JP4450474B2 - Electric water heater tank and tank body manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tank for an electric water heater and a method for manufacturing a tank body of the tank.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 10-238865 shows a conventional structure of an electric water heater tank in which an electric heater is attached to a tank body. The tank body of this known tank has a flat flange portion provided with a circular insertion hole for inserting an electric heater and an annular packing body storage groove surrounding the insertion hole and opening outward. Are integrally formed on the peripheral wall by press working. A plurality of mounting bolts are fixed to the flange portion so as to extend along the packing body housing groove outside the packing body housing groove. An electric heater attached to the heater flange is inserted into the tank body from the insertion hole. Then, with the annular packing body of the packing stored in the packing body storage groove, the heater flange is fixed to the peripheral wall of the tank body using a plurality of mounting bolts, thereby closing the insertion hole in a liquid-tight manner. It is out. In this conventional tank, the insertion hole is formed by the radially inner edge of the packing body housing groove. In such a structure, as shown in FIG. 10A, first, a through hole TH is formed at the same time that a flat portion is formed by pressing in the body of the tank body. Thereafter, as shown in FIG. 10 (B), it is obtained by forming a packing body accommodation groove PR by press working just outside the through hole TH.
[0003]
[Problems to be solved by the invention]
When the insertion hole IH for inserting the electric heater is formed by the radially inner edge ED of the packing body storage groove PR as in the prior art, burrs appear on the radially inner edge ED. A sharp corner toward the outside is formed by processing return. When such burrs and corners damage a part of the packing body that is compressed and deformed when the heater flange is attached to the tank body, there arises a problem that the sealing performance is remarkably lowered. In order to solve such a problem, it is conceivable to perform machining (finishing) for removing burrs and corners from the edge of the insertion hole. However, when such a finishing process is performed, there arises a problem that the manufacturing cost increases.
[0004]
An object of the present invention is to provide a tank for an electric water heater in which the sealing performance does not deteriorate.
[0005]
Another object of the present invention is to provide a tank for an electric water heater that is less likely to cause crevice corrosion in addition to the above object.
[0006]
An object of the method of the present invention is to provide a method for manufacturing a tank body that does not require finishing.
[0007]
Another object of the method of the present invention is to provide a method of manufacturing a tank body with high processing accuracy.
[0008]
[Means for Solving the Problems]
An electric water heater tank to be improved by the present invention includes a circular insertion hole for inserting an electric heater, and an annular packing body housing groove surrounding the insertion hole and opening outward. A tank body in which a flat flange portion is integrally provided on the peripheral wall by press working is used. A plurality of mounting bolts are arranged on the outer side of the packing body storage groove of the flange portion so as to extend along the packing body storage groove. Further, a heater flange having an electric heater inserted into the tank body through the insertion hole is fixed to the peripheral wall using a plurality of mounting bolts to close the insertion hole. In this case, the packing having an annular packing body housed in the packing body housing groove is disposed in a state where the packing body is compressed between the flange portion of the tank body and the heater flange.
[0009]
In such an electric water heater tank, in the present invention, an annular flat plate portion is integrally provided in the flange portion on the radially inner side of the packing body housing groove. When such a flat plate portion is provided, there are no burrs or sharp corners at the edge of the packing body storage groove, so that a part of the packing body that is compressed and protrudes from the packing body storage groove is The possibility of being hurt is greatly reduced. In particular, when the width dimension of the annular flat plate portion is determined so that the inner edge portion of the packing body compressed between the flange portion and the heater flange exceeds the radially inner edge portion of the flat plate portion, It is possible to reliably prevent damage and prevent deterioration in sealing performance.
[0010]
In this case, if the width dimension of the annular flat plate portion is determined so as not to form a gap that causes crevice corrosion between the radial inner edge of the flat plate portion and the heater flange, the flat plate portion is Even if provided, crevice corrosion can be prevented from occurring in the tank. The specific width dimension of the flat plate portion for realizing this is within three times the plate thickness dimension of the flange portion.
[0011]
In addition, the method of the present invention includes a circular insertion hole for inserting an electric heater, an annular packing body storage groove that surrounds the insertion hole and opens toward the outside, and a radially inner side of the packing body storage groove. An object of the improvement is a method of manufacturing a tank body in which a flat flange portion including an annular flat plate portion is integrally provided on a peripheral wall of a cylindrical body portion. In the method of the present invention, an inner die for pressing and an outer die for pressing are arranged on the radially inner side and the radially outer side of the cylindrical body part, respectively. And after forming the flat part provided with the packing main body storage groove in the body part, without replacing the inner mold for press and the outer mold for press, the insertion hole is inserted into the flat part with a time delay. An inner mold for pressing and an outer mold for pressing are configured to form. If the insertion hole and the packing body storage groove are formed at the same time, a relatively large strain is generated in the flat portion of the flange portion, the roundness of the packing body storage groove is reduced, and it is difficult to store the packing body in the packing body storage groove. Or the sealing performance may be reduced. When the insertion hole is formed without replacing the inner mold for pressing and the outer mold for pressing after forming the packing body housing groove as in the present invention, the distortion generated in the flat portion of the flange portion is reduced. In addition, the roundness of the packing main body storage groove can be increased, and deterioration of the sealing performance can be prevented.
[0012]
If the insertion hole is formed with a delay of 0.5 to 2 seconds after the flat portion is formed, it is not affected by plastic deformation due to the formation of the flat portion and the packing body housing groove, so that an insertion hole with high roundness can be formed. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG.1 and FIG.2 is the front view and top view of the cylindrical trunk | drum 1 which comprise a part of tank body of the tank for electric water heaters of this invention. 3 is an enlarged cross-sectional view taken along line III-III in FIG. 1, and FIG. 4 is an enlarged cross-sectional view of the main part of FIG. Although not shown in FIG. 1, a bowl-shaped end plate is welded to the lower end and the upper end of the body 1. As shown in FIGS. 1, 3 and 4, in the lower region of the peripheral wall 3 of the body portion 1, a circular insertion hole 5 for inserting an electric heater and a periphery of the insertion hole 5 are surrounded and directed outward. A flat flange portion 9 having an annular packing main body housing groove 7 that is open is integrally provided by pressing. The packing main body storage groove 7 has a shape in which the cross-sectional shape is substantially semicircular. The flange portion 9 is integrally provided with an annular flat plate portion 11 on the radially inner side of the packing body housing groove 7. The flat plate portion 11 is provided for the purpose of not damaging the packing described later. Furthermore, an annular inclined surface 12 extending toward the outer peripheral surface of the body portion 1 is formed on the radially outer side of the flange portion 9. Eight mounting bolts 13a to 13h called stud bolts are fixed to the outside of the packing body housing groove 7 of the flange portion 9 at equal intervals along the packing body housing groove 7 by welding. Although not shown in each figure, a male screw is formed on the outer periphery of the tip of the mounting bolts 13a to 13h.
[0014]
Here, as shown in FIG. 1, when the trunk portion 1 is arranged such that the longitudinal direction of the trunk portion 1 is directed in the vertical direction and the mounting bolts 13 a to 13 h extend in the horizontal direction, the insertion hole 5 is left and right. Assume a virtual vertical plane (SS) that bisects. In this example, among the eight mounting bolts 13a to 13h, the uppermost mounting bolt 13a and the lowermost mounting bolt 13e are divided into two by this virtual vertical plane (SS). The mounting bolts 13b to 13d and 13f to 13h are arranged at 45 ° intervals on both sides of the upper and lower mounting bolts 13a and 13e. As shown in FIG. 6, which will be described later, in this embodiment, hook pieces 17 and 19 of the packing 15 to be described later are attached to two mounting bolts 13b and 13h located on both sides of the uppermost mounting bolt 13a. Engaged or hooked.
[0015]
5A to 5C are a plan view, a front view, and a partially enlarged view of the packing 15 used in this embodiment. The packing 15 is hooked (engaged with) an annular packing body 16 and a mounting bolt 13b and 13h, part of which is housed or fitted in an annular packing body housing groove 7 surrounding the insertion hole 5. In a broad sense, the packing main body 16 is positioned at an appropriate position with respect to the insertion hole 5 while being hooked by two mounting bolts (or positioning of the packing main body 16 with respect to the insertion hole 5). Hook pieces 17 and 19 are provided to prevent the main body 16 from coming out of the packing main body storage groove 7. These hook pieces 17 and 19 have a curved shape so as to form hook portions 17a and 19a that extend in a direction away from the virtual vertical plane (SS) and open downward. An angle θ between imaginary lines PL1 and PL2 passing through the center of the space surrounded by the hook portions 17a and 19a and the center of the packing body 16 is 90 °. Therefore, in design, the centers of the two mounting bolts 13b and 13h are located at the center of the space surrounded by the hook portions 17a and 19a. The hook pieces 17 and 19 have a thickness that does not hinder the deformation of the annular projecting portion 16a, which will be described later, at a portion where the packing body 16 in the state of being housed in the packing body housing groove 7 projects from the packing body housing groove 7. It is provided integrally.
[0016]
The packing body 16 is provided on the surface opposite to the surface on which the annular protrusion 16a stored in the packing body storage groove 7 and the protrusion 16a are provided, and on the side opposite to the protruding direction of the protrusion 16a. An annular protrusion 16 b that protrudes and extends along the packing body 16 is integrally provided. The cross-sectional shape of the protrusion 16a is a shape in which a rectangular base is connected under a substantially semicircular portion. The annular protrusion 16b is located at the center of the bottom surface of the rectangular base, and its cross-sectional shape is a semicircular shape. The cross-sectional area of the annular protrusion 16b is set to be sufficiently smaller than the cross-sectional area of the annular protrusion. Specifically, the cross-sectional area or size of the annular protrusion 16b is such that when the packing main body 16 is disposed between the flange portion 9 and a heater flange, which will be described later, and compressed, the annular protrusion 16b. It is set to such an extent that its existence is hardly understood. When the annular protrusion 16b has such a size, the sealing performance on the heater flange side can be improved.
[0017]
FIG. 6 is a diagram schematically showing a state where the packing body 16 is stored in the packing body storage groove 7 and the hook pieces 17 and 19 of the packing 15 are hooked on the two mounting bolts 13b and 13h. is there. FIG. 7 shows a heater flange provided with an electric heater 21 after the protrusion 16a of the packing body 16 is stored in the packing body storage groove 7 and the hook pieces 17 and 19 of the packing 15 are hooked on the two mounting bolts 13b and 13h. When attaching (closing member) 23, the expanded sectional view of the state before fastening the nut 25 screwed together to the attachment bolt 13h is shown. The heater flange 23 has a disk shape, and in the vicinity of the outer peripheral edge of the heater flange 23, eight through holes through which the eight mounting bolts 13a to 13h pass are formed. Further, two through holes through which the case of the electric heater 21 penetrates in a liquid-tight manner are formed in the central portion of the heater flange 23. In the state shown in FIG. 7, since the nut 25 is not tightened, the annular protrusion 16b provided on the packing 15 still maintains its shape. When all the nuts 25 are tightened from this state, the packing body 16 of the packing 15 is compressed as shown in FIG. The compressed packing body 16 extends in the radial direction and enters the space between the flange portion 9 and the flat plate portion 11 and the heater flange 23. In this example, the width of the annular flat plate portion 11 (the size in the radial direction of the insertion hole) is set so that the inner edge portion 16c of the packing body 16 in a state compressed between the flange portion 9 and the heater flange 23 is the flat plate portion. 11 is defined so as to exceed the radially inner edge 11a. Therefore, even if the nut 25 is tightened, the radially inner edge portion 11a of the flat plate portion 11 does not bite into the packing body 16, and the packing body 16 is not damaged, so that the sealing performance is surely prevented from being deteriorated. Can do.
[0018]
In this case, the width (diameter dimension) of the annular flat plate portion 11 is set so as to cause a gap corrosion between the radial inner edge portion 11a of the flat plate portion 11 and the heater flange 23. If determined so as not to occur, crevice corrosion can be prevented from occurring in the tank even if the flat plate portion 11 is provided. The specific width dimension of the flat plate part 11 for realizing this is within three times the plate thickness dimension of the flange part 9. Specifically, in the case of a general household electric water heater tank, it is preferable to set the width dimension to about 0.9 mm to 3 mm.
[0019]
Next, referring to FIG. 9, a tank body in which a flat flange portion 9 having an annular packing body housing groove 7 and an annular flat plate portion 11 is integrally provided on the peripheral wall of the cylindrical body 1 is provided. An embodiment of a manufacturing method will be described. First, an inner mold 31 and a drawing die 32 supported on a mold base 30 are arranged on the inner side in the radial direction of the cylindrical body 1, and an outer mold 33 is arranged on the outer side in the radial direction of the body 1. The outer die 33 is formed with a recess into which the drawing die 32 is inserted, and the drawing die 32 is formed with a flat portion 8 having an annular packing body housing groove 7 into which the drawing die 32 is pushed. The outer mold 33 is a split mold so that a portion where the insertion hole 5 will be formed later moves radially outward. After the flat portion 8 is formed, the piercing rod 35 is driven radially outward using a driving means 36 using a hydraulic cylinder as a driving source, and the insertion hole 5 is formed in the flat portion 8 by the piercing punch 34. In this way, the insertion hole 5 is formed after the packing body housing groove 7 is formed. Therefore, after the flat portion 8 having the packing body housing groove 7 is formed in the body portion 1, the insertion hole is inserted into the flat portion 8 with a time delay without replacing the inner mold for pressing and the outer mold for pressing. 5 can be formed. Further, when the insertion hole is formed with a delay of 0.5 to 2 seconds after the flat portion 8 is formed, it is not affected by the plastic deformation due to the formation of the flat portion 8 and the packing body housing groove 7, so that the insertion hole has a high roundness. 5 can be formed. In this example, the driving means 36 of the piercing rod 35 is disposed inside the trunk portion 1 and the insertion hole 5 is formed by driving the piercing rod 35 radially outward of the trunk portion 1. Needless to say, the piercing rod driving means may be disposed outside and the piercing rod may be driven radially inward of the body 1 to form the insertion hole 5.
[0020]
【The invention's effect】
In the tank for electric water heater of the present invention, since the annular flat plate portion is integrally provided on the flange portion on the radially inner side of the packing body storage groove, there are burrs and sharp corners on the edge of the packing body storage groove. The possibility that the part of the packing body that is compressed and protrudes from the packing body storage groove is damaged by the burrs and the corners can be greatly reduced. In particular, when the width dimension of the annular flat plate portion is determined so that the inner edge portion of the packing body compressed between the flange portion and the heater flange exceeds the radially inner edge portion of the flat plate portion, There is an advantage that damage can be surely prevented and deterioration of the sealing performance can be prevented.
[0021]
Also, if the width dimension of the annular flat plate portion is determined so as not to form a gap that causes crevice corrosion between the radially inner edge of the flat plate portion and the heater flange, even if the flat plate portion is provided, There is an advantage that crevice corrosion can be prevented from occurring in the tank.
[0022]
If the insertion hole is formed without replacing the inner mold for pressing and the outer mold for pressing after forming the packing body housing groove as in the method of the present invention, the distortion generated in the flat portion of the flange portion is reduced. It is possible to increase the roundness of the packing main body storage groove, and there is an advantage that the deterioration of the sealing performance can be prevented.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view of a cylindrical body part constituting a part of a tank body of an electric water heater tank of the present invention.
FIG. 2 is a plan view of a cylindrical trunk portion constituting a part of a tank body of the electric water heater tank of the present invention.
3 is an enlarged sectional view taken along line III-III in FIG.
FIG. 4 is an enlarged cross-sectional view of a main part of FIG.
FIGS. 5A to 5C are a plan view, a front view, and a partially enlarged view of a packing used in the embodiment.
FIG. 6 is a diagram schematically showing a state where the packing body is housed in the packing body housing groove and hook pieces of the packing are hooked on two mounting bolts.
[Fig. 7] When the packing body is stored in the packing body storage groove and the hook piece of the packing is hooked on the two mounting bolts, and the heater flange equipped with the electric heater is installed, the nut screwed to the mounting bolt is It is an expanded sectional view of the state before tightening.
8 is an enlarged cross-sectional view of a state in which a nut is further tightened from the state of FIG.
FIG. 9 is a diagram showing a relationship between molds used for explaining a method of manufacturing a tank body.
FIGS. 10A and 10B are diagrams showing a manufacturing process of a conventional tank body, respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Body part 5 Insertion hole 7 Packing body accommodation groove | channel 8 Flat part 9 Flange part 11 Flat plate part 12 Inclined surface 13a-13h Mounting bolt 15 Packing 21 Electric heater 23 Heater flange 30 Mold stand 31 Inner metal mold 32 Diaphragm die 33 Outer metal mold Type

Claims (2)

A circular insertion hole for inserting an electric heater, an annular packing body storage groove surrounding the insertion hole and opening outward, and an annular flat plate positioned radially inward of the packing body storage groove A flat flange portion provided with a portion is a method of manufacturing a tank body integrally provided on a peripheral wall of a cylindrical body portion,
An inner mold for pressing and an outer mold for pressing are respectively disposed on the radially inner side and the radially outer side of the cylindrical body,
After forming a flat portion having the packing body housing groove in the body portion, the insertion hole is inserted into the flat portion with a time delay without replacing the inner mold for pressing and the outer mold for pressing. The inner mold for pressing and the outer mold for pressing are configured to form a tank body. 2. The method of manufacturing a tank body according to claim 1, wherein the insertion hole is formed with a delay of 0.5 to 2 seconds after the flat portion is formed.

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