JPS5842957B2 - Positive characteristic porcelain heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive characteristic porcelain heating element that can generate a large amount of heat with a small volume and is free from the risk of overheating and disconnection.

Conventionally, heating elements using positive temperature coefficient resistors, such as barium titanate-based positive temperature coefficient porcelain, have been made of positive temperature coefficient porcelain in the form of disks, and only a few watts of heat can be generated from each resistor. In order to generate several tens of watts of heat, a large heat sink must be attached, which imposes large structural constraints on the heating element, and also requires large amounts of power, such as I
In order to obtain a calorific value of KW or more, a large number of heating elements are required, making the entire heating element large and uneconomical.

It is also known to make a heater by making positive characteristic porcelain into a cylindrical shape and attaching electrodes to its outer and inner surfaces, but in order to obtain a surface area of about 1000 cr with this heater, the diameter should be about 50 mm and the length. It needs to be 300 mm or more, which occupies an extremely large volume and has poor mechanical strength, making it impractical.

Furthermore, there are heating elements made of positive temperature porcelain that have holes for heat dissipation in order to prevent heat from accumulating inside the cylindrical or disk shaped positive temperature porcelain. With methods such as drilling holes, it is difficult to make the surface area per unit volume after drilling the holes extremely larger than the surface area before drilling the holes, and furthermore, it is difficult to make the thickness of the partition wall separating the holes almost uniform σ. It is more difficult to rub and it is not possible to obtain a large amount of heat, for example, 300W with one piece of positive characteristic porcelain.
It has been impossible to industrially produce a heating element that generates a certain amount of heat.

The positive characteristic porcelain heating element of the present invention solves these conventional drawbacks, and has at least 5 or more through holes per die, and the thickness of the partition wall between the through holes is 1 μ or less. It is a heating element with a through hole.

A more detailed explanation of the structure of the present invention will be given with reference to FIGS. 1, 2, and 3, which are examples.
The number of through holes 1 is at least 5 or more, and the thickness of the floor wall 2 between the through holes 1 is 1 mr/or less, and more preferably, the electrodes 3 are provided on both end faces with the through holes 1. This is a heating element made of positive characteristic porcelain 4 having a through hole 1 of .

The number of through holes 1 provided in the positive characteristic porcelain 4 is the same as that of the positive characteristic porcelain 4.
They can be freely selected based on the specific resistance, specific strength, required calorific value, resistance, etc., but it is desirable to have five or more per unit area (-) in order to increase the calorific value per unit volume.

If the number is as small as less than 5, the heat dissipation surface area becomes small, so even if the fluid is forced to flow through the through hole 1, a practically large amount of heat cannot be obtained.

Further, the outer shape of the positive characteristic porcelain 4 can be freely selected as required, such as a cylindrical triangle, a disk, or a rectangular shape.

As shown in FIG. 2, the heat dissipation from the outer surface can be improved by providing unevenness on the outer surface of the heating element made of positive characteristic porcelain 4 having a large number of through holes 1.

Further, the shape of the through hole 1 can be freely selected from triangular, square, hexagonal, etc. as required.

The positive characteristic porcelain 4 having such a shape can be manufactured by a pressing method, an extrusion method, a method of dipping a raw material slurry that will become a porcelain body into water-absorbing honeycomb paper, or the like.

Size of through hole 1, partition wall 2 between through holes 1
The thickness of the partition wall 2 between the two through holes 1 can be freely selected depending on the specific resistance, specific strength, required heat generation amount, resistance, etc. of the positive characteristic porcelain body 4. The following is desirable.

If this thickness is large, a large surface area cannot be obtained even if the number of through holes 1 per unit area is increased, and furthermore, the area occupied by the through holes 1 per unit area becomes smaller, resulting in increased fluid flow resistance. In addition, even though the surface of the porcelain body around the through hole 1 is cooled and its resistance is reduced, the inside of the porcelain body is not cooled and has a high resistance, which causes a large amount of heat to be generated for practical purposes. This is so that you will not be affected.

Further, it is desirable that the thickness of the partition wall 2 is approximately uniform;
The reason is that there are parts where the thickness differs greatly,
This is because when used as a heating element, the temperature of each part differs, making it easy to break due to thermal strain.

The method for attaching electrodes to the positive characteristic porcelain 4 having a large number of through holes includes methods such as applying a paste containing silver as a main component, baking, metallicon of metal such as aluminum, and electroless nickel plating.

The electrodes can be attached to the positive characteristic porcelain 4 which has a large number of through holes 1 either on the surface with the through holes 1 or on the surface without the through holes 1, but as shown in FIG. When the electrodes 3 are provided on the surface, current flows evenly through the partition walls 2 that separate the through holes 1, and the amount of heat generated by each partition wall 2 becomes almost uniform, so that the fluid flowing through the through holes 1 is heated uniformly. more effective.

Examples of the fluid flowing through the through hole 1 include air as a gas and insulating oil as a liquid, but if necessary, other gases or liquids or these may be used without deteriorating the positive characteristic porcelain and its electrodes. Mixtures can be used.

Further, it is possible to freely select, as necessary, to cause gas or liquid to convect in parts other than the through-holes, for example, in the outer wall of the porcelain body.

The heating element of the present invention is constructed as described above, and in actual use, as shown in FIGS. A positive characteristic porcelain 4 having a large number of through holes 1 and a fan 7 for forcing air to pass through the through holes 1 are connected in parallel through a switch 8, and the positive characteristic porcelain 4 having a large number of through holes 1 and the fan 7 are connected in parallel as shown in FIG. (The positive characteristic porcelain 4 having a large number of through holes 1 was placed oppositely in the cylindrical frame 9 and fixed to the frame 9 with a heat-resistant insulating support 10.

A vent hole 11 is provided in the frame 9 on the opposite side to the positive characteristic magnet 4 having a large number of through holes 1 of the fan 7, and the positive characteristic porcelain 4 having a large number of through holes 1 has a diameter of 70 mmφ and a thickness of 10 mm, for example.
t, and the gap between the partition walls is a shape in which approximately 1800 rectangular through holes 1 of 1 mm are equally spaced (a surface area of approximately 720 i that can be in contact with fluid such as air passing through), and the through holes 1 are provided as described above. A structure was used in which electrodes 3 were provided on both end faces, and the temperature at which the resistance began to increase rapidly was 120° C., and the resistance at room temperature was 15 cj.

Apply a voltage of 1oov between power terminals 5 and 6, and switch 8
When the contacts 12 and 13 were closed and the fan 7 was rotated,
The positive characteristic porcelain 4 having a large number of through holes 1 has an ambient temperature of 25°C.
It generated 500W of heat.

After this, the contact 12 of the switch 8 was kept closed and the contact 13 was opened to stop the rotation of the fan 7 and the air was brought into a state of natural convection.
The calorific value decreased to 51 W, and the ratio of the calorific value in natural convection and forced convection was about 10 times.

Therefore, in the present invention, by forcing fluid to flow through the through hole 1, a heat generating device can be obtained in which the amount of heat generated can be relatively increased, and the amount of heat generated can be adjusted by changing the amount of fluid.

To explain yet another embodiment, as shown in FIG. 6, a positive characteristic porcelain 4 having a large number of through holes and a nichrome heater 14 are connected in series, and a fan 7 is connected in parallel with the nichrome heater 14. It was connected to power supply terminals 5 and 6 through switch 8.

The positive characteristic porcelain 4 having a large number of through holes had the same structure as in Example 1, and had a resistance value of 6 g at 25°C.

The nichrome heater 14 had a resistance of 5 g and was installed above the positive characteristic porcelain 4 having a large number of through holes.

Then, the ambient temperature of the heating device is set to 25℃, and the power terminal 5.6
When 100V was applied between them and the contacts 12 and 13 of the switch 8 were closed, a current of IOA instantly flowed, and 30 minutes later, the current was 8A, that is, the amount of heat generated was 800W.

When the contact 12 of the switch 8 was kept closed and the contact 13 was opened, the resistance of the positive characteristic porcelain 4 having many through holes increased and the current decreased slightly by 0.6 Aj.

At this time, the voltage applied to the positive characteristic porcelain 4 which has many through holes is 97■, and the amount of heat generated by the nichrome heater 14 is 3W, so even if the fan 7 stops, the nichrome heater 14 will not become red hot. The outer frame was also not heated.

Further, when the ambient temperature of the heat generating device was set to 0° C. with the contacts 12 and 13 of the switch 8 closed, the current increased to IOA, and heat of IKW was generated steadily.

In addition, if multiple heating elements made of positive characteristic porcelain are used and the air from the blower is passed through the through holes of the multiple heating elements,
Naturally, it is possible to obtain a heat generating device having a large amount of heat generated in accordance with the number of heat generating elements made of positive characteristic porcelain.

And, the diameter of the previous example is 70 mmφ and the thickness is 10 mm.
Positive characteristic porcelain with dimensions (hereinafter the same), the number of through holes per 1 d is approximately 47 and the thickness of the partition wall is approximately 0.4 mm (A), the number of through holes per 1 d is approximately 16 (B) with a partition wall thickness of approximately 0.5 mm, and IC11! The number of through holes per L is approximately 5 and the thickness of the partition wall is approximately 1.0 mm (3 types of Q, forced into the through holes of the heating element made of positive characteristic porcelain with a large number of through holes) The relationship between air volume and calorific value when air at a temperature of 25°C (the same applies hereinafter) is made to flow through is shown in Figure 7. , the amount of heat generated can be dramatically increased, and the amount of heat generated can be adjusted by changing the air volume.

In addition, the volume of air flowing through the through hole is approximately 0.6 m3.
/min, and the thickness of the partition wall is kept constant at approximately 0.4 am, the relationship between the number of through holes per 1 d and the amount of heat generation is as shown in Figure 8. As the number increases, the surface area per unit volume increases, so the calorific value increases significantly, but as mentioned above, 1
If the number of through holes per d is less than 5, the amount of heat generated becomes extremely small and a practical heat generating device cannot be obtained, so it is desirable that the number of through holes is 5 or more.

Furthermore, the amount of air flowing through the through hole is approximately 0.6
m3/min, and the number of through holes per 1-1 is approximately 47.
The relationship between the thickness of the partition wall between the through holes, the amount of heat generated, and the flow resistance is as shown in Fig. 9, assuming that the number of partition walls is constant. As the thickness of the partition wall increases, the surface area decreases. Therefore, the amount of heat generated decreases, and conversely, the size of the through hole decreases, so the flow resistance increases.

In particular, if the thickness of the partition wall exceeds 1 mm, the flow resistance increases significantly, and this, combined with the decrease in heat generation, makes it impossible to obtain a practical heat generating device. The following is desirable.

As detailed above, the positive characteristics of the present invention include a large number of through holes, in which the number of through holes per 1 d is at least 5 or more, and the thickness of the partition wall between the through holes is 1 mm or less. A porcelain heating element has a small volume and a large surface area, and by forcing gas or liquid to flow through the through hole, the inside of the porcelain body becomes high temperature, increasing the resistance and reducing the extreme current. Therefore, it is possible to generate an extremely large amount of heat compared to a case without a means to force the fluid to flow through it, and the amount of heat generated changes depending on the amount and temperature of the gas or liquid forced to flow through it. The heating element according to the invention has a low air flow or liquid volume, since there is no risk of overheating even if the fan as a means for forcing gas or liquid to flow through the through-holes fails. Even if the temperature of the heated gas or liquid changes, the temperature of the heated gas or liquid will not change. It is extremely useful industrially.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing different specific examples of the heating element of the present invention, FIG. 3 is an explanatory diagram showing a cross section of a specific example of the heating element of the present invention, and FIG. 4 is an explanatory diagram showing a specific example of the heating element of the present invention. FIGS. 5 and 6 are schematic diagrams showing the structure of a specific example of a heating device using the heating element of the present invention, and FIGS.
Figure 7 is a characteristic diagram showing the relationship between air volume and calorific value, Figure 8 is a characteristic diagram showing the relationship between the number of through holes per unit and calorific value, and Figure 9 is a characteristic diagram showing the relationship between partition wall thickness and calorific value. FIG. 3 is a characteristic diagram showing the relationship with flow resistance.

Claims (1)

[Claims] A characteristic porcelain heating pleasure characterized by having a large number of through holes in which the number of through holes per 11CrlL is at least 5 or more and the thickness of the partition wall between the through holes is iin or less.