diagram is printed to the back surface of the cover body3, there is a risk of the sheet breaking or separating from the cover body3and being lost. However, according to the present embodiment, there is no such a risk.

Since the coating layers representing the pattern D1, the characters D2, the positioning mark D3, and the electrical wiring diagram D4of the cover body3are all set as the ink jet printing layer4, it is possible to easily provide them using the above ink jet printer8. For example, unlike painting using a spray system, masking processing and paint color matching are not performed, and expert skills are not required. Therefore, it is possible to improve workability and productivity. In addition, it is easy to change the design of the pattern D1or the like, and production of small quantities of many different kinds is appropriate. Furthermore, according to ink jet printing, there is no or little waste of the ink paint, and the environmental load is also small. Since a base of the ink jet printing layer4is the paint layers30band30cof the colored steel plate30, it is possible to improve an appearance and weather resistance of a part in which the ink jet printing layer4is not provided.

The hot water unit U shown inFIG. 9is a water heater, and has a configuration in which the hot water device1for hot water production is accommodated in the exterior case C. The hot water device1includes the heat exchanger10through which hot water flows, the burner11configured to heat hot water in the heat exchanger10and the fan12configured to supply combustion air to the burner11.

The exterior case C includes the rectangular box-shaped exterior case main body2having the opening20on its front surface and the cover body3(front cover body) for blocking the opening20. The cover body3is detachably attached to a front part of the exterior case main body2using the screw body9, for example, a screw, and the screw insertion holes31and21into which the screw body9is inserted.

The exterior case main body2and the cover body3correspond to a metal plate part in the disclosure. In the present embodiment, as will be described below, the ink jet printing layers4and4A are provided on the cover body3, but they are not provided on the exterior case main body2. Therefore, hereinafter, a configuration of the cover body3will be mainly described, and the exterior case main body2will not be described. However, as will be described below, of course, an ink jet printing layer may be provided on the exterior case main body2.

The cover body3is formed by pressing the colored steel plate30to be described below and has a substantially rectangular panel shape in a front view. The cover body3includes the outer peripheral flange part32for allowing surface-to-surface contact with the front part of the exterior case main body2, the air supply port34through which outside air flows into the exterior case C, and the exhaust port35through which exhaust gas from which heat recovery by the heat exchanger10has been completed is discharged to the outside of the exterior case C.

The ink jet printing layer4is provided on a forward surface (front surface) of the cover body3, and the ink jet printing layer4a(refer toFIG. 12) is provided on a rear surface (back surface) of the cover body3. As will be described below, the ink jet printing layers4and4A are coating films provided by using the ink jet printer8. As an ink for ink jet printing, a water-based pigment ink or a solvent-based pigment ink can be used. However, in the present embodiment, an ink containing a UV curable resin, and a thermosetting resin is used.

As shown inFIG. 11, the colored steel plate30used as a material of the cover body3has a multi-layer structure including the plated steel plate30a, the front side paint layer30blaminated on a front surface of the plated steel plate30a, and the back side paint layer30cas a base coat laminated on a back surface of the plated steel plate30a.

The ink jet printing layer4is laminated and provided on the front side paint layer30b. On the other hand, the ink jet printing layer4ais laminated and provided on the back side paint layer30c.

As shown clearly inFIG. 10, the ink jet printing layer4is provided on substantially the entire area of the front surface of the cover body3, and has, for example, first to third areas D1to D3. The first area D1is an area on which, for example, a manufacturer name (including the logo) of the hot water unit U is displayed, and in the drawing, for convenience, the letters “AABBCC” are shown. The second area D2is an area on which instructions for use of the hot water unit U are displayed, for example, a mode shown inFIG. 10(b). The first and second areas D1and D2are areas on which device related information of the hot water unit U is displayed.

The third area D3is an area which is provided in a wide area other than the above first and second areas D1and D2within the front surface of the cover body3and on which a decoration pattern is displayed. In the drawing, for convenience, the third area D3is shown as a dot pattern part. However, the decoration pattern displayed on the third area D3is not limited thereto. For example, in addition to traditional patterns such as a grid pattern and a checkered pattern, it is possible to design various patterns in which animals, plants, or other appropriate motifs are scattered and arranged on a plurality of parts, or a small number of motifs are shown at a relatively large size.

On the other hand, as shown inFIG. 12, the ink jet printing layer4ahas the fourth area D4representing an electrical wiring diagram of the hot water unit U (strictly, the hot water device1). Like the first and second areas D1and D2, the fourth area D4is an area on which device related information of the hot water unit U is displayed. On the fourth area D4, in place of or in addition to the electrical wiring diagram, the piping diagram of the hot water unit U or other diagrams for explaining installation of parts can be displayed.

The above cover body3can be produced by the following processes.

First, as shown inFIG. 13(a), as a raw material of the cover body3, the flat colored steel plate30is prepared. Next, ink jet printing is performed on a front surface and a back surface (strictly, on the paint layers30band30c) of the colored steel plate30, and thus, as shown inFIG. 16(b), the ink jet printing layers4and4A are provided. The ink jet printing is performed, for example, using the ink jet printer8shown inFIGS. 7(a) and 7(b). Since the operation and action of the ink jet printer8are the same as those in Example 1, related descriptions thereof will be omitted.

After the ink jet printing on the colored steel plate30is completed, the colored steel plate30is heated, the ink jet printing layers4and4A are dried, and a thermosetting resin contained in the ink jet printing layers4and4A is cured. This heating is performed using, for example, a heating furnace. According to such processing, it is possible to increase the strength of the ink jet printing layers4and4A and impart excellent weather resistance.

Then, press processing is performed on the above colored steel plate30, and as shown inFIG. 13(c), the cover body3is molded. Examples of the press processing include a drawing process for making the colored steel plate30bulge and a process of forming the air supply port34and the exhaust port35.

Unlike the above series of processes, for example, when the above press processing is performed before ink jet printing is performed, it may be difficult to perform ink jet printing appropriately on an area formed in a nonplanar shape (an uneven shape, a curved surface shape, or the like) according to press processing. On the other hand, according to the series of processes, it is possible to appropriately avoid such circumstances.

Next, operations of the exterior case C and the hot water unit U described above will be described.

First, on the first to fourth areas D1to D4(excluding the third area D3) of the ink jet printing layers4and4A, a manufacturer name and instructions for use of the hot water unit U and the electrical wiring diagram are displayed. Therefore, it is possible to eliminate or reduce time and effort for preparing a label for displaying them and attaching it to the exterior case C. When no label is used, it is possible to appropriately avoid circumstances such as a poor appearance of the hot water unit U and loss of the label due to occurrence of bubbles inside the label or peeling of the label. The electrical wiring diagram is displayed on the back surface of the cover body3in the present embodiment. However, in such a configuration, it is useful when the cover body3is removed from the exterior case main body2and maintenance work of the hot water device1is performed.

The ink jet printing layers4and4A can be easily provided using the above ink jet printer8. For example, unlike painting using a transfer system or a spray system, a transfer plate and masking processing are not performed, and paint color matching and expert skills are also not required. Therefore, it is possible to improve workability and productivity and reduce production costs. In addition, it is easy to change a design represented on the ink jet printing layer4and production of small quantities of many different kinds is appropriate. Further, according to ink jet printing, there is almost no waste of an ink paint and the environmental load is also small.

In addition, according to a step of providing the ink jet printing layers4and4A, it is possible to finely represent small letters, complicated figures, and the like, and it is possible to form a favorable appearance. Since the ink jet printing layers4and4A are provided on the paint layers30band30c, it is more suitable for making letters displayed on the ink jet printing layers4and4A clear. In the present embodiment, since a decorative pattern is represented in a wide range of a front surface of the cover body3according to the third area D3of the ink jet printing layer4, it is possible to further improve design properties and decoration properties of the exterior case C. Since a base of the ink jet printing layer4is the paint layers30band30cof the colored steel plate30, it is possible to improve an appearance and weather resistance of a part in which the ink jet printing layer4is not provided.

The disclosure is not limited to content of the above embodiment. Designs of specific configurations of the exterior case for a hot water unit according to the embodiments of the disclosure and respective components of the hot water unit can be variously changed within a range intended by the disclosure. Specific configurations of operational processes of a method of producing an exterior case for a hot water unit according to the embodiments of the disclosure can be variously changed.

While an example in which ink jet printing is performed only on the cover body3has been shown in the above embodiment, in the embodiments of the disclosure, in place of or in addition thereto, of course, ink jet printing may also be performed on the exterior case main body2. Specific content such as letters and patterns represented on the ink jet printing layer of the embodiments of the disclosure is not limited, and at least one of letters, symbols, figures, and patterns may be represented.

In the above embodiment, device related information of the hot water unit in the embodiments of the disclosure is not limited to those exemplified in the above embodiment, but it includes, for example, a distributor name, a model, and a manufacture date of the hot water unit. In short, information that is related to the hot water unit in any aspect is device related information in the embodiments of the disclosure. In the embodiments of the disclosure, at least one of letters, symbols, figures, and patterns representing such device related information may be displayed on the ink jet printing layer.

The hot water unit according to the embodiments of the disclosure can have a configuration as a hot water storage tank unit in which a hot water device for hot water storage such as a hot water storage tank is accommodated in an exterior case in place of a configuration in which a hot water device for hot water production such as a water heater is accommodated in an exterior case. Therefore, the exterior case is not limited to a combination of an exterior case main body having a front opening and a cover body for blocking the front opening.

As a material of the exterior case, a flat metal plate is used. However, as the metal plate, a material other than commercially available colored steel plates can be used. In addition, as a material of the exterior case, a metal plate (for example, a stainless steel plate and an aluminum plate on which no paint layer is provided in advance) other than colored steel plates can be used.