Thermal insulation structure for a hot water storage tank, hot water storage tank unit, and method for manufacturing a thermal insulation structure for a hot water storage tank

Abstract

This heat-insulating structure of a hot water storage tank comprises an upper heat-insulating member (20) that covers an upper section of a hot water storage tank (2), a lower heat-insulating member (60) that covers a lower section of the hot water storage tank (2), and intermediate heat-insulating members (30), (40) that are provided between the upper heat-insulating member (20) and the lower heat-insulating member (60) and cover an intermediate section of the hot water storage tank (2). The intermediate heat-insulating members (30), (40) have upper heat-insulating sections (31), (41) that are formed from a first heat-insulating material having high heat insulation performance, and lower heat-insulating sections (32), (42) that are formed from a second heat-insulating material having low heat insulation performance. The upper heat-insulating sections (31), (41) and the lower heat-insulating sections (32), (42) are integrally molded. At least one of the first and second heat-insulating materials is a hard polyurethane foam.

Description

Technical Field

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[0001] The present disclosure relates to a heat insulation structure for a hot water storage tank, a hot water storage tank unit, and a method for manufacturing the heat insulation structure of the hot water storage tank.

Background Art

[0002] A hot water storage type water heater that stores hot water boiled by an outdoor unit, which is a heating means, in a hot water storage tank unit through a pipe is widely known. In such a hot water storage type water heater, in order to reduce the heat radiation loss of the stored hot water, the periphery of the hot water storage tank is covered with a heat insulating material.

[0003] Generally, the temperature of the water stored in the upper part of the hot water storage tank is higher than the temperature of the water stored in the lower part. Therefore, the heat insulating material covering the upper part of the hot water storage tank is required to have higher heat insulation performance than the heat insulating material covering the lower part. Patent Document 1 discloses a technique of covering the upper part of the hot water storage tank with a part having high heat insulation performance and covering the lower part of the hot water storage tank with a part having low heat insulation performance using a heat insulating material obtained by integrally molding heat resistant polystyrene having different expansion ratios.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the heat insulating material described in Patent Document 1, there is a difference in the amount of heat shrinkage between parts having different expansion ratios, and as a result, cracks are likely to occur at the boundary. As a result, there is a problem that heat is radiated from the cracked portion of the heat insulating material.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide a thermal insulation structure for a hot water storage tank that is less prone to cracking at the boundary where thermal insulation performance changes, even when a part with high thermal insulation performance and a part with low thermal insulation performance are molded together, a hot water storage tank unit having this thermal insulation structure, and a method for manufacturing the thermal insulation structure for a hot water storage tank. [Means for solving the problem]

[0007] The thermal insulation structure for a hot water storage tank according to this disclosure comprises an upper thermal insulation material covering the top of the hot water storage tank, a lower thermal insulation material covering the bottom of the hot water storage tank, and a middle thermal insulation material provided between the upper and lower thermal insulation materials and covering the middle of the hot water storage tank. The middle thermal insulation material has an upper thermal insulation portion formed from a first thermal insulation material having high thermal insulation performance and a lower thermal insulation portion formed from a second thermal insulation material having low thermal insulation performance. The upper thermal insulation portion and the lower thermal insulation portion are integrally molded. At least one of the first thermal insulation material and the second thermal insulation material is rigid polyurethane foam. In the middle section of the insulation, a partition plate is embedded along the boundary between the upper and lower insulation sections, and the outer surface of the middle section of the insulation and the partition plate are flush. . [Effects of the Invention]

[0008] According to this disclosure, since at least one of the upper insulation portion having high thermal insulation performance and the lower insulation portion having low thermal insulation performance is formed from rigid polyurethane foam, the high adhesive strength of rigid polyurethane foam can be utilized. As a result, even if the portion with high thermal insulation performance and the portion with low thermal insulation performance are molded together, it is possible to provide a thermal insulation structure for a hot water storage tank in which cracks are less likely to occur at the boundary where the thermal insulation performance changes. [Brief explanation of the drawing]

[0009] [Figure 1] Perspective view of a storage-type water heater equipped with a storage tank unit according to Embodiment 1 of the present disclosure [Figure 2] Configuration diagram of a storage-type water heater equipped with a storage tank unit according to Embodiment 1 of this disclosure. [Figure 3] A perspective view showing the inside of the hot water storage tank unit of Embodiment 1 of this disclosure. [Figure 4]A cross-sectional view of a hot water storage tank covered with an insulating structure, as shown in Figure 3, when cut along plane P and viewed from the direction of arrow B. [Figure 5A] Enlarged view of section Va, enclosed by the dashed line, of the hot water storage tank covered with the insulating structure shown in Figure 4. [Figure 5B] Enlarged view of section Vb, enclosed by the dashed line, of the hot water storage tank covered with the insulating structure shown in Figure 4. [Figure 6] This is a perspective view showing the manufacturing process of the thermal insulation structure for the hot water storage tank according to Embodiment 1 of this disclosure. [Figure 7A] A cross-sectional diagram showing the manufacturing method of the heat insulation structure of the hot water storage tank according to Embodiment 1 of this disclosure, in order of steps. [Figure 7B] Figure 7A continues to show a cross-sectional diagram illustrating the manufacturing method of the heat insulating structure of the hot water storage tank according to Embodiment 1 of this disclosure, in order of steps. [Figure 8A] Figure 7B onwards is a cross-sectional view showing the manufacturing method of the heat insulating structure of the hot water storage tank according to Embodiment 1 of this disclosure, in order of steps. [Figure 8B] Figure 8A continues to show a cross-sectional diagram illustrating the manufacturing method of the heat insulating structure of the hot water storage tank according to Embodiment 1 of this disclosure, in order of steps. [Figure 9A] This is a partially enlarged view of a hot water storage tank covered with an insulating structure according to Embodiment 2 of the present disclosure, and is an enlarged view of the portion corresponding to part Va in Figure 4. [Figure 9B] This is a partially enlarged view of a hot water storage tank covered with an insulating structure according to Embodiment 2 of the present disclosure, and is an enlarged view of the portion corresponding to part Vb in Figure 4. [Figure 10] A perspective view showing the manufacturing process of the thermal insulation structure for the hot water storage tank according to Embodiment 2 of this disclosure. [Figure 11A] A cross-sectional diagram showing the manufacturing method of the heat insulation structure of the hot water storage tank according to Embodiment 2 of this disclosure, in order of the steps. [Figure 11B] Figure 11A continues to show a cross-sectional diagram illustrating the manufacturing method of the heat insulation structure of the hot water storage tank according to Embodiment 2 of this disclosure, in order of the steps involved. [Figure 12A] Figure 11B onwards shows a cross-sectional diagram illustrating the manufacturing method of the heat insulating structure of the hot water storage tank according to Embodiment 2 of this disclosure, in order of the steps involved. [Figure 12B]Cross-sectional view showing the manufacturing method of the heat insulation structure of the hot water storage tank according to Embodiment 2 of the present disclosure, following FIG. 12A, in the order of steps [Figure 13A] FIG. showing Embodiment 3 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 13B] FIG. showing Embodiment 3 of the present disclosure, which is a cross-sectional view showing a state in which a partition plate is arranged in a mold when manufacturing the heat insulation structure of the hot water storage tank [Figure 14A] FIG. showing Embodiment 4 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 14B] FIG. showing Embodiment 4 of the present disclosure, which is a cross-sectional view showing a state in which a partition plate is arranged in a mold when manufacturing the heat insulation structure of the hot water storage tank [Figure 15A] FIG. showing Embodiment 5 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 15B] FIG. showing Embodiment 5 of the present disclosure, which is a cross-sectional view showing a state in which a partition plate is arranged in a mold when manufacturing the heat insulation structure of the hot water storage tank [Figure 16A] FIG. showing Embodiment 6 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 16B] FIG. showing Embodiment 6 of the present disclosure, which is a cross-sectional view showing a state in which a partition plate is arranged in a mold when manufacturing the heat insulation structure of the hot water storage tank [Figure 17A] FIG. showing Embodiment 7 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 17B] FIG. showing Embodiment 7 of the present disclosure, which is a cross-sectional view showing a state in which a partition plate is arranged in a mold when manufacturing the heat insulation structure of the hot water storage tank [Figure 18A] FIG. showing Embodiment 8 of the present disclosure, which is an enlarged view of a portion corresponding to the Va portion in FIG. 4, which is a portion of the hot water storage tank covered with a heat insulation structure [Figure 18B]This figure shows Embodiment 8 of the present disclosure, and is a cross-sectional view showing the arrangement of partition plates in a mold when manufacturing the heat insulation structure of a hot water storage tank. [Figure 19A] A cross-sectional diagram showing the manufacturing method of the heat insulation structure of the hot water storage tank according to Embodiment 9 of this disclosure, in order of steps. [Figure 19B] A cross-sectional view showing the manufacturing method of the heat insulating structure of the hot water storage tank according to Embodiment 9 of this disclosure, following Figure 19A, in order of steps. [Figure 20] This is a partially enlarged view of a hot water storage tank covered with an insulating structure according to Modification 1 of Embodiment 1 of the present disclosure, and is an enlarged view of the portion corresponding to part Va in Figure 4. [Figure 21] This is a partially enlarged view of a hot water storage tank covered with an insulating structure, which is a modified example of Embodiment 1 of the present disclosure, and is an enlarged view of the portion corresponding to part Va in Figure 4. [Figure 22A] This is a partially enlarged view of a hot water storage tank covered with an insulating structure, which is a modified example of Embodiment 1 of the present disclosure, and is an enlarged view of the portion corresponding to part Va in Figure 4. [Figure 22B] This is a partially enlarged view of a hot water storage tank covered with an insulating structure according to Modification 3 of Embodiment 1 of the present disclosure, and is an enlarged view of the portion corresponding to part Vb in Figure 4. [Modes for carrying out the invention]

[0010] Hereinafter, a preferred embodiment of the present disclosure, including an insulating structure for a hot water storage tank, a hot water storage tank unit, and a method for manufacturing the insulating structure for a hot water storage tank, will be described with reference to the drawings.

[0011] (Embodiment 1) The overall configuration of the storage-type water heater equipped with the storage tank unit of Embodiment 1 will be explained with reference to Figures 1 and 2. As shown in Figure 1, the front and rear directions of the storage tank unit 10 are defined and will be used as appropriate in the following explanation. The rear of the storage tank unit 10 is generally the direction facing the wall.

[0012] The storage-type water heater 1 consists of a storage tank unit 10 and a heat pump unit 200. As shown in Figures 1 and 2, the storage-type water heater 1 includes a heat pump unit 200 as a heating means for heating water, and a storage tank unit 10 for storing and supplying water heated by the heat pump unit 200. The heat pump unit 200 and the storage tank unit 10 are connected by a heat pump supply pipe 204 and a heat pump return pipe 205, and electrical wiring (not shown).

[0013] As shown in Figure 2, the hot water storage tank unit 10 includes a hot water storage tank 2 for storing water. The hot water storage tank unit 10 also includes a pressure reducing valve 101, a mixing valve 102, a switching valve 103, and a check valve 104 as functional valves for the functions of the hot water storage type water heater 1, such as heating, supplying hot water, and filling the bathtub. Cooling piping (not shown) that supplies water from the city water supply is connected to the bottom of the hot water storage tank 2.

[0014] The water stored in the lower part of the hot water storage tank 2 is sent by the heat source pump 105 to the heat pump unit 200 via the heat pump supply pipe 204. The water is then heated in the heat pump unit 200 using heat from the atmosphere, and the high-temperature water is returned to the upper part of the hot water storage tank 2 via the heat pump return pipe 205 and stored there.

[0015] The hot water storage tank 2 contains layers of water with a temperature distribution from low to medium to high temperatures, arranged from bottom to top. Multiple temperature sensors 106 are provided vertically on the outer surface of the hot water storage tank 2 to measure the temperature of the water inside the tank. For example, a thermistor is used as the temperature sensor 106.

[0016] The heat pump unit 200 is a heating means for raising the temperature of the low-temperature water sent from the hot water storage tank 2. The heat pump unit 200 includes a compressor that compresses a refrigerant, such as carbon dioxide, to a high temperature and pressure, a condenser that condenses the refrigerant discharged from the compressor and exchanges heat with the low-temperature water sent from the hot water storage tank 2, a pressure reducing valve that reduces the pressure of the refrigerant from the condenser, and an evaporator that absorbs heat from the atmosphere and evaporates the reduced-pressure refrigerant. The internal configuration of the heat pump unit 200 is not shown in the diagram.

[0017] Next, the structure of the hot water storage tank unit 10 will be described. As shown in Figure 3, the hot water storage tank unit 10 comprises a hot water storage tank 2 for storing hot water, an insulating structure 70 that surrounds the hot water storage tank 2 to suppress heat radiation from the stored hot water, a hot water outlet pipe 11 and a hot water supply pipe 12 shown in Figure 4 that are connected to the hot water storage tank 2, and an outer case 80 that houses these components of the hot water storage tank unit 10. Note that in Figure 3, a part of the outer case 80 is omitted from the illustration in order to show the internal structure of the hot water storage tank unit 10. Also, the plane P shown in Figure 3 includes the axis A extending in the vertical direction of the hot water storage tank 2 and is a plane parallel to the front-to-back direction of the hot water storage tank unit 10.

[0018] As shown in Figure 4, the hot water storage tank 2 has a cylindrical body 2a and bowl-shaped first end 2b and second end 2c connected to the open end of the body 2a. The first end 2b and second end 2c form a so-called end plate and are welded to the end of the body 2a. The axis A of the hot water storage tank 2 passes through the center of the body 2a in a cross-sectional view obtained by cutting the body 2a horizontally. The hot water storage tank 2 is used in a position where the first end 2b is on top and the second end 2c is on the bottom. The first end 2b is provided with a joint 6a that leads to the inside of the hot water storage tank 2. The second end 2c is also provided with a joint 6b that leads to the inside of the hot water storage tank 2. The hot water outlet pipe 11 is connected to the joint 6a, and the hot water supply pipe 12 is connected to the joint 6b.

[0019] As shown in Figure 3, the thermal insulation structure 70 includes an upper insulation material 20 that covers the top of the hot water storage tank 2, a middle insulation material 50 that covers the middle of the hot water storage tank 2, and a lower insulation material 60 that covers the bottom of the hot water storage tank 2. The thermal insulation structure 70 is formed from, for example, rigid polyurethane foam.

[0020] Rigid polyurethane foam is produced by a chemical reaction between a polyol component and an isocyanate component, resulting in high viscosity and strong adhesive properties. Furthermore, the thermal conductivity can be adjusted by the type of blowing agent pre-added to the polyol component. In this embodiment, rigid polyurethane foam is produced by mixing a polyol component with a viscosity of 100-10,000 mPa·s with an isocyanate component with a viscosity of 50-5,000 mPa·s. As the blowing agent, water, carbon dioxide, cyclopentane, or fluorine-based blowing agents (HFO, HCFO, etc.) can be used.

[0021] The upper insulation material 20 has a bowl-like shape, and the shape of its inner circumferential surface matches the shape of the outer circumferential surface of the upper part of the hot water storage tank 2. As shown in Figure 4, the upper insulation material 20 has a first opening 20a formed therein to expose the joint 6a provided in the hot water storage tank 2. This allows the exposed joint 6a to be connected to the hot water outlet pipe 11.

[0022] The lower insulation material 60 has a bowl-like shape, and the shape of its inner circumferential surface matches the shape of the outer circumferential surface of the lower part of the hot water storage tank 2. As shown in Figure 4, the lower insulation material 60 has a second opening 60a formed therein to expose the joint 6b provided in the hot water storage tank 2. This allows the exposed joint 6b to be connected to the hot water supply piping 12.

[0023] As shown in Figure 3, the central insulation material 50 comprises a first central insulation material 30 and a second central insulation material 40. The first central insulation material 30 and the second central insulation material 40 cover the body 2a of the hot water storage tank 2, which is located between the upper insulation material 20 and the lower insulation material 60, from the outside. The first central insulation material 30 and the second central insulation material 40 have a shape obtained by cutting the cylindrical central insulation material 50 that covers the perimeter of the body 2a into equal parts in the front-rear direction on a plane that includes the axis A of the hot water storage tank 2. The first central insulation material 30 is the front part of the central insulation material 50 and has a semi-cylindrical shape. The second central insulation material 40 is the rear part of the central insulation material 50 and has a semi-cylindrical shape. The body 2a of the hot water storage tank 2 is covered by the first central insulation material 30 and the second central insulation material 40, which are joined together in a cylindrical shape with their edges in contact.

[0024] As shown in Figure 4, the first central insulation material 30 has an upper insulation portion 31, which is the upper part of the first central insulation material 30, and a lower insulation portion 32, which is the lower part of the first central insulation material 30. The upper insulation portion 31 and the lower insulation portion 32 are integrally molded. As shown in Figure 5A, the thickness t1 of the upper insulation portion 31 and the thickness t2 of the lower insulation portion 32 are the same. An interface surface 33 is formed at the boundary between the upper insulation portion 31 and the lower insulation portion 32. This interface surface 33 is not perpendicular to the outer surface 30a of the first central insulation material 30, but is an inclined surface that extends downward from the outer surface 30a toward the inner surface 30b of the first central insulation material 30.

[0025] As shown in Figure 4, the second central insulation material 40 has an upper insulation portion 41, which is the upper part of the second central insulation material 40, and a lower insulation portion 42, which is the lower part of the second central insulation material 40. The upper insulation portion 41 and the lower insulation portion 42 are integrally molded. As shown in Figure 5B, the thickness t3 of the upper insulation portion 41 and the thickness t4 of the lower insulation portion 42 are the same. An interface surface 43 is formed at the boundary between the upper insulation portion 41 and the lower insulation portion 42. This interface surface 43 is not perpendicular to the outer surface 40a of the second central insulation material 40, but is an inclined surface that extends downward from the outer surface 40a toward the inner surface 40b of the second central insulation material 40.

[0026] As described above, the upper insulation section 31 and the lower insulation section 32 are formed from rigid polyurethane foam, but the upper insulation section 31 is formed from rigid polyurethane foam as a first insulation material with lower thermal conductivity, i.e., high insulation performance, than the lower insulation section 32. Similarly, the upper insulation section 41 is formed from rigid polyurethane foam as a first insulation material with lower thermal conductivity, i.e., high insulation performance, than the lower insulation section 42. Specifically, the upper insulation sections 31 and 41 are formed from high-insulation rigid polyurethane foam having a thermal conductivity of 10 mW / (m·K) or more and 30 mW / (m·K) or less. On the other hand, the lower insulation sections 32 and 42 are formed from low-insulation rigid polyurethane foam as a second insulation material having a thermal conductivity of 30 mW / (m·K) or more and 50 mW / (m·K) or less. If the foaming ratio is changed, the proportion (density) of the resin changes, and therefore the strength changes. However, in this embodiment, since the thermal insulation performance is adjusted by selecting a foaming agent, the resin ratio (density) does not change, and there is almost no change in strength.

[0027] Next, the manufacturing method of the first central insulation material 30 will be described. First, as a mold preparation step, a mold 100 shown in Figure 6 is prepared for molding the first central insulation material 30. The mold 100 has a first mold 110 called the lower mold and a second mold 120 called the upper mold.

[0028] The first mold 110 forms the outer portion of the first central insulation material 30 that does not face the hot water storage tank 2. The first mold 110 has a rectangular parallelepiped shape, and a recess 110a is formed on its upper surface 110b, extending along the longitudinal direction of the first mold 110. In a cross-section obtained by cutting the first mold 110 from a direction perpendicular to the longitudinal direction, the recess 110a is semicircular. That is, the first mold 110 has a shape in which a semi-cylindrical shape is hollowed out from the upper surface 110b of the rectangular parallelepiped. In addition, a plurality of rectangular air vents 119 are attached around the recess 110a on the upper surface 110b of the first mold 110. The first mold 110 is treated with a release agent to facilitate demolding.

[0029] The second mold 120 forms the inner portion of the first central insulation material 30 that faces the hot water storage tank 2. The second mold 120 has a flat plate portion 121 that contacts the upper surface 110b when placed over the first mold 110, and a protrusion 122 provided on the flat plate portion 121. The protrusion 122 is semi-cylindrical, and its cross-section when cut from a direction perpendicular to the longitudinal direction is semi-circular. It is also the surface of the flat plate portion 121, and an air vent 123 is attached around the protrusion 122. When the second mold 120 is placed over the first mold 110, the protrusion 122 is inserted into the recess 110a of the first mold 110. The second mold 120 is treated with a release agent to facilitate demolding.

[0030] Next, in the nozzle placement step, as shown in Figure 6, a first nozzle 115 for dispensing high-insulation rigid urethane foam to form the upper insulation section 31 and a second nozzle 116 for dispensing low-insulation rigid urethane foam to form the lower insulation section 32 are placed toward the recess 110a of the first mold 110. The first nozzle 115 is connected to a mixing head (not shown) for mixing the material for the high-insulation rigid urethane foam for the upper insulation section 31. The second nozzle 116 is connected to a mixing head (not shown) for mixing the material for the low-insulation rigid urethane foam for the lower insulation section 32. The first nozzle 115 and the second nozzle 116 are placed spaced apart from each other along the direction in which the recess 110a extends.

[0031] Next, in the dispensing process, as shown in Figure 7A, high-insulation rigid polyurethane foam 31a is dispensed from the first nozzle 115 toward the recess 110a of the first mold 110, and low-insulation rigid polyurethane foam 32a is dispensed from the second nozzle 116. As a result, within the recess 110a, the liquid high-insulation rigid polyurethane foam 31a spreads to the left region in Figure 7B, and the liquid low-insulation rigid polyurethane foam 32a spreads to the right region in Figure 7B.

[0032] Once the extrusion of the rigid polyurethane foams 31a and 32a is complete, the molding process involves retracting the first nozzle 115 and the second nozzle 116, and placing the second mold 120 over the first mold 110, as shown in Figure 8A. This closes the recess 110a of the first mold 110 with the second mold 120, and a cavity is formed between the first mold 110 and the second mold 120 for molding the first central insulation material 30 shown in Figure 4.

[0033] While the first mold 110 is closed by the second mold 120, the rigid polyurethane foams 31a and 32a foam up and expand, becoming viscous. The air inside the mold escapes to the outside through the air vents 119 and 123. At this time, at the interface 33a shown in Figure 8A, an unavoidable difference arises between the expansion force generated by the foaming of the high-insulation rigid polyurethane foam 31a and the expansion force generated by the foaming of the low-insulation rigid polyurethane foam 32a. As a result, the interface 33a tilts with respect to the vertical direction. Eventually, as shown in Figure 8B, the rigid polyurethane foams 31a and 32a fill the cavity between the first mold 110 and the second mold 120 and harden. As a result, the high-insulation rigid polyurethane foam 31a forms the upper insulation portion 31, and the low-insulation rigid polyurethane foam 32a forms the lower insulation portion 32.

[0034] Finally, the mold 100 is demolded to remove the first central insulation material 30, in which the upper insulation portion 31 and the lower insulation portion 32 are integrally molded. In this way, the upper insulation portion 31 of the first central insulation material 30 can be formed from an insulation material with high insulation performance, and the lower insulation portion 32 can be formed from an insulation material with low insulation performance.

[0035] Although the manufacturing method for the first central insulation material 30 has been described, the second central insulation material 40, which has the same structure, can be manufactured in the same manner. Furthermore, the upper insulation material 20 and the lower insulation material 60 can also be manufactured by molding rigid polyurethane foam with a mold.

[0036] The upper insulation material 20, the first middle insulation material 30, the second middle insulation material 40, and the lower insulation material 60, manufactured in this manner, cover the perimeter of the hot water storage tank 2 shown in Figure 4. While it is often easier to cover the hot water storage tank 2 with the lower insulation material 60 first, the assembly order is not particularly limited. In this way, the hot water storage tank 2, surrounded by the insulation structure 70, can be manufactured.

[0037] As described above, according to this embodiment 1, the first central insulation material 30 and the second central insulation material 40 covering the central part of the hot water storage tank 2 have upper insulation parts 31 and 41 having high insulation performance and lower insulation parts 32 and 42 having low insulation performance. As a result, the upper part where the temperature of the hot water stored in the hot water storage tank 2 is high can be covered with the upper insulation parts 31 and 41 having high insulation performance, and the lower part where the temperature of the hot water is low can be covered with the lower insulation parts 32 and 42 having low insulation performance, thereby effectively suppressing heat dissipation from the hot water stored in the hot water storage tank 2.

[0038] Furthermore, the first central insulation material 30 and the second central insulation material 40 are manufactured by integrally molding rigid polyurethane foam with different thermal insulation properties. This allows for strong adhesion at the interface surfaces 33 and 43 between the upper insulation sections 31 and 41 and the lower insulation sections 32 and 42, by utilizing the high adhesive strength of the rigid polyurethane foam. This makes it less likely for cracks to occur at the boundary where the thermal insulation performance changes.

[0039] Furthermore, by appropriately selecting the foaming agent for the rigid polyurethane foam, it is possible to form upper insulation sections 31, 41 and lower insulation sections 32, 42 with the desired thermal insulation performance without changing the foaming ratio. As a result, the density of the upper insulation sections 31, 41 and the lower insulation sections 32, 42 can be made to be approximately the same, preventing the formation of areas that are weak in terms of strength. This makes it less likely for cracks to occur at the boundaries between sections with different thermal insulation performance.

[0040] Furthermore, by extruding two types of rigid polyurethane foam with different thermal insulation properties, expanding them by foaming them in a mold 100, and then curing them, a first central thermal insulation material 30 and a second central thermal insulation material 40 can be manufactured as a single molded unit. This simplifies the manufacturing process of the thermal insulation structure 70 compared to separately molding and combining thermal insulation materials with different thermal insulation properties.

[0041] (Embodiment 2) Next, Embodiment 2 will be described. In Embodiment 1, it was explained that the interface surfaces 33, 43 between the upper insulation sections 31, 41 and the lower insulation sections 32, 42 are formed by the contact of rigid polyurethane foams with different thermal insulation properties. However, the configuration of the interface surfaces 33, 43 is not limited to that of Embodiment 1. In this embodiment, a partition plate is placed at the boundary to separate the upper insulation section from the lower insulation section. Thus, this embodiment is characterized by the placement of a partition plate in the middle insulation material, but the other configurations are the same as those of Embodiment 1. Therefore, in the following description, the focus will be on configurations that differ from Embodiment 1, and the same reference numerals will be used for similar configurations, and detailed descriptions will be omitted.

[0042] As shown in Figure 9A, the first central insulation material 130, which covers a portion of the outer surface of the hot water storage tank 2, has an upper insulation section 31, a lower insulation section 32, and a partition plate 131. The thickness t1 of the upper insulation section 31 and the thickness t2 of the lower insulation section 32 are the same. When the first central insulation material 130 is cut through a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 131 is rectangular, as shown in Figure 9A. The partition plate 131 is embedded at the boundary between the upper insulation section 31 and the lower insulation section 32 and is flush with the outer surface 30a of the first central insulation material 130. In addition, the height h1 of the partition plate 131 is lower than the thickness t1 of the upper insulation section 31 and the thickness t2 of the lower insulation section 32. Therefore, there is a portion of the boundary between the upper insulation section 31 and the lower insulation section 32 where the partition plate 131 is not provided, and in this portion, an interface surface 138 is formed where the upper insulation section 31 and the lower insulation section 32 are in contact with each other. The partition plate 131 is made of an insulating material, for example, rigid polyurethane foam. The thermal insulation performance of the partition plate 131 is greater than or equal to the thermal insulation performance of the lower insulation section 32, and more preferably lower than the thermal insulation performance of the upper insulation section 31 and higher than the thermal insulation performance of the lower insulation section 32.

[0043] As shown in Figure 9B, the second central insulation material 140, like the first central insulation material 130, has an upper insulation section 41, a lower insulation section 42, and a partition plate 141. The thickness t3 of the upper insulation section 41 and the thickness t4 of the lower insulation section 42 are the same. The second central insulation material 140, like the first central insulation material 130, has a rectangular cross-section. The partition plate 141 is embedded at the boundary between the upper insulation section 41 and the lower insulation section 42 and is flush with the outer surface 40a of the second central insulation material 140. The height h2 of the partition plate 141 is lower than the thickness t3 of the upper insulation section 41 and the thickness t4 of the lower insulation section 42. Therefore, there is a part of the boundary between the upper insulation section 41 and the lower insulation section 42 where the partition plate 141 is not provided, and in this area, an interface surface 148 is formed where the upper insulation section 41 and the lower insulation section 42 are in contact with each other. The partition plate 141 is formed from a foamed insulation material, for example, from rigid polyurethane foam. The thermal insulation performance of the partition plate 141 is greater than or equal to the thermal insulation performance of the lower insulation section 42, and more preferably lower than the thermal insulation performance of the upper insulation section 41 and higher than the thermal insulation performance of the lower insulation section 42.

[0044] Next, the manufacturing method of the first central insulation material 130 will be described. First, prepare the mold 100 shown in Figure 10 for molding the first central insulation material 130. The mold 100 can be the same as the mold shown in Figure 6 described in Embodiment 1.

[0045] Next, in the partition plate placement process, as shown in Figure 10, a partition plate 131 is placed in the center of the recess 110a formed in the first mold 110 in the longitudinal direction. The partition plate 131 has a semi-annular shape obtained by cutting a ring body in half, and partitions the recess 110a in the center. The cross-section of the semi-annular partition plate 131 when cut radially is rectangular, and the arc-shaped outer surface 131a of the partition plate 131 coincides with the semi-circular recess 110a in a cross-section obtained by cutting the first mold 110 from a direction perpendicular to the longitudinal direction. The partition plate 131 is placed with its outer surface 131a in contact with the recess 110a. Note that the height h1 of the partition plate 131 shown in Figure 9A is lower than the gap h3 shown in Figure 12A which is formed between the first mold 110 and the second mold 120.

[0046] Next, as shown in Figure 10, a first nozzle 115 for dispensing high-insulation rigid urethane foam to form the upper insulation portion 31 and a second nozzle 116 for dispensing low-insulation rigid urethane foam to form the lower insulation portion 32 are positioned toward the recess 110a of the first mold 110. The first nozzle 115 is positioned within the first region 117a of the recess 110a, which is partitioned in the center by a partition plate 131, and the second nozzle 116 is positioned within the second region 118a of the recess 110a.

[0047] Next, as shown in Figure 11A, high-insulation rigid polyurethane foam 31a is discharged from the first nozzle 115 toward the first region 117a of the recess 110a, and low-insulation rigid polyurethane foam 32a is discharged from the second nozzle 116 toward the second region 118a of the recess 110a. As a result, as shown in Figure 11B, liquid high-insulation rigid polyurethane foam 31a spreads in the first region 117a, and liquid low-insulation rigid polyurethane foam 32a spreads in the second region 118a. It is possible to discharge rigid polyurethane foam simultaneously from the first nozzle 115 and the second nozzle 116. This improves the productivity of the first central insulation material 130.

[0048] Once the dispensing of the rigid polyurethane foams 31a and 32a is complete, the first nozzle 115 and the second nozzle 116 are retracted, and the second mold 120 is placed over the first mold 110, as shown in Figure 12A. As a result, the inside of the mold 100 is divided into a first space 117b and a second space 118b by the partition plate 131. Since the height h1 of the partition plate 131 is lower than the gap h3 between the first mold 110 and the second mold 120, a gap is formed between the inner surface 131b of the semicircular partition plate 131 and the second mold 120.

[0049] While the first mold 110 is closed by the second mold 120, the high-insulation rigid polyurethane foam 31a foams and expands in the first space 117b, becoming viscous. The low-insulation rigid polyurethane foam 32a also foams and expands in the second space 118b, becoming viscous. Eventually, the expanded rigid polyurethane foams 31a and 32a extend beyond the partition plate 131 and come into contact with each other, forming an interface 138, as shown in Figure 12B. In this way, the rigid polyurethane foams 31a and 32a fill the cavity between the first mold 110 and the second mold 120 and harden.

[0050] Finally, the mold 100 is demolded to remove the first central insulation material 130, in which the upper insulation section 31, the lower insulation section 32, and the partition plate 131 are integrally molded. Although the manufacturing method of the first central insulation material 130 has been described, the second central insulation material 140, which has the same configuration, can be manufactured in the same manner.

[0051] According to this second embodiment, by arranging partition plates 131 and 141 in the mold 100, the internal space of the mold 100 can be divided into a first space 117b for forming the upper heat insulating sections 31 and 41 and a second space 118b for forming the lower heat insulating sections 32 and 42. As a result, the upper heat insulating sections 31 and 41 and the lower heat insulating sections 32 and 42 can be formed into the desired shape using the space partitioned by the partition plates 131 and 141.

[0052] Furthermore, the partition plates 131 and 141 are formed from foamed insulation material, and their insulation performance is greater than that of the lower insulation section 32. This prevents the partition plate 131 from becoming a weak point in insulating the hot water storage tank 2.

[0053] Furthermore, the heights h1 and h2 of the partition plates 131 and 141 are set lower than the gap h3 formed between the first mold 110 and the second mold 120. This prevents interference with the partition plates 131 and 141 and their displacement when the second mold 120 is placed over the first mold 110. This allows for the smooth manufacturing of the first central insulation material 130 and the second central insulation material 140. It also prevents problems such as the partition plates 131 and 141 hitting the second mold 120 and being damaged.

[0054] (Embodiment 3) Next, Embodiment 3 will be described. Embodiments 3 through 8 differ from Embodiment 2 only in the cross-sectional shape of the partition plate. The height, material, thermal insulation performance, and manufacturing method of the partition plate are the same as in Embodiment 2, so detailed explanations of these will be omitted in the following embodiments. Also, since the configuration of the first central insulation material and the configuration of the second central insulation material are the same, only the first central insulation material will be described below.

[0055] As shown in Figure 13A, the first central insulation material 230, which covers a portion of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 231. When the first central insulation material 230 is cut along a plane passing through axis A as shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 231 has a shape that combines an isosceles trapezoidal portion 231a and a rectangular portion 231b that shares one side with the shorter base of the isosceles trapezoidal portion 231a, as shown in Figure 13A. In addition, the longer base portion 231c of the isosceles trapezoidal portion 231a in the cross-section of the partition plate 231 is exposed on the outer surface 30a of the first central insulation material 230 and is flush with the outer surface 30a.

[0056] A method for manufacturing the first central insulation material 230 will now be described. First, the partition plate 231 is placed in the center of the recess 110a of the first mold 110 in the longitudinal direction. As shown in Figure 13B, the partition plate 231 is placed with the long base portion 231c of the isosceles trapezoidal portion 231a in contact with the first mold 110. In this way, the partition plate 231 can divide the space inside the mold 100 into a molding space for the upper insulation portion 31 and a molding space for the lower insulation portion 32. The subsequent steps are the same as those in Embodiment 2.

[0057] According to this third embodiment, the partition plate 231 is positioned so that the long base portion 231c of the isosceles trapezoidal portion 231a is in contact with the first mold 110, thereby stabilizing the posture of the partition plate 231. This prevents the partition plate 231 from collapsing when the rigid polyurethane foam is being extruded or when it is foaming and expanding, which would prevent the upper insulation portion 31 and the lower insulation portion 32 from being formed in the desired shape.

[0058] (Embodiment 4) Next, Embodiment 4 will be described. As shown in Figure 14A, the first central insulation material 330, which covers a part of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 331. When the first central insulation material 330 is cut by a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 331 has the shape of a parallelogram. The cross-section of this partition plate 331 has parallel short sides 331a, 331a and parallel long sides 331b, 331b. In addition, one of the short sides 331a of the partition plate 331 is exposed to the outer surface 30a of the first central insulation material 330 and is flush with the outer surface 30a. Note that the diagonals of the parallelogram cross-sectional shape of the partition plate 331 are not 90 degrees. Therefore, the long sides 331b, 331b are not perpendicular to the outer surface 30a of the first central insulation material 330, but form an inclined surface that moves toward the upper insulation portion 31 as it moves from the outer surface 30a toward the inner surface 30b.

[0059] A method for manufacturing the first central insulation material 330 will now be described. First, the partition plate 331 is placed in the center of the recess 110a of the first mold 110 in the longitudinal direction. At this time, as shown in Figure 14B, the partition plate 331 is positioned with one short side portion 331a in contact with the first mold 110 and tilted toward the first region 117a. In this way, the partition plate 331 can divide the space inside the mold 100 into a molding space for the upper insulation portion 31 and a molding space for the lower insulation portion 32. The subsequent steps are the same as those of Embodiment 2.

[0060] According to this fourth embodiment, the partition plate 331 is embedded in the first central insulation material 330 at an angle, rather than perpendicular to the outer surface 30a of the first central insulation material 330. This makes the contact area between the upper insulation portion 31 and the partition plate 331, and the contact area between the lower insulation portion 32 and the partition plate 331, larger than the contact area when the partition plate 331 is positioned perpendicular to the outer surface 30a. This makes it possible to strengthen the adhesive force at the interface between the upper insulation portion 31 and the lower insulation portion 32, and makes it less likely for cracks to occur at the boundary where the thermal insulation performance of the insulation portion changes.

[0061] (Embodiment 5) Next, Embodiment 5 will be described. As shown in Figure 15A, the first central insulation material 430, which covers a part of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 431. When the first central insulation material 430 is cut by a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 431 has a parallelogram shape, similar to the cross-section of the partition plate 331 in Embodiment 4. The difference from Embodiment 4 is that the direction in which the long sides 431b, 431b are inclined is different. That is, the long sides 431b, 431b form an inclined surface toward the lower insulation portion 32 as they move from the outer surface 30a of the first central insulation material 430 toward the inner surface 30b.

[0062] A method for manufacturing the first central insulation material 430 will now be described. First, the partition plate 431 is placed in the center of the recess 110a of the first mold 110 in the longitudinal direction. At this time, as shown in Figure 15B, the partition plate 431 is placed with one short side portion 431a in contact with the first mold 110 and tilted toward the second region 118a. In this way, the partition plate 431 can divide the space inside the mold 100 into a molding space for the upper insulation portion 31 and a molding space for the lower insulation portion 32. The subsequent steps are the same as those of Embodiment 2.

[0063] In this fifth embodiment, as in the fourth embodiment, the partition plate 431 is embedded in the first central insulation material 430 at an angle. This makes it possible to strengthen the adhesive force at the interface between the upper insulation section 31 and the lower insulation section 32, and makes it less likely for cracks to occur at the boundary where the insulation performance of the insulation section changes.

[0064] (Embodiment 6) Next, Embodiment 6 will be described. As shown in Figure 16A, the first central insulation material 530, which covers a part of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 531. When the first central insulation material 530 is cut by a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 531 has the shape of a right triangle. The cross-section of this partition plate 531 has a short side portion 531a and a long side portion 531b that enclose the right angle, and a hypotenuse portion 531c. The short side portion 531a of the partition plate 531 is exposed to the outer surface 30a of the first central insulation material 530 and is flush with the outer surface 30a. The long side portion 531b of the partition plate 531 is in contact with the upper insulation portion 31. On the other hand, the hypotenuse portion 531c of the partition plate 531 is in contact with the lower insulation portion 32.

[0065] A method for manufacturing the first central insulation material 530 will now be described. First, as shown in Figure 16B, the short side portion 531a of the partition plate 531 is brought into contact with the center of the recess 110a of the first mold 110 in the longitudinal direction. At this time, the partition plate 531 is positioned with its long side portion 531b facing the first region 117a and its slanted side portion 531c facing the second region 118a. In this way, the partition plate 531 can divide the space inside the mold 100 into a molding space for the upper insulation portion 31 and a molding space for the lower insulation portion 32. The subsequent steps are the same as those of Embodiment 2.

[0066] According to this embodiment 6, the partition plate 531 has a right-angled triangular cross-section and is positioned so that its short side portion 531a is in contact with the first mold 110, thereby stabilizing the posture of the partition plate 531. This prevents the partition plate 531 from collapsing when the rigid polyurethane foam is being extruded or when it is foaming and expanding, which would prevent the upper insulation portion 31 and the lower insulation portion 32 from being formed in the desired shape.

[0067] (Embodiment 7) Next, Embodiment 7 will be described. As shown in Figure 17A, the first central insulation material 630, which covers a part of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 631. When the first central insulation material 630 is cut along a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 631 has a first extension portion 631a at one end that is flush with the outer surface 30a of the first central insulation material 630 and perpendicular to the outer surface 30a, a second extension portion 631b perpendicular to the first extension portion 631a and connected at one end to the other end of the first extension portion 631a, and a third extension portion 631c perpendicular to the second extension portion 631b and connected at one end to the other end of the second extension portion 631b. In other words, the first extension portion 631a and the third extension portion 631c extend from the outer surface 30a toward the inner surface 30b, and the second extension portion 631b is parallel to the outer surface 30a of the first central insulation material 630.

[0068] A method for manufacturing the first central insulation material 630 will now be described. First, as shown in Figure 17B, one end of the first extension portion 631a of the partition plate 631 is brought into contact with the center of the recess 110a of the first mold 110 in the longitudinal direction. At this time, the partition plate 631 is positioned such that the first extension portion 631a is perpendicular to the recess 110a, and the third extension portion 631c is on the first region 117a side than the first extension portion 631a. In this way, the partition plate 631 can divide the space inside the mold 100 into a molding space for the upper insulation portion 31 and a molding space for the lower insulation portion 32. The subsequent steps are the same as those of Embodiment 2.

[0069] According to this embodiment 7, the partition plate 631 has a first extension portion 631a, a second extension portion 631b, and a third extension portion 631c whose connected portions are perpendicular to each other. This makes the contact area between the upper insulation portion 31 and the partition plate 631, and the contact area between the lower insulation portion 32 and the partition plate 631, larger than the contact area by the partition plate 131 in embodiment 2. This makes the adhesive force at the interface between the upper insulation portion 31 and the lower insulation portion 32 stronger, and makes it less likely for cracks to occur at the boundary where the thermal insulation performance of the insulation portion changes.

[0070] (Embodiment 8) Next, Embodiment 8 will be described. As shown in Figure 18A, the first central insulation material 730, which covers a part of the outer surface of the hot water storage tank 2, has an upper insulation portion 31, a lower insulation portion 32, and a partition plate 731. When the first central insulation material 730 is cut by a plane passing through axis A shown in Figure 4 of the hot water storage tank 2, the cross-section of the partition plate 731 has a rectangular portion 731a and a rectangular projection 731b protruding from the rectangular portion, as shown in Figure 18A. One side 731c of the rectangular portion 731a is flush with the outer surface 30a of the first central insulation material 730. The projection 731b protrudes toward the inner surface 30b from a position above the opposite side 731d that is opposite to one side 731c of the rectangular portion 731a. The vertical width W1 of the rectangular portion 731a is wider than the vertical width W2 of the projection 731b.

[0071] A method for manufacturing the first central insulation material 730 will now be described. First, a partition plate 731 is placed in the center of the recess 110a of the first mold 110 in the longitudinal direction. As shown in Figure 18B, the partition plate 731 is positioned so that one side 731c of the wide rectangular portion 731a is in contact with the first mold 110. This allows the protruding portion 731b to protrude toward the inner surface 30b of the first central insulation material 730. As a result, the partition plate 731 can divide the space inside the mold 100 into a space for forming the upper insulation portion 31 and a space for molding the lower insulation portion 32. The subsequent steps are the same as those in Embodiment 2.

[0072] According to this embodiment 8, the posture of the partition plate 731 can be stabilized by positioning the wide rectangular portion 731a of the partition plate 731 in contact with the first mold 110. This prevents the partition plate 731 from collapsing when the rigid polyurethane foam is being extruded or when it is foaming and expanding, which would prevent the upper insulation portion 31 and the lower insulation portion 32 from being formed in the desired shape.

[0073] (Embodiment 9) Next, Embodiment 9 will be described. In the above embodiment, the upper insulation material 20, the middle insulation material 50, and the lower insulation material 60 were described as being formed from rigid polyurethane foam, but it is not necessary to form all of these insulation materials from rigid polyurethane foam. The upper insulation material 20 and the lower insulation material 60, which are formed from a single material, may be formed from foamed insulation material, such as expanded polystyrene. On the other hand, the middle insulation material 50 uses materials with different insulation properties in the upper and lower parts, and it is necessary to ensure a desired adhesive strength at the interface between them. Therefore, by forming at least one of the upper insulation parts 31, 41 and the lower insulation parts 32, 42 from rigid polyurethane foam, the adhesive strength of the rigid polyurethane foam can be exerted at the interface.

[0074] As Embodiment 9, a case in which the upper insulation portion is formed from rigid polyurethane foam as the first insulation material and the lower insulation portion is formed from expanded polystyrene as the second insulation material will be described. First, as an insulation material placement step, as shown in Figure 19A, the lower insulation portion 832 formed from expanded polystyrene is placed in the recess 110a of the first mold 110. Next, liquid high-insulation rigid polyurethane foam 31a is discharged from the first nozzle 115. Once the discharge of the high-insulation rigid polyurethane foam 31a is complete, the first nozzle 115 is retracted and the second mold 120 is placed over the first mold 110 as shown in Figure 19B. Subsequently, the high-insulation rigid polyurethane foam 31a is expanded and hardened by foaming inside the mold 100 to form the upper insulation portion 831 in contact with the lower insulation portion 832.

[0075] According to this embodiment 9, even if the lower insulation portion 832 is made of expanded polystyrene, the adhesive strength of the upper insulation portion 831 formed from rigid urethane foam makes it possible to form a first central insulation material 830 with strong adhesive strength at the interface between the upper insulation portion 831 and the lower insulation portion 832.

[0076] This disclosure is not limited to the above-described embodiment, and various modifications and applications are possible. As shown in Figure 3, the central insulation material 50 is described as having a first central insulation material 30 and a second central insulation material 40 divided into front and rear sections of the hot water storage tank unit 10, but the division position of the central insulation material 50 is not particularly limited. Furthermore, although the central insulation material 50 is formed by combining the first central insulation material 30 and the second central insulation material 40, which are two divided sections, the number of divisions is not limited, and the central insulation material may be formed by combining two or more divided sections.

[0077] Furthermore, although the central insulation material 50 is formed from two types of insulation materials with different thermal insulation performance in the upper and lower sections, the central insulation material may also be formed from two or more types of insulation materials with different thermal insulation performance. In this case, the insulation materials should be gradually made to have lower thermal insulation performance from the upper to the lower section of the central insulation material. Also, the boundary where insulation materials with different thermal insulation performance come into contact with each other is not limited to a position that equally divides the vertical height of the central insulation material, but can be at any position.

[0078] Alternatively, a magnetic sheet may be placed at the contact point between the mold and the partition plate to secure the partition plate in the mold using magnetic force. Or, adhesive tape may be attached instead of a magnetic sheet to secure the partition plate.

[0079] Furthermore, as shown in Figure 16A, the partition plate 531 having a right-angled triangular cross-section was described as being positioned with its long side 531b facing the first region 117a and its hypotenuse 531c facing the second region 118a. However, the orientation of the partition plate 531 may be changed so that its long side 531b faces the second region 118a and its hypotenuse 531c faces the first region 117a. This change in the orientation of the partition plate can also be performed in the case of the partition plate 631 shown in Figure 17B of Embodiment 7 and the partition plate 731 shown in Figure 18B of Embodiment 8.

[0080] Furthermore, although the cross-section of the partition plate 531 shown in Figure 16B was described as a right triangle, it may also be a cross-sectional shape of another triangle, for example, an isosceles triangle. Also, in the partition plate 731 shown in Figure 18B, although the protruding portion 731b was described as protruding from the end of the opposite side portion 731d of the rectangular portion 731a, it may also protrude from the center of the opposite side portion 731d.

[0081] Furthermore, in Embodiment 1, it was explained that the interface surfaces 33, 43 between the upper insulation sections 31, 41 and the lower insulation sections 32, 42 are inclined with respect to the horizontal direction of the hot water storage tank 2 due to the unavoidable difference in the expansion force of the rigid polyurethane foam. However, as shown in Figures 5A and 5B, the interface surfaces 33, 43 may be formed not only when they are inclined at the same angle from the inner surfaces 30b, 40b to the outer surfaces 30a, 40a, but also when they have multiple interface surfaces facing different directions during the expansion process of the rigid polyurethane foam. Below, Modifications 1 and 2 of Embodiment 1, which have interface surfaces in a different manner than Embodiment 1, will be described. Note that the configuration of the first central insulation material and the configuration of the second central insulation material are the same, so only the first central insulation material will be described below.

[0082] Modification 1 of this embodiment 1, as shown in Figure 20, has a boundary surface 91 formed at the boundary between the upper heat insulating portion 31 and the lower heat insulating portion 32. The boundary surface 91 has a first boundary surface 91a, which is formed from the outer surface 30a and is an inclined surface that extends downward toward the inner surface 30b; a second boundary surface 91b, which is formed from the inner surface 30b and is an inclined surface that extends upward toward the outer surface 30a; and a third boundary surface 91c that horizontally connects the first boundary surface 91a and the second boundary surface 91b. The third boundary surface 91c connects the end of the first boundary surface 91a on the outer surface 30a side and the end of the second boundary surface 91b on the inner surface 30b side.

[0083] As described above, in Modification 1, a portion of the interface 91 is inclined with respect to the horizontal direction of the hot water storage tank 2 shown in Figure 2, allowing for a larger interface area than when the interface is extended horizontally. This makes it possible to strengthen the adhesive force at the interface between the upper insulation portion 31 and the lower insulation portion 32, and makes it less likely for cracks to occur at the boundary where the thermal insulation performance of the insulation portion changes. Other effects are the same as those in the first embodiment.

[0084] Modification 2 of this embodiment 1, as shown in Figure 21, has an interface 92 formed at the boundary between the upper insulation portion 31 and the lower insulation portion 32. The interface 92 has a first interface 92a, which is an inclined surface formed from the outer surface 30a and extends downward toward the inner surface 30b; a second interface 92b, which is an inclined surface formed from the inner surface 30b and extends upward toward the outer surface 30a; and a third interface 92c, which connects the first interface 92a and the second interface 92b in the horizontal direction. The first interface 92a is formed toward the inner surface 30b to a position beyond a part of the second interface 92b. Similarly, when viewed from the second interface 92b, the second interface 92b is formed toward the outer surface 30a to a position beyond a part of the first interface 92a. Therefore, when the hot water storage tank 2 shown in Figure 2 is cut vertically, the interface 92 is formed in a Z shape.

[0085] As described above, in this modified example 2 as well, a portion of the interface 92 is inclined with respect to the horizontal direction of the hot water storage tank 2 shown in Figure 2, which allows for a stronger adhesive force at the interface between the upper insulation portion 31 and the lower insulation portion 32. Furthermore, the other effects are the same as those in the first embodiment.

[0086] Furthermore, in Embodiment 1, it was explained that the interface surfaces 33, 43 between the upper insulation sections 31, 41 and the lower insulation sections 32, 42 extend downward from the outer surfaces 30a, 40a toward the inner surfaces 30b, 40b. However, the direction in which these interface surfaces extend is not particularly limited. In Modification 3 of Embodiment 1, as shown in Figure 22A, the interface surface 133 provided on the first central insulation material 30 is an inclined surface that extends upward from the outer surface 30a toward the inner surface 30b of the first central insulation material 30. Also, as shown in Figure 22B, the interface surface 143 provided on the second central insulation material 40 is an inclined surface that extends upward from the outer surface 40a toward the inner surface 40b of the second central insulation material 40. By forming such inclined surfaces, the adhesive force at the interface between the upper insulation section and the lower insulation section can be strengthened. Furthermore, other effects are the same as those in the first embodiment. Thus, changing the inclination direction of the interface can be appropriately applied to other examples of Embodiment 1 and other embodiments.

[0087] Furthermore, as explained with reference to Figures 11 and 12, when manufacturing the first central insulation material 130 and the second central insulation material 140 that cover the hot water storage tank 2, a partition plate 131 was installed in the mold to separate the insulation sections with different insulation performance. However, even when insert molding is performed with the entire hot water storage tank 2 fixed in the mold, a similar partition can be placed in the mold to separate the insulation sections with different insulation performance.

[0088] First, a mold capable of housing the hot water storage tank is prepared, and an annular partition plate is attached to the hot water storage tank 2. Next, the hot water storage tank 2 with the partition plate attached is fixed inside the mold, and rigid polyurethane foam is injected into the space between the hot water storage tank 2 and the mold. At this time, high-insulation rigid polyurethane foam is injected into one space separated by the partition plate, and low-insulation rigid polyurethane foam is injected into the other space. The partition plate is formed from an insulating material, for example, rigid polyurethane foam. The insulating performance of the partition plate is higher than the insulating performance of the insulating section molded from low-insulation rigid polyurethane foam. Then, by demolding the mold, the outer surface of the hot water storage tank 2 can be covered with the high-insulation section and the low-insulation section separated by the partition plate.

[0089] By installing the partition plate in this manner, it is possible to form a highly insulated section and a low-insulation section in the desired shape. Furthermore, since the insulation performance of the partition plate is greater than or equal to that of the low-insulation section, it is possible to prevent the partition plate from becoming a weak point in insulating the hot water storage tank 2. Although the case in which the entire oil storage tank 2 is fixed to a mold and insert molded has been described, partition plates made from insulating material can also be used when the sheet metal material of the oil storage tank 2 is fixed to a mold and insert molded.

[0090] Furthermore, although the hot water storage tank unit 10 of the above embodiment has been described in the case where it is used in a hot water storage type water heater 1, it can be used in other systems, for example, in a heating and hot water supply system.

[0091] This disclosure allows for various embodiments and modifications without departing from its broad spirit and scope. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of this disclosure. In other words, the scope of this disclosure is indicated by the claims, not by the embodiments. And any modifications made within the scope of the claims and equivalent disclosures are considered to be within the scope of this disclosure.

[0092] This application is based on Japanese Patent Application No. 2022-091966, filed on 7 June 2022. The entire specification, claims, and drawings of Japanese Patent Application No. 2022-091966 are incorporated herein by reference.

[0093] The various aspects of this disclosure are summarized below as an appendix.

[0094] (Note 1) The upper insulation material that covers the top of the hot water storage tank, The lower insulation material covers the lower part of the hot water storage tank, The system comprises a middle insulation material provided between the upper insulation material and the lower insulation material, which covers the middle part of the hot water storage tank, The aforementioned middle insulation material has an upper insulation portion formed from a first insulation material having high insulation performance and a lower insulation portion formed from a second insulation material having low insulation performance. The upper insulating portion and the lower insulating portion are molded together as one unit. At least one of the first and second insulating materials is a rigid polyurethane foam. Insulated structure for a hot water storage tank. (Note 2) The aforementioned central insulation material is formed by combining a first central insulation material and a second central insulation material, which are divided in a direction parallel to the vertical direction of the hot water storage tank. The first central insulation material and the second central insulation material each have an integrally molded upper insulation portion and a lower insulation portion. The thermal insulation structure of the hot water storage tank as described in Appendix 1. (Note 3) The upper insulating portion and the lower insulating portion are in contact with each other, forming an interface. The interface is inclined in at least a portion with respect to the horizontal direction of the hot water storage tank. The thermal insulation structure for the hot water storage tank as described in Appendix 1 or 2. (Note 4) A partition plate is embedded in the aforementioned middle insulation material along the boundary between the upper insulation section and the lower insulation section. The outer surface of the aforementioned central insulation material and the aforementioned partition plate are flush. The thermal insulation structure for the hot water storage tank as described in Appendix 1 or 2. (Note 5) The aforementioned partition plate is made of an insulating material, The thermal insulation performance of the partition plate is equal to or greater than that of the thermal insulation performance of the lower insulation section. The thermal insulation structure of the hot water storage tank as described in Appendix 4. (Note 6) The cross-section of the partition plate, when cut from a direction parallel to the vertical direction of the hot water storage tank, is rectangular. The thermal insulation structure for the hot water storage tank as described in Appendix 4 or 5. (Note 7) The cross-section of the partition plate, cut from a direction parallel to the vertical direction of the hot water storage tank, has a shape that widens outward toward the outside of the central insulation material. The thermal insulation structure for the hot water storage tank as described in Appendix 4 or 5. (Note 8) The cross-section of the partition plate, obtained by cutting it from a direction parallel to the vertical direction of the hot water storage tank, is a parallelogram. The thermal insulation structure for the hot water storage tank as described in Appendix 4 or 5. (Note 9) A hot water storage tank, A heat insulating structure for a hot water storage tank, as described in any one of the appendices 1 to 8, which covers the perimeter of the hot water storage tank in order to suppress heat dissipation, A hot water supply pipe connected to the aforementioned hot water storage tank for supplying hot water to the hot water storage tank, The system includes a hot water outlet pipe connected to the aforementioned hot water storage tank for dispensing hot water from the storage tank. Hot water storage tank unit. (Note 10) A mold preparation process for preparing a mold to form the central insulation material that covers the central part of the hot water storage tank, A nozzle arrangement step involves arranging a first nozzle for dispensing high-insulation rigid polyurethane foam, which is the material for the upper insulation portion forming the upper part of the aforementioned middle insulation material, into the mold, and a second nozzle for dispensing low-insulation rigid polyurethane foam, which is the material for the lower insulation portion forming the lower part of the aforementioned middle insulation material, into the mold. Discharge step of discharging high-insulation rigid polyurethane foam from the first nozzle into the mold and low-insulation rigid polyurethane foam from the second nozzle into the mold, The process includes a molding step of expanding the extruded high-insulation rigid polyurethane foam and the low-insulation rigid polyurethane foam inside the mold to integrally form the upper insulation portion and the lower insulation portion. A method for manufacturing an insulating structure for a hot water storage tank. (Note 11) Prior to the discharge step, the process further includes a partition plate placement step in which a partition plate is placed inside the mold prepared in the mold preparation step to separate the space for forming the upper heat insulating portion from the space for forming the lower heat insulating portion. In the molding process described above, the upper insulating portion, the lower insulating portion, and the partition plate are molded together as a single unit. A method for manufacturing the insulating structure of the hot water storage tank described in Appendix 10. (Note 12) The partition plates to be placed in the partition plate placement step are made of a heat insulating material. The thermal insulation performance of the partition plate is equal to or greater than that of the thermal insulation performance of the lower insulation section. A method for manufacturing the insulating structure of the hot water storage tank described in Appendix 11. (Note 13) The aforementioned central insulation material is formed by combining a first central insulation material and a second central insulation material, which are divided in a direction parallel to the vertical direction of the hot water storage tank. The mold is for forming the first central insulation material and the second central insulation material, and comprises a first mold as a lower mold having a recess formed by hollowing out a semi-cylindrical body, and a second mold as an upper mold having a semi-cylindrical protrusion which is inserted into the recess and combined with the first mold. In the partition plate placement step, the semicircular partition plate is placed in the recess of the first mold. A method for manufacturing an insulating structure for a hot water storage tank as described in Appendix 11 or 12. (Note 14) In the partition plate placement step, the height of the partition plate to be placed is lower than the gap between the first mold and the second mold that forms the internal space of the mold. A method for manufacturing the insulating structure of the hot water storage tank described in Appendix 13. (Note 15) The cross-section obtained by cutting the semicircular partition plate radially is rectangular. A method for manufacturing an insulating structure for a hot water storage tank as described in Appendix 13 or 14. (Note 16) The cross-section obtained by cutting the semicircular partition plate radially has a shape that widens towards the outer circumference of the partition plate. A method for manufacturing an insulating structure for a hot water storage tank as described in Appendix 13 or 14. (Note 17) The cross-section obtained by cutting the semicircular partition plate radially is a parallelogram. A method for manufacturing an insulating structure for a hot water storage tank as described in Appendix 13 or 14. (Note 18) The cross-section obtained by cutting the semicircular partition plate radially has a first extension, a second extension perpendicular to the first extension, and a third extension perpendicular to the second extension. The thermal insulation structure for the hot water storage tank as described in Appendix 13 or 14. (Note 19) A mold preparation process for preparing a mold to form the central insulation material that covers the central part of the hot water storage tank, An insulation material placement step is to form either an upper insulation portion having high insulation performance that forms the upper part of the aforementioned middle insulation material or a lower insulation portion having low insulation performance that forms the lower part of the aforementioned middle insulation material using foamed insulation material and then place it inside the mold. A nozzle placement step involves arranging a nozzle for dispensing rigid polyurethane foam, which is the material for the other of the upper and lower insulation sections, into the mold. A dispensing step of dispensing rigid polyurethane foam from the nozzle into the mold, The process includes a molding step of expanding the extruded rigid urethane foam inside the mold to integrally form the upper insulation portion and the lower insulation portion. A method for manufacturing an insulating structure for a hot water storage tank. (Note 20) A process for preparing a mold for forming an insulating structure having insulating parts with different insulating properties, The process involves attaching a partition plate, which separates the aforementioned insulated sections having different thermal insulation properties, to the hot water storage tank, The process of housing and fixing the hot water storage tank inside the mold, The process involves injecting high-insulation rigid polyurethane foam into one of the spaces between the hot water storage tank and the mold, which are separated by the partition plate, and injecting low-insulation rigid polyurethane foam into the other space, thereby forming the insulation structure. The process includes a step of demolding the mold, The aforementioned partition plate is made of an insulating material, The thermal insulation performance of the partition plate is greater than or equal to the thermal insulation performance of the insulation section formed from the low-insulation rigid polyurethane foam. A method for manufacturing an insulating structure for a hot water storage tank. [Explanation of Symbols]

[0095] 1 Storage-type hot water heater, 2 Storage tank, 2a Body, 2b First end, 2c Second end, 6a, 6b Fittings, 10 Storage tank unit, 11 Hot water outlet piping, 12 Hot water supply piping, 20 Upper insulation material, 20a First opening, 30 First middle insulation material, 30a Outer surface, 30b Inner surface, 31 Upper insulation section, 31a High-insulation rigid polyurethane foam, 32 Lower insulation section, 32a Low-insulation rigid polyurethane foam, 33,33a Interface, 40 Second central insulation, 40a Outer surface, 40b Inner surface, 41 Upper insulation section, 42 Lower insulation section, 43 Interface, 50 Central insulation, 60 Lower insulation, 60a Second opening, 70 Insulation structure, 80 Outer case, 91 Interface, 91a First interface, 91b Second interface, 91c Third interface, 92 Interface, 92a First interface, 92b Second interface, 92c Third interface, 100 Mold, 101 Pressure reducing valve, 102 Mixing valve, 103 Switching valve, 104 Check valve, 105 Heat source pump, 106 Temperature sensor, 110 First mold, 110a Recess, 110b Top surface, 115 First nozzle, 116 Second nozzle, 117a First region, 117b 1st space, 118a 2nd region, 118b 2nd space, 119 Air vent, 120 2nd mold, 121 Flat section, 122 Convex section, 123 Air vent, 130 1st central insulation material, 131 Partition plate, 131a Outer surface, 131b Inner surface, 133 Boundary surface, 138 Boundary surface, 140 2nd central insulation material, 141 Partition plate, 143 Boundary surface, 148 Boundary surface, 200 Heat pump unit, 204 Heat pump supply piping, 205 Heat pump return piping, 230 1st central insulation material, 231 Partition plate, 231a Isosceles trapezoidal section, 231b Rectangular section, 231c Base section, 330 1st central insulation material, 331 Partition plate, 331a Short side section, 331b Long side, 430; First central insulation, 431; Partition plate, 431a; Short side, 431b; Long side, 530; First central insulation, 531; Partition plate, 531a; Short side, 531b; Long side, 531c; Slanted side, 630; First central insulation, 631; Partition plate, 631a; First extension, 631b; Second extension, 631c; Third extension, 730; First central insulation, 731; Partition plate, 731a; Rectangular section, 731b; Projection, 731c; Side, 731d; Opposite side, 830; First central insulation, 831; Upper insulation, 832; Lower insulation, A; Axis, P; Plane, h1, h2; Height, h3; Gap, t1, t2, t3, t4 Thickness, W1, W2 width.

Claims

1. The upper insulation material that covers the top of the hot water storage tank, The lower insulation material covers the lower part of the hot water storage tank, The system comprises a middle insulation material provided between the upper insulation material and the lower insulation material, which covers the middle part of the hot water storage tank, The aforementioned middle insulation material has an upper insulation portion formed from a first insulation material having high insulation performance and a lower insulation portion formed from a second insulation material having low insulation performance. The upper insulating portion and the lower insulating portion are molded together as one unit. At least one of the first thermal insulation material and the second thermal insulation material is a rigid polyurethane foam. A partition plate is embedded in the aforementioned middle insulation material along the boundary between the upper insulation section and the lower insulation section. The outer surface of the aforementioned central insulation material and the aforementioned partition plate are flush. Insulated structure for a hot water storage tank.

2. The aforementioned partition plate is formed from an insulating material. The thermal insulation performance of the partition plate is equal to or greater than that of the thermal insulation performance of the lower insulation section. The thermal insulation structure for a hot water storage tank according to claim 1.

3. The cross-section of the partition plate, when cut from a direction parallel to the vertical direction of the hot water storage tank, is rectangular. The thermal insulation structure for a hot water storage tank according to claim 2.

4. The cross-section of the partition plate, cut from a direction parallel to the vertical direction of the hot water storage tank, has a shape that widens outward toward the outside of the central insulation material. The thermal insulation structure for a hot water storage tank according to claim 2.

5. The cross-section of the partition plate, obtained by cutting it from a direction parallel to the vertical direction of the hot water storage tank, is a parallelogram. The thermal insulation structure for a hot water storage tank according to claim 2.

6. A hot water storage tank, A heat insulating structure for a hot water storage tank according to any one of claims 1 to 5, which covers the perimeter of the hot water storage tank in order to suppress heat dissipation, A hot water supply pipe connected to the aforementioned hot water storage tank for supplying hot water to the hot water storage tank, The system includes a hot water outlet pipe connected to the aforementioned hot water storage tank for dispensing hot water from the storage tank. Hot water storage tank unit.

7. A mold preparation process for preparing a mold to form the central insulation material that covers the central part of the hot water storage tank, A nozzle arrangement step involves arranging a first nozzle for discharging high-insulation rigid polyurethane foam, which is the material for the upper insulation portion forming the upper part of the aforementioned middle insulation material, into the mold, and a second nozzle for discharging low-insulation rigid polyurethane foam, which is the material for the lower insulation portion forming the lower part of the aforementioned middle insulation material, into the mold. Discharge step of discharging high-insulation rigid polyurethane foam from the first nozzle into the mold and low-insulation rigid polyurethane foam from the second nozzle into the mold, The process includes a molding step of expanding the extruded high-insulation rigid polyurethane foam and the low-insulation rigid polyurethane foam inside the mold to integrally form the upper insulation portion and the lower insulation portion, In the molding process, the difference in expansion force between the high-insulation rigid polyurethane foam and the low-insulation rigid polyurethane foam is used to tilt the interface between the upper insulation portion and the lower insulation portion. A method for manufacturing an insulating structure for a hot water storage tank.

8. A mold preparation process for preparing a mold to form the central insulation material that covers the central part of the hot water storage tank, A nozzle arrangement step involves arranging a first nozzle for discharging high-insulation rigid polyurethane foam, which is the material for the upper insulation portion forming the upper part of the aforementioned middle insulation material, into the mold, and a second nozzle for discharging low-insulation rigid polyurethane foam, which is the material for the lower insulation portion forming the lower part of the aforementioned middle insulation material, into the mold. Discharge step of discharging high-insulation rigid polyurethane foam from the first nozzle into the mold and low-insulation rigid polyurethane foam from the second nozzle into the mold, A molding process in which the extruded high-insulation rigid polyurethane foam and the low-insulation rigid polyurethane foam are expanded inside the mold to integrally form the upper insulation part and the lower insulation part, Prior to the discharge step, the process includes a partition plate placement step in which a partition plate is placed inside the mold prepared in the mold preparation step to separate the space for forming the upper heat insulating portion from the space for forming the lower heat insulating portion. In the molding process described above, the upper insulating portion, the lower insulating portion, and the partition plate are molded together as a single unit. A method for manufacturing an insulating structure for a hot water storage tank.

9. The partition plates to be placed in the partition plate placement step are made of a heat insulating material. The thermal insulation performance of the partition plate is equal to or greater than that of the thermal insulation performance of the lower insulation section. A method for manufacturing an insulating structure for a hot water storage tank according to claim 8.

10. The aforementioned central insulation material is formed by combining a first central insulation material and a second central insulation material, which are divided in a direction parallel to the vertical direction of the hot water storage tank. The mold is for forming the first central insulation material and the second central insulation material, and comprises a first mold as a lower mold having a recess formed by hollowing out a semi-cylindrical body, and a second mold as an upper mold having a semi-cylindrical protrusion which is inserted into the recess and combined with the first mold. In the partition plate placement step, the semicircular partition plate is placed in the recess of the first mold. A method for manufacturing an insulating structure for a hot water storage tank according to claim 8 or 9.

11. In the partition plate placement step, the height of the partition plate to be placed is lower than the gap between the first mold and the second mold that forms the internal space of the mold. A method for manufacturing an insulating structure for a hot water storage tank according to claim 10.

12. The cross-section obtained by cutting the semicircular partition plate radially is rectangular. A method for manufacturing an insulating structure for a hot water storage tank according to claim 10.

13. The cross-section obtained by cutting the semicircular partition plate radially has a shape that widens towards the outer circumference of the partition plate. A method for manufacturing an insulating structure for a hot water storage tank according to claim 10.

14. The cross-section obtained by cutting the semicircular partition plate radially is a parallelogram. A method for manufacturing an insulating structure for a hot water storage tank according to claim 10.

15. The cross-section obtained by cutting the semicircular partition plate radially has a first extension, a second extension perpendicular to the first extension, and a third extension perpendicular to the second extension. A method for manufacturing an insulating structure for a hot water storage tank according to claim 10.

16. A process for preparing a mold for forming an insulating structure having insulating parts with different insulating properties, The process involves attaching a partition plate, which separates the aforementioned insulated sections having different thermal insulation properties, to the hot water storage tank, The process of housing and fixing the hot water storage tank inside the mold, The process involves injecting high-insulation rigid polyurethane foam into one of the spaces between the hot water storage tank and the mold, which are separated by the partition plate, and injecting low-insulation rigid polyurethane foam into the other space, thereby forming the insulation structure. The process includes a step of demolding the mold, The aforementioned partition plate is formed from an insulating material. The thermal insulation performance of the partition plate is greater than or equal to the thermal insulation performance of the insulation section formed from the low-insulation rigid polyurethane foam. A method for manufacturing an insulating structure for a hot water storage tank.

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