JP2008021494A - Microwave utilization device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave utilization device with a loss reduced and a higher efficiency aimed at, in a microwave generating device made of semiconductors. <P>SOLUTION: Drive voltages of microwave generating means 6, 7 for irradiating microwaves on a heated object 2 loaded in the heating chamber 1 are increased with the use of GaN semiconductor elements, and by providing a plurality of pieces of the microwave generating means 6, 7, a loss each of the individual microwave generating means is reduced to improve efficiency of the microwave utilization device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microwave utilization apparatus that dielectrically heats an object to be heated using microwaves.

  A typical microwave utilization apparatus of this type is a microwave oven that is widely used as a household cooking device. The microwave generating means mounted in the microwave oven is a magnetron, and this magnetron is a so-called vacuum tube, and can take a large microwave output, and has a high operating efficiency of over 70%. On the other hand, the magnetron cannot freely control the oscillation frequency, and the oscillation frequency of the magnetron itself varies depending on the impedance of the load including the object to be heated. For this reason, non-uniform heating may occur in the object to be heated due to standing waves generated in the heating chamber due to operation at an inappropriate oscillation frequency.

  There is a coaxial type magnetron configuration that variably controls the oscillation frequency of the magnetron, but the size of the component that variably controls the frequency is large, so the magnetron itself is upsized and very expensive, so it can be used for microwave ovens. Is not suitable.

  On the other hand, with the advancement of microwave circuit technology accompanying the development of mobile communication in recent years, technological innovation of semiconductor devices has advanced, and devices capable of operating at high frequencies have begun to be put into practical use.

The microwave generating means constituted by this semiconductor element can variably control the oscillation frequency by using a voltage controlled oscillator or a capacitance controlled oscillator as an oscillation source. There is one that uses a frequency self-excited solid-state oscillating unit and controls the oscillation frequency in accordance with the power supply impedance to the heating chamber to form an optimal matching state to efficiently heat (see, for example, Patent Document 1). .
JP 59-165399 A

  However, when trying to obtain a microwave output equivalent to or higher than that of a magnetron by a microwave generation means using a semiconductor element as an oscillation source, if constituted by a single microwave generation means, a semiconductor element corresponding to high-frequency operation is Since the withstand voltage is low, in order to earn electric power, the passing current must be increased naturally. On the other hand, the loss P caused by the passing current is expressed by the product of the resistance component R and the square of the passing current I. Therefore, the increase in the loss P must be large with respect to the increase in current. For this reason, there is a problem that the loss in the semiconductor element becomes very large and the efficiency of the entire apparatus is extremely deteriorated when an output equal to or higher than that of the magnetron is obtained.

  In order to solve this problem, a method of dividing the microwave generating means into a plurality of parts is conceivable. However, if the microwave generating means is configured using existing semiconductor elements, the generated loss in each microwave generating means is reduced to some extent. The number of divisions of the microwave generation means is extremely large to reduce it to the extent that it can be cooled, and the volume occupied by the microwave generation means increases with respect to the magnetron, so the mounting space is limited like a microwave oven. There is a problem that it is not practically used in applications.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a microwave utilization device that realizes high heating efficiency using a microwave generation means having a semiconductor element using a semiconductor having a large band gap. To do.

  In order to solve the above-described conventional problems, the microwave utilization apparatus of the present invention includes a plurality of microwave generation means having a semiconductor element using a semiconductor having a larger band gap than silicon, and a radiation means for radiating microwaves, The heating unit includes a control unit, the radiating unit radiates the microwave output from the microwave generating unit into the heating chamber, the control unit controls the output of the microwave generating unit, and the microwave The driving power of each of the generating means is set to 1/2 or less of the maximum supply power of the entire apparatus.

  Thereby, when a predetermined power is to be obtained in the entire apparatus, the driving voltage of the microwave generating means can be increased by a semiconductor element having a wider band gap than that of silicon, so that the driving current for obtaining the same power can be reduced. For this reason, since the loss due to the passing current can be reduced, when the outputs of the plurality of microwave generating means are combined, the outputs of the respective microwave generating means can be set high, so that the number of divisions can be reduced. Moreover, since the consumption current in each microwave generation means can be reduced by arranging a plurality of microwave generation means, the loss due to the passing current in each microwave generation means can be reduced, so that the apparatus The total loss can be reduced and the power conversion efficiency can be improved.

  According to the microwave utilization apparatus of the present invention, the driving power of each microwave generation means is reduced to 1/2 or less of the total power of the apparatus, thereby reducing the passing current of each microwave generation means. The total loss of the entire apparatus can be reduced and the power conversion efficiency can be improved. In addition, an energy saving effect can be expected by improving the power conversion efficiency.

  The first invention comprises a plurality of microwave generating means having a semiconductor element using a semiconductor having a larger band gap than silicon, radiating means for radiating microwaves, a heating chamber, and a control unit, and the radiating means Radiates the microwave output from the microwave generating means into the heating chamber, the control unit controls the output of the microwave generating means, and the driving power of each of the microwave generating means is the maximum of the entire apparatus. Since the current passing through each microwave generator can be reduced by setting the power supply to ½ or less of the supplied power, the generation loss in the microwave generator can be reduced, and the power conversion efficiency of the entire apparatus can be improved. be able to.

  In the second invention, in particular, a plurality of radiation means according to the first invention are arranged and connected to each microwave generating means in a ratio of 1: 1, whereby the passing current of each microwave generating means can be reduced. Therefore, the loss generated in the microwave generation means can be reduced, and the power conversion efficiency of the entire apparatus can be improved. Further, since each macro radiates the output of the generating means into the heating chamber from the radiation means connected to each macro, it is possible to improve the heating efficiency because there is no loss caused when the respective outputs are combined.

  According to the third aspect of the invention, in particular, since the output of each microwave generation means of the second invention is changed randomly in time, the passing current of each microwave generation means can be reduced. The generated loss in the generating means can be reduced and the power conversion efficiency of the entire apparatus can be improved. At the same time, the output of each microwave generating means is changed randomly in time to be heated. It is possible to change the temperature rising portion of the material at random to promote uniform heating.

According to the fourth aspect of the invention, in particular, the output of each microwave generation means of the second invention can be periodically changed in time, so that the passing current of each microwave generation means can be reduced. The generation loss in the wave generating means can be reduced and the power conversion efficiency of the entire apparatus can be improved, and at the same time, the output of each microwave generating means can be changed with a certain period in time. Thus, it is possible to change the temperature rising portion of the object to be heated and promote uniformization of the heating state.

  According to the fifth aspect of the invention, in particular, the period of change of the output of each microwave generation means of the fourth invention is different, so that the passing current of each microwave generation means can be reduced. It is possible to reduce the generation loss in the means and improve the power conversion efficiency of the entire apparatus, and at the same time, by changing the output of each microwave generation means with a different period in time. It becomes possible to change the temperature rising portion of the article to be heated and to promote uniformization of the heating state.

  The sixth aspect of the invention includes, in particular, temperature detection means for detecting the temperature of the object to be heated placed in the heating chamber of any one of the second to fifth aspects of the invention, each based on information of the temperature detection means. By controlling the output of the microwave generating means, the passing current of each microwave generating means can be reduced, so that the generation loss in the microwave generating means can be reduced and the power conversion of the entire apparatus The temperature of the object to be heated is observed and the output of each microwave generating means is controlled on the basis of the information. By adjusting the output of each microwave generating means so that the radio wave is strongly radiated, the heating state of the object to be heated can be made uniform.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited by this embodiment.

(Embodiment 1)
FIG. 1 is a block diagram of the microwave utilization apparatus according to the first embodiment of the present invention, and FIG. 2 is a block diagram of the microwave generation means of FIG.

  1 to 2, a heating chamber 1 for storing an object to be heated is provided with a door (not shown) for taking in and out the object to be heated 2 on one side, and other wall surfaces are made of a metal material and supplied. It is configured to confine the microwave to be confined inside. A mounting plate 3 made of a low dielectric loss material on which the object to be heated 2 is mounted with a predetermined distance from the bottom wall surface of the heating chamber 1 is disposed below the heating chamber 1. Further, radiation means 4 and 5 are provided on the left and right wall surfaces of the heating chamber 1.

  Below the heating chamber 1, microwave generating means 6 and 7 configured using semiconductor elements are arranged. The microwave generating means 6 and 7 include an oscillating unit 9 having a voltage variable type frequency variable function for generating a frequency from 2400 MHz to 2500 MHz, an initial stage amplifying unit 10 for amplifying the output of the oscillating unit 9 to a predetermined power, and The main amplification unit 11 amplifies the output of the first stage amplification unit 10.

  Further, each output of the main amplifying unit 11 is transmitted to the radiating means 4 and 5 arranged opposite to each other through a coaxial line. The semiconductor elements constituting the first stage amplifying unit 10 and the main amplifying unit 11 constitute a transistor using gallium nitride (hereinafter referred to as GaN) as a semiconductor material.

  This GaN material has a wide energy band gap as compared with silicon (Si), which is a widely known semiconductor material, and it is possible to construct an element with higher breakdown voltage, higher speed operation, and lower loss than Si semiconductor elements. . Therefore, the driving voltage can be increased by using the GaN semiconductor element for the first stage amplifying unit 10 and the main amplifying unit 11, and the driving current can be reduced.

Further, the control means 8 controls the amplification factor of the drive power source or the first stage amplifier 10 and the main amplifier 11 so that the output power of the microwave generation means 6 and 7 becomes a predetermined control value.

  About the microwave utilization apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the object to be heated 2 is stored in the heating chamber 1, the heating condition is input from an operation unit (not shown), and the heating start key is pressed. In response to the control output signal of the control means 8 that has received the heating start signal, the microwave generating means 6 and 7 start operating. The control unit 8 operates the drive power supply to supply power to the oscillation unit 9. At this time, the initial oscillation frequency of the oscillation unit 9 is supplied with a voltage signal set to 2450 MHz, for example, and oscillation starts. Thereafter, the drive power supply is controlled to operate the first stage amplification unit 10, and then the main amplification unit 11 is operated.

  When 100% of the microwave energy supplied into the heating chamber 1 is absorbed by the object to be heated 2, the reflected power from the heating chamber 1 is eliminated, but the type, shape, and amount of the object to be heated 2 are different. 2, and the reflected power that transmits the coaxial line in the reverse direction from the heating chamber 1 side based on the output impedance of the microwave generating means 6 and 7 and the impedance of the heating chamber 1. Occurs.

  This microwave is radiated into the heating chamber 1 in which the object to be heated 2 is accommodated from a pair of opposingly arranged radiation means 4 and 5 through a coaxial line. An electric field concentration region is formed in a predetermined portion of the heating chamber 1 by the emitted microwave. Due to the electric field concentration region formed in the heating chamber 1, the object to be heated 2 is strongly heated when the object to be heated 2 is stored in the electric field concentration region in the heating chamber 1.

  In this way, when the microwave supply is divided from two places as shown in FIG. 1 and the microwave power generated by the respective microwave generation means 6 and 7 is fed so as to be ½ of the total power, The passing current of each of the microwave generating means 6 and 7 can be reduced to about ½ as compared with the case where the total power is supplied from a single microwave generating means.

The loss P generated by the microwave generation means 6 and 7 can be classified into an ohmic loss Pa caused by the passing current and a loss Pf caused by the frequency. The ohmic loss Pa can be expressed by the following equation, Pa = I ² R, when the passing current I and the internal resistance R are used.

  Therefore, Pa can be reduced to ¼ by reducing the passing current to ½. For this reason, the loss P generated in the microwave generating means 6 and 7 can be reduced to about ½ as a total, and the efficiency of the apparatus can be improved.

  FIG. 3 is a diagram showing temporal changes in the microwave powers P1 and P2 radiated from the microwave generation means 6 and 7, respectively. The control means 8 controls the microwave power radiated by the microwave generation means 6 and 7 randomly in terms of time to make the heating of the article to be heated 2 uniform. By this microwave power variable control, the electric field concentration region formed by a pair of opposedly arranged radiating means moves randomly in the heating chamber 1 and moves the heating part of the object to be heated 2 to promote uniform heating.

  FIG. 3 shows a configuration in which the microwave powers P1 and P2 radiated by the microwave generation means 6 and 7 are randomly controlled in time, but the control means 8 has a certain pattern and a certain period in time. Even if the microwave power to be radiated is controlled, the electric field concentration region in the heating chamber 1 changes periodically, so that the heating part of the object to be heated 2 can be moved and uniform heating can be promoted. It is. Further, the effect of the present invention is not impaired at all even if the above-described period is changed at different periods by the respective microwave generation means.

(Embodiment 2)
FIG. 4 is a configuration diagram of the microwave utilization apparatus according to the second embodiment of the present invention.

  The difference between the present embodiment and the first embodiment is that the temperature detection means 12 is provided to measure the heating state of the article 2 to be heated, and the microwaves supplied by the microwave generation means 6 and 7 based on the information. This is a configuration that controls wave power. In FIG. 4, components having the same configuration or substantially the same function as those in the first embodiment are denoted by the same reference numerals.

  In FIG. 4, the heating chamber 1 for storing the object to be heated 2 is provided with a door (not shown) through which the object to be heated 2 is put in and out, and the other wall surfaces are made of a metal material and supplied. The microwave is confined inside. A mounting plate 3 made of a low dielectric loss material on which the object to be heated 2 is mounted with a predetermined distance from the bottom wall surface of the heating chamber 1 is disposed below the heating chamber 1. Further, radiation means 4 and 5 are provided on the left and right wall surfaces of the heating chamber 1.

  Below the heating chamber 1, microwave generating means 6 and 7 configured using semiconductor elements are arranged. The microwave generating means 6 and 7 include an oscillating unit 9 having a voltage variable type frequency variable function for generating a frequency from 2400 MHz to 2500 MHz, an initial stage amplifying unit 10 for amplifying the output of the oscillating unit 9 to a predetermined power, and The main amplification unit 11 amplifies the output of the first stage amplification unit 10. Further, each output of the main amplifying unit 11 is transmitted to the radiating means 4 and 5 arranged opposite to each other through a coaxial line.

  Further, the control means 8 controls the amplification factor of the drive power source or the first stage amplifier 10 and the main amplifier 11 so that the output power of the microwave generation means 6 and 7 becomes a predetermined control value.

  Further, the temperature detection means 12 sequentially measures the temperature of the object to be heated 2 heated by the microwave power irradiated from the microwave generation means 6 and 7. As a specific configuration, an infrared sensor that detects the temperature by infrared rays emitted from the heated object 2 from the outside of the heating chamber 1 may be used, or a thermocouple that measures the temperature by directly contacting the heated object 2. Such a measuring means may be used.

  In the microwave utilization apparatus configured as described above, the operation and action thereof will be described below in particular on differences from the first embodiment.

  The temperature measuring means 12 measures the heating state of the article 2 to be heated. Here, for example, when a portion where the temperature rise is insufficient is measured on either the left or right side of the object to be heated 2, the microwave of the microwave generating means 6 or 7 closer to the portion where the temperature rise is insufficient The output is increased, and the other microwave output is controlled to be lower. By controlling in this way, the electric field concentration region in the heating chamber 1 is moved to the side where the microwave output is larger. As a result, it is possible to promote uniform temperature rise of the entire object to be heated 2 by moving the electric field concentration region to a portion where the temperature increase of the object to be heated 2 is insufficient at a certain measurement timing. The temperature measuring means 12 sequentially measures the temperature of the article 2 to be heated, and the microwave power supplied from the microwave generating means 6 and 7 is determined by the control means 8 based on the detection signal. Can always maintain a uniform temperature rise, and uniform heating can be realized.

  As described above, according to the present invention, since the driving power of the microwave generating means is ½ or less of the total power of the apparatus, the passing current of each microwave generating means is reduced. It is possible to reduce the total loss and improve the power conversion efficiency, which is useful as an energy-saving device.

Configuration diagram of microwave utilization apparatus of embodiment 1 of the present invention Configuration block diagram of microwave generation means of the microwave utilization apparatus The figure which shows the time change of the microwave output of the microwave generation means of the same microwave utilization apparatus The block diagram of the microwave utilization apparatus of Embodiment 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating chamber 2 Object to be heated 4, 5 Radiation means 6, 7 Microwave generation means 8 Control means

Claims (6)

A plurality of microwave generating means having a semiconductor element using a semiconductor having a larger band gap than silicon, radiating means for radiating microwaves, a heating chamber, and a control unit, wherein the radiating means is the microwave generating means. The control section controls the output of the microwave generation means, and the drive power of each of the microwave generation means is ½ of the maximum supply power of the entire apparatus. The following microwave utilization device. The microwave utilization apparatus according to claim 1, wherein a plurality of radiation means are arranged and connected to each microwave generation means in a ratio of 1: 1. The microwave utilization apparatus according to claim 2, wherein the output of each microwave generation means is configured to randomly change in time. The microwave utilization apparatus according to claim 2, wherein the output of each microwave generation means is configured to periodically change in time. 5. The microwave utilization apparatus according to claim 4, wherein the period in which the output of each microwave generation means changes is different. The temperature detection means for detecting the temperature of the object to be heated placed in the heating chamber is provided, and the output of each microwave generation means is controlled based on the information of the temperature detection means. The microwave utilization apparatus of any one of Claims.

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