JP7744672B2 - Water heater manufacturing method - Google Patents

Description

The present invention relates to a sensible heat recovery water heater, a latent heat recovery water heater, and a method for manufacturing a water heater.

Conventionally, a water heater of a sensible heat recovery type is known, for example, from the water heater described in Japanese Patent Laid-Open No. 2018-31489 (Patent Document 1 below). The water heater of Patent Document 1 includes a burner unit, a heat exchanger, and an exhaust casing. The heat exchanger recovers sensible heat from the combustion exhaust gas generated by the burner unit. The combustion exhaust gas that passes through the heat exchanger is discharged to the outside through the exhaust casing.
Furthermore, a water heater described in Japanese Patent Laid-Open No. 2021-55888 (see Patent Document 2 below) is known as a latent heat recovery water heater. The water heater of Patent Document 2 includes a burner device, a primary heat exchanger, and a secondary heat exchanger. The primary heat exchanger recovers sensible heat from the combustion exhaust gas generated by the burner device. The secondary heat exchanger recovers latent heat from the combustion exhaust gas that has passed through the primary heat exchanger.

JP 2018-31489 A Japanese Patent Application Laid-Open No. 2021-55888

Sensible heat recovery water heaters like those described above are often designed at the same time as latent heat recovery water heaters as a variation of the latter, and most parts are shared between the two. However, the exhaust casings of sensible heat recovery water heaters are often designed separately and manufactured using newly created molds. For this reason, when the production lot size of sensible heat recovery water heaters is small, it can be difficult to keep manufacturing costs down.

This disclosure was completed based on the above circumstances, and aims to provide a sensible heat recovery water heater, a latent heat recovery water heater, and a method for manufacturing a water heater that can reduce manufacturing costs.

The sensible heat recovery water heater disclosed herein is a sensible heat recovery water heater comprising: a combustion device; a primary heat exchanger fixed to the top of the combustion device and recovering sensible heat from the combustion exhaust gas generated by the combustion device; and an exhaust casing arranged downstream of the primary heat exchanger and discharging the combustion exhaust gas discharged from the primary heat exchanger to the outside. The exhaust casing is constructed using a box having an inlet portion at the rear for receiving the combustion exhaust gas and an outlet portion at the front for discharging the combustion exhaust gas. The box is used as the housing of the secondary heat exchanger in a latent heat recovery water heater comprising the combustion device, the primary heat exchanger, and a secondary heat exchanger arranged downstream of the primary heat exchanger for recovering latent heat from the combustion exhaust gas discharged from the primary heat exchanger.

This disclosure makes it possible to provide a sensible heat recovery water heater, a latent heat recovery water heater, and a method for manufacturing a water heater that can reduce manufacturing costs.

FIG. 1 is a front view illustrating a schematic example of the internal structure of a latent heat recovery water heater according to an embodiment. FIG. 2 is an explanatory diagram conceptually illustrating the configuration of a latent heat recovery water heater. FIG. 3 is an enlarged partial cross-sectional view taken along line AA in FIG. FIG. 4 is a partially enlarged cross-sectional view showing a main part of the secondary heat exchanger. FIG. 5 is an enlarged partial cross-sectional view taken along line BB in FIG. FIG. 6 is a partially enlarged perspective view illustrating a schematic example of the internal structure of a latent heat recovery water heater. FIG. 7 is an enlarged partial cross-sectional view taken along line CC in FIG. FIG. 8 is a perspective view that schematically illustrates a secondary heat exchanger. FIG. 9 is an exploded perspective view that schematically illustrates the housing of the secondary heat exchanger. FIG. 10 is an explanatory diagram illustrating a state before the first assembly and the second assembly are attached to the main body. FIG. 11 is a front view illustrating a schematic example of the internal structure of a sensible heat recovery water heater. FIG. 12 is an explanatory diagram conceptually illustrating the configuration of a sensible heat recovery water heater. FIG. 13 is a partially enlarged cross-sectional view taken along line DD in FIG. FIG. 14 is an exploded perspective view illustrating a schematic example of an exhaust casing of a sensible heat recovery water heater.

Description of the embodiments of the present disclosure
First, embodiments of the present disclosure will be listed and described.

(1) The sensible heat recovery water heater of the present disclosure is a sensible heat recovery water heater comprising: a combustion device; a primary heat exchanger fixed to the top of the combustion device and recovering sensible heat from the combustion exhaust gas generated by the combustion device; and an exhaust casing arranged downstream of the primary heat exchanger and discharging the combustion exhaust gas discharged from the primary heat exchanger to the outside, wherein the exhaust casing is constructed using a box body having an inlet portion at the rear for receiving the combustion exhaust gas and an outlet portion at the front for discharging the combustion exhaust gas, and the box body is used as the housing of the secondary heat exchanger in a latent heat recovery water heater comprising the combustion device, the primary heat exchanger, and a secondary heat exchanger arranged downstream of the primary heat exchanger for recovering latent heat from the combustion exhaust gas discharged from the primary heat exchanger.

(2) The latent heat recovery water heater of the present disclosure is a latent heat recovery water heater comprising: a combustion device; a primary heat exchanger fixed to the top of the combustion device and recovering sensible heat from the combustion exhaust gas generated by the combustion device; and a secondary heat exchanger arranged downstream of the primary heat exchanger and recovering latent heat from the combustion exhaust gas discharged from the primary heat exchanger, wherein the housing of the secondary heat exchanger is constructed using a box body having an inlet portion at the rear for receiving the combustion exhaust gas and an outlet portion at the front for discharging the combustion exhaust gas, and the box body is used for the exhaust casing in a sensible heat recovery water heater comprising the combustion device, the primary heat exchanger, and an exhaust casing arranged downstream of the primary heat exchanger and discharging the combustion exhaust gas discharged from the primary heat exchanger to the outside.

With this configuration, the exhaust casing of the sensible heat recovery water heater and the housing of the secondary heat exchanger of the latent heat recovery water heater are constructed from a common box body. This eliminates the need to create a separate mold for the exhaust casing of the sensible heat recovery water heater, making it possible to reduce manufacturing costs even when the production lot size of sensible heat recovery water heaters is small.

Furthermore, when the exhaust casing is designed individually, it is necessary to verify the ability to assemble the exhaust casing with other parts. However, in the above configuration, the exhaust casing and the housing of the secondary heat exchanger are constructed from the same box body, so the process of verifying the ability to assemble the exhaust casing or the housing of the secondary heat exchanger with other parts can be minimized.
When assembling the exhaust casing or the housing of the secondary heat exchanger with other components, packing is placed between the edges of the inlet and outlet of the exhaust casing or the housing of the secondary heat exchanger and the other components to prevent the passage of gas. Because the exhaust casing and the housing of the secondary heat exchanger are formed from a common box body having an inlet and an outlet, the packing can also be common between the exhaust casing and the housing of the secondary heat exchanger.

(3) The method for manufacturing a water heater disclosed herein is a method for manufacturing a water heater including a combustion device and a primary heat exchanger fixed to an upper portion of the combustion device and recovering sensible heat from the combustion exhaust gas generated by the combustion device, wherein the water heater includes a latent heat recovery water heater further including a secondary heat exchanger that recovers latent heat from the combustion exhaust gas discharged from the primary heat exchanger, and a sensible heat recovery water heater further including an exhaust casing that discharges the combustion exhaust gas discharged from the primary heat exchanger to the outside. The method for manufacturing the water heater includes the step of forming a box having an inlet portion at the rear that receives the combustion exhaust gas and an outlet portion at the front that discharges the combustion exhaust gas. If the water heater is a latent heat recovery water heater, the method further includes the steps of forming openings on both side surfaces of the box to form a housing for the secondary heat exchanger and inserting multiple heat transfer tubes into the housing through the openings. If the water heater is a sensible heat recovery water heater, the method further includes the step of forming the exhaust casing using the box.

The manufacturing method for the above-mentioned water heater includes the steps of forming a box body and using this box body to construct the housing of the secondary heat exchanger of a latent heat recovery water heater or the exhaust casing of a sensible heat recovery water heater. This eliminates the need to separately manufacture a mold for the exhaust casing of the sensible heat recovery water heater, making it possible to reduce manufacturing costs even when the production lot size of sensible heat recovery water heaters is small.

Furthermore, when the exhaust casing is designed separately, it is necessary to verify the ability to assemble the exhaust casing with other parts. However, in the above-described water heater manufacturing method, the exhaust casing and the secondary heat exchanger housing are constructed from the same box body, so the process of verifying the ability to assemble the exhaust casing or the secondary heat exchanger housing with other parts can be minimized.
Furthermore, since the exhaust casing and the housing of the secondary heat exchanger have the same inlet and outlet portions, the gaskets placed between the rims of the inlet and outlet portions and other parts can be made common between the exhaust casing and the housing of the secondary heat exchanger.

<Embodiment>
Hereinafter, an embodiment will be described with reference to the drawings. A water heater 1 of this embodiment includes a latent heat recovery water heater 2 and a sensible heat recovery water heater 3. First, the latent heat recovery water heater 2 will be described with reference to Figures 1 to 10, and then the sensible heat recovery water heater 3 will be described with reference to Figures 11 to 14. Note that, for multiple identical components, only some of the components will be assigned reference numerals, and the reference numerals for the other components may be omitted.

[Overall configuration of latent heat recovery water heater]
As shown in FIGS. 1 to 3 , the latent heat recovery water heater 2 includes a primary heat exchanger 100 , a secondary heat exchanger 200 , a burner device 300 (an example of a combustion device), and an exhaust hood 400 .

The primary heat exchanger 100 comprises two heat exchangers: a hot water primary heat exchanger 110 and a bath primary heat exchanger 120.

The secondary heat exchanger 200 is located above the primary heat exchanger 100. The secondary heat exchanger 200 is equipped with two heat exchangers: a hot water supply secondary heat exchanger 210 connected upstream of the hot water supply primary heat exchanger 110, and a bath secondary heat exchanger 220 connected upstream of the bath primary heat exchanger 120.

The burner device 300 is connected to the lower part of the primary heat exchanger 100. The burner device 300 comprises two burner groups, a hot water supply burner group 310 and a bath burner group 320, and a burner case 330. The hot water supply burner group 310 generates combustion exhaust gas that is sent to the hot water supply primary heat exchanger 110 and the hot water supply secondary heat exchanger 210. The bath burner group 320 generates combustion exhaust gas that is sent to the bath primary heat exchanger 120 and the bath secondary heat exchanger 220.

The exhaust hood 400 has a lower end connected to the primary heat exchanger 100 and an upper end connected to the secondary heat exchanger 200. The lower end of the exhaust hood 400 opens downward and communicates with the space inside the primary heat exchanger 100. The upper end of the exhaust hood 400 opens forward and communicates with the space inside the secondary heat exchanger 200.

The latent heat recovery water heater 2 circulates the combustion exhaust gas generated by each burner group 310, 320 of the burner device 300 through the primary heat exchanger 100 above the burner device 300. The primary heat exchanger 100 exchanges heat between the combustion exhaust gas and the water flowing through the hot water supply primary heat exchanger 110 and the bath primary heat exchanger 120. The latent heat recovery water heater 2 functions to recover sensible heat from the combustion exhaust gas using the primary heat exchanger 100.

In the latent heat recovery water heater 2, the combustion exhaust from the burner device 300 is guided from the primary heat exchanger 100 through the exhaust hood 400 to the secondary heat exchanger 200. The combustion exhaust that passes through the primary heat exchanger 100 passes through the exhaust hood 400 and enters the secondary heat exchanger 200 from the rear. In other words, the secondary heat exchanger 200 is located downstream of the combustion exhaust path relative to the primary heat exchanger 100. The secondary heat exchanger 200 exchanges heat between the water passing through the hot water secondary heat exchanger 210 and the bath secondary heat exchanger 220 and the combustion exhaust. The latent heat recovery water heater 2 functions to recover the latent heat from the combustion exhaust using the secondary heat exchanger 200.

[Circuit configuration of latent heat recovery water heater]
As shown in FIG. 2, the latent heat recovery water heater 2 is configured to include two circuits: a hot water supply circuit 10 and a bath circuit 20.

The hot water supply circuit 10 is a circuit that heats water from a tap or the like and discharges it as hot water. As shown in Figures 1 and 2, the hot water supply circuit 10 receives water from a water inlet 11 connected to a water supply source such as a tap and flows it into a water inlet pipe 12. The water then passes through a hot water supply secondary heat exchanger 210 and a hot water supply primary heat exchanger 110 in that order, where it is heated by heat exchange with the combustion exhaust from the hot water supply burner group 310. The water then flows through a hot water outlet pipe 13 and discharges hot water from a hot water outlet 14.

The bath circuit 20 is a circuit that circulates and heats the hot water in the bathtub B. The bath circuit 20 uses a circulation pump P to draw the hot water from the bathtub B into the return pipe 22 from the hot water inlet 21, which is connected to an opening in the bathtub B. The water then passes through the bath secondary heat exchanger 220 and the bath primary heat exchanger 120 in that order, exchanging heat with the combustion exhaust from the bath burner group 320 to reheat the hot water. The hotter water is then discharged into the bathtub B from the hot water outlet 24 via the supply pipe 23.

As shown in Figures 1 and 2, the latent heat recovery water heater 2 is equipped with a drain hose 31 and a neutralizer 32. The upstream side of the drain hose 31 is connected to a drain outlet 251 (see Figure 4) of the secondary heat exchanger 200, which will be described later, and the downstream side is connected to the neutralizer 32. The drain generated by the recovery of latent heat in the secondary heat exchanger 200 is discharged outside the secondary heat exchanger 200 via the drain outlet 251 and sent to the neutralizer 32 through the drain hose 31.

As shown in FIG. 1, the latent heat recovery water heater 2 is equipped with a controller 33 as a control device. The controller 33 is configured, for example, as a known microcomputer, and is configured to acquire signals from various sensors provided in the latent heat recovery water heater 2 and to control various actuators provided in the latent heat recovery water heater 2. For example, when the latent heat recovery water heater 2 detects water flow in the water inlet pipe 12 using a water flow sensor (not shown), it operates the hot water burner group 310 to generate hot water. As another example, when the latent heat recovery water heater 2 detects water flow in the return pipe 22 using a water flow sensor (not shown), it operates the bath burner group 320 to reheat the bath, etc.

[Primary heat exchanger]
Next, the configuration of the primary heat exchanger 100 will be described.
The primary heat exchanger 100 is a sensible heat recovery type heat exchanger. As shown in Figures 3 and 5, the primary heat exchanger 100 is composed of a water heater body 130, a hot water supply primary heat exchanger 110, and a bath primary heat exchanger 120. The water heater body 130, the hot water supply primary heat exchanger 110, and the bath primary heat exchanger 120 can be made of copper, for example, which has excellent thermal conductivity.

As shown in Figure 5, the can body 130 has a generally rectangular shape in plan view that is elongated in the left-right direction, and is formed as a cylindrical shape that is perforated vertically. The interior of the can body 130 is divided into left and right sections by a partition 131. The primary heat exchanger 100 is divided by the partition 131 into a hot water supply primary heat exchanger 110 on the right side of the partition 131 and a bath primary heat exchanger 120 on the left side of the partition 131.

The hot water supply primary heat exchanger 110 has multiple first heat transfer pipes 111 and multiple connecting pipes 112 that connect them.

The first heat transfer tubes 111 are straight tubes with a circular cross section. Multiple first heat transfer tubes 111 (seven in this embodiment) are provided. Each first heat transfer tube 111 is arranged extending forward and backward, with both ends penetrating the front and rear surfaces of the can body 130. Each first heat transfer tube 111 is fixed to the penetration portion of the can body 130 by brazing or the like. The first heat transfer tubes 111 are arranged side by side in the left-right direction in the right-side space separated by the partition section 131. The front or rear ends of two adjacent first heat transfer tubes 111 are connected by a connecting tube 112, so that the multiple first heat transfer tubes 111 are connected in a serpentine manner.

The opening at the rear end of the first heat transfer pipe 111, farthest from the partition 131, is the hot water inlet opening 114 through which water from the hot water secondary heat exchanger 210 flows in. The opening at the front end of the first heat transfer pipe 111, closest to the partition 131, is the hot water outlet opening 115 through which heated water flows out. That is, in the hot water primary heat exchanger 110, water flowing in from the rear right side of the boiler body 130 meanders toward the partition 131 and flows out to the front side. One end of the hot water relay pipe 15 is connected to the hot water inlet opening 114. The other end of the hot water relay pipe 15 is connected to the outlet of the hot water secondary heat exchanger 210, which will be described later. The hot water outlet opening 115 is connected to the hot water outlet pipe 13.

The bath primary heat exchanger 120 is equipped with a plurality of first heat transfer pipes 121 and a plurality of connecting pipes 122 similar to the first heat transfer pipes 111 and connecting pipes 112 of the hot water supply primary heat exchanger 110. The bath primary heat exchanger 120 is equipped with a plurality of first heat transfer pipes 121 (three in this embodiment). The plurality of first heat transfer pipes 121 are arranged extending in the front-to-rear direction, with both ends fixed to the front and rear surfaces of the water heater body 130, respectively. The first heat transfer pipes 121 are arranged side by side in the left-to-right direction in the left-side space separated by the partition section 131. The front or rear ends of two adjacent first heat transfer pipes 121 are connected by the connecting pipe 122, so that the plurality of first heat transfer pipes 121 are connected in a serpentine manner.

The opening at the front end of the first heat transfer pipe 121 closest to the partition 131 is designated as the bath inlet opening 124, through which water from the bath secondary heat exchanger 220 flows in. The opening at the rear end of the first heat transfer pipe 121 farthest from the partition 131 is designated as the bath outlet opening 125, through which heated water flows out. In other words, in the bath primary heat exchanger 120, water flowing in from the front side near the partition 131 meanders in a direction away from the partition 131 and flows out to the rear side. One end of the bath relay pipe 40 is connected to the bath inlet opening 124. The other end of the bath relay pipe 40 is connected to the outlet of the bath secondary heat exchanger 220, which will be described later. A supply pipe 23 is connected to the bath outlet opening 125.

[Secondary heat exchanger]
Next, the configuration of the secondary heat exchanger 200 will be described.
The secondary heat exchanger 200 is a latent heat recovery type heat exchanger. As shown in Fig. 3, the secondary heat exchanger 200 is disposed above the primary heat exchanger 100. The secondary heat exchanger 200 and the primary heat exchanger 100 are connected by an exhaust hood 400 (described later) that introduces the combustion exhaust gas that has passed through the primary heat exchanger 100 into the secondary heat exchanger 200.

As shown in Figures 7 and 8, the secondary heat exchanger 200 is composed of a housing 230, a hot water secondary heat exchanger 210, and a bath secondary heat exchanger 220. The housing 230, hot water secondary heat exchanger 210, and bath secondary heat exchanger 220 can be made of stainless steel, which has excellent corrosion resistance.

A partition 231 is provided inside the housing 230, dividing the internal space of the housing 230 into left and right sections. The hot water supply secondary heat exchanger 210 and the bath secondary heat exchanger 220 are arranged side by side in the left-right direction within the housing 230, via this partition 231. The secondary heat exchanger 200 is divided by the partition 231 into the hot water supply secondary heat exchanger 210 on the right side of the partition 231 and the bath secondary heat exchanger 220 on the left side of the partition 231.

As shown in FIG. 9, the housing 230 comprises a main body 232 having a box-like shape that is long in the left-right direction, a lid 233, and a gasket 234. An upper opening 235 is provided at the upper end of the main body 232. The lid 233 is attached to the main body 232 so as to close the upper opening 235 from above. The gasket 234 is interposed between the main body 232 and the lid 233, and prevents gas from passing between the main body 232 and the lid 233. The main body 232 can be constructed by processing a box 291 (see FIG. 14), which will be described later.

The main body 232 comprises a bottom wall 240, a first wall 241, a second wall 242, a third wall 243, and a fourth wall 244. The first wall 241 is provided to rise upward from the front end of the bottom wall 240. The second wall 242 is provided to rise upward from the rear end of the bottom wall 240. The third wall 243 is provided to rise upward from the right end of the bottom wall 240 and connects the right ends of the first wall 241 and the second wall 242. The fourth wall 244 is provided to rise upward from the left end of the bottom wall 240 and connects the left ends of the first wall 241 and the second wall 242.

The second wall portion 242 is provided with an inlet 245 (an example of an inlet portion) that penetrates in the front-to-rear direction. The inlet 245 is an opening for introducing combustion exhaust gas into the interior of the housing 230. Two inlet ports 245 are provided; the right one introduces combustion exhaust gas into the hot water secondary heat exchanger 210 and the left one introduces combustion exhaust gas into the bath secondary heat exchanger 220. The first wall portion 241 is provided with an outlet 246 (an example of an outlet portion) that penetrates in the front-to-rear direction. The outlet 246 is an opening for discharging combustion exhaust gas from inside the housing 230. In other words, in the secondary heat exchanger 200, the combustion exhaust gas flows through the housing 230 from rear to front. Multiple connecting portions 242A are formed around the inlet 245 in the second wall portion 242. The connecting portions 242A are female-threaded and are used to attach the exhaust hood 400, which will be described later. Multiple connecting portions 241A are formed on the first wall portion 241 around the outlet 246. The connecting portions 241A are female-threaded and are used to attach the exhaust stack 500, which will be described later.

A right-side opening 247 is provided in the third wall 243, penetrating in the left-right direction. The right-side opening 247 is an opening for accommodating multiple second heat transfer tubes 211 (first assembly 281) assembled with the blocking member 260A within the housing 230. Multiple connecting portions 243A are formed around the right-side opening 247 in the third wall 243. The connecting portions 243A are female-threaded and are used to attach the blocking member 260A, which will be described later.

A left-side opening 248 is provided in the fourth wall portion 244, penetrating in the left-right direction. The left-side opening 248 is an opening for accommodating multiple second heat transfer tubes 221 (second assembly 282) assembled with the blocking member 260B within the housing 230. Multiple connecting portions 244A are formed around the left-side opening 248 in the fourth wall portion 244. The connecting portions 244A are female-threaded and are used to attach the blocking member 260B, which will be described later.

The bottom wall portion 240 has a protruding portion 249 and a groove portion 250. The protruding portion 249 is located approximately in the center of the bottom wall portion 240 and protrudes upward relative to the groove portion 250. The groove portion 250 is provided around the protruding portion 249 and forms the outer periphery of the bottom wall portion 240. A drain outlet 251 that penetrates the bottom wall portion 240 in the vertical direction is formed in front of the groove portion 250. The drain outlet 251 is provided at a position corresponding to the partition portion 231. The drain outlet 251 is connected to the drain hose 31 (see Figure 3). Drainage generated by the recovery of latent heat is discharged from the drain outlet 251 via the drain hose 31. The bottom wall portion 240 is tilted downward as it approaches the front.

As shown in FIGS. 6 to 8 and 10, a blocking member 260A, and a first header 265A and a second header 270A attached to the blocking member 260A are provided on the right side of the housing 230.
As shown in FIG. 10 , the blocking member 260A is a plate-shaped member that blocks the right-side opening 247 of the third wall portion 243. The blocking member 260A has a plate-shaped portion 261, a plurality of (seven in this embodiment) first through holes 262, a plurality of (seven in this embodiment) second through holes 263, and a plurality of insertion holes 264. The first through holes 262, the second through holes 263, and the insertion holes 264 are provided to penetrate the plate-shaped portion 261 in the left-right direction. The first through holes 262 and the second through holes 263 are spaced apart in the front-rear direction. The first through holes 262 are located on the front side of the plate-shaped portion 261, and the second through holes 263 are located on the rear side of the plate-shaped portion 261. The insertion holes 264 are holes through which the connecting member 243B (see FIG. 8 ) is inserted and are located near the outer edge of the blocking member 260A. The insertion hole 264 is provided at a position corresponding to the connected portion 243A. The connecting member 243B is inserted into the insertion hole 264 and connected to the connected portion 243A, thereby fixing the blocking member 260A to the third wall portion 243. An annular packing (not shown) is provided between the third wall portion 243 and the blocking member 260A. This prevents gas from passing between the third wall portion 243 and the blocking member 260A.

As shown in Figure 6, the first header 265A is the part that connects the inlet of the hot water supply secondary heat exchanger 210 to the downstream side of the water inlet pipe 12. As shown in Figure 7, the first header 265A has a first header body 266, a first header cover 267 that covers the opening of the first header body 266, and a hot water supply inlet portion 268. The hot water supply inlet portion 268 is connected to the downstream side of the water inlet pipe 12.

The second header 270A connects the outlet of the hot water supply secondary heat exchanger 210 to the inlet side piping of the hot water supply primary heat exchanger 110 (specifically, the upstream end of the hot water supply relay pipe 15). The second header 270A has a second header body 271, a second header cover 272 that covers the opening of the second header body 271, and a hot water supply outlet section 273. The hot water supply outlet section 273 is connected to the upstream side of the hot water supply relay pipe 15.

As shown in FIG. 7 , the hot water supply secondary heat exchanger 210 is configured with multiple second heat transfer tubes 211. The second heat transfer tubes 211 extend in a serpentine pattern along a predetermined planar direction. The multiple second heat transfer tubes 211 are stacked vertically and housed within the housing 230. The second heat transfer tubes 211 have one end and the other end opening in the same direction (to the right). One end (front side) of each second heat transfer tube 211 is inserted into the first through-hole 262 of the blocking member 260A (see FIG. 10 ) and communicates with the hot water supply inlet 268. The other end (rear side) of each second heat transfer tube 211 is inserted into the second through-hole 263 of the blocking member 260A (see FIG. 10 ) and communicates with the hot water supply outlet 273. In the hot water supply secondary heat exchanger 210, water is passed through the second heat transfer tubes 211 in parallel to perform heat exchange.

Similarly to the right side of the housing 230, the left side of the housing 230 is also provided with a blocking member 260B, and a first header 265B and a second header 270B attached to the blocking member 260B.
The closing member 260B is a plate-shaped member that closes the left opening 248 of the fourth wall portion 244. The configuration of the closing member 260B is similar to that of the closing member 260A described above, and therefore a description thereof will be omitted.

The first header 265B connects the inlet of the bath secondary heat exchanger 220 to the downstream side of the return pipe 22. The first header 265B has a first header body 266, a first header cover 267, and a bath inlet section 269. The bath inlet section 269 is connected to the downstream side of the return pipe 22.

The second header 270B connects the outlet of the bath secondary heat exchanger 220 to the inlet side piping of the bath primary heat exchanger 120 (specifically, the upstream end of the bath relay pipe 40). The second header 270B has a second header main body 271, a second header cover 272, and a bath outlet section 274. The bath outlet section 274 is connected to the upstream side of the bath relay pipe 40.

As shown in Figure 7, the bath secondary heat exchanger 220 is configured with multiple second heat transfer tubes 221, similar to the hot water supply secondary heat exchanger 210. The second heat transfer tubes 221 have one end and the other end that open in the same direction (left). One end (front side) of each second heat transfer tube 221 is inserted into the first through hole 262 of the blocking member 260B (see Figure 10) and communicates with the bath inlet 269. The other end (rear side) of each second heat transfer tube 221 is inserted into the second through hole 263 of the blocking member 260B (see Figure 10) and communicates with the bath outlet 274. The bath secondary heat exchanger 220 performs heat exchange by passing water through each second heat transfer tube 221 in parallel.

[Burner device]
The burner device 300 burns combustion gas to generate combustion exhaust. As shown in FIG. 3 , the burner device 300 includes a burner case 330, a hot water supply burner group 310 (see FIG. 2 ), and a bath burner group 320 (see FIG. 2 ). The burner case 330 is provided below the can body 130 of the primary heat exchanger 100. The burner case 330 has a generally rectangular shape in plan view that is elongated in the left-right direction and is open at the top. The burner case 330 has a rectangular cylindrical shape similar to the can body 130. The interior of the burner case 330 is divided into left and right spaces by a partition 331. The partition 331 provided in the burner case 330 is connected to the lower end of the partition 131 of the primary heat exchanger 100. As a result, the left and right spaces within the burner case 330 are partitioned in a manner that they are connected to the left and right spaces within the can body 130 of the primary heat exchanger 100, respectively.

As shown in FIG. 2, the hot water supply burner group 310 is arranged on the right side of the burner device 300 (the space on the right side separated by the partition 331 in the burner case 330), and the bath burner group 320 is arranged on the left side of the burner device 300 (the space on the left side separated by the partition 331 in the burner case 330). As a result, the hot water supply burner group 310 is arranged below the hot water supply primary heat exchanger 110 and supplies combustion exhaust to the hot water supply circuit 10. The bath burner group 320 is arranged below the bath primary heat exchanger 120 and supplies combustion exhaust to the bath circuit 20.

An ignition plug 311 and a flame rod 312 are arranged in the space above the hot water supply burner group 310. Similarly, an ignition plug 321 and a flame rod 322 are arranged above the bath burner group 320. Wiring (not shown) is connected to the rear ends of the ignition plugs 311, 321 and the flame rods 312, 322, respectively.

[Exhaust hood]
As shown in Figure 3, the exhaust hood 400 is disposed between the primary heat exchanger 100 and the secondary heat exchanger 200. The exhaust hood 400 connects the upper opening of the can body 130 of the primary heat exchanger 100 with the inlet 245 at the rear of the housing 230 of the secondary heat exchanger 200, forming a passage for the combustion exhaust. The interior of the exhaust hood 400 is divided into left and right sections by a partition 401. The partition 401 connects the upper end of the partition 131 of the primary heat exchanger 100 with the rear end of the partition 231 of the secondary heat exchanger 200, forming spaces corresponding to the hot water supply circuit 10 and the bath circuit 20, respectively.

As shown in Figure 6, the exhaust hood 400 is composed of an exhaust hood main body 410 and an exhaust hood rear portion 420.

The exhaust hood body 410 is formed to bulge upward in the front-to-rear direction, gradually increasing in height from the front end toward the rear. The rear end of the exhaust hood body 410 opens to the rear, and a plate-shaped mounting portion 411 is provided around the periphery of this opening. The exhaust hood rear portion 420 is formed in the shape of a square dish that bulges rearward. The lower portion of the exhaust hood rear portion 420 is attached to the mounting portion 411 of the exhaust hood body 410 so as to close the rear opening of the exhaust hood body 410.

The exhaust hood rear portion 420 has an insertion hole 421 at a position corresponding to the connecting portion 242A of the second wall portion 242. The connecting member 242B is inserted into the insertion hole 421 and connected to the connecting portion 242A, thereby fixing the exhaust hood rear portion 420 to the second wall portion 242. As shown in FIG. 4, an annular gasket 422 is provided between the second wall portion 242 and the exhaust hood rear portion 420. The gasket 422 prevents gas from passing between the second wall portion 242 and the exhaust hood rear portion 420.

[Exhaust stack]
As shown in FIG. 1 , the exhaust pipe 500 is fixed to the front of the housing 230 and has a generally rectangular tubular shape that protrudes generally horizontally forward. The exhaust pipe 500 protrudes to the front of the outer box (not shown) through a through-hole provided in the front panel of the outer box that covers the outside of the latent heat recovery water heater 2, and functions to discharge the combustion exhaust gas after latent heat is recovered in the secondary heat exchanger 200 to the outside of the latent heat recovery water heater 2. Also, as shown in FIG. 4 , an exhaust outlet 501 is provided at the front of the exhaust pipe 500. The exhaust outlet 501 is formed in a generally elliptical shape that is elongated in the left-right direction when viewed from the front. A flange portion 502 that protrudes outward in a flange-like shape is provided at the rear end of the exhaust pipe 500. The flange portion 502 is formed in a generally rectangular ring shape that is elongated in the left-right direction when viewed from the front.

The flange portion 502 has an insertion hole 503 at a position corresponding to the connected portion 241A of the first wall portion 241. The connecting member 241B is inserted into the insertion hole 503 and connected to the connected portion 241A, thereby fixing the flange portion 502 to the first wall portion 241. This fixes the exhaust tube 500 to the front side of the front portion of the housing 230, and the exhaust outlet 501 of the exhaust tube 500 is positioned in front of the outlet 246 of the housing 230. Therefore, the exhaust tube 500 can discharge combustion exhaust gas received through the outlet 246 of the housing 230 to the outside through the exhaust outlet 501. An annular gasket 504 is provided between the first wall portion 241 and the flange portion 502. The gasket 504 prevents gas from passing between the first wall portion 241 and the flange portion 502.

[Method of manufacturing latent heat recovery water heater]
The above is the configuration of the latent heat recovery water heater 2 of this embodiment, and next, a description will be given of a method for manufacturing the latent heat recovery water heater 2. The method for manufacturing the latent heat recovery water heater 2 of this embodiment includes the process of manufacturing the secondary heat exchanger 200, which will be described below. The processes for manufacturing the components other than the secondary heat exchanger 200 (the primary heat exchanger 100, the burner device 300, the exhaust hood 400, the exhaust stack 500, etc.) and the process of assembling these components with the secondary heat exchanger 200 are not particularly limited.

[Manufacturing method of secondary heat exchanger]
The manufacturing method of the secondary heat exchanger 200 includes the steps of forming a box body 291, constructing a housing 230 using the box body 291, and inserting the second heat transfer pipes 211, 221 into the housing 230.
As shown in Figure 14, the box body 291 is open at the top and has a box shape that is long in the left-right direction. An inlet 245 is provided in the rear wall (second wall 242) of the box body 291, and an outlet 246 is provided in the front wall (first wall 241) of the box body 291. Connecting portions 241A, 242A are formed in the first wall 241 and the second wall 242. The box body 291 is formed by drawing a metal plate or the like. The box body 291 is also adapted to be used as an exhaust casing 290 of the sensible heat recovery water heater 3 described below. The lid 233 that covers the box body 291 from above is also formed by drawing a metal plate or the like.

A right-side opening 247 and a left-side opening 248 are provided in the right and left walls of the box body 291, forming the main body 232, which is part of the housing 230 (see Figure 9). The right-side opening 247 and the left-side opening 248 are formed, for example, by punching or cutting. Connectable portions 243A and 244A are formed around the right-side opening 247 and the left-side opening 248. A drain outlet 251 is provided in the bottom wall of the box body 291.

Plate-shaped blocking members 260A, 260B are formed by processing a metal plate. Blocking members 260A, 260B have a plurality of first through holes 262, a plurality of second through holes 263, and a plurality of insertion holes 264 formed therein. The first through holes 262, second through holes 263, and insertion holes 264 are formed by, for example, punching or cutting.

The partition section 231 that separates the interior of the housing 230 is formed by processing a metal plate. The partition section 231 is formed, for example, by bending. The partition section 231 is positioned inside the main body section 232.

As shown in FIG. 10 , a plurality of second heat transfer tubes 211 are fixed to the blocking member 260A. In this embodiment, the front end of each of the second heat transfer tubes 211 is inserted into the first through-hole 262, and the rear end of each of the second heat transfer tubes 211 is inserted into the second through-hole 263. Then, each of the second heat transfer tubes 211 is fixed to the blocking member 260A by, for example, welding or brazing. This results in the production of a first assembly 281 in which the plurality of second heat transfer tubes 211 and the blocking member 260A are integrally assembled.

Furthermore, a first header 265A is fixed by welding or brazing to the end of the second heat transfer tube 211 inserted into the first through hole 262 of the blocking member 260A (see Figures 7 and 8). A second header 270A is fixed by welding or brazing to the end of the second heat transfer tube 211 inserted into the second through hole 263 of the blocking member 260A (see Figures 7 and 8).

The blocking member 260B and the multiple second heat transfer tubes 221 are assembled in the same manner as above to produce the second assembly 282. The first header 265B and the second header 270B are also fixed to the second assembly 282 in the same manner.

The first assembly 281, which is an integral assembly of multiple second heat transfer tubes 211 and a blocking member 260A, is inserted into the main body 232 (housing 230) through the right-hand opening 247. The multiple second heat transfer tubes 211 are disposed within the main body 232, and the right-hand opening 247 is blocked by the blocking member 260A. The blocking member 260A is fixed to the third wall 243 by connecting the connecting member 243B, which is inserted into the insertion hole 264 of the blocking member 260A, to the connected portion 243A.

The second assembly 282, in which multiple second heat transfer tubes 221 and closing member 260B are integrally assembled, is inserted into the main body 232 (housing 230) through the left opening 248. The multiple second heat transfer tubes 221 are disposed within the main body 232, and the left opening 248 is closed by the closing member 260B. A connecting member (not shown) inserted into the insertion hole 264 of the closing member 260B is connected to the connected portion 244A, thereby fixing the closing member 260B to the fourth wall 244.

A process is then carried out in which the upper opening 235 of the main body 232, to which the first assembly 281 and the second assembly 282 are attached, is closed with the lid 233. By carrying out these processes, the secondary heat exchanger 200 is completed (see Figure 8).

[Assembly of secondary heat exchanger with exhaust hood and exhaust stack]
Secondary heat exchanger 200 is connected to exhaust hood 400 at its rear surface and to exhaust stack 500 at its front surface (see FIG. 4 ). Specifically, connecting member 242B inserted into insertion hole 421 of exhaust hood 400 is fixed to connected portion 242A of second wall portion 242 of housing 230 via packing 422. Also, connecting member 241B inserted into insertion hole 503 of exhaust stack 500 is fixed to connected portion 241A of first wall portion 241 of housing 230 via packing 504.

[Sensible heat recovery water heater]
Next, a sensible heat recovery water heater 3 according to an embodiment will be described with reference to Figures 11 to 14. The sensible heat recovery water heater 3 includes a primary heat exchanger 100, a burner device 300, an exhaust hood 400, and an exhaust pipe 500, which are the same as those of the latent heat recovery water heater 2. In the following description of the configuration of the sensible heat recovery water heater 3, the same components as those of the latent heat recovery water heater 2 will not be described. The sensible heat recovery water heater 3 includes an exhaust casing 290 instead of the secondary heat exchanger 200.

As shown in FIG. 11, the sensible heat recovery water heater 3 does not have a secondary heat exchanger 200, so water introduced into the sensible heat recovery water heater 3 is introduced directly into the primary heat exchanger 100 without passing through the secondary heat exchanger 200. That is, the water inlet pipe 12 is connected to the hot water inlet opening 114 (see FIG. 5), and the return pipe 22 is connected to the bath inlet opening 124 (see FIG. 5). In detail, as shown in FIG. 12, the hot water circuit 10 of the sensible heat recovery water heater 3 flows water from the water inlet 11 into the water inlet pipe 12, passes the water through the hot water primary heat exchanger 110, and heats the water by exchanging heat with the combustion exhaust gas from the hot water burner group 310, and then flows through the hot water outlet pipe 13 and discharges hot water from the hot water outlet 14. In addition, the bath circuit 20 of the sensible heat recovery water heater 3 uses a circulation pump P to draw hot water from the bathtub B into the return pipe 22 from the hot water inlet 21, which is connected to an opening in the bathtub B. The water is then passed through the bath primary heat exchanger 120, where it is reheated by heat exchange with the combustion exhaust from the bath burner group 320. The hot water is then discharged into the bathtub B from the hot water outlet 24 via the supply pipe 23.

Sensible heat recovery water heater 3 does not recover latent heat from the combustion exhaust, so no drain is generated. Therefore, sensible heat recovery water heater 3 does not have the drain hose 31, drain outlet 251, neutralizer 32, etc. that latent heat recovery water heater 2 has (see Figure 2).

[Exhaust casing]
14 , exhaust casing 290 is box-shaped and includes box body 291, packing 234, and lid 233. That is, exhaust casing 290 of sensible heat recovery water heater 3 is made up of the same materials as those used to form housing 230 of secondary heat exchanger 200 of latent heat recovery water heater 2. Therefore, it is not necessary to provide a separate mold for manufacturing exhaust casing 290.

As shown in Figure 13, the exhaust casing 290 is disposed at the position of the housing 230 of the secondary heat exchanger 200 in the latent heat recovery water heater 2 (see Figure 4). That is, the exhaust casing 290 is attached to the exhaust hood 400 and exhaust stack 500, similar to the housing 230 of the secondary heat exchanger 200. The exhaust casing 290 is configured to take in combustion exhaust air from the exhaust hood 400 through the inlet 245 and discharge the combustion exhaust air from the outlet 246 to the exhaust stack 500. Similar to the housing 230, a partition 231 is provided inside the exhaust casing 290.

[Effects of the embodiment]
As described above, in this embodiment, exhaust casing 290 of sensible heat recovery water heater 3 and housing 230 of secondary heat exchanger 200 of latent heat recovery water heater 2 are configured from a common box body 291. In other words, the manufacturing method for water heater 1 of this embodiment includes a step of forming box body 291 and a step of using this box body 291 to configure housing 230 of secondary heat exchanger 200 of latent heat recovery water heater 2 or exhaust casing 290 of sensible heat recovery water heater 3. This eliminates the need to separately manufacture a mold for exhaust casing 290 of sensible heat recovery water heater 3, making it possible to reduce manufacturing costs even when the manufacturing lot size of sensible heat recovery water heater 3 is small.

Furthermore, when the exhaust casing 290 is designed individually, it is necessary to verify the fitment of the exhaust casing 290 to the exhaust hood 400 and the exhaust stack 500. However, in this embodiment, the exhaust casing 290 and the housing 230 of the secondary heat exchanger 200 are constructed from the same box body 291, so the process of verifying the fitment of the exhaust casing 290 or the housing 230 of the secondary heat exchanger 200 to the exhaust hood 400 and the exhaust stack 500 can be minimized.
Furthermore, since the common exhaust tube 500 is fixed in the same manner to each of the exhaust casing 290 and the housing 230, which are made up of a common box body 291, the work required to verify the fitment of the exhaust tube 500 to the through hole in the front panel can also be minimized.

When assembling the exhaust casing 290 or the housing 230 of the secondary heat exchanger 200 with the exhaust hood 400 and exhaust stack 500, gaskets 422, 504 are placed between the edges of the inlet 245 and outlet 246 of the exhaust casing 290 or the housing 230 of the secondary heat exchanger 200 and the exhaust hood 400 and exhaust stack 500. In this embodiment, the exhaust casing 290 and the housing 230 of the secondary heat exchanger 200 are composed of a common box 291 having the inlet 245 and outlet 246, and therefore the gaskets 422, 504 can also be shared between the exhaust casing 290 and the housing 230 of the secondary heat exchanger 200.

<Other Embodiments>
The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or following embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or following embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiment may be modified as follows.

In the embodiment, a water heater 1 is illustrated in which the secondary heat exchanger 200 is divided into a hot water supply secondary heat exchanger 210 and a bath secondary heat exchanger 220, but the water heater according to the present disclosure may also be a water heater in which the secondary heat exchanger is composed solely of a hot water supply secondary heat exchanger.

1...water heater, 2...latent heat recovery water heater, 3...sensible heat recovery water heater 10...water supply circuit, 11...water inlet, 12...water inlet pipe, 13...hot water outlet pipe, 14...hot water outlet, 15...hot water relay pipe, 20...bath circuit, 21...hot water inlet, 22...return pipe, 23...supply pipe, 24...hot water outlet, 31...drain hose, 32...neutralizer, 33...controller, 40...bath relay pipe 100...primary heat exchanger, 110...hot water primary heat exchanger, 111...first heat transfer pipe, 112...connecting pipe, 114...hot water inlet opening, 115...hot water outlet opening, 120...bath primary heat exchanger, 121...first heat transfer pipe, 122...connecting pipe, 124...bath Inlet opening, 125... Outlet opening for bath, 130... Can body, 131... Partition part 200... Secondary heat exchanger, 210... Secondary heat exchanger for hot water supply, 211... Second Heat exchanger tube, 220... Secondary heat exchanger for bath, 221... Second heat exchanger tube 230... Housing, 231... Partition section, 232... Main body section, 233... Lid section, 234... Pad 235... Upper opening, 240... Bottom wall, 241... First wall, 241A... Connected part, 241B... Connecting member, 242... Second wall, 242A... Connected part, 242B... Connecting member, 243... Third wall, 243A... Connected part, 243B... Connecting member, 244... Fourth wall, 244A... Connected part , 245...inlet (an example of an inlet portion), 246...outlet (an example of an outlet portion), 247...right opening, 248...left opening, 249...projection portion, 250...groove portion, 251...drain discharge port, 260A, 260B...blocking member, 261...plate-shaped portion, 262...first through hole, 263...second through hole, 264...insertion hole, 265A, 265B...first header, 266...first header main body, 267...first header cover body, 268...hot water supply inlet portion, 269...bath inlet portion, 270A, 270B...second header, 271...second header main body, 272...second header cover body, 273...hot water supply outlet portion, 274...bath outlet Nose portion, 281...first assembly, 282...second assembly 290...exhaust casing, 291...box body 300...burner device (an example of a combustion device), 310...hot water supply burner group, 311, 321...ignition plug, 312, 322...frame rod, 320...bath burner group, 330...burner case, 331...partition portion 400...exhaust hood, 401...partition portion, 410...exhaust hood body, 411...mounting portion, 420...exhaust hood rear portion, 421...insertion hole, 422...packing 500...exhaust pipe, 501...exhaust outlet, 502...flange portion, 503...insertion hole, 504...packing B...bathtub, P...circulation pump

Claims (1)

A method for manufacturing a water heater including a combustion device and a primary heat exchanger fixed to an upper portion of the combustion device and recovering sensible heat from combustion exhaust gas generated in the combustion device,
The water heater includes a latent heat recovery water heater further including a secondary heat exchanger that recovers latent heat from the combustion exhaust gas discharged from the primary heat exchanger, and a sensible heat recovery water heater further including an exhaust casing that discharges the combustion exhaust gas discharged from the primary heat exchanger to the outside,
The method for manufacturing the water heater includes a step of forming a box having an inlet portion at a rear side for receiving combustion exhaust gas and an outlet portion at a front side for discharging the combustion exhaust gas,
When the water heater is a latent heat recovery type water heater, the method further includes the steps of: forming openings on both sides of the box body to form a housing for the secondary heat exchanger; and inserting a plurality of heat transfer tubes into the housing through the openings.
When the water heater is a sensible heat recovery water heater, the method for manufacturing a water heater further includes a step of constructing the exhaust casing using the box body.