JPS60160925A - Electric liquid heating machinery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electric liquid heating device having an anti-bumping layer.

Conventional Structure and Problems As a representative example of an electric liquid heating device, a jar pot, which has grown significantly in recent years and has strong latent demand among users, will be cited and explained.

Jar pots have the functions of a thermos bottle and an electric kettle, and are energy efficient and economical, so they have become explosively popular in recent years. Therefore, as the penetration rate gradually increases, the mass production effect increases, and the cost also increases.
In terms of thermal efficiency, we are now in a situation where we must pursue even greater economic effects.

Fig. 1 is a block diagram showing the electric liquid heating function of a typical conventional jar pound. 700W main heating elements 2 and 6 on the outside surface
The 0W auxiliary heating elements 3 are each insulated with a synthetic mica plate 4, reinforced with a metal belt-like reinforcing material, and mechanically fixed to the container 1 with a fitting.

The drawbacks of this conventional method are as follows: (1) The band heater, which is composed of two synthetic mechanical strength plates, a ribbon heater, and a belt-shaped reinforcement made of whole eggs, is difficult to mass produce and is expensive.

(2) At first glance, the band heater appears to be in close contact with the container 1, but since the synthetic mica plate and metal belt-shaped reinforcing material are not very flexible, in reality, it is a point contact. Since the band heater reaches a high temperature, the insulation cost is high and the life of the heater is shortened.

(3) Since the contact between the band heater and container 1 is not good,
The thermal efficiency of the heating element is poor. (2) Since the band heater becomes hot, the watt density per unit area cannot be increased beyond the current level. (@The heater does not have a high temperature, so the watt density cannot be increased, so the heating element is placed in the container 1.
cannot be installed at the bottom of the

(6) Since the heater is provided on the side surface of the container 1, the heating of the bottom surface is delayed, the bumping noise is loud, and as a result, temperature unevenness is likely to occur in the heating of the liquid. (It had various drawbacks, such as poor thermal efficiency and the need for a large amount of heat insulating material for the heating element, making it difficult to make the jar pot lightweight and compact.)

OBJECTS OF THE INVENTION It is an object of the present invention to provide an electric liquid heating device that can eliminate the problems of the conventional example as described above and further has a practical fire resistance.

Structure of the Invention In order to achieve the above object, the present invention forms a bumping prevention layer by surface enlarging treatment on the inner surface of the heat exchange part of the container of an electric liquid heating device.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, the present invention can be implemented in a mode in which a bumping prevention layer is formed on the inner wall of the conventional jar pot container shown in FIG. An example of an electric liquid heating device, that is, an electric liquid heating device in which a heating element is covered with a hollow glass layer and a bonded heating element is installed will be described.

In particular, the above-mentioned electric liquid heating equipment has an integrated container and heating element, so it is an excellent method for heat transfer and transport, but due to the bumping phenomenon, the amount of heat transfer and transport becomes pulsating. The effectiveness of this method is also reduced by half. In contrast, the bumping prevention layer of the present invention is effective.

FIGS. 2 to 4 show an example of the basic configuration of an electric liquid heating device according to an embodiment of the present invention.

In the figure, reference numeral 11 denotes a cylindrical container body constituting a jar pot, and this container body 11 is made of special stainless steel with a thickness of 0.8 sugar, which conforms to JIS 5US444. 1
2 is a bottom substrate of the jar pot, and this bottom substrate 12 is also made of 5US444 like the container body 11. A protrusion prevention layer 13 is formed on the inner surface of the bottom substrate 12, and a heat generating portion 14 is formed on the outer surface of the bottom substrate 12. This is what makes up the jar pot container.

Here, FIG. 3 shows an enlarged cross-sectional configuration diagram of the bottom A of the jar pore in FIG. 2. As shown in FIG. 3, an insulating hollow layer 16 is provided on one side of the outer surface of the bottom substrate 12, and on top of this insulating hollow layer 16, a 5US430 stainless steel ribbon having a thickness of 60 μm is placed as shown in FIG. A planar heating element 17 obtained by pressing or etching as described above is disposed, and this heating element 17 is bonded and fixed with an outer covering hollow layer 18. After that, the bottom substrate 12
The bumping prevention layer 13 is formed by subjecting the inner surface to a blast treatment and plasma spraying aluminum powder.

Next, the constituent elements of the present invention will be described.

(1) Metal base material The metal base material constituting the electric liquid heating device of the present invention must have corrosion resistance, thermal conductivity, and hollow coating properties as a heating device.

Therefore, the base material used in the present invention is preferably a stainless steel base material, and as shown in the following table, SUS 304°430.444
etc. is good. Among them, 5US444 is the most preferred.

Table (8) Electric Heating Element The heating element 17 that can be applied to the present invention is basically a ribbon-like one.
For example, if a coil-shaped or thick band-shaped heating element is used, the hollow layer 18 will be completely covered.
The film thickness becomes large. As a result, the adhesion of the hollow layer 18 is extremely reduced, and an external shock can easily cause the hollow layer 18 to deteriorate.
8 peels off and the heating element is exposed.

The thickness of the heating element ribbon is suitably 10 to 20 m, preferably 30 to 100 m. 1011
It is difficult to process a thin ribbon with a diameter of less than m, and when manufacturing a planar heating element, the ribbon may be torn, bent, or bent, resulting in extremely poor workability. Further, if the thickness is 200 μm or more, in addition to the above-mentioned reason, if a heat cycle is applied to the planar heating element, cracks may occur in the hollow layer, which is not preferable.

In addition to the usual methods of cold rolling and hot rolling, metal can be made into a thin ribbon using an ultra-quenching method. Etching and press working are suitable methods for forming a thin metal strip into a desired pattern. The etching method can be applied when the production quantity is small, and the press processing method can be applied for mass production. The film thickness and metal shape of the electric heating element can be arbitrarily determined in consideration of the rated power, heat generation area, temperature distribution, etc.

Various electric heating materials can be used for the monthly charge of the heating element, but the shape of the heating element (width of the pattern)

A material with appropriate values for specific resistance and coefficient of thermal expansion, which are factors that determine the length, thickness, etc., as well as excellent adhesion with the hollow layer and workability, is selected. From these points of view, the specific resistance at 20'C is 6060μΩ・c
The thermal expansion coefficient at m, 100' (: is 104X10
'deg' ferritic stainless steel is suitable, but considering the type, shape, and wall thickness of the base material of the heating element application equipment, austenitic stainless steel vs. Fe-Cr-A
6 alloy, Fe-Cr alloy.

Ni-Cr alloy, Ni-Cr-41 alloy, Fa-Or
It is possible to obtain a thin ribbon from -Ni-AI2 alloy or the like and use it for a heating element.

(3) Insulating Hollow Layer The electrical insulation properties of the glass layer that fixes the heating element 17 of the heating section of the present invention are particularly important. In the present invention, in particular, since the heating element is constructed in a laminated manner, a low-alkali glass having excellent electrical insulation properties is required. Table 1 shows the preferred range of glass necessary to achieve the purpose of the present invention and typical glass compositions used in the following examples.

Table 1 ■ Since the glass coating layer is required to have high insulation properties in the application examples of the present invention, the slip compositions shown in Table 2 were used. In addition,
In Table 2, in addition to benzyl alcohol, isophorone, microhexanol, carpitol, etc. can also be used as the organic solvent.

In addition, it is soluble in organic solvents as a colloid stabilizer, and has a 160%
It is possible to use small amounts of thickeners that oxidize and burn at ~360°C.

Table 2 (4) Formation of bumping prevention layer (a) Surface enlarging treatment of base material In FIG. As a pre-treatment, surface enlarging process of the bottom substrate 12 is required. Sandblasting is most suitable for this pretreatment. The surface roughness at this time was R&2 to 20 using a Talysurf surface roughness meter.
71 m was preferable, and the most preferable range was about 6 to 10 μm.

Below this range, adhesion cannot be obtained, and above this range, adhesion deteriorates and it is not possible to obtain favorable results in the corrosion test. Therefore, the range shown in Table 3 is suitable for the purpose of the present invention. It will come true.

Table 3 (b) Surface roughness of bumping prevention layer The role of the bumping prevention layer is to prevent bumping and bumping noise.

When a liquid boils, the larger the temperature difference between the heat source and the liquid, the more nucleate boiling and film boiling will occur, and the bumping phenomenon will occur at the heat transfer interface of the heat source, resulting in the following drawbacks. (1) Produces bumping and boiling sounds. (2) The amount of heat transfer becomes pulsating, and the heat source becomes high temperature. (3) Thermal efficiency decreases. (4) Insulation is uneconomical.

(＠ It is difficult to make it lightweight and compact, which can cause problems with the pipes.) As a solution to this problem, a material such as aluminum, which is a good conductor of heat and has excellent corrosion resistance, is used to create a heat exchange surface with the liquid. It is an object of the present invention to form a bumping prevention layer by applying a surface enlarging treatment to increase the surface area of the heat exchange surface and to easily dissipate generated gas from the heat exchange surface.

The surface roughness of this surface enlarging treatment is as shown in Table 3 above.
The ten-point average roughness Rz was preferably in the range of 25 to 260 μm, and particularly optimal was the range of 50 to 16011 m. Rz
When Rz is less than 25 μm, it is not so effective; on the other hand, when Rz is 26
When it is 0 μm or more, the surface area tends to become smaller, so the effect of preventing bumping is small, and therefore Rz is 50~50 μm.
A range of 160 μm was optimal. This surface roughness has a correlation with the watt density per unit area and the viscosity, specific heat, and boiling point of the heated object, but when Rz is 60 to 150 (r
The level was optimal for practical use.

(C) Material of Bumping Prevention Layer As mentioned above, the base material of the container used in the present invention is preferably a stainless steel base material. Stainless steel is Fe.

The basic elements are Cr, Ni, and a trace amount of G depending on the application.
o, Ti, Mn, etc. are added.

The thermal spraying materials for the bumping prevention layer to achieve the bumping prevention effect, which is the object of the present invention, are aluminum, copper, and iron.

Metals or alloys such as nickel, stainless steel, iron-chromium alloy, = Tsukeru chromium alloy, or Ae203°Ti
O2,5i02. ZrO□, Cr2O3, MgO,
Metal oxides or composite oxides such as Cab and BaO were effective. Select a material from among these sprayed materials for the bumping prevention layer, taking into account the electrochemical potential difference with the container base material, corrosion resistance, thermal expansion coefficient, thermal conductivity, cost, productivity, bumping prevention effect, etc. There is a need to.

According to the results of the studies conducted by the present inventors, aluminum, aluminum alloy, stainless steel + A403/TlO2, etc. were suitable for compatibility with already commercially available melt base materials.

((11) Method of forming the bumping prevention layer and its thickness As the method of forming the bumping prevention layer, the metallicon method, the arc method, and the plasma spraying method are suitable in the present invention.

In particular, the arc spraying method and the plasma spraying method were particularly efficient from the viewpoint of being able to adjust the surface roughness of the bumping prevention layer arbitrarily depending on the intended use and adhesion strength, and had a large bumping prevention effect. As shown in Table 3 above, the thickness of the bumping prevention layer was preferably in the range of 25 to 100077 m, and most preferably in the range of 50 to 400 μm. The porous layer of the bumping prevention layer is thin! ,,b It was also found that if this effect was not obtained, and on the other hand, the porous layer was too thick, the porous layer acted as a heat insulating layer, resulting in the opposite effect.

Specific Example (Jar Pot) Using the low alkali glass shown in Table 1 above and a highly insulating glass frit, the slip composition shown in Table 2 was milled in a ball mill for 2 hours to remove the slip. It was adjusted.

The implementation process of the jar pot will be explained according to FIGS. 2 to 4. First, as mentioned above, 5US4 with a wall thickness of 0.8 mm
A cylindrical container main body 11 and a bottom substrate 12 are manufactured using the No. 44 base material. The part of the bottom substrate 12 where the heat generating layer is to be provided is first subjected to Branut treatment using a 6O mesh alumina grid, and then the surface is heated at 830''C in a nitrogen atmosphere using the slip shown in Table 2. The insulating hollow layer 16 is baked and fixed on one side of the bottom substrate 12 for 7 to 8 minutes. Thereafter, a 5US430 stainless steel plate with a thickness of 60 μvn is punched out as shown in FIG. The heat-generating element 17 is placed on the insulating hollow layer 16 using a slip of the above-mentioned material, and the heat-generating element 17 is bonded and fixed by the outer coating hollow layer 18 at 840'C for 7 minutes in a nitrogen atmosphere. However, if necessary, the auxiliary heater can be constructed in a laminated structure on top of the heating element 17, or it can be installed on the side surface of the main body.

Next, a method for creating the bumping prevention layer 13 will be described. Said long heat section 1
The other inner surface of No. 4 is subjected to surface enlarging treatment using an alumina blasting material so that the surface roughness Ra becomes 5 to 10111, and then pure aluminum having a particle size of 62 to 84 μl is plasma sprayed. The plasma condition is 42V,
Thermal spraying was carried out at 65 oA with an argon-helium mixed gas flame so that the surface roughness Rz was 1251 tmK. The thickness of the sprayed layer is approximately 145 μm.

Next, for comparison, a bumping prevention layer made of a composite oxide of A4203/TiO□ containing Al2O3 and 8 TiO2 was formed. A, Ill'203 and A1203T102 have particle sizes ranging from 62 to 8471 m, plasma conditions 1d45V, 630A, argon-
Helium mixed gas flame, surface roughness Rz is 125/1m
It was sprayed to make it look vibrant.

In this way, the heat generating part 14 and the bumping prevention layer 13 are provided on the surface of the bottom substrate 120 constituting the base material, and finally, the cylindrical container body 11 and the end surface 16 of the bottom substrate 12 are electrically welded to integrate them. , complete the jar pot container.

Three types of inventive products (550W) completed in this way
In order to compare the above conventional product (700W), 25
A comparison was made in a temperature raising test in which 21 liters of water was injected and the temperature reached 100'C. The conventional product required 15 minutes at 7010W, but the product of the present invention required 16 minutes at 560W.

Next, we measured energy efficiency and bumping noise. The results are shown in Table 4.

In other words, the energy efficiency of the product of the present invention was improved by about 6% compared to the conventional product, and the value was closer to the theoretical energy efficiency. The reason why the energy efficiencies of Al2O3 and Al2O3.TiO2 are slightly lower is considered to be due to the difference in thermal conductivity. A sound level meter was used to measure the loud noise. The conventional product produced a bumping sound from 45 to 5 o'C, produced large nucleate boiling bubbles, and produced a pre-bumping temperature of 70 to 82 phon at the boiling point. However, the product of the present invention generates so many tiny bubbles that you can't see the bottom until it approaches 60'C, and there is no sound.
There is only a slight noise of 3 to 49 phons up to the boiling point, which is hardly noticeable.

Other advantages of the product of the present invention include: (1) Energy saving rate of about 6% is possible. ((2) The amount of insulation material can be halved to approximately 〃. (3) Bumping and boiling noises can be almost eliminated. (4)
1. To prevent bumping, create a space at the top as a part to prevent bumping.
4 Cm, it is possible to reduce this space to μ~14. (Since the bumping space and the heat insulation space can be reduced, it is possible to reduce the container space by 20 to 26%. It is also possible to extend the practical durability life.

Effects of the Invention As described above, according to the present invention, nucleate boiling and film boiling due to bumping are eliminated when a liquid is rapidly heated, so there are no complaints regarding pre-bumping or boiling noise as in conventional products. Therefore, convective diffusion by microscopic air bubbles is also effective during heating, improving energy efficiency, increasing the wattage density per unit area, and reducing the space required to prevent bumping. As a result, the electric liquid heating device can be designed to be more lightweight and compact than before, which is also advantageous in terms of cost.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a conventional jar pot, FIG. 2 is a vertical sectional view of a jar pot showing an embodiment of the present invention, FIG. 3 is an enlarged sectional view of section A in FIG. 2, and FIG. 4 FIG. 2 is a plan view of a planar heating element used in an embodiment of the present invention. 11...Container body, 12...Bottom board,
13... Bumping prevention layer, 14... Heat generating part,
16...Insulating hollow layer, 1γ...Heating element, 18...Exterior coating hollow layer.

Claims (1)

[Scope of Claims] (1) An electric liquid heating device characterized in that a bumping prevention layer is formed on the inner surface of a heat exchange portion of a container of the electric liquid heating device by surface enlarging treatment. (2) The electric liquid heating device according to claim 1, wherein the surface enlarging treatment as the bumping prevention layer has a ten-point average roughness Rz in the range of 50 to 150μ. (3) The electric liquid heating device according to claim 1 or 2, wherein the bumping prevention layer has a thickness in the range of 6° to 40,011°. (4) Bumping prevention layer is aluminum, copper, iron, nickel,
Metals or alloys such as stainless steel, iron-chromium alloy, nickel-chromium alloy, or AN203 +Tie2.5
in2. ZrO,,0r203. MgO,Cab
. The electric liquid heating device according to any one of claims 1 to 3, which is formed of at least one member selected from the group consisting of metal oxides such as BaO or composite oxides. (phrase) The electric liquid heating device according to any one of claims 1 to 4, in which the bumping prevention layer is formed by thermal spraying using any one of metallicon, electric arc, and plasma spraying. (6) Electric A patent for a container of a liquid heating device having, on one side of the base material, a heating part composed of a heating element covered and bonded with hollow glass, and a bumping prevention layer formed on the other inner surface of the heating part. An electric liquid heating device according to any one of claims 1 to 5.