PIPING-MEMBER MANUFACTURING METHOD

Abstract

 An object of the present invention is to manufacture a piping member more quickly and at a lower cost. A method of manufacturing a cylindrical piping member, wherein one end becomes a welding part that is welded to another member, comprises a process group (S1-S6) and a process group (S8-S10). In the process group (S1-S6), a plate shaped raw material is molded by press molding into a shape that includes a cylindrical, thick walled first part (51f) and a thin walled second part (52f), which is contiguous with and intersects the first part (51f) and becomes a welded part. In the process group (S8-S10), a second part (52f, 52g) is molded by press molding into a cylindrical shape and a step (56h) is created at the boundary between a first part (51h) and a second part (52h).

Description

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing a cylindrical piping member, wherein one end of the cylindrical piping member is a welding part that is welded to another member.

BACKGROUND ART

[0002] In recent years, hot water supply systems have appeared (e.g., refer to Patent Document 1) wherein a heat pump collects heat from the atmosphere, hot water heated by that heat is stored in a tank, and hot water is supplied from that tank. Numerous pipings, such as a hot water supply piping, a water supply piping, and a piping connected to a heat pump, wherethrough water, hot water, and the like pass, are connected to the tank. To connect these pipings, piping members called pipe seats are connected to the tank.

[0003] As shown in FIG 10, a cylindrical part 31b, which is folded toward the inner part of the tank, and a hole, which is surrounded by the cylindrical part 31b, are formed in a welding flat part 31a of a pipe seat of the tank. A tip thin walled cylindrical part 262 of a piping member 260 (i.e., a pipe seat) is fitted into the hole such that the tip thin walled cylindrical part 262 contacts the inner circumferential surface of the cylindrical part 31b; furthermore, the entire circumferences of an end part of the cylindrical part 31b of the tank and of an end part of the tip thin walled cylindrical part 262 of the piping member 260 are welded together. Moreover, a flange part 263 is formed in the piping member 260 at a portion on the side opposite the tip thin walled cylindrical part 262. The flange part 263 is coupled to a separate flange part 181 of a piping 180, wherethrough water, hot water, and the like passes, by a quick fastener 190 (i.e., a piping joint member that utilizes spring characteristics). A tip cylindrical part 182, which projects from an inner circumferential part of the flange part 181 of the piping 180 in the axial directions, is inserted into an internal space of the piping member 260 and makes close contact with an inner circumferential surface 261a of the piping member 260 via a sealing member 170. Thereby, the water, hot water, and the like that flows from the tank via the piping member 260 to the piping 180 (or from the piping 180 to the tank) does not leak out.

Patent Document 1

[0004] Japanese Unexamined Patent Application Publication No. 2007-285655

DISCLOSURE OF THE INVENTION

<Technical Problem>

[0005] The piping member 260 discussed above is often made of a ferritic stainless steel equivalent to SUS 444, which has excellent resistance to stress, corrosion, and cracking; as a result, the thickness of the tip thin walled cylindrical part 262 must be less than that of the other portion and the outer diameter size of the tip thin walled cylindrical part 262 must be highly accurate. Consequently, the piping member 260 is conventionally manufactured by machining (e.g., cutting) a thick walled, cylindrical raw material.

[0006] However, manufacturing the piping member 260 by machining makes the manufacturing time long and the manufacturing cost high, which are problems.

[0007] An object of the present invention is to manufacture a piping member more quickly and at a lower cost.

<Solution to Problem>

[0008] A method of manufacturing a piping member according to a first aspect of the present invention is a method of manufacturing a cylindrical piping member wherein one end becomes a welding part that is welded to another member. In the manufacturing method, press molding is used to mold a plate shaped raw material into a shape that includes a first part and a second part. At that time, molding is performed such that a step is created at the boundary between the first part and the second part. The first part is a thick walled, cylindrical portion. The second part is a thin walled, cylindrical portion, which becomes the welding part, and is contiguous with the first part.

[0009] In the first aspect of the present invention, the thin walled, cylindrical second part, which is becomes a welding part, is not molded by machining as in the conventional art; instead, the piping member is manufactured by press molding such that the step is created at the boundary between the first part and the second part. Consequently, it is possible to manufacture the piping member faster and more inexpensively than the piping member manufactured by conventional machining.

[0010] A method of manufacturing a piping member according to a second aspect of the present invention is a method of manufacturing a cylindrical piping member, wherein one end becomes a welding part welded to another member, that comprises a first step and a second step. The first step uses press molding to mold a plate shaped raw material into a shape that includes the first part and the second part. The first part is a thick walled, cylindrical portion. The second part is a thin walled portion, which becomes the welding part, that is contiguous with and intersects the first part. The second step, which is performed after the first step, uses press molding to mold the second part into a cylindrical shape and creates a step at the boundary between the first part and the second part.

[0011] In the second aspect of the present invention, the plate shaped raw material is molded, in the first step, by press molding the cylindrical, thick walled first part and the contiguous, thin walled second part such that it intersects the first part; subsequently, in the second step, the second part is also molded into a cylindrical shape and the step is created at the boundary between the first part and the second part.

[0012] Furthermore, because the first part and the second part have already been created with different thicknesses in the first step, it is possible to easily produce the step in the second step.

[0013] In addition, because the second part in the first step intersects the cylindrical first part, it is easy to reduce the thickness of the second part even using press molding by moving the mold along the axial directions of the cylindrical first part.

[0014] Thus, in the second aspect of the present invention, the shape prior to performing the second step (i.e., the shape molded by the first step) is such that the second part can easily be made thin walled; in addition, in the second step, the second part is molded into a cylindrical shape and the step is created at the boundary between the first part and the second part; thereby, the piping member is manufactured; consequently, the piping member can be manufactured by press molding in a short time and with good yield. Furthermore, because the piping member can be manufactured by press molding, the manufacturing time is shorter than that of the piping member manufactured by conventional machining.

[0015] A method of manufacturing a piping member according to a third aspect of the present invention is the manufacturing method according to the second aspect of the present invention wherein the first step comprises the first press molding process and the second press molding process. In the first press molding process, the plate shaped raw material is molded such that the second part takes on a discoidal shape that closes one end of the cylindrical first part. In the second press molding process, the thickness of the discoidal second part is reduced.

[0016] In the third aspect of the present invention, the first press molding process molds the plate shaped raw material into a drinking glass shape that comprises the cylindrical first part and the discoidal second part, which closes one end of the first part, and the subsequent second press molding process reduces the thickness of the second part. Consequently, in the second press molding process, the mold contacts both surfaces of the discoidal second part and thereby can apply force to the second part in the plate thickness directions. Consequently, the second part can be made thin walled more easily and faster than in the method wherein the second part is first molded from its initial shape into a cylindrical shape and then made thin walled.

[0017] A method of manufacturing a piping member according to a fourth aspect of the present invention is the manufacturing method according to the third aspect of the present invention wherein the second step comprises a hole-making process and a third press molding process. The hole-making process removes a center portion of the discoidal second part. The third press molding process molds the annular second part that has undergone the hole-making process into a cylindrical shape and creates the step at the boundary between the first part and the second part.

[0018] In the fourth aspect of the present invention, first, the center portion of the second part is removed and, subsequently, the second part, which is now annular, is molded into a cylindrical shape; consequently, the thin walled, cylindrical welding part can be formed more quickly and more accurately than in a method wherein the unnecessary portion is cut out after the discoidal second part is molded into a cylindrical shape.

[0019] A method of manufacturing a piping member according to a fifth aspect of the present invention is the manufacturing method according to the fourth aspect of the present invention with the addition of a third step. The third step, which is performed after the third press molding process of the second step, applies force that compresses in the axial directions the second part, which has become cylindrical, and molds the second part into the final shape of the welding part.

[0020] In the fifth aspect of the present invention, the third step is additionally performed to apply compression force in the axial directions to the cylindrical second part, thereby making it possible to finish the second part into the final shape of the welded part with good accuracy.

<Advantageous Effects of Invention>

[0021] According to the first and second aspects of the present invention, it is possible to manufacture the piping member faster and more inexpensively than a piping member manufactured by conventional machining.

[0022] According to the third aspect of the present invention, the second part can be made thin walled easily and quickly.

[0023] According to the fourth aspect of the present invention, the thin walled, cylindrical welding part can be formed quickly and with good accuracy.

[0024] According to the fifth aspect of the present invention, the second part can be finished into the final shape of the welded part with good accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 

FIG. 1 is an external oblique view of a storage type water heater according to the present embodiment.

FIG. 2 is a schematic block diagram of the storage type water heater.

FIG. 3 is a circuit diagram of pipings that connect a hot water storage apparatus of the storage type water heater with a hot water supply port and a bathtub.

FIG. 4A is a top view of a hot water storage tank.

FIG. 4B is a cross sectional view taken along the IV-IV arrows in FIG 4A.

FIG. 5 is a longitudinal cross sectional view of a piping member.

FIG. 6A is a front view of a quick fastener.

FIG. 6B is a cross sectional view taken along the VI-VI arrows in FIG. 6A.

FIG. 7 is a plan view of a plate shaped raw material before and after a first drawing process.

FIG. 8 is a cross sectional view (corresponding to a cross sectional view taken along the VIII-VIII arrows in FIG 7) of the plate shaped raw material before and after first through fourth drawing processes.

FIG. 9 is a cross sectional view of the plate shaped raw material before and after fifth and sixth drawing processes, a hole-making process, the first and second drawing processes, and an outer diameter removing process.

FIG. 10 is a longitudinal cross sectional view of a conventional piping member.

EXPLANATION OF THE REFERENCE NUMERALS

[0026] 

31

Hot water storage tank (other member)

50

Plate shaped raw material

51a ... 51j

First parts

52a ... 52j

Second parts

56h

Step

60

Piping member

61

Cylindrical part

62

Tip thin walled cylindrical part (welding part)

S1

First drawing process (first step; first press molding process)

S2

Second drawing process (first step; second press molding process)

S3

Third drawing process (first step; second press molding process)

S4

Fourth drawing process (first step; second press molding process)

S5

Fifth drawing process (first step; second press molding process)

S6

Sixth drawing process (first step; second press molding process)

S7

Hole-making process (second step)

S8

First finishing drawing process (second step; third press molding process)

S9

Second finishing drawing process (third step)

BEST MODE FOR CARRYING OUT THE INVENTION

<Configuration of a Storage Type Water Heater>

[0027] FIG. 1 is an external oblique view of a storage type water heater that uses piping members (i.e., pipe seats) according to the present embodiment, and FIG 2 is a block diagram of the storage type water heater. In FIG 1, a storage type water heater 1 comprises a heat pump unit 2 and a hot water storage apparatus 3, a vapor compression type refrigeration circuit is housed inside a casing of the heat pump unit 2, and a hot water storage tank 31 is housed inside a casing of the hot water storage apparatus 3.

[0028] In FIG 2, the heat pump unit 2 comprises a vapor compression type refrigeration circuit 20, wherein a muffler 21a, a compressor 21, a refrigerant pipe 22a inside a water heat exchanger 22, an expansion valve 23 that serves as a pressure reducing means, and an air heat exchanger 24 are connected in a ring by a refrigerant piping 25.

[0029] In addition, to exchange heat between high pressure, high temperature refrigerant that comes out of the water heat exchanger 22 and low pressure, low temperature refrigerant that comes out of the air heat exchanger 24, a liquid-gas heat exchanger 26 is disposed in the refrigeration circuit 20. Specifically, heat is exchanged between a refrigerant passageway that couples the water heat exchanger 22 and the expansion valve 23 and a refrigerant passageway that couples the air heat exchanger 24 and the compressor 21.

[0030] The hot water storage apparatus 3 comprises a water circulation circuit 30 wherein the hot water storage tank 31, a water pipe 22b in the water heat exchanger 22, and a water circulation pump 32 are connected in a ring by a water circulation piping 35. A control apparatus 4 operates and controls the heat pump unit 2 and the hot water storage apparatus 3.

<Configuration of a Hot Water Storage Apparatus that Comprises a Hot Water Storage Tank>

[0031] FIG 3 is a circuit diagram of a piping that connects the hot water storage apparatus 3 of the storage type water heater 1 and loads. Furthermore, the loads spoken of herein refer to a hot water supply and a bath. A hot water supply pipe 71 connects a head part of the hot water storage tank 31 and a hot water supply mixing valve 73. The hot water supply pipe 71 comprises hot water supply branch pipes 71a, 71b, wherein the hot water supply branch pipe 71a connects the hot water supply pipe 71 and a hot water filling mixing valve 74 and the hot water supply branch pipe 71b connects the hot water supply pipe 71 and a relief valve 75.

[0032] A water supply pipe 72 connects a water supply source and the hot water supply mixing valve 73. The water supply pipe 72 comprises water supply branch pipes 72a, 72b. The water supply branch pipe 72a connects the water supply pipe 72 and the hot water filling mixing valve 74, and the water supply branch pipe 72b connects the water supply pipe 72 and a bottom part of the hot water storage tank 31. Furthermore, a pressure reducing check valve 76 is connected upstream of the water supply branch pipe 72a and the water supply branch pipe 72b. In addition, a water temperature sensor 41 is provided at a position spaced apart from the hot water storage tank 31 of the water supply branch pipe 72b. The water temperature sensor 41 is adapted such that it is not affected by the temperature of the hot water storage tank 31.

[0033] A hot water circulation piping 77 connects the head part and the bottom part of the hot water storage tank 31, and a reheating heat exchanger 78 and a circulation pump 79 are connected midway therebetween.

[0034] A second hot water supply pipe 81 connects the hot water supply mixing valve 73 and a hot water supply port 82, and a hot water supply amount sensor 42a is disposed midway therebetween. A third hot water supply pipe 83 connects the hot water filling mixing valve 74 and a bath water circulation piping 91, and a compound water valve 84 is disposed midway therebetween. The compound water valve 84 comprises a hot water filling solenoid valve 84a, a water discharge valve 84b, and a hot water filling amount sensor 42b.

[0035] The bath water circulation piping 91 exits from and returns to a bathtub 92, and a bath water circulating pump 93 is connected midway therebetween. Furthermore, in the reheating heat exchanger 78, heat is exchanged between the bath water circulation piping 91 and the hot water circulation piping 77.

[0036] Temperature sensors 44a-44e, which serve as means of detecting the amount of residual hot water, are provided to a sidewall of the hot water storage tank 31 at fixed spacings between the head part and the bottom part. The temperature sensors 44a-44e detect the temperature of the hot water at each height position of the hot water storage tank 31, and thereby the temperature of the hot water and the amount of residual hot water are calculated. Furthermore, the head part, the bottom part, and the entire circumference of the sidewall of the hot water storage tank 31 are covered with a heat insulating material.

<Configuration of Piping Members Welded and Fixed to the Hot Water Storage Tank>

[0037] As discussed above, numerous pipings, such as the hot water supply pipe 71, the water supply pipe 72, the hot water circulation piping 77, and the water circulation piping 35, wherethrough water, hot water, and the like pass, are connected to the hot water storage tank 31. To connect each of these pipings (hereinafter, called pipings 180) with the hot water storage tank 31, piping members 60, which are called pipe seats, are used. As shown in FIG. 5, each of the piping members 60 principally comprises: a cylindrical part 61; a tip thin walled cylindrical part 62, whose outer diameter is smaller and whose walls are thinner than those of the cylindrical part 61; and a flange part 63, which is disposed on the side of the cylindrical part 61 opposite the tip thin walled cylindrical part 62. The flange part 63 is an annular portion that extends outward in the radial directions from one end of the cylindrical part 61.

[0038] As shown in FIG. 4A, FIG 4B, and FIG 5, the piping member 60 is inserted into a hole formed by the flat part 31a of the hot water storage tank 31 and is welded to the hot water storage tank 31. Specifically, a hole and a cylindrical part 31b (refer to FIG 5), which is folded from the circumference of the hole toward the inner part of the hot water storage tank 31, are formed in the flat part 31a of the hot water storage tank 31. The tip thin walled cylindrical part 62 of the piping member 60 is inserted into the hole of the hot water storage tank 31. Furthermore, the entire circumferences of an end part of the tip thin walled cylindrical part 62 of the piping member 60 and a tip part of the cylindrical part 31b of the hot water storage tank 31 are welded together. Thereby, the piping member 60 is fixed to the hot water storage tank 31.

[0039] To, for example, insert and weld around the entire circumference of the tip thin walled cylindrical part 62 of the piping member 60, the tip thin walled cylindrical part 62 must be manufactured with particularly good accuracy with respect to its external size; furthermore, a step 66, which is pressed to the flat part 31a around the hole of the hot water storage tank 31, must be formed at the boundary between an outer circumferential surface of the tip thin walled cylindrical part 62 of the piping member 60 and an outer circumferential surface of the cylindrical part 61.

[0040] Moreover, as shown in FIG 5, the flange part 63 of the piping member 60 contacts a flange part 181 of the piping 180 connected to the hot water storage tank 31 and is coupled to the flange part 63 by a quick fastener 190 such that it cannot be separated therefrom. The quick fastener 190 is a piping joint member that is made of metal and has a shape as shown in FIG 6A and FIG 6B; furthermore, the quick fastener 190 utilizes its spring characteristic to grasp cylindrical trunk parts of both members to be connected by grasping parts 191, 192 positioned on the left and right of a long hole 190a. Specifically, in a state in which they contact one another, the flange part 63 of the piping member 60 and the flange part 181 of the piping 180 are fitted into the long hole 190a of the quick fastener 190; furthermore, the grasping part 191, which grasps the cylindrical part 61 of the piping member 60, and the grasping part 192, which grasps the cylindrical trunk part of the piping 180, prevent the piping member 60 and the piping 180 from separating in the axial directions (refer to FIG 5).

[0041] Because the quick fastener 190 becomes the piping joint, it is necessary to ensure that a thickness L3 (i.e., a length in the axial directions) of the flange part 63 of the piping member 60 is of a prescribed size; in addition, it is necessary to ensure that the surface that the grasping part 191 of the quick fastener 190 catches on is a prescribed size in the radial directions.

[0042] To meet the requirements of the piping member 60 described above and to shorten the excessive manufacturing time required in the conventional art, wherein the piping member is manufactured from a thick walled raw material by a cutting process and the like, the piping member 60 herein is manufactured by a plurality of press molding processes, and attention is given to how to shape the piping member 60.

[0043] The piping member 60, which is integrally formed from a plate shaped raw material 50 (refer to FIG. 7 and FIG 8) by a plurality of press molding processes, has a cross sectional shape (refer to FIG 5) wherein the flange part 63 of the piping member 60 includes a step 67. Furthermore, the thickness L3 of the flange part 63 is greater than a thickness t1 of the plate shaped raw material 50. Here, the thickness t1 = 1.5 mm and the thickness L3 = 2.8 mm. In addition, the step 67 of the flange part 63 includes a bent part, which is bent by approximately 90°; furthermore, the step 67 is formed such that a size r4 (refer to FIG 5), which is a radius of curvature R of a surface of the bent part, is less than 0.5 mm.

[0044] In addition, the piping member 60 is press molded such that the step 66 is formed at the boundary between the thick walled cylindrical part 61 (which has the thickness t1) and the thin walled tip thin walled cylindrical part 62 (which has a thickness t2), the outer diameter of the tip thin walled cylindrical part 62 and the inner diameter of the hole of the flat part 31a of the hot water storage tank 31 coincide, and the tip of the tip thin walled cylindrical part 62 and the tip of the cylindrical part 31b of the hot water storage tank 31 are at the same height position.

[0045] Furthermore, each of the sizes indicated in FIG 5 is set based on the following ranges: D1 = 20 mm or 26 mm, D2 = 22 mm or 27 mm, L1 = 6.5-10.0 mm, L2 = 1.5-4.0 mm, L3 = 2.6-3.0 mm, L4 = 1.0-4.3 mm, t1 = 0.5-2.0 mm, t2 = 0.5-1.8 mm (wherein, t2 < t1), r1 > 1.0 mm, r2 < 0.5 mm, r3 < 0.5 mm, and r4 < 0.5 mm. Here, the piping member 60 is manufactured such that D1 = 20 mm, D2 = 22 mm, L1 = 9.0 mm, L2 = 2.0 mm, L3 = 2.8 mm, L4 = 4.2 mm, t1 = 1.5 mm, t2 = 1.0 mm, r1 > 1.0 mm, r2 < 0.5 mm, r3 < 0.5 mm, and r4 < 0.5 mm.

<Piping Member Manufacturing Method>

[0046] The abovementioned piping member 60 can be regarded as one wherein the lower part in FIG. 5 is the tip thin walled cylindrical part 62, which is welded to the hot water storage tank 31, and the upper part in FIG. 5 is the flange part 63, which constitutes the connecting part connected to the piping 181; furthermore, the piping member 60 has a step 66 between the tip thin walled cylindrical part 62 and the cylindrical part 61 and a step 67 between the flange part 63 and the cylindrical part 61. As shown in FIG. 7-FIG. 9, the piping member 60 is manufactured by 10 processes (S1-S10), which include numerous press molding processes. However, because each process is completed within several seconds and the processes are performed successively in a transverse flow across the figure, the worker hours needed to manufacture the piping member 60 are fewer than that required by the manufacturing method wherein conventional machining is used.

[0047] Here, as shown in the left end portions of FIG. 7 and FIG. 8, press molding processes and the like are performed in order on the substantially circular plate shaped raw material 50. The plate shaped raw material 50 is made of ferritic stainless steel wherein the chrome (Cr) content is 17-20%, the molybdenum (Mo) content is 1.7-2.5%, and the carbon (C) content is less than 0.03. Setting the thickness of the plate shaped raw material 50 to less than 2 mm makes it possible to employ press molding even when the raw material has such a composition; furthermore, press molding the plate shaped raw material 50 results in virtually no loss of material. Here, the plate shaped raw material 50 used has a plate thickness of 1.5 mm.

[0048] Each of the processes (S1-S10) will be discussed in detail later; first, the overall manufacturing method will be discussed.

[0049] In the method of manufacturing the piping member 60, the plate shaped raw material 50 is press molded into a shape that includes thick walled, cylindrical first parts (51a, ... 51h) and thin walled, cylindrical second parts (52a, ... 52h), which are contiguous with the first parts (51a, ... 51h) and become the tip thin walled cylindrical part 62; furthermore, the plate shaped raw material 50 is press molded such that a step (56h) is created at the boundary between the first part (51h) and the second part (52h).

[0050] In addition, regarding the portion that becomes the step 66, the piping member 60 manufacturing method can be broken down into three steps: the group of processes that occurs before hole-making (S1-S6), the hole-making process S7 itself, and the group of processes that occurs after hole-making (S8-S10). In the process group (S1-S6), which occurs before hole-making, the plate shaped raw material 50 is press molded into a shape that includes the cylindrical thick walled first parts (51a, ... 51f) and the thin walled second part (52f), which is contiguous with the first parts (52a, ... 51f) and becomes the tip thin walled cylindrical part 62. The first parts (51a, ... 51f) and the second parts (52a, ... 52f) are orthogonal to one another and respectively correspond to a cylindrical portion and a discoidal portion, which closes one end of the cylindrical portion. The thicknesses of the first part (51f) and the second part (52f) completed by the sixth drawing process S6 are t1 and t2 (t2 < t1), respectively; the second part (52f) further undergoes a plurality of drawing processes (i.e., press molding processes), which makes its plate thickness t2 even smaller. In the process group (S8-S10), which occurs after hole-making, and particularly in the first finishing drawing process S8, the annular second part (52g) whose center portion is cut out is molded into a cylindrical shape, and a step (56h) is created at the boundary between the first part (51h) and the second part (52h). Furthermore, in the second finishing drawing process S9, a force is applied that compresses the second part (52h), which has become cylindrical, in the axial directions, and thereby the second part is molded into the final shape of the tip thin walled cylindrical part 62.

[0051] Furthermore, the process group (S1-S6), which occurs before hole-making, can be broken down into two steps: the first drawing process S1, which molds the plate shaped raw material 50 such that the second part (52a) becomes a disc that closes one end of the cylindrical first part (51a); and the wall thinning process group (S2-S6), which reduces the thickness of the second part (52a).

[0052] In addition, regarding the molding of the flange part 63, the process group (S1-S6), which occurs before hole-making, can be broken down into two steps: the first drawing process S1, which occurs before the formation of the flange part 63; and the subsequent flange part molding process group (S2, ...). The first drawing process S1 molds the plate shaped raw material 50 into an initial shape, which includes the cylindrical first part (51a), by press molding. Furthermore, in the flange part molding process group, which occurs after the second drawing process S2, the portion of an intermediate molding material, which is the material that has taken the initial shape, in the vicinity of the end part of the first part (51a) is bent and extended outward in the radial directions, and the first part (51a) is molded into the first parts (51b, ...) and third parts (53b, ...) and then molded into the shapes of the cylindrical part 61 and the flange part 63.

[0053] In addition, regarding the portion that becomes the step 67, the process group (S1-S6), which occurs before hole-making, can be broken down into two steps: the preparatory process group (S1-S3), which occurs before the molding of the detailed shape of the flange part 63; and the process group (S4-S6) that molds the detailed shape of the flange part 63. In the preparatory process group (S1-S3), which occurs before the molding of the detailed shape of the flange part 63, the plate shaped raw material 50 is molded into an intermediate molding material, which includes the first part (51c) that becomes the cylindrical part 61 and the third part (53c) that becomes the flange part 63, by a plurality of drawing processes (i.e., press molding processes). Furthermore, in the process group (S4-S6) that molds the detailed shape of the flange part 63, a step (57e) is formed in the third parts (53d, ... 53f) of the intermediate molding material by a plurality of drawing processes. The step (57e) is a step that is oriented in both the axial and the radial directions.

[0054] Furthermore, regarding the portion that becomes the step 67, the hole-making process S7 and the process group (S8-S10), which occurs after hole-making, can be broken down into two steps: the finishing process group (S7-S9), which finishes the step 67; and the outer diameter removing process S10, which completes the step 67. In the finishing process group (S7-S9), which finishes the step 67, the third part (53f) of the intermediate molding material wherein the step (57e) is formed is finished by a plurality of processes into a shape that includes the shape of a final step. Furthermore, in the outer diameter removing process S10, a radial directions outer side portion (55j) of the third part (53i) of the intermediate molding material, which has taken a shape that includes the final step shape, is cut off to make the third part (53j) of the intermediate molding material. Thereby, the flange part 63, wherein the third part (53j) has a prescribed external size, is completed.

[0055] Next, each of the processes (S1-S10) will be discussed in detail.

(S1: First Drawing Process)

[0056] As shown in FIG. 7 and FIG 8, first, the first drawing process S1, which is the initial press molding process, is performed on the circular plate shaped raw material 50, which has been cut out at its circumference with the exception of parts thereof. Here, a mold vertically sandwiches the plate shaped raw material 50, which is press molded into the shape of a drinking glass that comprises the cylindrical first part (51a) and the discoidal second part (52a). Thereby, as shown in FIG. 8, the plate shaped raw material 50 is molded into the initial shape wherein the cross section is recessed (i.e., is shaped as a drinking glass).

(S2: Second Drawing Process)

[0057] Next, the plurality of press molding processes (i.e., processes S2-S6) bends and extends outward in the radial directions the portion in the vicinity of the end part of the first part (51a) on the side opposite the second part (52a) and reduces the plate thickness of the second part (52a).

[0058] First, in the second drawing process S2, the first part (51a) is bent such that the upper part of the first part (51a) is oriented diagonally upward, and the first part (51a) is made into the first part (51b) and the third part (53b). In addition, a compression force from the mold is applied to the second part (52a) in the plate thickness directions (i.e., the vertical directions), and the second part (52a) is made into the second part (52b), whose plate thickness is slightly less than that of the second part (52a).

(S3: Third Drawing Process)

[0059] In the third drawing process S3, press molding is performed such that the third part (53b) is oriented more in the horizontal directions, and the second part (52b) is made into the second part (52c), whose plate thickness is slightly less than that of the second part (52b).

(S4: Fourth Drawing Process)

[0060] In the fourth drawing process S4, substantially half of a tip side of the third part (53c) is bent on the side reverse that of the side bent so far such that the third part (53c) faces upward at a midpoint. A step is created in the third part (53c) that undergoes this press molding.

[0061] In addition, in the fourth drawing process S4, too, the second part (52c) is made into the second part (52d), whose plate thickness is slightly less than that of the second part (52c).

(S5: Fifth Drawing Process)

[0062] In the fifth drawing process S5, a tip portion of substantially half of the tip side of the third part (53d), which faces upward, is further press molded such that the tip is bent outward and approaches the horizontal directions. Thereby, the step (57e), which is in both the axial directions (i.e., the vertical directions) and the radial directions (i.e., the horizontal directions), is created in the third part (53e) that undergoes the fifth drawing process S5.

[0063] In addition, in the fifth drawing process S5, too, the second part (52d) is made into the second part (52e), whose plate thickness is slightly less than that of the second part (52d).

(S6: Sixth Drawing Process)

[0064] In the sixth drawing process S6, the third part (53e) is press molded such that the angle of the bent part of the step (57e) is further reduced. Thereby, the third part (53e) becomes the third part (53f), which more closely approximates the final shape.

[0065] In addition, in the sixth drawing process S6, too, the second part (52e) is made into the second part (52f), whose plate thickness is slightly less than that of the second part (52e). The plate thickness of the second part (52f) of the intermediate molding material that undergoes the sixth drawing process S6 is t2. Moreover, the plate thickness of the first part (51f) of the intermediate molding material is t1.

(S7: Hole-making Process)

[0066] In the hole-making process S7, which is performed after the sixth drawing process S6, the center portion of the second part (52f), which is the bottom part of the intermediate molding material shaped as a drinking glass, is cut off. Specifically, a round hole whose diameter is slightly smaller than the inner diameter of the first part (51f) is opened in the second part (52f). Thereby, the second part (52f) becomes the annular second part (52g) wherein a circular center portion (54g) is cut away.

[0067] In addition, the third part (53f) becomes the third part (53g), which more closely approximates the final shape.

(S8: First Finishing Drawing Process)

[0068] In the first finishing drawing process S8, press molding is performed such that the annular second part (52g) is made to face downward. Thereby, the tip of the annular second part (52g) is extended in the vertical directions from the portion in the vicinity of its boundary with the first part (51g). Thereby, the annular second part (52g) becomes the cylindrical second part (52h). In addition, attendant therewith, the step (56h) is created in the portion of the boundary between the second part (52h) and the first part (51h).

[0069] In addition, the third part (53g) becomes the third part (53h), which more closely approximates the final shape.

(S9: Second Finishing Drawing Process)

[0070] The second finishing drawing process S9 is performed to make the outer diameter of the tip thin walled cylindrical part 62 and the inner diameter of the hole of the flat part 31a of the hot water storage tank 31 coincide and to give the tip of the tip thin walled cylindrical part 62 and the tip of the hot water storage tank 31 the same height position.

[0071] In the second finishing drawing process S9, a force that compresses the second part (52h), which has become cylindrical, in the axial directions is applied and the second part (52h) is molded into the second part (52i), whose shape is identical to the final shape of the tip thin walled cylindrical part 62.

[0072] In addition, the third part (53h) becomes the third part (53i), whose shape is identical to the final shape with the exception of its outer diameter. In the third part (53i), the bent part transitions to a state wherein it is bent by approximately 90°, and the size r4 (refer to FIG 5), which is the radius of curvature R of the surface of the bent part, becomes less than 0.5 mm.

(S10: Outer Diameter Removing Process)

[0073] In the outer diameter removing process S10, the radial directions outer side portion (55j) of the third part (53i) of the intermediate molding material is cut off and the third part (53i) is made into the third part (53j), whose external size is the same as that of the flange part 63. The cutting performed in the process S10 targets the outer side of the step (57j), which has the final step shape of the step 67 of the flange part 63, in the radial directions.

<Characteristics of the Piping Member Manufacturing Method>

(1)

[0074] Usually, when a member that comprises a cylindrical part and a flange part is manufactured by press molding, a raw material is press molded such that it takes on either a final shape that includes the flange part or a shape that approximates that final shape; however, in such a manufacturing method, if the raw material becomes hard or bulky, press molding is difficult to perform well. For example, even if the size of the press molding equipment is increased, the rate of loss of the raw material subject to press molding will increase. Consequently, in the conventional art, as shown in FIG. 10, a piping member 260 is manufactured with a manufacturing method that uses machining, wherein a thick walled, cylindrical raw material with a plate thickness of 3.5 mm is cut and the plate thickness of a tip thin walled cylindrical part 260e is reduced to less than 1.0 mm; however, that manufacturing (process) takes a long time and is costly.

[0075] In contrast, in the method of manufacturing the piping member 60 discussed above, first, in the first drawing process S1, press molding is performed to create an initial shape that includes the cylindrical first part (51a); from there, in the flange part molding process group (S2-), the portion in the vicinity of the end part of the cylindrical first part (51a) is bent via press molding, and the first part (51a) is molded into the first parts (51a, ... 51j) and the third parts (53b, ... 53j), which correspond to the cylindrical part 61 and the flange part 63, respectively. Consequently, although a plurality of press molding processes is needed, less of the plate shaped raw material 50, the intermediate molding material, and the like is lost owing to press molding in both the first drawing process S1 and the flange part forming process group (S2-), and therefore the piping member 60 can be manufactured with good yield. In addition, adopting such a manufacturing method makes it possible to manufacture the piping member 60 by press molding, which reduces the manufacturing time compared with that of the piping member manufacturing method based on conventional machining.

[0076] Thus, the manufacturing method discussed above makes it possible to manufacture the piping member 60 at a lower cost and more quickly.

(2)

[0077] In addition, in the manufacturing method discussed above, the numerous press molding processes (S2-) mold the cylindrical first part (51a) into the first parts (51b, ... 51j) and the third parts (53b, ... 53j) and, in turn, mold the first parts (51b, ... 51j) and the third parts (53b, ... 53j) into the cylindrical part 61 and the flange part 63; consequently, even if the flange part 63 includes a complex step shape, the flange part 63 can be molded with good accuracy while avoiding loss of material.

(3)

[0078] In the method of manufacturing the piping member 60 discussed above, in the first drawing process S1, the plate shaped raw material 50 is press molded such that its cross section is recessed, namely, such that it turns into the initial shape, which is that of a drinking glass; afterwards, in the flange part molding process group (S2-), the third part (53b) is extended outward in the radial directions and, in the hole-making process S7, the center portion (54g) of the second part (52f) is cut away; thereby, the piping member 60 is manufactured. Thus, because the initial shape molded in the first drawing process S1 is that of a drinking glass and includes the discoidal second part (52a), the press molding that starts with the plate shaped raw material 50 formed in the first drawing process S1 is performed smoothly and satisfactorily, there is virtually no loss of the plate shaped raw material 50, and a high yield rate is obtained.

(4)

[0079] In the piping member 60 discussed above, adopting the flange part 63 whose cross sectional shape includes a step ensures that the thickness (L3) of the flange part 63 is larger than the thickness (t1) of the plate shaped raw material 50. Consequently, press molding the plate shaped raw material 50 makes it possible to obtain the flange part 63 of the desired thickness (L3).

[0080] If the cross sectional shape of a flange part 263 is a simple oblong (refer to FIG. 10) as in the conventional art, then, to ensure that thickness, the plate thickness of the plate shaped raw material must be of equal thickness, which makes press molding impossible; furthermore, even if press molding were possible, it would be impossible to avoid the increased cost of the press equipment and the increased time required to perform the pressing. However, in the case of the piping member 60, which includes the step 67 as discussed above, the comparatively thin plate shaped raw material 50 can be press molded, making it possible to obtain the flange part 63 of the desired thickness (L3).

[0081] Thus, in the case of the piping member 60, press molding makes it possible to integrally mold the cylindrical part 61 and the flange part 63, which has the desired thickness (L3). Consequently, manufacturing time can be made shorter than that required to manufacture the piping member by conventional machining.

(5)

[0082] In the method of manufacturing the piping member 60 discussed above, in the preparatory process group (S1-S3), which is performed before the molding of the detailed shape of the flange part 63, the third parts (53b, 53c) are created; in the process group (S4-S6), which molds the detailed shape of the flange part 63, the step is formed in the third part (53c); and in the hole-making process S7 and the process group (S8-S10), which is performed after the hole-making, the third parts (53d, ... 53f), wherein the steps are formed, are finished into the shape that includes the final step. Thereby, it is possible to ensure the desired thickness (L3) of the flange part 63 while reducing the plate thickness (t1) of the plate shaped raw material 50 to less than 2 mm (herein, 1.5 mm) and to reduce the cost of the press molding equipment.

(6)

[0083] In the method of manufacturing the piping member 60 discussed above, numerous press moldings are performed such that the radius of curvature r4 of the surface of the bent part, which is bent at approximately 90°, is less than 0.5 mm. Consequently, it becomes possible to ensure that the length in the radial directions of a surface 63a, namely, the portion of the flange part 63 that extends by a length L2 from the upper end of the cylindrical part 61 outward in the radial directions, is large. Here, a length of the surface 63a in the radial directions of 1 mm or greater, which is the thickness of the quick fastener 190, is ensured. Accordingly, once the quick fastener 190 is fastened to the flange part 63 for the purpose of connecting with the piping 180, the quick fastener 190 will not unfasten on its own.

(7)

[0084] In the method of manufacturing the piping member 60 discussed above, in the outer diameter removing process S10, the radial directions outer side portion (55j), which is the portion in the vicinity of the outer circumferential edge of the third part (53j), is cut off, and consequently the accuracy of the shape of the outer circumferential edge of the flange part 63 is increased.

(8)

[0085] In the method of manufacturing the piping member 60 discussed above, in the outer diameter removing process S10, when the material is cut at the step (57j) portion, consideration is given to ensuring that the thickness of the cut is large, and therefore the cut is made on the outer side of the step (57j) in the radial directions. Thereby, only the amount of the plate thickness (t1) of the plate shaped raw material 50 should be cut in the outer diameter removing process S10; furthermore, the size of the cutting apparatus and the cost of the equipment are prevented from increasing.

(9)

[0086] In the method of manufacturing the piping member 60 discussed above, a tip thin walled cylindrical part 262 (refer to FIG. 10), which becomes a welding part, is not molded by machining as in the conventional art; instead, in the first finishing drawing process S8, the piping member 60 is manufactured by press molding such that the step (56h) is created at the boundary between the first part (51h) and the second part (52h). Consequently, it becomes possible to manufacture the piping member 60 more inexpensively and faster than the piping member manufactured by conventional machining.

(10)

[0087] In the method of manufacturing the piping member 60 discussed above, in the process group (S1-S6), which is performed before the hole-making, the plate shaped raw material 50 is molded by press molding the cylindrical thick walled first part (51f) and the thin walled second part (52f), which is contiguous with and intersects the first part (51f); subsequently, in the hole-making process S7 and in the process group (S8-S10), which is performed after the hole-making, the second part (52g) is molded into a cylindrical shape and the step (56h) is created at the boundary between the first part (51h) and the second part

(52h).

[0088] Furthermore, because a difference between the thickness (t1) of the first part (51f) and the thickness (t2) of the second part (52f) has already been created in the process group (S1-S6), which is performed before the hole-making, it is possible to easily produce the step (56h) in the process group (S8-S10), which is performed after the hole-making.

[0089] In addition, because the second parts (52a, ... 52e) in the process group (S1-S6), which is performed before the hole-making, are orthogonal to the cylindrical first parts (51a, ... 51e), reducing the thickness of the second parts (52a, ... 52e) is easy when press molding is performed by moving the mold along the axial directions of the cylindrical first parts (51a, ... 51e).

[0090] Thus, herein, in the process group (S1-S6), which is performed before the hole-making, the shape (i.e., the drinking glass shape) of the intermediate molding material is such that the second parts (52a, ... 52e) can easily be made thin walled; in addition, in the process group (S8-S10), which is performed after the hole-making, the second part (52g) is molded into a cylindrical shape and the step (56h) is created at the boundary between the first part (51h) and the second part (52h); thereby, the piping member is manufactured. Consequently, the piping member 60 can be manufactured by press molding with good yield and in a short time. Furthermore, because the piping member 60 can be manufactured by press molding, the manufacturing time is shorter than that of the piping member manufactured by conventional machining.

(11)

[0091] In the method of manufacturing the piping member 60 discussed above, the first drawing process S1 molds the plate shaped raw material 50 into a drinking glass shape that comprises the cylindrical first part (51a) and the discoidal second part (52a), which closes one end of the first part (51a), and the subsequent wall thinning process group (S2-S6) reduces the thickness of the second part (52a). Consequently, in the wall thinning process group (S2-S6), the mold contacts the surfaces both above and below the discoidal second parts (52a, ... 52e) and thereby can apply force to the second part (52a, ... 52e) in the plate thickness directions. Consequently, the second parts (52a, ... 52e) can be made thin walled more easily and faster than in the method wherein the second part is first molded from its initial shape into a cylindrical shape and then made thin walled.

(12)

[0092] In the method of manufacturing the piping member 60 discussed above, in the hole-making process S7, the center portion of the second part (52f) is removed and, subsequently, the second part (52g), which is now annular, is molded into a cylindrical shape; consequently, the thin walled, cylindrical tip thin walled cylindrical part 62 can be formed more quickly and more accurately than in a method wherein the unnecessary portion is cut out after the discoidal second part is molded into a cylindrical shape.
In addition, after the first finishing drawing process S8, wherein the second part (52g) that is now annular is molded into a cylindrical shape, the second finishing drawing process S9 is performed in order to apply compression force in the axial directions to the second part (52h), which is now cylindrical, thereby making it possible to finish the second part (52h) into the final shape of the tip thin walled cylindrical part 62 with good accuracy.

Claims

1. A method of manufacturing a cylindrical piping member (60), wherein one end becomes a welding part (62) that is welded to another member (31), comprising a step of:

using press molding to mold a plate shaped raw material (50) into a shape that includes a thick walled, cylindrical first part (51h) and a thin walled, cylindrical second part (52h), which is contiguous with the first part and becomes the welding part such that a step (56h) is created at the boundary between the first part and the second part.

2. A method of manufacturing a cylindrical piping member (60), wherein one end becomes a welding part (62) that is welded to another member (31), comprising:

a first step (S1-S6), which uses press molding to mold a plate shaped raw material (50) into a shape that includes a cylindrical thick walled first part (51f) and a thin walled second part (52f), which is contiguous and intersects with the first part and becomes the welding part; and

a second step (S8), which is performed after the first step, that uses press molding to mold the second part into a cylindrical shape and creates a step (56h) at the boundary between the first part and the second part.

3. A method of manufacturing a piping member according to claim 2, wherein
the first step comprises:

the first press molding process (S1), wherein the plate shaped raw material is molded such that the second part takes on a discoidal shape that closes one end of the cylindrical first part; and

the second press molding process (S2-S6), which reduces the thickness of the discoidal second part.

4. A method of manufacturing a piping member according to claim 3, wherein
the second step comprises:

the hole-making process (S7), which removes a center portion (54g) of the discoidal second part (52f); and

the third press molding process (S8), which molds the annular second part (52g) that has undergone the hole-making process into a cylindrical shape and

creates the step (56h) at the boundary between the first part and the second part.

5. A method of manufacturing a piping member according to claim 4, further comprising:

a third step (S9), which is performed after the third press molding process of the second step, that applies force that compresses the second part (52h), which has become cylindrical, in the axial directions and molds the second part into the final shape of the welding part.

Drawing