JP2005298290A - Microwave calcining furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a microwave calcining furnace which is capable of drying securely for a short time a body to be treated. <P>SOLUTION: The furnace radiates intermittently a microwave to heat a body to be treated and counts the off-times for every time of a magnetron's off since a time for the furnace inside temperature to reach the warmth-retaining temperature capable of drying suitably the body to be treated, and simultaneously judges whether or not the said off-times exceed a definite period of an index for the drying finish, regarding the drying as the finish at a time when the off-times exceed the said time, and then stops the magnetron radiation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microwave firing furnace that manufactures a fired body by firing an object to be processed formed of a ceramic material or a fine ceramic material.

A microwave firing furnace using a microwave is known as a ceramic firing furnace (see, for example, Patent Document 1). A conventional microwave baking furnace includes an unbaking pattern for performing unbaking and a baking pattern for performing main baking, and the pre-dried object is processed at 80 to 200 ° C. until the moisture content becomes approximately 0%. The unbaking is performed by drying and finally baking at about 700 ° C. After the unbaking, the main baking is performed at a heating temperature of about 1200 ° C.
In the following description, the term “drying” as referred to in the present specification refers to so-called dry soil drying, which means that the moisture content of the object to be treated is about 25% to about 6-8%. For this drying, a sundryer in the shade or an electric dryer called an electric furnace using a heater has been used (see, for example, Patent Document 2 and Patent Document 3).

JP 2004-75458 A Japanese Patent Laid-Open No. 11-116321 JP 2002-87875 A

  By the way, although the conventional microwave baking furnace has a function of performing unglazed baking and main baking, none of them has a drying function. Therefore, the microwave baking furnace still takes a long time to complete the product even if the baking time can be shortened compared with the electric furnace. Incidentally, it takes about 3 to 7 days for sun drying in the shade, and about 1 day under high temperature and high humidity conditions of about 60 ° C. and about 60% in an electric furnace using a heater. In particular, in the case of an electric furnace using a heater, the temperature is raised to a certain temperature, and after a predetermined time has passed, the temperature is cooled and the drying is finished. Therefore, when the moisture content of the object to be treated is small, it can be sufficiently dried, but when the shape of the object to be treated is large or when the moisture content is large, the treatment ends without being sufficiently dried. In that case, it is necessary to dry again, and a considerable time is eventually required.

  This invention is made | formed in view of such a situation, and it aims at providing the microwave baking furnace which can dry a to-be-processed object reliably in a short time.

The above object is achieved by the following configuration.
(1) A microwave firing furnace including a microwave generator that radiates microwaves and firing an object to be processed accommodated in the furnace, the temperature measuring means for measuring the furnace temperature, and the microwave generator ON / OFF control is performed to radiate microwaves intermittently, and the temperature is turned off each time the temperature in the furnace exceeds the heat retention temperature from the time when the temperature in the furnace reaches a heat retention temperature at which the object to be treated can be suitably dried. On / off control means, off-time counting means for counting off time each time the microwave generator is turned off from the time when the furnace temperature reaches the heat retention temperature, and the microwave generator is turned off Each time the off time exceeds a certain time, which is an indicator of the end of drying, and when the off time exceeds the certain time, the radiation generator stops the radiation of the microwave generator. A microwave firing furnace.

(2) A program for executing a drying process for drying an object to be processed in a microwave baking furnace, and a temperature measurement procedure for measuring the temperature in the furnace, and the microwave generator is turned on and off at the start of drying. On / off control for turning off each time the furnace temperature exceeds the heat retention temperature from the time when the temperature in the furnace reaches a heat retention temperature at which the object to be treated can be suitably dried. A procedure, an off-time counting procedure for counting off time each time the microwave generator is turned off from the time when the furnace temperature reaches the heat retaining temperature, and each time the microwave generator is turned off. A determination procedure for determining whether or not the off time exceeds a certain time as an index for the completion of drying, and stopping the radiation of the microwave generator when the off time exceeds the certain time Morphism has a stop procedure, a program, characterized in that to execute the respective steps by a computer.

  According to the microwave baking furnace described in the above (1), the object to be processed is heated by intermittently radiating microwaves, and the temperature inside the furnace reaches a heat retaining temperature at which the object can be suitably dried. Each time the microwave generator is turned off, the off time is counted, and it is determined whether or not the off time exceeds a certain time that is an index of the end of drying. Since the generator radiation is stopped, the object to be processed can be reliably dried in a short time. In other words, when the moisture content of the object to be treated is small, it can be sufficiently dried in a shorter time than before, and it can be surely dried even when the shape of the object to be treated is large or the moisture content is large. Become.

  According to the program described in (2) above, microwaves are generated from the point in time when the object to be processed is heated by intermittently radiating microwaves, and the furnace temperature reaches a temperature at which the object to be processed can be suitably dried. Each time the unit is turned off, the off time is counted, and it is determined whether or not the off time exceeds a certain time, which is an index for the completion of drying. Thus, the object to be processed can be reliably dried in a short time. In other words, when the moisture content of the object to be treated is small, it can be sufficiently dried in a shorter time than before, and it can be surely dried even when the shape of the object to be treated is large or the moisture content is large. Become.

Hereinafter, a microwave baking furnace according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram showing an embodiment of a microwave baking furnace according to the present invention.

A microwave baking furnace 10 according to the present embodiment is configured to radiate microwaves to heat a workpiece 11 and to drive a magnetron (microwave generator) 12 and to drive the magnetron 12 by on / off control. , The thermocouple 15 serving as a temperature measuring means for measuring the temperature in the furnace in which the object 11 is enclosed and surrounded by the heat insulating material 14, and the furnace temperature is set to a certain level. In order to hold at the heat insulation temperature (the temperature at which the object can be suitably dried), it has a function of detecting the difference between the temperature inside the furnace measured by the thermocouple 15 and the heat insulation temperature, and the furnace temperature exceeds the heat insulation temperature. Immediately after, the drive unit 13 is controlled immediately after the off-time of the magnetron 12 is monitored, and immediately after the off-time exceeds a certain time (a time serving as an index to finish drying the object to be processed). Magnetron Control unit comprising a microcomputer having a function of stopping the second radiation (off-time counting means, the radiation stopping means) and a 16.
The drive unit 13 and the control unit 16 also function as on / off control means.

FIG. 2 is a waveform diagram showing temporal changes in the furnace temperature with respect to on / off control of the magnetron 12 in the drying process of drying the object 11 to be processed.
First, the control unit 16 controls the driving unit 13 to intermittently radiate microwaves from the magnetron 12 and gradually raises the temperature in the furnace to a heat retention temperature (for example, 60 ° C.). At this time, the drive unit 13 turns the magnetron 12 on / off by the control unit 16. Moisture on the surface of the object to be processed 11 evaporates during the time Ta until the furnace temperature reaches the heat retention temperature. Incidentally, the time Ta for removing the moisture on the surface of the object 11 is about 30 minutes.

When the in-furnace temperature exceeds the heat retention temperature due to intermittent microwave radiation (time t ₁ ), the control unit 16 controls the driving unit 13 at that time to turn off the magnetron 12. When the magnetron 12 is turned off, the temperature in the furnace decreases, and when the temperature becomes lower than the heat retention temperature (time t ₂ ), the control unit 16 turns on the magnetron 12 again. By repeatedly performing on / off control of the magnetron 12 with this heat retention temperature as a target, the object to be processed 11 is gradually heated, and moisture gradually evaporates from the inside of the object to be processed 11. That is, the microwaves act efficiently to perform drying.

  Due to the characteristics of the microwave, since the water is immediately heated, the temperature in the furnace frequently fluctuates when the moisture content of the object 11 is high. However, the on / off control of the magnetron 12 is performed to intermittently reduce the radiation amount. By optimizing, the water vapor in the furnace gradually evaporates, and the temperature in the furnace is eventually stabilized at the heat retention temperature.

  When the microwaves continue to be intermittently radiated, the moisture in the object 11 evaporates (vaporizes), and the furnace temperature rises accordingly. Therefore, the time during which the furnace temperature exceeds the heat retention temperature is increased, and the time during which the magnetron 12 is turned off is inevitably increased.

The controller 16 counts the off time each time the magnetron 12 is turned off after the furnace temperature reaches the heat insulation temperature. Then, the magnetron as it exceeds a certain time have time to clear the magnetron 12 (time as an index drying of the object 11 is completed) (time t _8), is a drying at that time was achieved 12 is stopped. The symbol Tc in the figure indicates one off time of the magnetron 12, and when this off time Tc exceeds the above-mentioned fixed time, it is considered that the drying is finished. Incidentally, the time Tb for removing the water inside the object 11 is about 3 hours. In this way, the object 11 is dried.

Here, the said drying process is demonstrated with reference to the flowchart shown in FIG.
When the drying process is started, the magnetron 12 is first turned on / off, microwaves are intermittently emitted from the magnetron 12, and the furnace temperature is raised (step S10). Then, it is determined whether or not the furnace temperature has reached the heat retention temperature (step S11).

  When the furnace temperature has not reached the heat retention temperature (in the case of No in step S11), the process returns to step S10, and the on / off control of the magnetron 12 is continued. On the other hand, when the furnace temperature reaches the heat retention temperature (Yes in step S11), the furnace temperature is confirmed (step S12). When this step S12 is executed for the first time, that is, when the process proceeds from step S11 to step S12, the temperature inside the furnace is the heat retention temperature (furnace temperature = heat retention temperature). Is stopped (step S13).

  Then, counting of the off time of the magnetron 12 is started (step S14). After the counting of the off time of the magnetron 12 is started, it is determined whether or not the off time is equal to or longer than the predetermined time (a time serving as an index for ending the drying of the workpiece 11) (step S15), and is less than the time. If this is the case (No in step S15), the process returns to step S12 to check the furnace temperature. The loop of step S12 to step S15 is repeated until the off-time of the magnetron 12 is less than the predetermined time and the furnace temperature falls below the heat retention temperature.

  When the furnace temperature falls below the heat retention temperature (in the case of “furnace temperature <heat insulation temperature” in step S12), the process proceeds from step S12 to step S16, the magnetron 12 is turned on (step S16), and then The count value of the off time of the magnetron 12 is reset (step S17). That is, after the magnetron 12 is turned on, the count value of the previous off time is cleared.

  In step S16, the magnetron 12 is turned on. In step S17, the count value of the off time of the magnetron 12 is reset, and then the furnace temperature is checked again (step S12). The magnetron 12 is kept on until the furnace temperature becomes equal to or higher than the heat retention temperature.

  When the on-state of the magnetron 12 continues and the furnace temperature rises, and the furnace temperature becomes equal to or higher than the heat retention temperature, the magnetron 12 is turned off as in the previous time (step S13), and the counting of the magnetron 12 off time is started. (Step S14). The loop of step S12 to step S15 is repeated until the off-time of the magnetron 12 is less than a predetermined time and the furnace temperature falls below the heat retention temperature. If the furnace temperature falls below the heat insulation temperature during that time, step S12, step S16, Step S17 is performed.

  Thus, every time the magnetron 12 is turned off from the time when the temperature in the furnace reaches the heat retaining temperature at which the object to be treated can be suitably dried, the off time is counted, and the off time is a constant that is an indicator of the end of drying. Determine if the time is exceeded. And when the OFF time of the magnetron 12 exceeds a fixed time (in the case of Yes of step S15), a drying process is complete | finished (step S18).

  As described above, according to the microwave baking furnace 10 according to the present embodiment, the object 11 is heated by intermittently radiating the microwaves with the magnetron 12, and the furnace temperature is suitable for the object 11 to be processed. Each time the magnetron 12 is turned off from the time when it reaches a heat retention temperature at which it can be dried, the off time is counted, and it is determined whether or not the off time exceeds a certain time that is an index for the completion of drying. Since the radiation of the magnetron 12 is stopped assuming that the drying is completed, the object 11 can be reliably dried in a short time. That is, when the water content of the object 11 is small, sufficient drying can be performed in a shorter time than before, and the object 11 can be reliably dried even when the shape of the object 11 is large or when the water content is large. it can.

  The present invention can be applied to a microwave baking furnace for baking an object to be processed using microwaves.

It is a lineblock diagram showing the microwave baking furnace concerning one embodiment of the present invention. It is a figure which shows the on / off control waveform and furnace temperature waveform of a magnetron in a drying process. It is a flowchart which shows the operation | movement in a drying process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Microwave baking furnace 11 To-be-processed object 12 Magnetron 13 Drive part 14 Heat insulating material 15 Thermocouple 16 Control part

Claims (2)

A microwave firing furnace comprising a microwave generator for radiating microwaves, and firing an object to be processed housed in the furnace,
Temperature measuring means for measuring the temperature in the furnace;
The microwave generator is turned on and off to radiate microwaves intermittently, and when the temperature in the furnace reaches a heat insulation temperature at which the object to be treated can be suitably dried, the temperature in the furnace becomes the heat insulation temperature. An on / off control means that turns off each time it exceeds,
Off time counting means for counting off time each time the microwave generator is turned off from the time when the furnace temperature reaches the heat retention temperature;
Each time the microwave generator is turned off, it is determined whether or not the off time exceeds a certain time that is an indicator of the end of drying, and when the off time exceeds the certain time, radiation of the microwave generator is stopped. Radiation stopping means for
The microwave baking furnace characterized by comprising. A program for executing a drying process for drying an object to be processed in a microwave baking furnace,
A temperature measurement procedure for measuring the furnace temperature;
The microwave generator is intermittently radiated by controlling on / off of the microwave generator at the start of drying, and the furnace temperature is changed from the time when the furnace temperature reaches a heat retaining temperature at which the object to be treated can be suitably dried. An on / off control procedure that turns off each time the temperature is exceeded,
An off time counting procedure for counting off time each time the microwave generator is turned off from the time when the furnace temperature reaches the heat retaining temperature;
Each time the microwave generator is turned off, a determination procedure for determining whether or not the off time exceeds a certain time, which is an indicator of the end of drying,
A radiation stopping procedure for stopping radiation of the microwave generator when the off-time exceeds the predetermined time;
And having the computer execute the steps described above.

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