JPS63207082A - Cartridge heater and manufacture of the same - 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] <Industrial Application Field> The present invention relates to a cartridge heater (hereinafter simply referred to as a heater).
and its manufacturing method.

Heaters of various structures and shapes are widely used in various industrial fields. For example, when heating an object to be heated, typically water, in a closed or open container, the heater is easily attached to the container.

The present invention relates to such a heater, particularly a heater using a positive temperature coefficient thermistor element, and a method for manufacturing the same.

<Conventional technology and its problems> Conventionally, a heating wire is wound inside a metal sealed pipe.
A heater filled with thermally conductive insulating powder is used.

However, such conventional heaters have the following problems.

1) As the metal pipe is used, scale adheres to the outer circumferential surface of the metal pipe, which gradually enlarges and obstructs the thermal conductivity between the heater and the object to be heated in the container in which it is installed. In this case, in order to ensure the desired heating temperature of the object to be heated, the heater itself has to reach an excessively high temperature, which often results in damage to the inside of the heater. If you continue to use it as it is, the scale will eventually carbonize, which will further promote internal damage to the heater and, in some cases, lead to pitting of the metal pipe.

2) In order to prevent abnormal overheating such as dry firing and ensure the safety of the entire device including the container equipped with the heater, it is essential to install a protective member such as a thermostat, which makes the structure of the entire device complex and expensive. become. In addition, in order to prepare for dry baking as described above, the container is inevitably made of metal, which increases the weight accordingly.

<Problems to be Solved by the Invention and Means for Solving the Problems> The present invention provides a new heater that solves the conventional problems as described above.

Therefore, in the present invention, an electrode with a lead wire is fitted with an insulating material fitted around the outer periphery of the metal sealed pipe in which only the heat generating part is reduced in diameter and a mounting member is welded to the outer periphery of the base end. positioned through the
A positive temperature coefficient thermistor element is sandwiched between the electrodes from both sides, and the electrode and the positive temperature coefficient thermistor element in the heat generating part are closely fixed with thermally conductive insulating powder compacted by the diameter reduction compression, and the sealed pipe A cartridge heater consisting of a terminal section taken out from the base end, and a metal pipe with a closed end that has been welded with a mounting member to the outer periphery of the base end and then annealed are prepared. An insulating material is fitted around the outer periphery of the electrode while holding the positive temperature coefficient thermistor element between them, and the electrode, which has the positive temperature coefficient thermistor element sandwiched therein, is made of metal while the insulating material is in sliding contact with the inner peripheral surface of the metal pipe. After charging into the pipe and filling the gap in the metal pipe with thermally conductive insulating powder, the insulating powder is compacted by reducing the diameter of only the heat generating part of the metal pipe from its outer circumferential surface. The present invention relates to a method of manufacturing a cartridge heater, characterized in that a positive temperature coefficient thermistor element is closely fixed while being sandwiched between electrodes from both sides thereof.

The important point in the present invention is that only the heat generating portion of the metal pipe into which the positive temperature coefficient thermistor element is inserted as a heat source is compressed to reduce its diameter. In order to improve the thermal efficiency of a heater, it is important to compact the insulating powder filled inside the metal pipe to improve its thermal conductivity. Consolidation of such insulating powder is also necessary to
A mounting member made of metal fittings such as a screw plug or flange is generally welded to the outer periphery of the base end of a metal pipe to facilitate the use of a heater, but if the welded part is left as is, stress cracking may occur. This causes the
In order to prevent such stress cracking, it is necessary to anneal the metal pipe after the above-mentioned welding to temporarily convert the entire pipe into a solution. Therefore, in the above case, normally, the entire metal pipe into which the PTC thermistor element and electrodes are charged and further filled with insulating powder is compressed to reduce its diameter to consolidate the insulating powder, and then the base end of the metal pipe is compressed. After welding the mounting members, it is conceivable to subject the entire body to annealing, but for example, the annealing temperature for metal pipes normally made of stainless steel is 1000°C.
Since the annealing is required to be performed at a temperature of about .degree. C., the positive temperature coefficient thermistor element will be destroyed during the annealing.

In the present invention, only the heat generating part of the metal pipe into which the PTC thermistor element is inserted is reduced in diameter and compressed.The reason is that a mounting member is welded to the outer periphery of the base end, and then the PTC thermistor element is inserted into the annealed metal pipe. By inserting the elements and electrodes and filling them with insulating powder, we reduce the diameter of only the heat-generating part and compress it to prevent stress cracking in the welded part, and on the other hand, improve the thermal conductivity of the insulating powder in the heat-generating part. This is to do so.

Hereinafter, the configuration of the present invention will be explained in more detail based on the drawings.

<Embodiment and its operation> Fig. 1 is a vertical sectional view (partially omitted) showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view of this embodiment, in which a plug material 11 whose distal end is closed by welding, for example, and whose proximal end has insulating elasticity.
Positive temperature coefficient thermistor elements 41a to 41d, which are sandwiched from both sides by aluminum electrodes 31a and 31b, are placed inside a metal pipe 21 that is sealed by electrodes 31a and 31b.
2 (insulating materials 51a, 51 fitted at 91 places) on the outer periphery of 31b.
In the illustrated embodiment, the insulating material 51a has a circular plate shape with a ring-shaped peripheral end, and the insulating material 51b has a ring shape, but the insulating material 51a The electrodes 31a and 31b have a disk shape to also serve as an insulator between the electrodes 31a and 31b and the closed end surface of the metal pipe 21. Therefore, if a disc-shaped insulator, for example, is separately interposed to perform such an insulating function,
What corresponds to the insulating material 51a can be made into a simple ring shape like the insulating material 51b.

Furthermore, lead wires 61a and 61b are inserted into the parallel through holes of the electrodes 31a and 31b, and terminal portions 62a*62b of the lead wires 61a and 61b penetrate the wire 11 and are taken out to the outside. ing. Further, the gap in the metal pipe 21 is filled with thermally conductive insulating powder 71, which is compacted by diameter reduction compression described later, and is used to connect the electrodes 31a, 31b and the positive temperature coefficient thermistor element 41a. - 41d are fixedly attached to each other by compacted insulating powder 71 with the help of insulating materials 51a and 51b.

The metal pipe 21 is a heat generating part A that includes electrodes 31a, 31b and positive temperature coefficient thermistor elements 41a to 41d.
Only the diameter of the screw plug 12 is compressed to reduce its diameter, and a screw plug 12 as a mounting member is welded to the outer periphery of the base edge at the edge 12a.

FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

In the case of the embodiment shown in FIG. 3, the metal pipe 22, the electrode 32a
, 32b, positive temperature coefficient thermistor element 42d, insulating material 52b
, lead wires 63a, 63b and compacted insulating powder 7
2 are similar to the embodiments of FIGS. 1 and 2, except for the following points: That is, in the embodiment shown in FIG. 3, the positive temperature coefficient thermistor element 42d is
The leads 63a and 63b are fitted into recessed portions opposite to the electrodes 32a and 32b, respectively.
The insulating material 52b is embedded in small recesses 32c and 32d recessed in the circumferential surface of the insulating material 52b, and is fixed by compressing the openings of the small recesses 32c and 32d, and the insulating material 52b has a simple ring shape. In the embodiment shown in FIGS. 1 and 2, the notch 51c of the insulating material 51b is used when filling the gap in the metal pipe 21 with the insulating powder 71, but in the embodiment shown in FIG. When filling the gap in the manufactured pipe 22 with the insulating powder 72, the small gap 52c formed by the electrodes 32a, 32b, the positive temperature coefficient thermistor element 42d, and the insulating material 52b is utilized.

FIGS. 4 and 5 are longitudinal cross-sectional views of essential parts showing how the order of positive temperature coefficient thermistor elements relative to electrodes is determined in still other embodiments of the present invention. In the case of FIG. 4, the positive temperature coefficient thermistor elements 43a to 43C are connected to the electrodes 33 from both sides.
They are arranged at a predetermined interval so as to be sandwiched between a and 33b. In addition, in the case of FIG. 5, positive temperature coefficient thermistor elements 44a to
The electrodes 44c are similarly arranged at predetermined intervals, but are fitted into the recessed portions facing the electrodes 34a and 34b on both sides.

FIG. 6 is a schematic perspective view illustrating the state of use 7g of the heater according to the present invention. A heater 10 is screwed into a closed container 81, and a suitable voltage is applied to the heater lO.
The structure is such that the liquid introduced from the lower side of the container 81 is heated, and the heated liquid is sent out from the upper side of the container 81. In this case, the self-maintaining W! of the positive temperature coefficient thermistor element which is the heat generation source of the heater 10! Because of this function, there is no need to separately attach a protective member such as a thermostat, and the container 81 can also be made of plastic, for example.

Next, an example of manufacturing a heater according to the present invention will be described.

First, a metal pipe with a closed tip is prepared, a mounting member is welded to the outer periphery of the base end, and this is annealed. Stainless steel #l (e.g. 5U) where metal pipes are commonly used
S316L), its annealing temperature is 950-11
It is about 00℃. Separately, attach two electrodes with lead wires attached.
A plurality of positive temperature coefficient thermistor elements are sandwiched between these electrodes, and an insulating material is fitted around the outer periphery of the electrode, and the electrodes with the positive temperature coefficient thermistor elements sandwiched therebetween are slidably contacted. Charge into the metal pipe. This charge is automatically positioned within the metal pipe as it is restricted by the insulation. As mentioned above, if the insulating material fitted to the electrode is, for example, in a simple ring shape and does not serve as an insulator between the electrode and the end closing surface of the metal pipe, Another insulating material such as an insulator is inserted into the closed end surface of the metal pipe.Next, the gap in the metal pipe is filled with insulating powder. Referring to the illustrated embodiment, this filling is performed in the notch 51c of the insulating material 51b in FIG.
This is done using the small gap 52c in FIG. After filling the insulating powder, the heat-generating portion of the metal pipe is compressed to reduce its diameter by pressing from the outer peripheral surface toward the central axis. By this diameter-reducing compression, the insulating powder is compacted, and the electrodes and the positive temperature coefficient thermistor element are tightly fixed with the aid of the insulating material. lastly,
A plug material is inserted into the base end of the metal pipe that has undergone the above steps so as to take out the terminal portion.

In the present invention, the metal pipe is not limited to the circular cross-section shown in the drawings, but also those with an elliptical cross-section or a rectangular cross-section can be used.

In addition, in the present invention, the insulating material fitted around the outer periphery of the electrodes plays an important role. That is, the insulating material stably holds the positive temperature coefficient thermistor elements between the electrodes, making their handling extremely easy, and When an electrode holding a characteristic thermistor element is inserted into a metal pipe, the electrode is automatically positioned, and when filling an insulating powder into a gap in the metal pipe or after that, the electrode is automatically positioned. This completely prevents the inconvenience of insulating powder entering between the electrode and the positive temperature coefficient thermistor element when compressing the heat generating part to reduce its diameter. The insulating material may have various shapes depending on the relationship with the metal pipe, the electrode, and the positive temperature coefficient thermistor element, but it is preferable to use a material such as fluororubber.

Further, in the present invention, the positive temperature coefficient thermistor element may have various shapes that are already commercially available, such as a disk shape, a square plate shape, a donut shape, etc. in plan view. The positive temperature coefficient thermistor element has a self-protection function in which the electrical resistance increases rapidly at a certain temperature due to the material properties of the combination, and therefore the current value suddenly decreases when the certain temperature is reached to keep the heating temperature constant. The present invention takes full advantage of the characteristics of such a positive temperature coefficient thermistor element to rapidly heat an object while keeping its temperature constant, and on the other hand, to This prevents self-damage of the built-in heater. Therefore, the positive temperature coefficient thermistor element incorporated in the heater according to the present invention should be carefully selected from its combination of materials and shape (planar area,
thickness) is selected as appropriate.

In the present invention, the insulating powder may be magnesium oxide, which is conventionally filled as an insulating powder, but it is preferable to use powders such as boron nitride, alumina, and beryllia. In comparison, it has sufficient insulation properties and much higher thermal conductivity.

<Effects of the Invention> As explained above, the present invention has the advantage that, in addition to being able to quickly heat an object to be heated, there is no self-damage of the heater, and a protective member such as a thermostat is separately attached. Furthermore, since a container made of plastic, for example, can be used as the container in which the heater is attached, the overall structure of the device can be simplified, making it lightweight and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view (partially omitted) showing an embodiment of the present invention.
, FIG. 2 is a cross-sectional view showing this embodiment, FIG. 3 is a cross-sectional view showing another embodiment of the present invention, and FIGS. 4 and 5 are each a further embodiment of the present invention. FIG. 6 is a longitudinal cross-sectional view of a main part showing an example, and a schematic perspective view showing an example of a usage state of the heater according to the present invention. 10...Heater, 11...Plug material 12...Screw plug 21.22-.Metal pipes 31a, 31b, 32a, 32b, 33a, 33b, 3
4a, 34b...electrodes 41a to 41d, 42d, 43a to 43c, 44a
~44c... Positive temperature coefficient thermistor elements 51a, 51b, 5
2b@Fist insulation material 51c...Notch, 52c...Small gaps 61a, 61b, 63a, 63b--Lead wire 62a,
62bee terminal part 71.72...Insulating powder A- and heat generating part

Claims (1)

[Scope of Claims] 1. In a metal sealed pipe in which only the heat generating part is reduced in diameter and compressed and a mounting member is welded to the outer periphery of the base end, an electrode with a lead wire attached is fitted on the outer periphery of the electrode. A positive temperature coefficient thermistor element is sandwiched between the electrodes from both sides, and the electrodes and the positive temperature coefficient thermistor element in the heat generating part are tightly fixed with a thermally conductive insulating powder compacted by the diameter reduction compression. A cartridge heater in which a terminal portion is taken out from the base end of the sealed pipe. 2. Prepare a closed-end metal pipe with a mounting member welded to the outer periphery of the base end and then annealed, and attach the positive temperature coefficient thermistor element to the outer periphery of the electrode while holding the positive temperature coefficient thermistor element from both sides with electrodes with separate lead wires attached. An insulating material is fitted in advance, and an electrode holding a positive temperature coefficient thermistor element is inserted into the metal pipe while the insulating material is in sliding contact with the inner circumferential surface of the metal pipe. After filling the gap with thermally conductive insulating powder, only the heat generating part of the metal pipe was compressed to reduce its diameter from its outer circumferential surface to compact the insulating powder, and the positive temperature coefficient thermistor element was sandwiched between electrodes from both sides. A method for manufacturing a cartridge heater characterized by tightly fixing the cartridge heater.