JPS60247902A - Current limiting resistance element - 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] [Technical field of invention] The present invention relates to a current limiting resistance element that limits excessive current.

[Technical background of the invention and its problems]

BACKGROUND ART In electrical circuits, particularly in large-capacity power receiving equipment circuits, a current limiter and a voltage breaker are connected in series to interrupt the current in order to protect the electrical circuit from excessive current in the event of an accident.

As a self-healing type current limiting resistance element, a resistor having a positive temperature coefficient, a so-called PTO material, is generally used. These PTO materials include alkali metals such as sodium and potassium and their alloys, lead, soot, mercury,
Examples include ceramic materials such as pure iron and semiconducting barium titanate.

The specific resistance of lead and soot approximately doubles when the metal melts due to heat generation and temperature rise due to excessive current.

This increase in specific resistance is utilized.

Since alkali metals and mercury have low boiling points, the rapid increase in specific resistance when vaporized by self-heating is utilized.

Pure iron utilizes the fact that it has a relatively large temperature coefficient of resistivity.

Barium titanate that has been converted into a semiconductor exhibits the so-called PTO effect in which the resistivity rapidly increases from the vicinity of one point on the key. The aim is to utilize this phenomenon as a current limiting element.

However, for lead and soot, the change in resistivity is approximately 2
The drawback was that even pure iron could only provide an insufficient change as a current limiting element, at most 10 times as small.

Alkali metals and mercury use the increase in resistivity caused by vaporization, which is sufficient to change the resistivity, but as is well known, these metals are very active and are difficult to use when manufacturing current limiting elements. The drawbacks are that the work must be done in a completely inert atmosphere and that the current limiting element is difficult to handle, such as by increasing its airtightness.

In the case of semiconducting titanium oxide, the resistivity changes by about 5 orders of magnitude from the vicinity of the key IJ point at around 120°C, which is sufficient for a current limiting element, but because it is made of ceramic, excessive current is applied. It has the disadvantage that it is vulnerable to thermal shock due to heat, and the element can be destroyed.

This destruction is laminar destruction, and the present inventors have found that such laminar destruction occurs because a large temperature distribution occurs in the current axis direction within the element.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a current limiting resistance element with excellent thermal shock resistance.

. [Summary of the Invention] As a result of studying the thermal dynamic characteristics such as temperature distribution caused by self-heating due to energization of a ceramic PTO element, the present inventors made the ceramic part thin and layered them alternately, taking into account the heat dissipation effect of metal. We have found that it is effective to form an element by

That is, the present invention is a current-limiting resistance element characterized in that it is formed by alternately laminating ceramic resistor layers (ceramic PTO element) having a positive temperature coefficient and metal layers.

By adopting such a configuration, the entire element can be maintained at a substantially uniform temperature, and the layer breakdown during energization as described above can be prevented.

Additionally, ceramic PTO materials generally have a resistance value of 100
The resistance is as high as Ω・α, and when used as a breaker, the 7pt loss will be large, but by intervening the metal layer in this way, the resistance value as an element is lowered, and the watt loss is also reduced. Become.

The ceramic PTO material used for the ceramic resistor layer having a positive temperature coefficient in the present invention contains barium titanate (BaTiOa) as a main component, and La10
3 * 0102 + G d@ 01 T NJ O
s + V, O, etc. are added to make a semiconductor, that is, the composition is (Ba, -xXx) (Ti1, Yy) O, +z - Z (
X=La, Oe, Sr, , Pb, Gd, Os Y=8n
, Zr.

Nb, V, z=Ag, o, At, o3.8 io,
O<x+y+z<0. Oi). Any of those generally known as PTO ceramics can be used.

Various materials such as copper, iron, and aluminum can be used as the metal layer, but in consideration of heat dissipation and electrical resistance, it is preferable to use a copper plate.

The thickness of each layer can be set appropriately, but if the ceramic resistor layer is too thick, the effect of metal layer intervention will not be achieved.
The thickness is preferably 500 μm or less. Furthermore, if the thickness is too thin, problems will occur in the PTO characteristics, so it is preferable that the thickness is 50 μm or more.

Although the thickness of the metal layer does not particularly matter, a thickness of approximately 100 μm or more will provide sufficient effects.

In the present invention, any number of layers may be laminated, but in order to improve the electrical connection between the ceramic resistor layer and the metal layer, I
It is preferable to form an electrode layer of n-Ga, Ag, Ni, etc. by a conventional method for attaching electrodes to ceramics, such as an electroless plating coating method or a paste printing method.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a current limiting resistance element with low element resistance and low watt loss, and it is possible to improve thermal shock resistance due to excessive current application.

[Embodiments of the invention] Hereinafter, the present invention will be explained with reference to examples.

First, a barium titanate-based material was created as a ceramic positive temperature coefficient resistor. Barium carbonate, cerium oxide, and titanium oxide are weighed to form the basic component barium cerium titanate (Ba 1-xoex) Tie, and are wet mixed and pulverized using a ball mill. Next, these are dried, calcined at 1100° C. for 1 hour, and ground again in a ball mill to obtain a blended powder. An organic binder is added to this and kneaded, and a thin plate of baked clay having a size of 9100 μm is formed using a doctor blade method. After drying, this thin plate was
Fired at 0 to 1400°C for 1 hour to obtain a PTO thin plate. InGa electrodes were applied to both sides of this PTO thin plate, and then 100%
Laminate the copper plates of μ book. These PTO thin plates and copper plates are stacked, for example, with 10 and 11 sheets of 1 nGa sandwiched therebetween, respectively. Although the 1nGa electrode is not applied to the copper plate here, it may be applied to the copper plate as well. Furthermore, although the thin plate was formed using a doctor blade, it may also be obtained by grinding or cutting a relatively thick fired body.

Electrode layers are provided on both end surfaces of the copper plates at both ends of this laminate to serve as current-limiting resistance elements.

FIG. 1 is a cross-sectional view of the element, and both end faces A and B of the element each serve as electrodes. A ceramic resistance layer (1) exhibiting thin plate PTO characteristics is connected to a copper plate (3) via an electrode layer (2).
). Note that the terminals may be provided directly from both end faces A and B of the element.

The resistance value of the current limiting resistor element obtained in this way is approximately 0°3Ω.
The temperature change was as shown in FIG.

When a current of 10 OA was applied to this current limiting resistor element, a sufficient current limiting effect was obtained without cracking or peeling. On the other hand, as a comparative example, a PTO element made only of barium titanate without a metal layer had a resistance of about 10Ω, and when the same current was applied, many cracks occurred in the direction perpendicular to the current axis.

As described above, the current limiting resistor element according to the present invention has a low element resistance at room temperature and can reduce watt loss.

Furthermore, when an excessive current flows, the temperature of the entire element rises uniformly due to Zeel heat, so that thermal shock resistance can also be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of the device of the present invention, and FIG. 2 is a resistance temperature characteristic diagram.

Claims (1)

[Claims] A current limiting resistance element characterized in that ceramic PTO resistor layers and metal layers are alternately laminated.