JP2002280206A - Ferrite temperature transducer and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite temperature transducer which has a plurality of temperature sensitive points, and also can be baked at low temperatures, and further is miniaturized and enhances precision; and its manufacturing method. SOLUTION: In a ferrite temperature transducer which uses a spinel type- ferrite material containing an oxide of Ni, Cu, Zn, Fe, or Cu, Zn, Fe as main components, the ferrite material is structured by a ferrite sinter which is integrally baked with a molding body obtained by compositing ferrite powders of different compositions, and inductance is continuously decreased along with the increase in temperatures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a ferrite thermosensitive element utilizing the Curie temperature Tc of a temperature-sensitive oxide magnetic material, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive element is configured to show an ON / OFF operation when a certain temperature is reached. Among these temperature-sensitive elements, a thermal reed switch using Tc of a magnetic material and a thermistor using a temperature change of electric resistance are well known.

Heretofore, as the former magnetic materials for temperature sensing elements utilizing Tc, Mn-Cu ferrites and Mn-
Oxide magnetic materials such as Zn-based ferrite and Ni-
There is a metallic magnetic material represented by a Cu-based alloy. The former ferrite-based magnetic material has the advantage that the temperature can be easily set at around room temperature and the electric resistance can be easily increased by about five digits, as compared with the latter magnetic material.

Hitherto, temperature-sensitive oxide magnetic materials have a high magnetic permeability and a high temperature change among spinel ferrites.
Zn-based ferrite materials have been used.

[0005] In addition, temperature sensors using these are:
Combined with permanent magnets, only at a certain temperature
Many have been used as elements that operate as N, OFF temperature switches. Therefore, the number of elements in proportion to the set temperature number is required.

[0006]

However, the conventional ferrite material has a sintering temperature of about 1250 ° C. and an electric resistance of about 10 ⁴ Ωcm or less. For this reason, simultaneous firing with a low-resistance electric conductive material is impossible, and an electric insulating layer is indispensable between a magnetic material and a conductive material for forming a conductor, and there are many industrial disadvantages. . Therefore, this material is most used exclusively for thermal reed switches configured in combination with a magnet for applying a magnetic field.
The downsizing and high-speed response were negative factors.

Therefore, a technical problem of the present invention is to use an oxide material for a temperature-sensitive element which can be fired at a low temperature in a ferrite material and has a high resistance, so that one element has a plurality of temperature-sensitive points. An object of the present invention is to provide such a ferrite thermosensitive element and a method for manufacturing the same. It is another object of the present invention to provide a ferrite thermosensitive element whose size and accuracy are improved by integrally firing a conductor and a ferrite material, and a method of manufacturing the same.

[0008]

SUMMARY OF THE INVENTION The present invention provides Ni, Cu,
In a ferrite thermosensitive element using a spinel-type ferrite material containing Zn, Fe or an oxide of Cu, Zn, Fe as a main component, the ferrite material is formed by integrally forming a molded body obtained by compounding different ferrite powders. A ferrite thermosensitive element characterized by being sintered and formed of a ferrite sintered body having a smooth magnetic change in temperature.

Further, the present invention has a step of obtaining a ferrite sintered body by integrally sintering a molded body obtained by compounding ferrite powders having different compositions, and the sintering temperature of the molded body is controlled by the ferrite. Sinter density is 95% of theoretical density in powder
20 ° C. to 250 ° C. higher than the highest sintering temperature
A method for producing a ferrite thermosensitive element, wherein the temperature is in a high temperature range.

Further, the present invention is the above-mentioned method for producing a ferrite thermosensitive element, wherein the method of compounding the molded body is a lamination by printing using the paste containing the ferrite powder.

Further, the present invention is the above-described method for producing a ferrite thermosensitive element, wherein the method of compounding the molded body is a mixture of the ferrite powder.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The electrical resistance of a magnetic material is such that, if the DC specific resistance ρ _DC is 10 ⁶ Ωcm or more, it is possible to form a temperature-sensitive element by forming an electrical conductor by contacting with a magnetic substance. However, in the present invention, ρ
_DC is set to be about 10 ⁸ Ωcm or more.

In the present invention, Ni, Cu, Zn, Fe or Cu, Z can be used as a soft magnetic oxide magnetic material which can be fired at a low temperature, has a high ρ _DC and can change Tc.
A spinel type ferrite material containing an oxide of n and Fe as a main component is used. This ferrite material
By changing each main component, Tc of about 550 ° C. or lower can be arbitrarily selected while maintaining the above characteristics.

In the present invention, as a method of constructing a temperature sensor for sensing a plurality of temperatures with one temperature sensing element,
A ferrite sintered body whose magnetic permeability μ continuously decreases with increasing temperature is used as a temperature-sensitive element. This thermosensitive element
After integrally molding multiple ferrite powders with different compositions,
It is obtained from a sintered body obtained by integrally firing.

The temperature range that functions as a temperature-sensitive element is a range corresponding to the Tc of each single ferrite composition to be mixed, and μ decreases as the temperature rises, thereby functioning as a temperature sensor.

Further, in order to obtain a temperature sensor in which a molded body obtained by compounding ferrites having different compositions is sintered and the μ is linearly reduced by increasing the temperature, sintering is performed in a ferrite having a single composition to be mixed. The sintering temperature of the composite molded body is set to 20 ° C. to 25 ° C. from the highest sintering temperature at which the density becomes 95% of the theoretical density.
The temperature must be higher by 0 ° C. Below 20 ° C,
This is because the diffusion of atoms in the ferrite powder is insufficient, the temperature change of μ becomes step-like, and the linearity of L decrease with temperature is impaired. The reason why the temperature is set to less than 250 ° C. is that at a temperature higher than 250 ° C., the abnormal growth of the crystal grains of the sintered body causes a swell in the temperature change of μ, thereby impairing the linearity of μ reduction. By setting the sintering temperature to a temperature range higher by 20 to 250 ° C., a temperature sensor which shows a good linearity with a change in μ temperature can be obtained.

[0017]

Embodiments of the present invention will be described below.

Example 1 A composition ratio of 20 (Ni _1-a C)
and _{u a) O · 32ZnO · 48Fe} 2 O 3, where a
= 0.2, 0.4, 0.6, 0.8, 1.0, using iron oxide, nickel oxide, cupric oxide and zinc oxide as raw materials, ball mill mixing, calcination, pulverization, After mixing the PVA, the mixture was compression molded, kept at 920 ° C. in the atmosphere for 4 hours, and fired. The density of these sintered bodies was 97% or more of the theoretical density, and the DC specific resistance ρ _DC was 10 ⁸ to 10 ¹² Ωcm. Note that the sintered body density of these compositions is 95% of the theoretical density.
% Was 840 to 880 ° C. Table 1 shows the measurement results of the magnetic permeability μ and the Curie temperature Tc at 100 kHz of these sintered bodies.

[0019]

[Table 1]

Next, a printing ink was prepared by using a pulverized ferrite powder of each composition and a binder containing polyvinyl butyral as a main component. In addition, using a commercially available Ag-Pd paste as a printing ink for conductors, each composition ferrite thick film and Ag were screen-printed.
After laminating the Pd powders, they are integrally fired at 920 ° C., and each composition has 4 to 5 ferrite layers, 9 turns of the inner conductor, and an outer dimension of 3.0 × 1.5 × 1.0 mm. A chip-shaped inductor was manufactured. This inductor had an inductance L of 100 kHz at room temperature and about 10 μH at 10 mA.

Next, the laminated chip inductor was heated in an oven, and the change in inductance L was measured. As the temperature rose, L decreased linearly in the range from about 60 ° C to about 160 ° C.

From this, it can be seen that this composite ferrite sintered body functions as a temperature sensor utilizing a change in L.

(Example 2) The composition was the same as in Example 1.
The ratio is (52-x) (Ni_0.7Cu_0.3) O.xZnO.4
8Fe_TwoO_ThreeWhere x = 0, 10, 20, 30, 3,
Sintering was performed at 970 ° C. so as to obtain a sample No. 5. Of these sintered bodies
The density is greater than 97% of the theoretical density and ρ _DCIs 10⁸
-10^TenΩcm. In addition, the sintered compact of these compositions
The sintering temperature at which the degree becomes 95% of the theoretical density is 870 to 92
It was 0 ° C. The measurement results of μ and Tc of these sintered bodies
It is shown in Table 2.

[0024]

[Table 2]

Next, the ferrite powder of each composition was granulated to 0.5 mm or less, and then the ferrite granulated powder of each composition was 70% for x = 0, 18% for x = 10, and 7% for x = 20. %, X = 30 was 4%, and x = 35 was 1%, and then molded into a ring and sintered at 970 ° C. A conductor is directly wound around this sintered body for 20 turns,
The mixture was heated in an electric furnace, and the change in L at 10 kHz was measured. L increased linearly in the range from about 40 ° C. to about 520 ° C. with increasing temperature.

From this, it can be seen that this composite ferrite sintered body functions as a temperature sensor utilizing a change in L.

Example 3 In the same manner as in Example 1, the composition ratio was changed to (67-y) (Ni _0.7 Cu _0.3 ) O.33ZnO.
yFe ₂ O ₃ , where y = 45, 46, 47, 48,
Sintering was performed at 950 ° C. so as to be 49. The density of these sintered bodies is 97% or more of the theoretical density, and ρ _DC is 10
It was ⁸ to 10 ¹¹ Ωcm. The sintering temperature at which the sintered body density of these compositions becomes 95% of the theoretical density is 870 to 9
00 ° C. Table 3 shows the measurement results of μ and Tc of these sintered bodies.

[0028]

[Table 3]

Next, the ferrite powder of each composition is granulated to 0.5 mm or less, and then the ferrite granulated powder of each composition is converted to 45% for y = 45, 25% for y = 46, and y = 47.
Was mixed so that 15%, y = 48 became 10%, and x = 49 became 5%, then formed into a ring shape, and sintered at 950 ° C. A conductor was wound directly around the sintered body for 10 turns, heated in an oven, and the change in L at 200 kHz was measured.
L increased linearly in the range from about 80 ° C. to about 160 ° C. as the temperature rose.

From this, it can be seen that this composite ferrite sintered body functions as a temperature sensor utilizing a change in L.

Example 4 The sintering temperatures of 900, 920 and 95 were obtained using the composite molded articles of each composition prepared in Example 3.
0, 1000, 1050, 1100, 1150, 120
Sintered at 0 ° C. The density of these sintered bodies is 9% of the theoretical density.
It was 5% or more. The temperature change of L of these sintered bodies at 100 kHz was measured by heating in an oven.

In all the sintered bodies, L decreased from about 80 ° C. as the temperature rose, and stopped decreasing at about 160 ° C.

The curve of decrease in L due to the rise in temperature shows that the sintering temperature is 9
At 00 ° C., a step-like discontinuous tendency is observed, and the sintering temperature is 9
At 20 ° C., the tendency tends to be almost linear, and the sintering temperature is 95%.
Between 0 ° C and 1150 ° C, there was a good linear tendency. At a sintering temperature of 1200 ° C., abnormally grown crystal grains were generated, and a swell was observed in a curve of decrease in L due to an increase in temperature, and linearity was reduced. Therefore, the sintering temperature is 920 ° C
It can be said that the range of １1150 ° C. is good.

The sintering temperature is preferably 20 ° C. to 250 ° C. higher than the highest sintering temperature at which the sintered body density becomes 95% of the theoretical density in the single-component ferrite to be mixed. It can be said that.

In this embodiment, only the change in μ of the element is described. However, a change in magnetic temperature is sensed by a resonance frequency, or a magnetic flux (magnetic field, magnetization, magnetic resistance, etc.) is sensed. The present invention is also within the scope of the present invention as long as it utilizes a continuous change in magnetism (not limited to linearity, but also a continuous change in a curve) accompanying the Tc of the ferrite material.

[0036]

As described above, according to the present invention,
A ferrite thermosensitive element which has a plurality of thermosensitive points, can be fired at a low temperature, can be further miniaturized and has improved accuracy, and a method for manufacturing the same can be provided.

Claims (4)

[Claims] 1. Ni, Cu, Zn, Fe, or Cu, Z
n, a ferrite thermosensitive element using a spinel-type ferrite material containing an oxide of Fe as a main component, wherein the ferrite material is obtained by integrally firing a molded body obtained by compounding different ferrite powders, A ferrite thermosensitive element comprising a ferrite sintered body having a smooth temperature change. 2. A step of obtaining a ferrite sintered body by integrally sintering a molded body obtained by compounding ferrite powders having different compositions, wherein a sintering temperature of the molded body is within the ferrite powder. A method for producing a ferrite thermosensitive element, wherein the temperature range is 20 ° C. to 250 ° C. higher than the highest sintering temperature at which the sintered body density becomes 95% of the theoretical density. 3. The method of manufacturing a ferrite thermosensitive element according to claim 2, wherein the method of compounding the molded body is lamination by printing using the paste containing the ferrite powder. 4. The method for producing a ferrite thermosensitive element according to claim 2, wherein the method of compounding the molded body is mixing of the ferrite powder.