JP2003002736A - Equipment for producing ferrite and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and easily produce a ferrite having good characteristics. SOLUTION: Gaseous nitrogen as an inert gas, air as an active gas and LPG as a reducing gas are introduced into a kiln 11 for firing a ferrite from a gas introducing inlet 12 disposed in the kiln 11. The partial pressure of oxygen in the kiln 11 is lowered by the inert gas and oxygen in the kiln 11 is consumed by burning the reducing gas to control the partial pressure of oxygen in the kiln 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite production apparatus and a production method for producing ferrite by firing a raw material mainly containing iron oxide, zinc oxide and manganese oxide in a firing furnace.

[0002]

2. Description of the Related Art Conventionally, in switching power supplies, television receivers, etc.
N-Zn based low loss ferrite is often used. Such low-loss ferrite is obtained by mixing, pre-baking, pulverizing / granulating, press-molding raw materials mainly composed of iron oxide (Fe ₂ O ₃ ), zinc oxide (ZnO) and manganese oxide (MnO).
It is manufactured by main sintering, and exhibits excellent characteristics as a high-frequency magnetic core.

For example, when low-loss ferrite is used for the magnetic core of the transformer, it is possible to cope with a switching frequency of about 10 kHz to 100 kHz and a maximum magnetic flux density of about 200 mT or less.

[0004]

By the way, in recent years,
The miniaturization and high efficiency of various electric products are being promoted, and along with this, it is required to reduce heat generated from the electric parts used and to improve the efficiency of the electric parts. For example, in the case of a transformer, it is required that the maximum magnetic flux density is improved and the heat generation is sufficiently small in order to cope with a higher switching frequency. However, the low-loss ferrite produced by the conventional firing method has a problem that it is difficult to sufficiently meet such requirements in terms of heat generation and efficiency.

Therefore, for example, Japanese Patent Laid-Open No. 5-238817.
As described in Japanese Patent Publication No. JP-A-2003-264, when firing ferrite, the oxygen partial pressure during the temperature rise from the binder decomposition temperature to the maximum reached temperature is set to 1% or less to further reduce loss. A method of manufacturing a low loss ferrite has been proposed.

Here, as a method of controlling the oxygen partial pressure in the firing furnace, an inert gas such as nitrogen (N ₂ ) is fed into the firing furnace as is conventionally done in the firing process of various materials. It is conceivable to adopt a method of controlling the oxygen partial pressure by introducing it. However, in order to realize an extremely low oxygen partial pressure of about 1% or less when firing ferrite by using such a method, the following problems occur.

That is, since an oxygen component is generated from the ferrite itself during firing of the ferrite, an extremely large amount of inert gas is required to dilute the oxygen component and realize an oxygen partial pressure of about 1% or less. Need to be introduced into the firing furnace. At this time, a large amount of energy is required to warm the inside of the firing furnace by the heating element in order to compensate for the decrease in the furnace temperature due to the introduced large amount of inert gas.

If a large amount of inert gas having a temperature different from the temperature inside the furnace is introduced, not only it becomes difficult to appropriately control the temperature inside the furnace, but also the oxygen partial pressure at the maximum temperature is properly adjusted. It also becomes difficult to control.

Therefore, the method of controlling the oxygen partial pressure by introducing an inert gas into the firing furnace not only causes a large energy loss when used during firing of ferrite, but also increases the temperature inside the furnace and the furnace temperature. There has been a problem that the control of the oxygen partial pressure becomes complicated and the production efficiency is extremely reduced.

Therefore, it is an object of the present invention to provide a ferrite manufacturing apparatus and manufacturing method capable of easily manufacturing low-loss ferrite with high energy efficiency.

[0011]

A ferrite production apparatus according to the present invention is a ferrite production apparatus for producing ferrite by firing a raw material mainly containing iron oxide, zinc oxide and manganese oxide in a firing furnace. In addition to introducing an inert gas and an active gas and a reducing gas into the firing furnace, a gas introduction mechanism is provided for varying the flow rate ratio of these gases in accordance with the temperature in the firing furnace. To do.

The ferrite production apparatus according to the present invention configured as described above is provided with the gas introduction mechanism, so that the inert gas and the active gas and the reducing gas are burned at a flow rate ratio of these gases. It can be introduced into the firing furnace while changing the temperature according to the temperature in the furnace. Therefore, the oxygen partial pressure in the firing furnace is reduced by the partial pressure of an inert gas such as nitrogen (N ₂ ) or argon (Ar), and the oxygen in the firing furnace is efficiently converted by burning the reducing gas. Not only can it be consumed well, but the temperature inside the furnace can be prevented from lowering due to the heat generated by combustion.
Therefore, when controlling the oxygen partial pressure in the firing furnace during firing of ferrite, it is not necessary to introduce a large amount of inert gas, so that the temperature decrease in the furnace is suppressed and energy efficiency is improved, and It is possible to easily control the internal temperature and the oxygen partial pressure.

The method for producing ferrite according to the present invention is the method for producing ferrite in which the raw material mainly containing iron oxide, zinc oxide and manganese oxide is fired in the firing furnace. It is possible to control the oxygen partial pressure in the firing furnace by introducing an inert gas and an active gas and a reducing gas into the firing furnace and controlling the flow ratio of these gases according to the temperature in the firing furnace. It is a feature.

In the method for producing ferrite according to the present invention having the above-described structure, when controlling the oxygen partial pressure in the firing furnace during firing of the ferrite, an inert gas and an active gas and a reducing gas are placed in the firing furnace. This is achieved by introducing and. Therefore, for example, nitrogen (N ₂ ) or argon (A
In addition to reducing the oxygen partial pressure in the firing furnace by the partial pressure of the inert gas such as r), the reducing gas is burned so that the oxygen in the firing furnace can be efficiently consumed and is generated by the combustion. The heat can prevent the temperature in the furnace from decreasing. Therefore, when controlling the oxygen partial pressure in the firing furnace during firing of ferrite, it is not necessary to introduce a large amount of inert gas, so that the temperature decrease in the furnace is suppressed and energy efficiency is improved, and It is possible to easily control the internal temperature and the oxygen partial pressure.

That is, the present invention is characterized in that the oxygen partial pressure is controlled by introducing a reducing gas at the time of firing the oxide ferrite. In this way, the method of introducing a reducing gas during the firing of ferrite is completely different from the conventional wisdom in the conventional manufacturing method that a large amount of nitrogen is required when manufacturing an oxide.

In the present invention, the reducing gas introduced into the firing furnace is, for example, various LPG (Liquefie).
It is not particularly limited as long as it is in a liquefied state as long as it has a reducing property such as d Petroleum Gas) or hydrogen gas (H ₂ ), but it is particularly preferable to use LPG. . LPG is cheaper than hydrogen gas, etc., and is safe with less risk of explosion. Therefore, by using LPG, low-loss ferrite can be manufactured safely at low cost. Here, LPG generally means propane, butane,
It refers to a liquefied mixed gas of lower hydrocarbons derived from petroleum such as butylene and propylene, but the LPG suitable for use in the present invention is not limited to such mixed gas, for example, pure gas. Alternatively, propane gas, methane gas, butane gas or the like may be used. However,
In general, LPG is enclosed in a container in a liquefied state of a mixed gas containing propane as a commerce, and is used for commerce. Therefore, in the present invention, it is the simplest and preferable to use the mixed gas in such a state.

Further, in the present invention, the control of the flow rate ratio of the inert gas and the active gas to be introduced into the firing furnace and the reducing gas is performed by increasing the temperature in the firing furnace from the binder decomposition temperature to the maximum reached temperature. It is desirable to perform in the temperature range.
This is because when manufacturing low-loss ferrite exhibiting good characteristics, the oxygen partial pressure at the highest temperature is set to about 4%, while the oxygen partial pressure is 1% or less in the temperature rising range up to the highest temperature. In particular, by introducing the inert gas and the reducing gas in this temperature rising range, the oxygen partial pressure can be controlled efficiently and highly accurately.

Further, in the present invention, the control of the flow rates of the inert gas and the active gas to be introduced into the firing furnace and the reducing gas is carried out within the temperature falling range from the highest temperature reached to the cooling inside the firing furnace. Is desirable. This is based on the finding that the characteristics of the low-loss ferrite can be improved by keeping the oxygen partial pressure low not only in the temperature rising range but also in the temperature falling range. By introducing the inert gas and the active gas and the reducing gas in this temperature decreasing range, the oxygen partial pressure can be efficiently and easily controlled.

Further, in the ferrite manufacturing apparatus according to the present invention, a transport mechanism for transporting the raw material in the firing furnace having a predetermined temperature distribution is provided, and an inert gas and an active gas are used as the gas introduction mechanism. It is desirable that a plurality of gas inlets in which the flow rate ratios of the reducing gas and the reducing gas are set are respectively provided at positions where a predetermined temperature is obtained in the firing furnace. As a result, the present invention can be easily applied to a so-called continuous firing furnace in which both ends of the firing furnace for firing the raw material are opened. That is, in the firing furnace having a predetermined temperature distribution, a feed mechanism is provided in the firing furnace where the amount of the inert gas and the introduction amount of the active gas and the reducing gas are appropriately controlled at each position. By carrying by, the ferrite can be fired continuously and in a large amount, and the production efficiency can be improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. INDUSTRIAL APPLICABILITY The present invention is applied when manufacturing ferrite, and includes, for example, a closed firing furnace (batch furnace) having a structure in which the firing furnace is closed during firing, or a firing furnace having a predetermined temperature distribution. The structure is such that the ferrite is transported while being transported,
The present invention can be applied to a continuous firing furnace (continuous furnace) capable of continuously firing ferrite and a case where low-loss ferrite is produced using these firing furnaces.

Therefore, hereinafter, first, a closed firing furnace 10 as shown in FIG. 1 will be described as one structural example to which the present invention is applied.

As shown in FIG. 1, the closed type firing furnace 10 has
A firing furnace 11 for firing a low-loss ferrite material,
A gas inlet 12 for introducing an inert gas and a mixed gas of an active gas and a reducing gas is provided in the firing furnace 11.

Here, in the closed firing furnace 10 of this example, nitrogen (N ₂ ) gas is used as the inert gas, air is used as the active gas, and LPG is used as the reducing gas.
Shall be used. However, the inert gas is not limited to nitrogen gas, and may be any gas that does not chemically react with the ferrite to be fired. Specifically, for example, argon (Ar) gas may be used as the inert gas. Further, the reducing gas is not limited to LPG, and is not particularly limited as long as it shows a reducing property by reacting with oxygen regardless of whether it is in a liquefied state or not. Absent. Specifically, for example, hydrogen (H ₂ ) gas may be used as the reducing gas.

The LPG generally means a liquefied mixed gas of lower hydrocarbons derived from petroleum such as propane, butane, butylene, propylene, etc., which is suitable for use in the closed firing furnace 10. The mixed gas is not limited to such a mixed gas, and pure propane gas, methane gas, butane gas, or the like may be used. However, since LPG is usually placed in a container in a liquefied state in which a mixed gas containing propane is liquefied for commercial transactions, it is most preferable to use the mixed gas in such a state in the closed firing furnace 10. Simple and desirable. Also,
LPG has the characteristics that it is cheaper than hydrogen gas and the like, and that it is safe with less risk of explosion and the like. Therefore, by using LPG as the reducing gas, low-loss ferrite can be manufactured safely at low cost.

In the closed firing furnace 10, for example, air, nitrogen gas, and LPG are supplied to the mixing device 13 through supply paths from a container arranged outside, for example. Further, the air, nitrogen gas, and LPG are respectively mixed by the first flow rate control valve 14, the second flow rate control valve 15, and the third flow rate control valve 16 which are arranged in the respective supply paths, respectively. It is possible to freely control the flow rate supplied to the. That is, in the closed firing furnace 10, the first flow control valve 14, the second flow control valve 15,
The third flow rate control valve 16 makes it possible to change the flow rate ratio between the nitrogen gas as the inert gas and the air as the active gas, and the LPG as the reducing gas. The mixing device 13 mixes the supplied air, nitrogen gas, and LPG into a uniform gas, and then introduces the mixed gas into the firing furnace 10 through the gas introduction port 12.

In the above description, the inert gas and the active gas and the reducing gas are mixed by the mixing device 13 and introduced into the firing furnace 11 through the single gas introduction port 12. However, for example, Alternatively, the inert gas and the reducing gas may be introduced into the firing furnace 11 through different gas inlets.

Next, the low-loss ferrite produced by the closed type firing furnace 10 configured as described above will be explained.

Low-loss ferrite is iron oxide (Fe
₂ O ₃ ), zinc oxide (ZnO) and manganese oxide (Mn
O) is the main starting material and is manufactured according to the usual manufacturing process of polycrystalline sintered ferrite. That is, the starting materials described above are weighed and mixed, heat-treated (so-called calcination), and then pulverized. After that, it is granulated into an appropriate size and molded into an arbitrary shape by a method such as pressing.

Next, the formed ferrite is fired in a firing furnace 10.
As shown in FIG. 2, the binder is removed from the firing furnace 10 by raising the temperature in the firing furnace 10 to a temperature of about 600 ° C. at which the binder added for molding decomposes (binder decomposition temperature). . At this time, a certain amount of oxygen partial pressure is required when raising the temperature to the binder decomposition temperature. In addition,
In FIG. 2, the oxygen partial pressure when the temperature is raised to the binder decomposition temperature is equal to the oxygen partial pressure in the atmosphere.
The case where it is set as% is shown.

After debinding as described above, the main sintering temperature (maximum attainable temperature. 1250 ° C. to 1350 ° C.)
℃ is desirable. The temperature in the firing furnace 10 is further increased to (4). In this main sintering step, it is known that when the oxygen partial pressure in the firing furnace 10 is large, many voids remain inside the ferrite to reduce the density and increase the loss of the completed ferrite. There is.

Therefore, for example, Japanese Patent Laid-Open No. 5-238817.
As described in Japanese Patent Laid-Open Publication No. JP-A No. 2004-187, when firing ferrite, a low-loss ferrite is produced by setting the oxygen partial pressure at the time of temperature increase from the binder decomposition temperature to the maximum reached temperature to 1% or less. Is desirable.

However, according to the conventional method in which a large amount of inert gas such as nitrogen gas is introduced into the firing furnace, the oxygen component is generated from the ferrite itself, and as shown by the dotted line in FIG. However, there is a problem that the oxygen partial pressure cannot be reduced sufficiently. In addition, there is a problem that a large energy loss occurs in order to compensate for the temperature decrease in the firing furnace caused by introducing a large amount of inert gas into the firing furnace.

However, the closed firing furnace 10 in this example
It is possible to introduce not only an inert gas but also LPG as a reducing gas into the firing furnace 10. Therefore, by operating the first to third flow rate control valves 14, 15 and 16 in the temperature rising range (the area indicated by A in FIG. 2) from the binder decomposition temperature to the maximum reached temperature, the inertness becomes inactive. It is possible to control the flow rate ratio between the gas and the active gas and the reducing gas, and to introduce a small amount of LPG together with the inert gas and the active gas.

As described above, by introducing a small amount of LPG during the temperature rise in the main sintering step, the oxygen gas existing in the firing furnace 10 and the oxygen component generated from the ferrite itself can be consumed by combustion. . Therefore, the oxygen partial pressure can be easily reduced to about 1% or less without introducing a large amount of inert gas into the firing furnace 10.

When the low-loss ferrite is produced in the closed type firing furnace 10, it is inactive even in the temperature falling range (the area indicated by B in FIG. 2) from the maximum temperature reached to the inside of the firing furnace 10 to cooling. It is desirable to control the flow rate ratio of the gas and the active gas to the reducing gas. This is based on the finding that the characteristics of the low-loss ferrite can be improved by keeping the oxygen partial pressure low not only in the temperature rising range but also in the temperature falling range. By introducing the reducing gas together with the inert gas and the active gas into the firing furnace 11 in this temperature decreasing range, the oxygen partial pressure can be efficiently and easily controlled in the same manner as in the above-mentioned temperature increasing range. it can.

When controlling the flow rate ratio of the inert gas and the active gas to the reducing gas in the predetermined temperature range in the closed firing furnace 10, for example, the first to third flow rate control valves 14, 15 and 16 may be manually operated, or the first to third flow rate control valves 1 can be automatically operated by combining a temperature sensor or a gas concentration sensor arranged in the firing furnace 11 with a control circuit or the like.
It may be configured such that 4, 15, 16 are driven.

Next, as another structural example to which the present invention is applied, a continuous firing furnace 20 as shown in FIG. 3 will be described.

As shown in FIG. 3A, the continuous firing furnace 20 is provided with a firing furnace 21 for firing a raw material of low-loss ferrite, and an inert gas and an active gas and a reducing gas are provided in the firing furnace 21. A plurality of gas inlets 22 for introducing a mixed gas of
Is equipped with.

Inside the firing furnace 21, there are provided a plurality of transfer trays 23 for transferring the ferrite raw material, that is, the ferrite that has not been formed and not yet sintered, along the firing furnace 21. Each transport tray 23 is moved in a direction indicated by an arrow C in FIG. 3A by a drive mechanism such as a hydraulic cylinder or a belt drive. That is, each transport tray 23 and the drive mechanism form a transport mechanism that transports the ferrite raw material.

A heater 24 is provided around the firing furnace 21.
Is provided. The inside of the firing furnace 21 is the heater 2
4 is set so that a predetermined temperature distribution is obtained along the moving direction of the transport tray 23. This temperature distribution is set such that the furnace temperature corresponding to the transport position of the transport tray 23 corresponds to, for example, the temperature corresponding to the time variation of the firing furnace temperature shown in FIG. There is.

On the other hand, from a plurality of gas inlets 22 provided in the firing furnace 21, for example, nitrogen gas as an inert gas and air as an active gas, and a reducing gas from a container or the like arranged outside. And LPG are supplied to the firing furnace 21 through the respective supply paths. Here, each of the plurality of gas introduction ports 22 is sequentially arranged according to the arrangement position along the moving direction of the transport tray 23, that is, the first gas introduction port 22a, the second gas introduction port 22b, and the third gas introduction port 22b. Gas inlet 2
2c ...

Although FIG. 3 (a) shows up to the seventh gas introduction port 22g in the continuous firing furnace 20, in actuality, as the transfer tray 23 moves, FIG. The firing furnace 21 is configured with a length long enough to have a temperature distribution corresponding to the time variation of the firing furnace temperature shown in the figure, and in the firing furnace 21, a sufficient number and intervals are provided at positions where the temperature is a predetermined value. It is arranged.

Further, in the continuous firing furnace 20, a flow rate control device 25 is arranged in front of each gas introduction port 22 in the supply path of the inert gas and the active gas and the reducing gas. The flow rate control device 25 can control the flow rate ratio of the inert gas and the active gas and the reducing gas supplied from each gas inlet 22 into the firing furnace 21.

The continuous firing furnace 20 in this example is constructed as described above, so that the inert gas and the active gas are supplied from the respective gas inlets 22 respectively arranged at the positions where the predetermined temperature is reached. The reducing gas can be supplied into the firing furnace 21 at a predetermined flow rate ratio.

As a result, the oxygen partial pressure at each position in the firing furnace 21 along the moving direction of the transfer tray 23 is set as shown in FIG. 3 (b), for example. That is, in the temperature rising range (in FIG. 3B) from the binder decomposition temperature (indicated by D in FIG. 3B) to the maximum reached temperature (indicated by E in FIG. 3B). In the region indicated by F), the oxygen partial pressure can be about 1% or less.

At this time, as in the case of the closed type firing furnace 10 described above, by introducing a reducing gas into the firing furnace 21, oxygen in the firing furnace 21 can be consumed by combustion, and The temperature decrease in the firing furnace 21 due to the introduction of the inert gas can be supplemented by combustion. Therefore, the oxygen partial pressure can be reduced to about 1% or less without introducing a large amount of the inert gas into the firing furnace 21, and the temperature inside the furnace can be prevented from lowering due to the introduction of the inert gas, resulting in efficient operation. The oxygen partial pressure can be controlled easily and easily.

FIG. 3 (b) also shows the change in oxygen partial pressure when the method of introducing only the inert gas into the firing furnace 21 is adopted. in this way,
It is difficult to sufficiently reduce the oxygen partial pressure by the conventional method of introducing only the inert gas into the firing furnace 21.

The low-loss ferrite produced by the closed-type firing furnace 10 and the continuous-type firing furnace 20 described above has an oxygen partial pressure of 1% or less in the temperature rising range from the binder decomposition temperature to the highest reached temperature. It is desirable that the equilibrium oxygen partial pressure is 4% or less in the temperature falling range from the highest temperature to the cooling. Here, the binder decomposition temperature differs depending on the type of binder. Therefore, the binder decomposition temperature is a value measured by, for example, a thermogravimetric analysis method (TGA method). That is, when looking at the binder alone, the weight change when heat is applied to the binder is observed, and the temperature when the weight becomes 0 is defined as the binder decomposition temperature.

However, since the binder is actually mixed in the ferrite powder, it is necessary to observe the weight change when heat is applied to the ferrite powder containing the binder. In this case, the temperature at which no change in weight is observed (the weight does not decrease) may be set as the binder decomposition temperature.

However, in the thermogravimetric analysis method, the heating rate, the partial pressure of oxygen, the filling state of the sample, the molecular weight of the binder and the like affect the values, so caution is required. Therefore, for example, when the binder is polyvinyl alcohol, the decomposition is completed at a temperature lower than 500 ° C when viewed alone, and it is considered that the decomposition is completed at a temperature lower than 600 ° C even in actual data. Therefore, the temperature rising range for controlling the flow rate ratio of the inert gas and the active gas to the reducing gas in the closed firing furnace 10 and the continuous firing furnace 20 is, for example, 5
It is desirable to set the temperature rising range from 00 ° C. to the highest reached temperature.

The temperature at which the ferrite is cooled is the temperature before the temperature rises from the binder decomposition temperature (for example, 30).
0 ° C.), the temperature lowering range for controlling the flow rate ratio of the inert gas and the active gas to the reducing gas may be a temperature range from the highest temperature to 300 ° C.

Further, as the low-loss ferrite produced by applying the present invention, iron oxide (Fe
₂ O ₃ ), zinc oxide (ZnO), and manganese oxide (M
It is desirable that the composition range of (nO) has soft magnetic characteristics, for example, Fe ₂ O ₃ of 50 to 60 mol%, Z
It is desirable that nO is 5 to 15 mol% and the rest is MnO. In particular, ZnO is preferably 5 to 15 mol% because it is desired to realize a high saturation magnetic flux density in response to large amplitude excitation.

The iron oxide (Fe ₂ O ₃ ) may be of any type such as iron chloride type or iron sulfate type, but is synthesized via iron chloride from the viewpoint of material cost and various characteristics. It is desirable that the iron chloride-based iron oxide (α-Fe ₂ O ₃ ) is used. However, iron chloride-based iron oxide contains a large amount of chloride ions, and the density of the obtained ferrite may decrease due to the chloride ions, so the content of chloride ions is 1000 ppm or less. It is preferable to use iron oxide.

The components of the low-loss ferrite are:
In addition to the above-mentioned main component, it is optional to add a sub-component as necessary. Examples of such subcomponents include CaO, SiO ₂ , ZrO ₂ , SnO ₂ , and Ti.
_{O 2, Ta 2 O 5,} Al 2 O 3, Ga 2 O 3, In 2 O
₃ etc. can be mentioned.

In the above description, the present invention is applied to the case of producing a so-called low-loss ferrite, but the present invention is particularly limited to the case of producing a low-loss ferrite. However, it can be widely applied to the production of various ferrites. The present invention exerts a particularly excellent effect when applied to the production of Mn—Zn-based ferrite in which it is important to highly control the atmosphere during firing.

[0056]

EXAMPLES Hereinafter, a case where a low-loss ferrite is actually produced by using the above-mentioned closed type firing furnace 10 will be described.

First, as a first embodiment, the inert gas introduced into the firing furnace 11 of the hermetically sealed firing furnace 10 and the flow ratio of the active gas and the reducing gas are controlled so that the binder decomposition temperature is controlled to the maximum. A low-loss ferrite was produced by controlling the oxygen partial pressure in the temperature rising range up to the ultimate temperature to 1%. Similarly, the oxygen partial pressure in the temperature rising range was controlled to 0.3% to produce low-loss ferrite, which was used as the second embodiment.

In addition, as a comparative example, a low-loss ferrite was produced without particularly changing the oxygen partial pressure in the temperature rising range, and this was used as the first comparative example. Further, when reducing the oxygen partial pressure in the temperature raising range, a conventional method of introducing a large amount of only an inert gas into the firing furnace 11 was adopted, and the oxygen partial pressure in this temperature raising range was set to 1% to make a low value. Loss ferrite was used as the second comparative example.

Next, with respect to the low-loss ferrites produced in the first and second examples and the first and second comparative examples produced as described above, the density d (kg / m
³ ), loss Pcv (kW / m ³ ), and saturation magnetic flux density B
s (mT) was measured.

The density d is in accordance with the apparent density measuring method of weighing in liquid, which is defined by "C2561: Material performance test method of ferrite core 7.8.1" in Japanese Industrial Standard (JIS). It was measured.

The loss Pcv was measured according to the waveform storage device method defined in "C2514: Method of measuring core loss of E-type ferrite core 6.3.3" in Japanese Industrial Standard (JIS). The measurement conditions are a frequency of 100 kHz, a maximum magnetic flux density of 200 mT, and a measurement temperature of 90 ° C.

The saturation magnetic flux density is determined by the Japanese Industrial Standard (J
The measurement was performed according to the DC BH characteristic measurement conditions specified in “Method of measuring core loss of E-type ferrite core 6.5” in IS). The applied magnetic field during measurement is 800A.
/ M.

The result of the above measurement is shown in FIG.
As is clear from FIG. 4, the ferrite obtained in the first comparative example in which the oxygen partial pressure at the time of temperature rise was not particularly controlled has a high loss and a low saturation magnetic flux density. Further, in this case, the density is low, and it is understood that the obtained ferrite has many voids.
On the other hand, in the ferrite obtained in the second comparative example in which a large amount of inert gas was introduced at the time of temperature rise, the characteristics of the density, loss, and saturation magnetic flux density were all higher than those of the first comparative example. Although it is improved, there are problems caused by introducing a large amount of inert gas, that is, problems such as deterioration of energy efficiency during the production of ferrite and complexity of controlling oxygen partial pressure.

On the other hand, the ferrites according to the first and second embodiments produced by applying the present invention have the same good characteristics in density, loss and saturation magnetic flux density as those of the second comparative example. It turns out that it has been obtained. Further, in the first and second embodiments, since it is not necessary to introduce a large amount of inert gas, it is possible to easily manufacture the low-loss ferrite exhibiting good characteristics with high energy efficiency. .

Next, a case where a low-loss ferrite is actually produced by using the above continuous firing furnace 20 will be described.

First, as a third embodiment, nitrogen gas and LPG are introduced at a predetermined flow rate ratio from each gas inlet 22 provided in the firing furnace 21 of the continuous firing furnace 20, and firing is performed. A low-loss ferrite was produced by controlling the oxygen partial pressure at each position in the furnace 21. At this time, each gas inlet 22
The flow rate ratio of the nitrogen gas and LPG introduced from the above and the oxygen partial pressure in the firing furnace 21 at the position of each gas introduction port 22 were measured. The measurement result at this time is shown in FIG.

As a third comparative example, low-loss ferrite was produced by introducing only nitrogen gas from each gas inlet 22. That is, only the nitrogen gas was introduced from each gas introduction port 22 at a flow rate ratio of 100%. At this time, the oxygen partial pressure in the firing furnace 21 at the position of each gas inlet 22 was measured. The measurement results at this time are also shown in FIG.

In FIG. 5, among the gas introduction ports 22 shown in FIG. 3A, the flow rate ratios of the second to sixth gas introduction ports 22b to 22f and the gas introduction ports 22b to 22f are shown. The oxygen partial pressure at the position of 22f is shown.

As is clear from the results shown in FIG.
In the third embodiment to which the present invention is applied, the firing furnace 21
While the oxygen partial pressure in the furnace can be reduced to 1% or less, in the third comparative example in which only nitrogen gas is introduced by the conventional method, the oxygen partial pressure in the firing furnace 21 can be sufficiently reduced. It turns out that not. That is, in the third embodiment, by controlling the flow rate ratio of nitrogen gas and LPG, the oxygen partial pressure in the firing furnace 21 can be easily and effectively adjusted according to the temperature at each gas inlet 22. Can be controlled dynamically.

Although nitrogen gas is used as the inert gas in the third embodiment, air which is an active gas may be used instead of nitrogen gas. However, since air can be considered to be a mixed gas of about 79% nitrogen and about 21% oxygen, when air is used instead of nitrogen gas, each gas of LPG as a reducing gas is used. It is necessary to set the introduction amount from the introduction port 22 to 5% or more.

Further, in the above-mentioned first to third embodiments, the characteristics of the low-loss ferrite obtained are affected by the water vapor, carbon dioxide, etc. generated when the reducing gas burns in the firing furnace. I was able to confirm that it was not possible.

[0072]

The ferrite manufacturing apparatus and method according to the present invention provide an inert gas and an active gas and a reducing gas in the firing furnace when controlling the oxygen partial pressure in the firing furnace when firing the ferrite. It is realized by introducing it.
Therefore, the oxygen partial pressure in the firing furnace is reduced by the partial pressure of an inert gas such as nitrogen (N ₂ ) or argon (Ar), and the oxygen in the firing furnace is efficiently converted by burning the reducing gas. Not only can it be consumed well, but the temperature inside the furnace can be prevented from lowering due to the heat generated by combustion. Therefore, when controlling the oxygen partial pressure in the firing furnace during firing of ferrite, it is not necessary to introduce a large amount of inert gas, so that the temperature decrease in the furnace is suppressed and energy efficiency is improved, and It is possible to easily control the internal temperature and the oxygen partial pressure. Therefore, according to the present invention, it is possible to realize a ferrite manufacturing apparatus and manufacturing method capable of easily manufacturing low-loss ferrite with high energy efficiency.

The low loss ferrite obtained by the present invention is, for example, a transformer in a switching power supply,
It is possible to sufficiently satisfy various characteristics required for the magnetic core in the flyback transformer of the television receiver. Therefore, according to the present invention, it is possible to efficiently and easily manufacture the low-loss ferrite with the characteristics improved to the maximum, and to reduce the size and weight of the internal circuit in the switching power supply, the television receiver, or the like. Can be realized.

[Brief description of drawings]

FIG. 1 is a schematic view of a closed firing furnace as an example of the configuration to which the present invention is applied.

FIG. 2 is a schematic diagram showing changes with time in oxygen partial pressure and temperature in the firing furnace in the closed firing furnace.

FIG. 3 is a diagram showing a continuous firing furnace as another configuration example to which the present invention is applied, (a) is a schematic diagram showing a schematic structure, and (b) is a position in the firing furnace. It is a schematic diagram which shows the oxygen partial pressure according to.

FIG. 4 is an oxygen partial pressure P _O2 during heating, a density d, and a loss P in a low-loss ferrite actually manufactured by applying the present invention.
It is a figure which shows the relationship between cv and saturation magnetic flux density Bs.

FIG. 5 is a diagram showing the relationship between the oxygen partial pressure at each gas inlet and the flow rate ratio of nitrogen gas and LPG when low-loss ferrite is produced in a continuous firing furnace to which the present invention is applied.

[Explanation of symbols]

10 Closed Type Firing Furnace, 11 Firing Furnace, 12 Gas Inlet, 13 Mixing Device, 14 First Flow Control Valve, 1
5 second flow rate control valve, 16 third flow rate control valve, 20 continuous firing furnace, 21 firing furnace, 22 gas inlet, 23 transfer tray, 24 heater, 25 flow rate control device

[Procedure amendment]

[Submission date] June 25, 2001 (2001.6.2)
5)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

9. The inert gas to be introduced into the firing furnace and the flow rate ratio of the reducing gas to the inert gas are controlled in a temperature falling range from the highest temperature reached to cooling in the firing furnace. The method for producing a ferrite according to claim 6. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 24, 2001 (2001.7.2)
4)

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

Continued front page    (72) Inventor Toshiaki Yokota             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation (72) Inventor Yukio Kumagai             Miyagi prefecture Tome gun Nakata town Takae Shinida character Kagano boundary             No. 30 Inside Sony Miyagi Co., Ltd. (72) Inventor Masao Kato             156 Minamigaoka-cho, Seto City, Aichi Co., Ltd.             Maruuchi (72) Inventor Akira Kagohashi             2 Takasago, 2321 Dachi-cho, Toki City, Gifu Prefecture             Business (72) Inventor Koichi Kachi             2 Takasago, 2321 Dachi-cho, Toki City, Gifu Prefecture             Business F-term (reference) 4G018 AA21 AA25 AC12 AC15                 4K063 AA06 AA15 BA04 CA01 CA03                       DA01 DA05 DA07 DA31 DA32                       DA34                 5E041 AB02 CA02 HB09

Claims (9)

[Claims] 1. A ferrite production apparatus for producing ferrite by firing a raw material mainly containing iron oxide, zinc oxide and manganese oxide in a firing furnace, wherein an inert gas, an active gas and a reducing property are provided in the firing furnace. An apparatus for producing ferrite, comprising: a gas introduction mechanism for introducing a gas and changing a flow rate ratio of these gases according to a temperature in the firing furnace. 2. The ferrite production apparatus according to claim 1, wherein the gas introduction mechanism introduces LPG (Liquefied Petroleum Gas) as the reducing gas. 3. The inert gas, the active gas, and the reducing gas to be introduced into the firing furnace in the temperature rising range from the binder decomposition temperature to the highest reached temperature in the firing furnace. 2. The ferrite manufacturing apparatus according to claim 1, wherein the flow rate ratio of is set to be variable. 4. The gas introduction mechanism is configured such that a flow rate ratio of an inert gas and a reducing gas introduced into the firing furnace is variable in a temperature falling range from the maximum temperature reached to cooling in the firing furnace. The apparatus for producing ferrite according to claim 1, wherein: 5. A transport mechanism for transporting the raw material in the firing furnace having a predetermined temperature distribution, wherein the flow rate ratio of an inert gas and an active gas to a reducing gas is set as the gas introduction mechanism. 2. The ferrite manufacturing apparatus according to claim 1, wherein the plurality of gas inlets are arranged at respective positions in the firing furnace where a predetermined temperature is reached. 6. A method for producing ferrite by producing a ferrite by firing a raw material mainly containing iron oxide, zinc oxide and manganese oxide in a firing furnace, wherein an inert gas, an active gas and a reducing property are provided in the firing furnace. A method for producing ferrite, characterized in that the oxygen partial pressure in the firing furnace is controlled by introducing gas and controlling the flow rate ratio of these gases according to the temperature in the firing furnace. 7. The LPG (Liquef) is used as the reducing gas.
ied Petroleum Gas) is used, The manufacturing method of the ferrite of Claim 6 characterized by the above-mentioned. 8. The flow rate ratio between the inert gas and the active gas and the reducing gas introduced into the firing furnace is controlled in the temperature rising range from the binder decomposition temperature to the highest reached temperature in the firing furnace. 7. The method for producing a ferrite according to claim 6, wherein: 9. The inert gas to be introduced into the firing furnace and the flow rate ratio of the reducing gas to the inert gas are controlled in a temperature falling range from the highest temperature reached to cooling in the firing furnace. The method for producing a ferrite according to claim 6.