JP2013091590A - Ferrite composition for noncontact type temperature measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite composition for noncontact type temperature measurement which is usable suitably as a part of a temperature sensor for measuring a temperature from the outside.SOLUTION: This ferrite composition for noncontact type temperature measurement has a main component constituted of 48.0-49.7 mol% iron oxide in terms of FeO, 29.0-30.35 mol% zinc oxide in terms of ZnO, 5.5-6.8 mol% copper oxide in terms of CuO, and magnesium oxide as the residue, and further includes 30-350 ppm silicon oxide in terms of SiOwith respect to the 100 wt% main component as a sub-component.

Description

  The present invention relates to a non-contact temperature measurement ferrite composition that can be suitably used as part of a temperature sensor for measuring temperature from the outside without contacting an inspection object.

  For example, for canned beverages and bottled beverages sold in a sealed state, the temperature of the liquid cannot be measured by opening the product during temperature control. For this reason, in general, such temperature management of beverages and the like is carried out by imitating the temperature in the cabinet of a heat retaining machine or vending machine with a cooling and heating function as the liquid temperature of the beverage or the like, and the temperature in the cabinet is controlled by the product temperature. It is common to control the liquid temperature suitable for sale (for example, 55 to 60 ° C.) (Patent Document 1).

  However, it has been difficult to accurately grasp the actual liquid temperature by the method of imitating the temperature in the cabinet with the liquid temperature of a beverage or the like.

  In particular, in the case of hot beverages and the like, excessive heating may cause deterioration of quality, breakage of containers, etc., and insufficient heating may cause problems such as being sold without reaching an appropriate temperature (for example, 55 to 60 ° C.). Therefore, accurate temperature control is required, and accurate grasp of the actual beverage liquid temperature is required.

Japanese Patent Laid-Open No. 5-166051

  The present invention has been made in view of such a situation, and an object thereof is to accurately confirm from the outside that the liquid temperature of the inspection object has reached a predetermined temperature (55 to 60 ° C.) without contacting the inspection object from the outside. It is to provide a non-contact type temperature measurement ferrite composition that can be suitably used as part of a temperature sensor that can be grasped.

In order to achieve the above object, the ferrite composition for non-contact temperature measurement according to the present invention,
Iron oxide is 48.0 to 49.7 mol% in terms of Fe ₂ O ₃ , zinc oxide is 29.0 to 30.35 mol% in terms of ZnO, and copper oxide is 5.5 to 6.8 mol% in terms of CuO. The balance has a main component composed of magnesium oxide, and 30 to 350 ppm of silicon oxide in terms of SiO ₂ is contained as an accessory component with respect to 100% by weight of the main component.

  According to the ferrite composition for non-contact temperature measurement according to the present invention, the magnetic flux density changes rapidly at a temperature of 55 to 60 ° C. although it has a high magnetic flux density near room temperature. That is, the change rate of the magnetic flux density becomes maximum in this temperature range. By measuring the change in the magnetic flux, it is possible to measure the temperature to be measured (for example, the upper limit of the temperature appropriate for selling hot beverages, etc.). Therefore, non-contact type temperature measurement is possible by injecting the ferrite composition for non-contact type temperature measurement according to the present invention into a dummy inspection object, for example, in the form of particles, and measuring the change in magnetic flux from the outside. It becomes.

FIG. 1A and FIG. 1B are conceptual diagrams of a non-contact temperature measurement system having a temperature-sensitive magnetic body composed of a ferrite composition for non-contact temperature measurement according to an embodiment of the present invention. . FIG. 2 is a graph showing the relationship between temperature and magnetic flux density in the non-contact temperature measurement ferrite composition according to the present invention. FIG. 3 is a graph showing the relationship between the temperature and the magnetic flux density in the non-contact temperature measurement ferrite compositions according to Examples and Comparative Examples of the present invention.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
The ferrite composition according to this embodiment is an Mg—Zn-based ferrite composition, containing iron oxide, zinc oxide, copper oxide, and magnesium oxide as main components, and silicon oxide as a subcomponent.

Specifically, the ferrite composition according to the present embodiment is
48.0 to 49.7 mol% of iron oxide calculated as _Fe 2 _{O 3,} preferably 48.0 to 49.1 mol%,
Zinc oxide in terms of ZnO is 29.0-30.35 mol%, preferably 29.0-30.0 mol%,
Copper oxide is 5.5 to 6.8 mol%, preferably 5.5 to 6.5 mol% in terms of CuO,
The remainder has a main component composed of magnesium oxide,
Silicon oxide is contained in an amount of 30 to 350 ppm, preferably 30 to 200 ppm in terms of SiO ₂ as an accessory component with respect to 100% by weight of the main component.

  Although the ferrite composition according to the present embodiment has a high magnetic flux density below a predetermined temperature, the magnetic flux density changes abruptly at a predetermined temperature (55 to 60 ° C.). By setting it as the said composition range, the rapid change of the magnetic flux density of this ferrite composition can be observed in 55-60 degreeC.

  In this embodiment, the temperature at which the magnetic flux density of the ferrite composition changes abruptly is taken as the inflection point, and the change rate α of the magnetic flux density at the inflection point is 1.2 or more, more preferably 1.4 or more. A large change rate α of the magnetic flux density means an abrupt change of the magnetic flux density, which is preferable because the inflection point can be easily determined as compared with the case where the change rate α is small.

  When the content of iron oxide is small, the inflection point tends to be lower than a predetermined temperature (55 to 60 ° C.). When the content of iron oxide is large, the inflection point of magnetic flux density is a predetermined temperature (55 to 60 ° C.). ).

  When the content of zinc oxide is small, the inflection point of the magnetic flux density tends to exceed a predetermined temperature (55 to 60 ° C.), and when the content of zinc oxide is large, the inflection point of the magnetic flux density becomes the predetermined temperature (55 ˜60 ° C.).

  When the content of copper oxide is small, the inflection point of the magnetic flux density tends to exceed a predetermined temperature (55 to 60 ° C.), and when the content of copper oxide is large, the inflection point of the magnetic flux density is at a predetermined temperature (55 ˜60 ° C.).

The content of silicon oxide is 30 to 350 ppm, preferably 30 to 200 ppm in terms of SiO _{2 with} respect to 100% by weight of the main component. When the content of silicon oxide is small, the inflection point of the magnetic flux density tends to be lower than a predetermined temperature (55 to 60 ° C.). When the content of silicon oxide is large, the inflection point of the magnetic flux density is at a predetermined temperature (55 ˜60 ° C.).

  In addition, the ferrite composition according to the present embodiment may include about several ppm to several hundred ppm of inevitable impurity element oxides in the raw material.

  Specifically, B, C, P, S, Cl, As, Se, Br, Te, I, Li, Na, Al, K, Ga, Ge, Sr, Cd, In, Sn, Sb, Ba, Examples include typical metal elements such as Pb and Bi, and transition metal elements such as Sc, Ti, V, Cr, Co, Ni, Y, Zr, Nb, Mo, Pd, Ag, Hf, and Ta.

Next, an example of a method for producing a ferrite composition according to this embodiment will be described.
First, starting materials (raw materials of main components and raw materials of subcomponents) are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer. It is preferable to use a starting material having an average particle size of 0.1 to 3 μm.

As a raw material of the main component, iron oxide (α-Fe ₂ O ₃ ), zinc oxide (ZnO), copper oxide (CuO), magnesium hydroxide (Mg (OH) ₂ ), or the like can be used. In addition, various compounds that become oxides or composite oxides by firing can be used. Examples of the oxide that becomes the above-mentioned oxide upon firing include simple metals, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds, and the like. The content of magnesium oxide in the main component is calculated in terms of MgO, but Mg (OH) ₂ is preferably used as the main component material.

  Next, the raw material mixture is calcined to obtain a calcined material. Calcining causes thermal decomposition of raw materials, homogenization of ingredients, formation of ferrite, disappearance of ultrafine powder due to sintering and grain growth to an appropriate particle size, and converts the raw material mixture into a form suitable for the subsequent process. Done for. Such calcination is preferably performed at a temperature of 800 to 1100 ° C. for about 1 to 3 hours. The calcination may be performed in the air (air), or may be performed in an atmosphere having a higher oxygen partial pressure or in a pure oxygen atmosphere than in the air. The mixing of the main component raw material and the subcomponent raw material may be performed before calcining or after calcining.

  Next, the calcined material is pulverized to obtain a pulverized material. The pulverization is performed in order to break down the coagulation of the calcined material to obtain a powder having appropriate sinterability. When the calcined material forms a large lump, wet pulverization is performed using a ball mill or an attritor after coarse pulverization. The wet pulverization is performed until the average particle diameter of the calcined material is preferably about 1 to 2 μm.

  Next, the pulverized material is granulated (granular) to obtain a granulated product. The granulation is performed in order to convert the pulverized material into aggregated particles having an appropriate size and convert it into a form suitable for molding. Examples of such a granulation method include a pressure granulation method and a spray drying method. The spray drying method is a method in which a commonly used binder such as polyvinyl alcohol is added to the pulverized material, and then atomized in a spray dryer and dried at a low temperature.

  Next, the granulated product is molded into a predetermined shape to obtain a molded body. Examples of the molding of the granulated product include dry molding, wet molding, and extrusion molding. The dry molding method is a molding method in which a granulated product is filled in a mold and compressed and pressed (pressed). The shape of the molded body is not particularly limited, and may be appropriately determined according to the application.

  Next, the molded body is fired. Firing is performed in order to obtain a dense sintered body by causing sintering in which the powder adheres at a temperature lower than the melting point between the powder particles of the compact including many voids. Such firing is preferably performed at a temperature of 1000 to 1200 ° C., usually for about 1 to 5 hours. The temperature rising rate is preferably 150 to 250 ° C./hour, and the temperature decreasing rate is preferably 150 to 250 ° C./hour. Firing may be performed in the air (air) or in an atmosphere having a higher oxygen partial pressure than in the air.

  Next, the obtained sintered body is pulverized to obtain the ferrite powder of the present embodiment. For grinding, a vibrator mill or jaw crusher is used. The particle size of the ferrite powder is preferably 40 to 150 μm, more preferably 80 to 120 μm. By using the ferrite powder having such a particle size as a temperature-sensitive magnetic material as described below, it becomes easier to inject the ferrite powder into the liquid to be inspected.

  Next, a method for measuring temperature using a temperature-sensitive magnetic body made of the ferrite composition according to the present embodiment will be described.

  As shown in FIG. 1A, a magnetic flux M1 is generated from the temperature measurement drive coil 4 toward the temperature-sensitive magnetic body 2 with respect to the temperature-sensitive magnetic body 2 made of the ferrite composition according to the present embodiment. At this time, when the temperature T of the temperature-sensitive magnetic body 2 is lower than the Curie temperature Tc of the temperature-sensitive magnetic body 2, the magnetic flux M <b> 1 is concentrated near the temperature-sensitive magnetic body 2. When the concentration of the magnetic flux M1 occurs, the magnetic flux M2 in the vertical direction of the magnetic flux M1 can be detected by the detection coil 6.

  The degree of concentration of the magnetic flux M1 (corresponding to the magnetic flux density) varies depending on the temperature T of the temperature-sensitive magnetic body 2. That is, the concentration degree of the magnetic flux M1 decreases as the temperature T of the temperature-sensitive magnetic body 2 approaches the Curie temperature Tc, and the temperature T of the temperature-sensitive magnetic body 2 becomes lower than that of the magnetic body 2 as shown in FIG. When the temperature is equal to or higher than the Curie temperature Tc, the degree of concentration of the magnetic flux M1 becomes substantially zero, and the magnetic flux M2 in the vertical direction of the magnetic flux M1 becomes substantially zero.

  Therefore, it is possible to detect the temperature of the temperature-sensitive magnetic body 2 by detecting the change of the magnetic flux M2 detected by the detection coil 6, particularly the inflection point of the magnetic flux change. In the present embodiment, the composition range of the ferrite constituting the temperature-sensitive magnetic body 2 is determined in consideration of use at an appropriate temperature of the hot beverage, specifically 55 to 60 ° C.

  Next, an example of temperature measurement of a hot beverage or the like using the ferrite composition according to the present embodiment will be described.

  A dummy can prepared by injecting a temperature-sensitive magnetic material composed of the ferrite composition according to the present embodiment together with a liquid (inspection object) is prepared, and is kept in a warehouse such as a warmer having a heating function together with a hot beverage as a product. To do.

  At least a part of the dummy can is made of a non-magnetic material, the temperature measuring drive coil 4 and the detection coil 6 are arranged outside the dummy can, and the change in the magnetic flux density of the temperature-sensitive magnetic body in the dummy can is observed from the outside. By detecting the inflection point of the magnetic flux density, it becomes possible to accurately measure the temperature (55 to 60 ° C.) of the liquid inside the can.

  Thereby, it becomes possible to grasp | ascertain correctly, without opening goods, about the temperature (the upper limit of temperature optimal for provision) of the hot drink similarly heat-retained in the same store | warehouse | chamber as a dummy can.

  If a magnetic material other than the temperature-sensitive magnetic body made of the ferrite composition according to the present embodiment is interposed between the temperature measuring drive coil 4 and the detection coil 6, the magnetic flux density of the magnetic material interferes. It becomes impossible to accurately grasp the change in the magnetic flux density of the temperature-sensitive magnetic material.

  Therefore, at least a part of the dummy can is preferably made of a nonmagnetic material, and the temperature measuring drive coil 4 and the detection coil 6 are arranged outside the nonmagnetic material. As the nonmagnetic material, materials such as paper, plastic, and glass can be used.

  Further, the liquid injected into the dummy can together with the temperature-sensitive magnetic body may be the same liquid as that of a hot beverage or the like, or may be a liquid having the same thermal conductivity.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  For example, the non-contact temperature measurement ferrite composition according to the present invention includes other components such as typical non-metallic elements such as B, C, S, Cl, As, Se, Br, Te, and I, Li, Typical metals such as Na, Al, K, Ca, Ga, Ge, Sr, Cd, In, Sn, Sb, Ba, Pb, Bi, Sc, Ti, V, Cr, Co, Y, Nb, Mo, Pd , Transition metal elements such as Ag, Hf, and Ta may be included.

  In addition, the temperature-sensitive magnetic body composed of the ferrite composition for non-contact temperature measurement according to the present invention is desirably used in powder form, but is not necessarily in powder form, and is used in other forms. May be.

  The temperature measurement using the temperature-sensitive magnetic material composed of the ferrite composition of the present invention is not limited to the temperature measurement of canned beverages, but can be used to measure the temperature of a liquid or the like that cannot be directly measured from the outside in a non-contact manner. Can be applied in the field.

  For example, it is possible to measure the temperature of a liquid flowing (or stationary) inside a tube or a container from the outside. Note that at least a part of the tube and the container is made of a nonmagnetic material, and the temperature measuring drive coil 4 and the detection coil 6 are arranged outside thereof.

  Further, the inspection target may be other than liquid, and the temperature can be measured with a similar method for slurry, jelly-like substances, and the like. In addition, the measurement object may be a solid as long as the ferrite composition according to the present invention can be injected.

  In addition, when measuring the temperature with the temperature-sensitive magnetic material composed of the ferrite composition of the present invention, the liquid is stirred and the specific gravity of the liquid so that the temperature-sensitive magnetic material is dispersed (floating) in the liquid to be inspected. You may make adjustments.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.
Examples 1-11

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

First, Fe ₂ O ₃ , ZnO, CuO, and Mg (OH) ₂ were prepared as main component materials. SiO ₂ was prepared as a raw material for the accessory component.

  Next, the raw material powder of the main component prepared was weighed, and further, the powder of the subcomponent raw material was weighed to the amount shown in Table 1, and then wet mixed with a ball mill for 5 hours to obtain a raw material mixture. .

  Next, the obtained raw material mixture was calcined in air at 950 ° C. for 2 hours to obtain a calcined material, and then wet pulverized with a ball mill for 20 hours to obtain a pulverized material having an average particle diameter of 1.5 μm. Obtained.

Next, this pulverized material was dried, and then granulated by adding 1.0% by weight of polyvinyl alcohol as a binder to 100% by weight of the pulverized material, and granulated with a 20 mesh sieve to obtain granules. This granule was pressure-molded at a pressure of 196 MPa ( ² ton / cm ² ) to obtain a molded body having a toroidal shape (size = outer diameter 22 mm × inner diameter 12 mm × height 6 mm).

  Next, each of these molded bodies was fired in air at 1000 to 1200 ° C. for 2.5 hours to obtain a toroidal core sample as a sintered body. The obtained sample was subjected to fluorescent X-ray analysis to measure the composition of the ferrite core. The results are shown in Table 1. Furthermore, the following characteristics evaluation was performed with respect to the sample.

<Magnetic flux density (B)>
A primary winding and a secondary winding were wound around the obtained toroidal core sample five times, and the magnetic flux density (B) was measured at 100 A / m, 100 kHz, and 40 to 70 ° C. The measurement was performed using a BH analyzer (SY-8232 manufactured by Iwasaki Tsushinki Co., Ltd.).

From the magnetic flux density (B) at each measurement temperature, the rate of change α at the inflection point of the magnetic flux density of each sample was obtained by the following equation (1).
α = (B _{at i ° C.−} B _{at i + 2 ° C.} ) / (B _{at i−2 ° C.−} B _{at i ° C.} ) (1)
Here, in the equation (1), i ° C represents an inflection point, i + 2 ° C represents an inflection point + 2 ° C, and i-2 ° C represents an inflection point-2 ° C. The relationship between temperature and magnetic flux density is shown in FIG.

  As shown in FIG. 2, the magnetic flux density of the ferrite core changes abruptly at the inflection point. In this example, the temperature at which the change rate α of the magnetic flux density of each sample is 1.2 or more is taken as the inflection point of the magnetic flux density. The results of examining the inflection point of the magnetic flux density of each sample are shown in Table 1, Table 2, and FIG.

From Table 1, when the content of Fe ₂ O ₃ is outside the range of the present invention (Comparative Examples 1 and 2), the inflection point of the magnetic flux density is not within the range of the predetermined temperature (55 to 60 ° C.). Was confirmed. On the other hand, when the content of Fe ₂ O ₃ is within the range of the present invention (Examples 1 to 3), the inflection point of the magnetic flux density is within a predetermined temperature range (55 to 60 ° C.). Was confirmed.

From Table 1 and FIG. 3, when the ZnO content is outside the range of the present invention (Comparative Examples 3 and 4), the inflection point of the magnetic flux density is not within the predetermined temperature range (55 to 60 ° C.). Was confirmed. In contrast, ZnO When the content of C is within the range of the present invention (Examples 2 and 4 to 7), it was confirmed that the inflection point of the magnetic flux density was within the range of a predetermined temperature (55 to 60 ° C.).

  From Table 1, when the content of CuO is outside the range of the present invention (Comparative Examples 5 and 6), it is confirmed that the inflection point of the magnetic flux density is not within the range of the predetermined temperature (55 to 60 ° C.). It was. On the other hand, when the content of CuO is within the range of the present invention (Examples 2, 8 and 9), the inflection point of the magnetic flux density may be within a predetermined temperature range (55 to 60 ° C.). confirmed.

From Table 2, when the content of SiO ₂ is outside the range of the present invention (Comparative Examples 7 and 8), it is confirmed that the inflection point of the magnetic flux density is not within the range of the predetermined temperature (55 to 60 ° C.). It was done. On the other hand, when the content of SiO ₂ is within the range of the present invention (Examples 2, 10 and 11), the inflection point of the magnetic flux density is within a predetermined temperature (55 to 60 ° C.) range. Was confirmed.

  The temperature-sensitive magnetic body composed of such a ferrite composition is pulverized into a powder to have a particle size of 40 to 150 μm, and poured into a dummy can made of, for example, plastic together with water (measuring object), By measuring the change in the magnetic flux M2 from the dummy can with the detection coil 6 shown in FIG. 1, for example, the temperature-sensitive magnetic body has reached the temperature of the inflection point, that is, the water inside the can has a predetermined temperature (55 to 55). 60 ° C.) can be accurately confirmed.

2 ... Temperature-sensitive magnetic body 4 ... Driving coil 6 ... Detection coil

Claims (1)

Iron oxide is 48.0 to 49.7 mol% in terms of Fe ₂ O ₃ , zinc oxide is 29.0 to 30.35 mol% in terms of ZnO, and copper oxide is 5.5 to 6.8 mol% in terms of CuO. In addition, for the non-contact type temperature measurement, the balance has a main component composed of magnesium oxide, and silicon oxide is contained in an amount of 30 to 350 ppm in terms of SiO ₂ as an accessory component with respect to 100% by weight of the main component. Ferrite composition.

Images