JP5104048B2 - Microwave processing equipment - Google Patents

Description

  The present invention relates to a microwave processing apparatus including a microwave generation unit configured using a semiconductor element.

In the conventional microwave processing apparatus of this type, a vacuum tube called a magnetron is generally used for a microwave generation section as represented by a microwave oven.

  The main issues when constructing this microwave generator using semiconductor elements are high-power operation that can practice speed heating, high-efficiency operation for high-power operation under available commercial power supply, general This is the provision of value that can be purchased by consumers.

  For the first problem, a multiple power feeding method has been proposed. For example, there is one in which the heating chamber is formed in a polyhedron having six or more surfaces, and a radiation antenna is disposed so as to protrude from a part or all of each surface into the heating chamber (for example, see Patent Document 1).

  And it is supposed that mutual interference can be prevented by arranging the mutual radiation antennas on different surfaces. Furthermore, since the radiating antennas are directed in different directions, the radiated radio wave propagates in all directions in the heating chamber and is reflected and scattered by the wall surface, so that the radio wave is uniformly distributed in the heating chamber.

  In addition, there is a type in which a plurality of microwave generation units are dispersedly arranged on the wall surface of the heating chamber, and the generation units arranged on at least two of the generation units are operated in a time-sharing manner (for example, see Patent Document 2).

  Then, the microwave generation unit selected for operation is operated in a time-sharing manner to prevent the generation unit from being destroyed due to interference and to be operated simultaneously. In addition, the generators arranged on the orthogonal wall surfaces can be excited so as not to interfere with each other by appropriately selecting the coupling between the heating chamber and the generator, and can be simultaneously oscillated.

  The second problem is the evolution of semiconductor elements using SiC or GaN, which have a large band gap with respect to Si and GaAs and can be operated at high voltage and high temperature.

  For the third problem, there is promotion of uniform heating and improvement in heat receiving efficiency of microwaves received by the object to be heated.

  On the other hand, as a newly provided phase shifter, a semiconductor oscillating unit, a distributing unit that divides the output of the oscillating unit into a plurality, a plurality of amplifying units that respectively amplify the distributed output, and an amplifying unit Some have a combining unit that combines outputs, and a phase shifter is provided between the distributing unit and the amplifying unit (see, for example, Patent Document 3).

  The phase shifter is configured to switch the microwave pass line length according to the on / off characteristics of the diode. In addition, the synthesis unit can use two 90 degree and 180 degree hybrids, so that the output of the synthesis unit can be made two. By controlling the phase shifter, the power ratio of the two outputs can be changed, or the phase between the two outputs can be changed. Can be in phase or out of phase.

For improving the heat receiving efficiency, the reflected power returning from the heating chamber containing the object to be heated to the microwave generator side is detected, and, for example, the reflected power is minimized based on the reflected power signal. Some track the oscillation frequency (see, for example, Patent Document 4).
JP-A-52-193242 Japanese Patent Laid-Open No. 53-5445 JP 56-132793 A JP-A-56-96486

  However, although the conventional multiple power feeding method can increase the amount of microwave power that can be supplied into the heating chamber, the supplied microwaves can be supplied to all of the objects to be heated in various shapes and amounts stored in the heating chamber. It is difficult to receive heat efficiently even if various conventional technologies are combined together.

  This difficulty has an important practical problem of causing the semiconductor element to be thermally destroyed by the microwave power reflected from the heating chamber and returning to the microwave generation unit.

  The present invention solves the above-described conventional problems, and in the multiple power feeding method, various operations are performed by optimally controlling the operation inside the microwave generation unit based on the reflected power signal returning from the heating chamber side. An object of the present invention is to provide a microwave processing apparatus that increases the heat receiving efficiency for heated objects of different types and amounts and heats the heated objects to a desired state.

In order to solve the conventional problems, the microwave processing apparatus of the present invention includes a heating chamber for storing an object to be heated, a microwave generating unit for generating microwaves, and an opposing wall surface constituting the heating chamber, respectively. A plurality of power supply units arranged to supply the microwave generated by the microwave generation unit to the heating chamber, a phase variable device that varies the phase difference of the microwaves radiated from the power supply unit, and the power supply unit a reflected power detecting section for detecting an amount of power received from the heating chamber, on the basis of the reflected power detection part of the signal and a control unit for controlling said phase changing with the microwave generation part, wherein the control unit The placement position of the object to be heated is determined based on the signal of each reflected power detection unit when there is no phase difference , and the power feeding unit is configured to be disposed on each opposing wall surface that constitutes the heating chamber. And It is possible to heat an object to be heated from different directions by Les.

In addition, by changing the phase difference between the multiple microwaves supplied from each power supply unit, the timing at which each microwave collides in the heating chamber space and the timing at which power is absorbed by entering the object to be heated change. The placement position of the object to be heated can be determined and the reflected power to each power feeding unit can be reduced.

  By optimally combining these controls, the microwave energy radiated from each power feeding section can be efficiently supplied to the object to be heated.

  The microwave processing apparatus of the present invention has various shapes, types, and quantities by optimally controlling the operation inside the microwave generation unit based on the reflected power signal returned from the heating chamber side in the multiple power feeding method. It is possible to provide a microwave processing apparatus that increases the heat receiving efficiency of an object to be heated and heats the object to be heated to a desired state.

1st invention arrange | positions in the heating chamber which accommodates to-be-heated material, the microwave generation part which generates a microwave , and the opposing wall surface which comprises the said heating chamber, respectively, The microwave which the said microwave generation part generate | occur | produces A plurality of power feeding units that supply the heating chamber, a phase variable device that varies the phase difference of the microwaves radiated from the power feeding unit, and a reflected power detection that detects the amount of power that the power feeding unit receives from the heating chamber parts and the equipped with the microwave generating unit based on the signal of the reflected power detecting section and the control section for controlling the phase changing, the control unit, of the reflected power detecting section at the time of no phase difference The placement position of the object to be heated is determined based on the signal , and the power feeding unit is configured to be disposed on each of the opposing wall surfaces constituting the heating chamber, thereby heating the object to be heated from different directions. It is possible to Kill. In addition, by changing the phase difference between the multiple microwaves supplied from each power supply unit, the timing at which each microwave collides in the heating chamber space and the timing at which power is absorbed by entering the object to be heated change. The placement position of the object to be heated can be determined and the reflected power to each power feeding unit can be reduced. By optimally combining these controls, the microwave energy radiated from each power feeding section can be efficiently supplied to the object to be heated.

In addition, the control unit determines the placement position of the object to be heated based on the signal of each reflected power detection unit when there is no phase difference, and the amount of reflected power to the power supply unit disposed oppositely. On the basis of the magnitude relationship, it can be determined that the object to be heated is biased and placed on the side of the power feeding unit having a large reflected power. The microwave energy can be more efficiently supplied to the object to be heated by optimally controlling the phase difference between the power feeding units with respect to the object to be heated placed in a biased manner.

In the second aspect of the invention, in particular, the control unit of the first aspect of the invention is far from the object to be heated based on the placement position determination result of the object to be heated. By controlling so as to be smaller than the amount of microwave supplied from the power supply unit on the side, the uneven heating distribution due to direct incidence can be relaxed, and the object to be heated can be heated in a good state.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
In FIG. 1, a microwave generation unit 10 includes an oscillation unit 11 configured using semiconductor elements, a distribution unit 12 that distributes the output signal of the oscillation unit 11, and outputs each of the distribution units 12 to subsequent semiconductor elements. Main amplification units 15a and 15b configured using semiconductor elements for further amplifying the respective outputs of the microwave transmission paths 14a and 14b guided to the first stage amplification units 13a and 13b configured using the first stage amplification units 13a and 13b, Microwave transmission paths 17a and 17b for guiding the outputs of the main amplification sections 15a and 15b to the output sections 16a and 16b of the microwave generation section 10, the phase shifter 18 inserted in the microwave transmission path 14b, and the microwave transmission path It is comprised by the reflected power detection part 19a, 19b which detects at least the reflected power inserted and arrange | positioned at 17a, 17b.

  The first stage amplifying units 13a and 13b and the main amplifying units 15a and 15b constitute a circuit with a conductor pattern formed on one surface of a dielectric substrate 20 made of a low dielectric loss material, and are semiconductor elements which are amplifying elements of the respective amplifying units. Matching circuits are arranged on the input side and the output side of each semiconductor element in order to operate the semiconductor device satisfactorily.

  The microwave transmission paths 14 a, 14 b, 17 a, and 17 b form a transmission circuit having a characteristic impedance of 50Ω by a conductor pattern provided on one surface of the dielectric substrate 20.

  The power distributor 12 has a 3 dB branch line coupler configuration, has a characteristic impedance of 50Ω, and has an electrical length of λ / 4 (λ is an effective wavelength of the center frequency of the used frequency band), and a characteristic impedance of 35. The microstrip lines 12b and 12c are 35Ω and have an electrical length of λ / 4.

  With this configuration, the output power of the oscillating unit 11 generates an output that is distributed approximately ½ by the power distributor 12. When the microwave signal transmitted through the microwave transmission path 14b is used as a reference, the microwave signal transmitted through the microwave transmission path 14a is transmitted as a signal delayed by 90 degrees in phase. The phase shifter 18 performs a phase delay of about 180 degrees, and thereby, the phase difference of the microwaves input to the first stage amplifying units 13a and 13b can form a maximum of about 180 degrees.

On the other hand, a heating chamber 100 in which an object to be heated is accommodated and the output of the microwave generator 10 is supplied is provided. The heating chamber 100 has a door (not shown) for taking in and out the object to be heated on one side, the other wall surfaces are made of a metal material, and the supplied microwave is confined inside. Yes.

  Below the heating chamber 100, a mounting plate 102 made of a low dielectric loss material on which the object to be heated is mounted with a predetermined distance from the heating chamber bottom wall surface 101 is disposed.

  Further, radiating means 105 and 106 that are power feeding units are arranged at substantially the center of the left and right wall surfaces 103 and 104 that are the opposing wall surfaces of the heating chamber 100.

  The oscillation unit 11 of the microwave generation unit 10 has a frequency variable function for generating a frequency from 2400 MHz to 2500 MHz. The outputs 16a and 16b of the microwave generator 10 and the radiation means 105 and 106 are connected by coaxial lines 21a and 21b.

  The control unit 22 receives the signals detected by the reflected power detection units 19 a and 19 b of the microwave generation unit 10 and performs various processes, and then performs variable control of the oscillation frequency of the oscillation unit 11 and the phase of the phase variable unit 18. Variable control and drive voltage control supplied to each of the main amplifiers 15a and 15b are performed.

  The reflected power detectors 19a and 19b are configured by directional couplers having a coupling degree of about 40 dB, and extract an amount of power that is about 1/10000 of the reflected power.

  The power signals are rectified by a detection diode (not shown), smoothed by a capacitor (not shown), and the output signal is input to the control unit 22.

  The microwave generator 10 is provided with a heat radiating means (not shown) for radiating heat generated by the semiconductor element.

  The operation and action of the microwave processing apparatus configured as described above will be described below with reference to FIG.

  First, the object to be heated is stored in the heating chamber 100, the heating condition is input from an operation unit (not shown), and the heating start key is pressed. The microwave generator 10 is set to the first output power, for example, less than 100 W, by the control output signal of the controller 22 that has received the heating start signal, and the operation is started (S11). At this time, the control unit 22 supplies a signal for setting the initial oscillation frequency of the oscillation unit 11 to 2450 MHz, for example, and starts oscillation. Thereafter, a predetermined drive power supply voltage is supplied to the first stage amplifiers 13a and 13b to operate the first stage amplifier, and then a predetermined drive voltage is supplied to the main amplifiers 15a and 15b to operate the main amplifier.

  The driving voltage supplied to each main amplifying unit at this time is a voltage at which each main amplifying unit outputs microwave power of 50 W, for example. Further, the phase variable device 18 is controlled to a phase delay of 90 degrees.

  As a result, the two outputs of the microwave generator 10 are in a state with no phase difference.

  Next, in S12, the oscillation frequency of the oscillating unit 11 is changed from the initial 2450 MHz to a lower frequency side with a 0.1 MHz pitch (for example, 1 MHz in 10 milliseconds), and when the frequency reaches the lower limit of 2400 MHz, the 1 MHz pitch. Then, the frequency is changed to high, and when it reaches 2450 MHz, it is changed again to 2500 MHz which is the upper limit of the frequency variable range at a pitch of 0.1 MHz.

  The reflected power obtained from the reflected power detectors 19a and 19b in the variable frequency is stored, and the process proceeds to S13. In S13, a frequency (f1) that minimizes the total value of the two reflected powers is selected.

  In next S14, the reflected power value received by each power feeding unit at the frequency with the minimum reflected power is compared with a predetermined value.

  This default value is determined when the microwave generator is operated under non-reflective conditions (ie matched load) from the maximum heat loss allowed by the microwave generator determined based on the heat dissipation configuration built into the microwave generator. This is a value obtained by subtracting the heat loss amount of the microwave generation part.

  Note that the predetermined value may be either an absolute value method or a relative ratio value with respect to the output of the microwave generation unit.

  Then, in the comparison between the reflected power value of each power feeding unit and the default value, if it is equal to or less than the default value, the process proceeds to S15. On the other hand, when the predetermined value is exceeded, the process proceeds to S16, and the reflected power value becomes equal to or lower than the predetermined value under the operating environment in which the second output power corresponding to the so-called rated output of the microwave generation unit 10 is generated. Thus, the drive voltage supplied to each main amplifier 15a, 15b is extracted.

  In this extraction, the driving voltage is 100%, 90%, 75%, 60%, and 15% of the rated output of the microwave generation unit 10 (this is used when the first output power is generated). A stage drive voltage group is prepared, and a drive voltage that can generate a maximum output without exceeding a predetermined value is extracted from the drive voltage group.

  The driving voltage can be optimally selected for each main amplifier. When this drive voltage extraction process is completed, the process proceeds to S15.

  In S15, the driving voltages of the main amplifiers 15a and 15b are set so that the microwave generator 10 generates the second output power that is the rated output.

  Note that the drive voltage at this time is set to the drive voltage determined in S16 in the case of processing via S16.

  In S17, the main heating of the object to be heated is started with the oscillation frequency f1 extracted in S13 and the second output power determined in S15.

  In S18, the phase shifter 18 is controlled to change the phase difference of the microwave supplied from the power feeding unit in order to perform uniform heating of the object to be heated at high speed.

  In S19, it is determined whether or not the reflected power value received by each power supply unit under the changed phase difference is equal to or less than the above-described predetermined value.

  If it is equal to or less than the predetermined value, the process proceeds to S20. When the predetermined value is exceeded, the process proceeds to S21, the drive voltage of the target main amplification unit is changed to an optimum drive voltage so as to be equal to or less than the predetermined value, and the process proceeds to S20.

  In S20, the degree of finish of the object to be heated is determined. For example, in the case of an apparatus equipped with an infrared ray detection means, the surface temperature of the object to be heated is extracted to determine whether the target finish temperature has been reached. Judge by comparison.

If the target temperature has not been reached, the process returns to S18. When it reaches the target temperature that Ryosu final heating is stopped the operation of the microwave generation part 10.

  The contents of the heating control have been described above, but the operation in this control will be described below.

  By changing the frequency, it is possible to change the load impedance when the heating chamber 100 side in which the object to be heated is stored is viewed from the power feeding units 105 and 106. Then, by selecting the optimum frequency, the reflected power to each power supply unit can be reduced by bringing the load impedance closer to the power supply impedance when the microwave generation unit 10 is viewed from each power supply unit.

  In addition, by changing the phase difference between the multiple microwaves supplied from each power supply unit, the timing at which each microwave collides in the heating chamber space and the timing at which power is absorbed by entering the object to be heated change. The reflected power to each power feeding unit can be changed.

  By optimally combining these controls, the microwave energy radiated from each power feeding section can be efficiently supplied to the object to be heated.

  Further, in the control of the phase variable 18 that promotes uniform heating of the object to be heated, when the reflected power amounts detected by the reflected power detectors 19a and 19b exceed a predetermined value, the output of the microwave generator 10 is set. By reducing the output to be supplied into the heating chamber, the reflected power can be reduced and the microwave generator 10 can be reliably protected from thermal destruction.

  Further, the phase variable device 18 is provided between the power distribution unit 12 and the amplification unit 13b, so that the phase difference of the microwaves supplied between the amplification unit outputs, that is, the power supply units 105 and 106 into the heating chamber 100 is provided. Can be reliably controlled.

  Further, the output of the microwave generator 10 is configured to variably control the drive voltages of the main amplifiers 15a and 15b. When the reflected power exceeds a predetermined value, the drive voltage is reduced to reduce the heat accompanying the amplification operation. By reducing the amount of loss and reducing the reflected power, the heat loss experienced by the semiconductor element of the amplifying unit can be reduced to an allowable maximum value or less to ensure the reliability of the apparatus.

  Further, based on the practical heat radiation design of the microwave generation unit 10 on the device mounting, the value corresponding to the maximum reflected power amount that the microwave generation unit can tolerate without thermal destruction is set as the default value. It is possible to prevent thermal destruction of the semiconductor element used in the wave generating unit and to ensure practical reliability of the apparatus.

  Further, the power feeding units 105 and 106 are configured to be disposed on the opposing wall surfaces 103 and 104 constituting the heating chamber 100, respectively, whereby the object to be heated can be heated from different directions.

(Embodiment 2)
Next, a second embodiment of the present invention will be described.

  This is because the reflected power received by each of the power supply units 105 and 106 when a microwave having no phase difference is supplied from each power supply unit into the heating chamber 100 in a configuration in which the power supply units are respectively disposed on the opposing wall surfaces constituting the heating chamber. Based on this, the placement position of the object to be heated is determined.

That is, based on the magnitude relationship of the amount of reflected power to the power supply units arranged oppositely, microwaves that are frequently directly incident on the object to be heated are likely to receive microwaves reflected on the surface of the object to be heated.

  Using this characteristic, it can be determined that the object to be heated is placed on the power feeding unit side where the reflected power is large.

  The microwave energy can be more efficiently supplied to the object to be heated by optimally controlling the phase difference between the power feeding units with respect to the object to be heated placed in a biased manner.

  In addition, when the bias is large or when the object to be heated is present in a region close to the power supply unit, supply from the power supply unit closer to the object to be heated in order to alleviate uneven heating distribution due to direct incidence. Control is performed so that the amount of microwaves is less than the amount of microwaves supplied from the power feeding unit on the side far from the object to be heated.

  By this control, the uneven heating distribution due to direct incidence can be relaxed, and the object to be heated can be heated to a good state.

  Even in the above control, when the reflected power exceeds a predetermined value, the control of the driving voltage of the main amplifier described in the first embodiment is followed.

  As described above, the microwave processing apparatus according to the present invention is configured to optimally control the operation inside the microwave generation unit based on the reflected power signal returning from the heating chamber side in the multiple power feeding method, and thus the object to be heated Can be provided at a high speed in a desired state, so that a microwave power source of a plasma power source, such as a heating device, a garbage disposal machine, or a semiconductor manufacturing device using dielectric heating as represented by a microwave oven can be provided. It can be applied to other uses.

Configuration diagram of microwave processing apparatus according to Embodiment 1 of the present invention Control flow chart of microwave processing apparatus in Embodiment 1 of the present invention

DESCRIPTION OF SYMBOLS 10 Microwave generation part 11 Oscillation part 12 Power distribution part 13a, 13b, 15a, 15b Amplification part 18 Phase variable device 19a, 19b Reflected power detection part 22 Control part 100 Heating chamber 103, 104 Opposite wall surface 105, 106 Radiation means Part)

Claims (2)

A heating chamber for storing an object to be heated;
A microwave generator for generating microwaves;
A plurality of power feeding units that are arranged on opposing wall surfaces that constitute the heating chamber, and that supply the microwave generated by the microwave generating unit to the heating chamber,
A phase variable device that varies the phase difference of the microwaves radiated from the power supply unit;
A reflected power detector that detects the amount of power that the power feeding unit receives from the heating chamber;
Based on the signal of the reflected power detecting section and a control section for controlling said phase changing with the microwave generation part,
The said control part is a microwave processing apparatus which determines the mounting position of a to-be-heated object based on the signal of each reflected power detection part when there is no phase difference . The control unit determines the amount of microwaves supplied from the power supply unit on the side far from the object to be heated, based on the placement position determination result of the object to be heated. The microwave processing apparatus of Claim 1 controlled so that it might become less.

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