JPH0922774A - Heater device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater device which has high heat transfer efficiency without requiring the surface of a ceramic heater to be polished. SOLUTION: A cylindrical ceramic heater 4 is fitted into a cylindrical metallic case 1, and a metal layer 7 made of a metal whose melting point is lower than that of the material from which the metallic case 1 is made is cast into the space between the inner surface 1a of the metallic case 1 and the surface 4a of the ceramic heater 4. Therefore, the metal layer of high packing density is formed throughout the gap between the surface 4a of the ceramic heater and the inner surface 1a of the metallic case 1 without polishing the surface 4a.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is directed to obtaining hot water.
Alternatively, a heater device using a ceramic heater (hereinafter, also simply referred to as a device) used to keep the bath water warm, and further to keep the cooling water of an automobile engine warm.
About.

[0002]

2. Description of the Related Art In this type of heater device, when the operation of a circulating pump for heated water is stopped, water in a portion in contact with a ceramic heater (hereinafter, also simply referred to as a heater) will boil instantly. Therefore, the surface (ceramic) of the heater has a portion where water and air (air bubbles) come into contact with each other. For this reason, in a heater having a structure in which a ceramic heater is heated in a state of being in direct contact with water, the heater itself may be cracked by the generated thermal stress or thermal shock. Also, heater cracking does not depend on the pump being stopped,
Occurrence of air entrapment may occur as well. Such cracking of the heater also causes electric leakage when the heater is used in water. Moreover, since the surface of the heater becomes hot, calcium and the like in the water adhere to the surface of the ceramic heater during long-term use, which further increases the heater temperature and reduces the heater performance. There is.

As a technique for solving such a problem of a device which is directly heated by a ceramic heater, there is a technique described in JP-A-60-127689. In this device, a rod-shaped ceramic heater is fitted and covered in a cylindrical metal case (cover member), and metal powder (metal fine particles such as copper or aluminum) is provided between the inner surface of the metal case and the surface of the ceramic heater. ) Or the like, and the water is indirectly heated through the metal powder and the metal case.

On the other hand, unlike the heater device described in the above publication using a rod-shaped ceramic heater, a plate-shaped ceramic heater is sandwiched between two metal bodies (metal heaters).
A heater device having a structure in which a fluid (water) passing through the inside of the metal tube is indirectly heated by heating the metal body by this heater and heating a metal tube provided so as to penetrate the metal body ( Various fluid heating devices have been developed (Japanese Patent Laid-Open No. 6-185804, Japanese Patent Laid-Open No. 6-193789, etc.).

[0005]

However, Japanese Patent Application Laid-Open No.
In the technique described in Japanese Patent No. 127689, in order to increase the heat transfer efficiency, the packing density of the metal powder between the heater and the metal case must be increased. It cannot be pressure-filled at a too high pressure. In other words, in this device, there is a limit to making the packing density super-high, so that the efficiency of heat transfer from the heater to the object to be heated is considerably lower than that by direct heating. Therefore, there is a problem that the heater itself has to be upsized in order to increase the relative amount of heat.

Further, in a device in which a plate-shaped ceramic heater is sandwiched by two metal bodies (metal heaters), the ceramic heater is not brought into close contact with the metal body in order to improve heat transfer (heating) efficiency. I can't. Also,
In this device, it is necessary to prevent cracking (damage) of the heater caused by unevenness of stress during tightening due to warp (deformation) of the heater when sandwiching the heater between metal bodies. For this reason, the ceramic heater of this type of device has a problem in that its surface needs to be highly accurately finished by polishing or the like, which causes a high cost.

An object of the present invention is to eliminate these problems in the above heater device.
Without the need to polish the surface of the ceramic heater,
It is an object of the present invention to provide a heater device having excellent heat transfer efficiency or temperature rising characteristics.

[0008]

In order to solve the above-mentioned problems, a heater device according to the present invention is a heater device in which a ceramic heater is fitted (inserted) in a metal case. A metal layer made of a metal having a melting point lower than that of the material of the metal case is cast between the surface of the ceramic heater and the surface of the ceramic heater. The melting point in the present specification refers to the liquidus point of the composition of the alloy (metal), and when there is a eutectic point, the eutectic point.

The thickness of the metal layer is preferably as thin as possible in order to enhance the heat transfer efficiency of the heater. It causes some defective products and reduces the production yield. If there is such a poor bathing or a large cavity, the heat transfer efficiency at the time of using the heater decreases at that portion, the temperature of the heater itself rises too much, and the performance of the heater device decreases. Furthermore, the heater may be cracked due to local thermal stress or thermal shock. On the other hand, the thicker the metal layer, the lower the heat transfer efficiency and the higher the temperature of the heater itself, and the lower the heat capacity of the heater device.

In consideration of these matters, the thickness of the metal layer formed by casting is generally appropriate in the range of 0.3 to 5.0 mm. The thickness of this metal layer is 0.3
When it is as thin as ˜5.0 mm, it is preferable to use one having a melting point of 450 ° C. or less. When the melting point is 450 ° C. or higher, a strong oxide film is formed on the inner surface of the metal case and the surface of the molten metal during the process of forming the metal layer unless a special casting method such as vacuum casting is used. This is because if the thickness of the layer is thin, defective porosity and cavities such as relatively large pores are likely to occur, which lowers the production yield.

Although it is necessary to form the metal layer with a metal having a melting point as high as possible in order to increase the heat generation density of the heater device, as described above, the thickness of the metal layer formed by casting is 0. If it is as thin as 3 to 5.0 mm,
It is preferable to use a metal that does not melt when the heater is energized and has a melting point of 450 ° C. or lower (generally 100 ° C. to 450 ° C.). Specifically, it is preferable to use a low melting point metal such as tin (Sn), lead (Pb), bismuth (Bi), or zinc (Zn), or an alloy containing these metals as a main component. It is particularly preferable to use zinc or an alloy containing zinc as a main component, which has a relatively high casting property.

The material of the metal case may be a good heat conductive material such as aluminum or copper, an aluminum alloy or a copper alloy, and has a corrosion resistance, although it depends on the heat capacity of the heater and the melting point of the metal forming the metal layer. Stainless steel (such as SUS316L) is preferred for required applications. Particularly, aluminum alloy is preferable in terms of weight reduction of the device. Incidentally, the material of the heater is alumina (Al ₂ O
₃ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and boron nitride (BN).

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment in which the apparatus according to the present invention is embodied will be described in detail with reference to FIGS. In FIG. 1, reference numeral 1 is a cylindrical metal (copper) case with one end closed, and a circular flange for mounting the device through a stepped portion 2 with an enlarged diameter at the end on the opening side (left in FIG. 1). Equipped with 3. A cylindrical ceramic heater 4 made of alumina is fitted and inserted in the inner side of the coaxial core. However, the ceramic heater 4 has its tip 5 sealed (closed) and its outer peripheral surface is not polished. Although not shown, a heating wire (heating element) made of a high melting point metal such as molybdenum or tungsten is embedded and formed in the ceramic heater 4, and a heater electrode (not shown) forming both ends thereof is formed. The leads 6 for connecting the electric wires are joined (connected) by brazing.

On the other hand, the heater 4 is provided between the inner surface 1a of the metal case 1 and the surface 4a of the ceramic heater 4 (gap).
In this example, the eutectic solder having a melting point of 183 ° C. is filled by casting, including the tip 5 and the tip 5, and the heater 4 is cast into a metal layer 7 having a predetermined thickness. There is. However, in the device of this example, the metal (copper) case 1 has an inner diameter of 15
The ceramic heater 4 has an outer diameter of 13 mm, an inner diameter of 8 mm, and a length of 80 mm, and the metal layer 7 has a thickness (design value) of 1 mm. In addition,
The ceramic heater 4 has a resistance value of 20 ° C. of 5.5Ω,
The temperature coefficient of resistance is 4000 ppm / ° C.

By the way, the method for casting the metal layer 7 is as follows.
The metal case 1 is heated and melted by placing a predetermined amount of solder with its opening side facing upward, and the ceramic heater 4 heated to a predetermined temperature is pushed into the metal case 1 to be inserted and simultaneously positioned coaxially with the case 1. An example is a method of causing molten solder to overflow and then cooling and solidifying. However, the ceramic heater 4 may be fitted in the center of the metal case 1 in advance, and then molten metal such as solder may be poured into the gap to solidify.
In the present invention, the space between the surface 4a of the heater 4 and the inner surface 1a of the case 1 serves as a mold cavity, and a metal having a melting point lower than that of the material of the metal case 1 is cast into the space to form a metal. Any method may be used as long as the layer is effectively formed.

The thickness of the metal layer 7 is set to be 1 mm on average in this example, but this thickness may be set appropriately in consideration of the dimensional tolerance between the case 1 and the ceramic heater 4. Good. That is, in manufacturing the device, an unpolished ceramic heater may be of a size that can be inserted into a metal case while holding a predetermined gap, and a metal layer can be formed by casting in the gap, but the gap is preferable. Is 0.3 as described above
The range is up to 5.0 mm. However, it is of course possible to use a ceramic heater whose surface is polished.

The bonding between the heater electrode and the lead 6 is
It is possible even after the ceramic heater 4 is fitted in the metal case 1 and the metal layer 7 is formed in the gap by casting, but when joining is performed by soldering after forming the casting, the joining space is narrow and heat is applied. Is a metal layer (cast metal) 7 and case 1
There is a problem in work such as a large soldering iron is required to escape from (heat). Therefore, it is preferable that the lead 6 is bonded to the heater electrode in advance, and then the ceramic heater 4 is fitted into the metal case 1 to form the metal layer 7 by casting. For this reason, the metal used for joining the heater electrode and the lead 6 should have a melting point higher than that of the metal layer 7 to be cast (silver) so that the joining of the leads 6 does not melt when the metal layer 7 is cast. It is recommended to use such as low.

-Test 1- One sample S was prepared for the above-described embodiment (metal layer casting heater), and the heat transfer efficiency and the like were tested as follows. However, as a comparative example, in the above-described embodiment example, a metal case and a metal layer alone, which is composed only of a ceramic heater (a structure in which a ceramic heater directly contacts a liquid, referred to as a direct heating heater), Using the same metal case and heater, instead of the metal layer in the above-described embodiment example, two kinds of comparative samples each having a gap filled with copper powder (referred to as a copper powder filled heater) were prepared. The temperature rise test of tap water was performed under the conditions of.
The ceramic heater itself is the same in both the sample S and both comparative examples.

That is, as shown in FIG. 3, each sample S is attached to a casing C in which tap water can be circulated as shown by an arrow, and this is piped as shown in FIG. The tap water W (3 liters) was circulated by the pump P at 6 liters per minute, and the time required to raise the temperature to 70 ° C. and the heater temperature at that time were measured and compared. The heater power supply is AC100V. The results are as shown in Table 1.

[Table 1]

As shown in Table 1, the heater of the embodiment (heater for casting metal layer) has a temperature rising time which is almost the same as that of the direct heating heater of the comparative example, and also the copper powder filling of the comparative example. It was about half that of the heater. From this, it was confirmed that the metal layer casting formation heater of the embodiment example has a very excellent heat transfer efficiency. Also, the heater temperature is 205 ° C. lower than that of the comparative example. As the temperature of the ceramic heater rises, the resistance value rises, and the current flow deteriorates, so the amount of heat generated decreases, and it takes an extra time to raise the temperature and durability also decreases. Therefore, it is important to prevent the temperature of the heater from rising, but it can be seen from this temperature difference that the device of this example has extremely high performance.

-Test 2-Preparation of the same sample as used in the above test, under the conditions shown in FIGS. 3 and 4, 3 liters of water at 6 liters per minute, similar to the above test. When the water was circulated, heated at AC 100 V, and the water temperature reached from 50 ° C. to 20 ° C., the pump P was stopped (water circulation stopped), and a test was conducted assuming an abnormal time such as water flow stop. However, in this test, as a safety circuit, a thermostat (not shown) that is set to turn off the heater energizing circuit when the casing C reaches 130 ° C. is attached to the casing C, and the time until the thermostat operates is set. , Measure the heater temperature at that time,
Compared. The results are as shown in Table 2.

[Table 2]

As shown in Table 2, in the example of the embodiment, the thermostat was activated after 2 minutes without the occurrence of heater cracking which is considered to be caused by instantaneous boiling like the direct heating heater of the comparative example. And the heater temperature is also 18
Only rose to 0 ° C. From this, it is understood that the example embodiment has not only high safety but also high heat transfer efficiency and durability. In the copper powder-filled heater of the comparative example, no heater cracking occurred, but it took as long as 5 minutes for the thermostat to operate, and the heater temperature rose to 800 ° C. This means not only that the heat transfer efficiency is poor, but also that there is a risk of breaking the heating wire (heating element) in the heater, and in terms of durability, compared to that of this embodiment example. It can be seen that the performance is extremely poor. As demonstrated by this result, in this example, the water pump can be operated by setting a predetermined safety circuit such as a thermostat as described above and setting the power supply to be cut off at a predetermined temperature. It was confirmed that it is safe even in the case of an abnormality such as a stop.

As described above, the heater device of this embodiment does not require polishing of the surface of the ceramic heater in the manufacturing process thereof, and further has excellent performance in terms of heat transfer efficiency, temperature rising characteristics, and safety. You know that you have. Moreover, in the copper powder filling heater of the comparative example, when the ceramic heater is cracked, the cracked portion (crack)
There is a risk that metal powder may enter the inside of the heater and come into contact with a heating wire (heating element) embedded in the heater to cause a short circuit. However, according to the apparatus of this example, there is no such risk.

-Test 3- Now, the embodiment example of FIG. 1 (set thickness of metal layer 1)
mm), 20 samples each having a different melting point were prepared for the metal (metal layer 7) used for casting, and the occurrence (rate) of casting defects (such as defective molten metal and porosity) in the metal layer 7 of each sample was confirmed. Tested. However, the defect (quality) judgment criteria are shown in FIG.
Alternatively, as illustrated in FIG. 6, of the metal layer 7 formed between the metal case 1 and the ceramic heater 4, the depth or the major axis is 3 mm or more in the range (length 55 mm) of the heater heating portion H. The one in which at least one metal-unfilled portion M was found was regarded as a casting defect. Note that the measurement was performed by X-ray imaging and confirmation from the entire side surface of the illustrated heater. The results are shown in Table 3.
As shown in FIG. In addition, Case 1 is SUS316
For each metal used for casting, a metal case 1 is put into the metal case 1 with its opening side facing upwards, a predetermined amount of metal is put therein, and the mixture is heated and melted, and a ceramic heater 4 heated to a predetermined temperature is pushed thereinto. As a result, it is obtained by being fitted and positioned at the same time as the case 1 so as to be coaxial therewith, so that the molten metal overflows, and then cooled and solidified.

[Table 3]

As shown in Table 3, the melting point is 221 to 45.
In Samples 1 to 5 at 0 ° C, the defect occurrence rate was 5% to 15%, whereas in Samples 6 and 7 having a melting point of 500 to 577 ° C.
Then, the defect occurrence rate was extremely high at 40% and 90%. Considering the production yield from this result, the melting point is 4
A metal or alloy having a temperature of 50 ° C. or lower is preferable. In particular, alloys containing zinc as the main component as shown in Samples 4 and 5,
It can be said that it is a preferable material having a high melting point and a relatively low defect occurrence rate.

In the present invention, the shape of the ceramic heater may be any shape such as a cylindrical shape, a cylindrical shape, a plate shape, regardless of the shape and structure of the metal case and its inner surface. As illustrated in the above embodiment, in the case of a columnar shape (the cross section is circular), during the casting of the metal layer, the thermal contraction (stress) in the cross section (radial) direction due to its solidification is ceramic. Since it is uniformly applied to the heater, the ceramic heater itself is unlikely to crack. In particular, the cylindrical heater (annular cross section) is easily deformed because it is hollow, and therefore the ceramic heater which is a problem when cooling and solidifying the melted metal (layer) formed by casting. It is easy to absorb the stress due to the difference in the coefficient of thermal expansion between and. When a cylindrical heater is used, it is preferable to use a heater whose tip is sealed (closed) as in the above embodiment so that the metal layer formed by casting does not enter the inside.

Further, the cross section (shape) of the ceramic heater
Whether the shape is circular or annular, the cross section does not have to be uniform (identical) over the entire length. Specifically, a ceramic heater is used in the above-described embodiment example (FIG. 1), a stepped heater 14 as in the embodiment example 2 shown in FIG. 7, or an embodiment example 3 shown in FIG. The tapered heater 14 may be used. In FIGS. 7 and 8, 1 is a metal case, 7 is a metal layer formed by casting, which is similar to those in FIG. 1, but the metal layer 7 is the same as that of the ceramic heater 14. Since the cross section (shape) is not uniform, the thickness changes correspondingly as shown in each figure. In this example as well, the metal layer 7 has a thickness of 0.3 to 5.0 as described above.
It is preferable to set the shapes and dimensions of the metal case 1 and the ceramic heater 14 so as to be in the range of mm. The metal forming the metal layer 7 does not melt when the heater is energized and has a melting point of 450 ° C. or less (a low melting point metal such as Sn, Pb, Bi, Zn, or the like, as described above). (Alloy containing metal as a main component) is preferably used, and among these, zinc having a relatively high melting point and good castability or an alloy containing zinc as a main component is preferably used. The same applies to the following embodiments.

A fourth embodiment of the present invention will be described in detail with reference to FIGS. 9 and 10. In this embodiment, the metal case 21 has a block-like shape made of aluminum, copper or an alloy thereof. And two metal pipes (stainless steel pipes) that penetrate the top and bottom and left and right.
2 and 22 are different, but the other points are basically the same as those of the first embodiment, and therefore the difference will be mainly described.

That is, in this example, the metal case 21 is in the form of a block, and is disposed along the axial direction between the two metal pipes 22, 22 which pass through it at the center thereof. At this point, a hole 23 having a circular cross section is provided, and a cylindrical or columnar ceramic heater 24 having an outer diameter slightly smaller than the inner diameter of the hole 23 is fitted therein, and solder such as solder is inserted in the gap. The low melting point metal is cast and formed, and has a lower melting point than the material of the metal case 21 between the inner surface 23a of the hole 23, that is, the inner surface of the metal case 21 of this example and the surface 24a of the ceramic heater 24. A metal layer 27 made of metal is formed. In addition, 26 is a lead for electric wire connection joined to the heater electrode (not shown).

In this example as described above, the two metal tubes 22,
22 is used by connecting one end (right of FIG. 9) with a vent pipe 28 as shown by the chain double-dashed line in the figure, and connecting the other end in the middle of piping such as a circulating water heater (not shown). However, by energizing the heater 24, the metal layer 27,
The metal case 21 and the metal tube 22 are heated,
It is configured to indirectly heat water flowing (circulating) through the metal tube 22.

Also in this example, the metal case 21 is used as in the previous example.
That is, since the ceramic heater 24 is inserted into the hole 23 and the surface 24a and the hole inner surface 23a are filled with a metal having a melting point lower than that of the material of the metal case 21 without any gap, Similar to the above, high heat transfer efficiency can be obtained even if the surface of the ceramic heater 24 is not polished. This example is suitable when it is provided in the middle of piping such as a circulating water heater such as a bathtub. As will be understood from this example, the metal case according to the present invention is the same as the first to third embodiments.
The shape and the structure are not limited to the cylindrical shape in FIG. 1 and can be any shape as long as the ceramic heater can be fitted (inserted).

Next, a fifth embodiment of the present invention will be described in detail with reference to FIGS. 11 and 12, but since this embodiment is basically the same as the above embodiment, The difference will be mainly described.

That is, in this example, the metal case 31 is a block-shaped case made of aluminum, copper or an alloy thereof, and the metal tube (stainless steel tube) 32 penetrates in a U-turn shape so that the metal case is formed. It is provided in the shape of a cast body in 31. The metal pipe 3 is provided on one side of the block-shaped metal case 31 (on the right side in FIG. 11).
A groove (slit) -shaped recess 33 having a V-shaped or U-shaped cross section is provided between the two 2 and 32, and a plate-shaped heater 34 is fitted into the recess 33. It is configured. Then, in the same manner as described above, the heater 34 is fitted into the recess 33, and the inner surface 33 of the recess 33 is inserted.
A, that is, a metal layer 37 made of a metal having a melting point lower than that of the material of the metal case 31 is formed by casting between the inner surface of the metal case 31 and the surface 34a of the heater 34.

Also in this example, as in each of the above-described embodiments, the metal layer 37 formed by casting is formed without a gap between the surface 34a of the heater 34 and the inner surface of the metal case 31. Even if the surface 34a of the heater 34 is not polished, high heat transfer efficiency can be obtained. In particular, in this example, since the ceramic heater 34 is plate-shaped, it is easy to manufacture, so that it can be realized at a relatively low cost. Moreover, since the metal case and the ceramic heater are not brought into close contact with each other by mechanical tightening, cracking of the ceramic due to uneven tightening force does not occur. Like the previous example, this example apparatus is also suitable when it is provided in the middle of piping such as a circulating water heater such as a bathtub.

[0035]

According to the present invention, since the metal layer made of a metal having a melting point lower than that of the material of the metal case is cast between the inner surface of the metal case and the surface of the ceramic heater, the ceramic is formed. The heater has a structure surrounded by the metal layer. According to such a structure of the heater device according to the present invention, a metal layer having no gap and a high packing density is formed between the surface of the ceramic heater and the inner surface of the metal case without polishing the surface of the ceramic heater. Since it can be formed, the heater device can have high heat transfer efficiency.

[Brief description of drawings]

FIG. 1 is a central vertical sectional front view showing a first embodiment in which a heater device according to the present invention is embodied.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is an explanatory diagram of a performance test of the heater of FIG.

FIG. 4 is an overall view of FIG.

FIG. 5 is a vertical cross-sectional front view illustrating an example of a casting defect of a metal layer in an embodiment that embodies a heater device according to the present invention.

FIG. 6 is a vertical cross-sectional front view illustrating an example of a casting defect of a metal layer in an embodiment that embodies a heater device according to the present invention.

FIG. 7 is a central longitudinal front view showing a second embodiment of the heater device according to the present invention.

FIG. 8 is a central longitudinal front view showing a third embodiment which embodies the heater device according to the present invention.

FIG. 9 is a partially cutaway front view showing a fourth embodiment of the heater device according to the present invention.

10 is a sectional view taken along the line BB in FIG. 9 and an enlarged view of a main part.

FIG. 11 is a partially broken cross-sectional view and an enlarged view of a main part showing a fifth embodiment of the heater device according to the present invention.

12 is a partially cutaway view of the device of FIG. 11 as viewed from the right side.

[Explanation of symbols]

 1 Metal Case 4, 14, 24, 34 Ceramic Heater 1a, 23a, 33a Metal Case Inner Surface 4a, 24a, 34a Ceramic Heater Surface 7, 27, 37 Metal Layer

Claims (7)

[Claims] 1. A heater device having a ceramic heater fitted in a metal case, wherein a metal having a melting point lower than that of the material of the metal case is provided between an inner surface of the metal case and a surface of the ceramic heater. A heater device having a metal layer formed by casting. 2. The metal layer has a thickness of 0.3 to 5.0 m.
The heater device according to claim 1, wherein m is m. 3. The heater device according to claim 2, wherein the metal layer is made of a metal having a melting point of 450 ° C. or lower. 4. The heater device according to claim 2, wherein the metal layer is made of zinc or an alloy containing zinc as a main component. 5. The heater device according to claim 1, wherein a cross section of the ceramic heater is circular or annular. 6. The heater device according to claim 1, wherein the ceramic heater has a cylindrical shape or a cylindrical shape. 7. The heater device according to claim 1, wherein the ceramic heater has a plate shape.