JP5234353B2 - Microwave power controller - Google Patents

Description

  The present invention relates to a microwave power control apparatus that controls a power value of a microwave output from a microwave oscillator including a magnetron.

FIG. 6 is a simplified configuration diagram of a microwave application apparatus shown as a conventional example.
In this microwave application apparatus, microwave power (in this example, 2.45 GHz band) output from a microwave oscillator 11 including a magnetron is supplied to a launcher waveguide (directional coupler) 12 and a tapered waveguide 13. The isolator 14, the power monitor 15, and the EH tuner 16 are sent to the applicator 18 through the waveguide system circuit 10 connected in sequence.

The launcher waveguide 12 includes a magnetron antenna provided in the microwave oscillator 11 and couples the microwave power output from the microwave oscillator 11.
The microwave power coupled by the launcher waveguide 12 is sent to the standard waveguide by the tapered waveguide 13.

As shown in FIG. 7, the isolator 14 is formed of a circulator 14a and a dummy load 14b, and absorbs microwave power returning from the applicator 18 side to the microwave oscillator 11 side.
That is, the microwave power traveling toward the applicator 18 is transmitted, but the microwave power traveling from the applicator 18 toward the microwave oscillator 11 is bent by the circulator 14a and is absorbed by the dummy load 14b.
Therefore, there is no microwave power returning to the microwave oscillator 11.

The power monitor 15 monitors the traveling wave and reflected wave of the microwave power.
The EH tuner 16 adjusts the impedance of the microwave power and realizes a state without a reflected wave, and includes an E tuner 16a and an H tuner 16b.
As shown in FIG. 8, the E tuner 16a of the EH tuner 16 sets the distance L0 from the virtual wall surface D0 to the short-circuit surface 16c of the main waveguide to 0 to 1/4 of the guide wavelength, and can be freely adjusted. ing.
Although FIG. 8 shows the E tuner 16a, the H tuner 16b has a configuration like a main waveguide, the E tuner 16a is on the H surface of the main waveguide, and the H tuner 16b is on the main waveguide. The EH tuner 16 is configured on the E plane so that the respective centers are located at the same position of the main waveguide.

The EH tuner 16 adjusts the reflected wave instruction value to zero by moving the short-circuit plate positions of the E tuner 16a and the H tuner 16b while confirming the reflected wave instruction value of the power monitor 15.
If the reflected wave of the microwave power becomes zero, the microwave power directed from the EH tuner 16 to the irradiation antenna 17 is the microwave power oscillated by the microwave oscillator 11 and becomes the oscillation power of the magnetron 11 transmitted through the isolator 14. .
The microwave power irradiated into the applicator 18 from the irradiation antenna 17 acts on the microwave workpiece 20 placed on the turntable 19 and performs microwave processing.

The above microwave application apparatus adjusts the power value of the microwave by controlling the anode current of the magnetron.
Specifically, the microwave power value is increased or decreased by adjusting the voltage while monitoring the anode current value of the magnetron by the magnetron anode voltage adjusting circuit provided in the drive circuit 21 of the microwave oscillator 11. .
This adjustment utilizes the fact that the microwave power and the anode current are in a proportional relationship.

However, the adjustment for controlling the anode current value as described above cannot finely control the microwave power value.
The reason is that the permanent magnet (ferrite magnet) included in the magnetron has a temperature coefficient of −0.2% / ° C., and therefore the peak anode voltage of the magnetron and the microwave output change with this temperature coefficient.
Therefore, in order to obtain a stable output, the microwave oscillator 11 is continuously operated for 20 to 30 minutes, and the temperature is in an equilibrium state, and the microwave processing operation is started.

However, since the thermal equilibrium state is reached at a temperature higher than room temperature, there is a problem that the power value of the microwave in a state where a stable output is obtained becomes a slightly low value.
In order to avoid this, there is a method in which the microwave power is detected and the microwave voltage is increased / decreased, but a device for ensuring reliability is required.

On the other hand, there is a problem of the spectrum of the magnetron in the adjustment of the microwave power value performed by changing the anode current.
That is, when the anode power is changed to increase or decrease the microwave power value, both the fundamental wave oscillation frequency (hereinafter referred to as “oscillation frequency”) and the spectrum including the oscillation frequency change.
FIG. 9 shows an example of performance characteristics and spectrum when a magnetron is driven by a DC anode power source.
In the upper spectrum diagram, the horizontal axis indicates the frequency, and the vertical axis indicates the intensity of the frequency component.

As can be seen from this figure, although the magnetron is operated in a matched state, the spectrum is largely broken in the range of DC anode current 50 mA to 150 mA.
A stable spectrum is obtained at 200 mA or more.
Therefore, even a direct current anode power source estimated to obtain a stable spectrum has an unstable spectrum as shown in FIG. 9 when actually measured.

The above-mentioned spectrum problem is presumed to be a characteristic characteristic of the magnetron, and can be observed in any magnetron.
Even in the same type of magnetron, the anode current value (that is, the microwave power value) causing the oscillation frequency to change as described above is different, and it is affected by the type and circuit constant of the magnetron anode power supply circuit. Different.

  As an example of a microwave application apparatus, there is a surface modification processing apparatus using microwave plasma. The plasma intensity of this apparatus is adjusted by increasing / decreasing the power value of the microwave. There is a problem that the plasma becomes unstable under the influence of a spectrum in which the oscillation frequency is divided into two.

JP 2002-280196 A JP 2008-218362 A

  In view of the above circumstances, an object of the present invention is to provide a microwave power control apparatus capable of finely adjusting the power value of the microwave output from the microwave oscillator including the magnetron.

  In order to achieve the above-described object, in the present invention, as a first invention, a waveguide system circuit for sending microwave power output from an microwave oscillator including a magnetron to an applicator is used. A microwave power comprising a microwave variable attenuator comprising an isolator, a variable reactance element (variable susceptance element), and a power measuring means, which are sequentially connected to each other, and configured to control a microwave power value. A control device is proposed.

  According to a second aspect of the present invention, an isolator, a variable reactance element (sequentially connected from a microwave oscillator to an applicator) is connected to a waveguide circuit that sends microwave power output from a microwave oscillator including a magnetron to an applicator. The present invention proposes a microwave power control apparatus comprising a microwave variable attenuator including a variable susceptance element), power measuring means, and an isolator, and configured to control the power value of the microwave.

  As a third invention, in the microwave power control apparatus according to the first or second invention described above, the variable reactance element is formed of any one of a stub tuner, an E tuner, an H tuner, and an EH tuner. A featured microwave power controller is proposed.

  As a fourth invention, in the microwave power control apparatus according to the first or second invention described above, the power measuring means includes a traveling wave extracted via a directional coupler coupled to the waveguide. Formed by a device such as a power monitor that measures the power of both the reflected wave or the traveling wave or only the reflected wave and determines the power value of both the traveling wave and reflected wave propagating in the waveguide or the traveling wave or reflected wave only A microwave power control apparatus characterized by the above is proposed.

  As a fifth invention, the microwave power control apparatus according to the first or second invention described above further comprises a magnetron anode current control means for controlling the power value of the microwave, the anode current control means and the microwave A microwave power control device is proposed in which a microwave power value is controlled by using a variable attenuator together.

The microwave power control apparatus according to the first aspect of the present invention has a configuration in which a waveguide variable circuit includes a microwave variable attenuator in which an isolator, a variable reactance element, and a power measuring unit are sequentially connected.
Therefore, when the variable reactance element is adjusted to increase or decrease the reflected wave power so that the indicated value of the power measurement means becomes a desired power value, the microwave power from the variable reactance element to the applicator is finely adjusted. The power value of the microwave can be set to a desired value.
The reflected power reflected by the variable reactance element is absorbed by the isolator.

A microwave power control device according to a second aspect of the present invention is a waveguide system circuit comprising a microwave variable attenuator comprising an isolator, a variable reactance element, power measuring means, and an isolator sequentially connected from a microwave oscillator to an applicator. It is as a configuration provided.
Therefore, even if the condition of the microwave workpiece placed in the applicator changes, the reflected wave of the microwave power propagating in the waveguide circuit changes, that is, the phase and magnitude of the reflected wave change. Since the reflected wave is absorbed by the isolator on the applicator side, a microwave power state without a reflected wave can always be maintained between the variable reactance element and the isolator on the microwave oscillator side.

Therefore, since the power measurement means indicates a correct indication value of the microwave power directed to the applicator, the reflected wave is increased or decreased by the variable reactance element based on the indicated value, and the microwave directed from the variable reactance device to the applicator The power can be finely controlled and the power value of the microwave can be set.
Thus, according to the second aspect of the invention, the microwave power control apparatus can cope with the situation where the state of the microwave workpiece changes and the reflected wave changes.

  Incidentally, in the first invention, if the reflected wave changes when the state of the object to be processed is changed by continuing to irradiate the microwave power, the indicated value of the power measuring means is affected. After canceling the reflected wave from the applicator with an EH tuner installed between the applicator and the power measuring means, the variable reactance element is adjusted and set to a desired microwave power value.

  The microwave power control apparatus according to a third aspect of the invention is characterized in that the variable reactance element is formed of any one of a stub tuner, an E tuner, an H tuner, and an EH tuner.

  According to a fourth aspect of the present invention, there is provided a microwave power control apparatus that includes both the traveling wave and the reflected wave, or only the traveling wave or the reflected wave, which are extracted through the directional coupler coupled to the waveguide. The invention is characterized in that it is formed by a power monitor or the like that determines the power value of both the traveling wave and the reflected wave propagating in the waveguide and the traveling wave or the reflected wave alone.

In the microwave power control device according to the fifth aspect of the invention, the microwave power value output from the microwave oscillator is set to the upper limit of the microwave power required by the microwave application device using the anode current control means of the magnetron. Thereafter, the above-described microwave variable attenuator is used to reduce and adjust to the required microwave power value.
This minimizes the generation of reflected waves when adjusting the power value of the microwave, which is advantageous for energy saving.

  Furthermore, if the microwave power value is set to the upper limit as described above and then controlled to decrease with the microwave variable attenuator, the magnetron oscillation frequency and the fundamental oscillation spectrum waveform will be maintained at a constant state. Microwave power can be finely adjusted for an applicator or microwave workpiece that is sensitive to the frequency characteristics of microwave power.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a simplified configuration diagram of the microwave application apparatus shown as the first embodiment.
The microwave application apparatus according to the present embodiment is variable by connecting a variable reactance element 30 between the isolator 14 and the power monitor (power measurement means) 15 of the microwave application apparatus shown in FIG. A characteristic is that the microwave variable attenuator 31 is formed by the type reactance element 30 and the isolator 14.
Therefore, since the other configuration is the same as that of the conventional microwave application apparatus of FIG. 6, the same members are denoted by the same reference numerals and the description thereof is omitted.
However, the power monitor 15 of the present embodiment is a power measurement unit that can measure both traveling waves and reflected waves.

  As shown in FIG. 2, the variable reactance element 30 described above is sub-waveguided on the E plane (plane parallel to the electric field) or H plane (plane parallel to the magnetic field) of the waveguide circuit (main waveguide) 10. A tube 30a is provided, and a movable short-circuit plate (back plunger) 30b is provided in the sub-waveguide 30a. The reactance can be varied from 0 to ∞ by moving the short-circuit plate 30b.

FIG. 3 is a characteristic diagram showing the relationship between the back plunger distance (distance from the imaginary wall surface D1 of the main waveguide to the short-circuit plate 30b) L1 and the reactance amount of the variable reactance element 30 described above.
FIG. 4 is a characteristic diagram showing the relationship between the back plunger distance, the reflected power coefficient, and the transmitted power coefficient.
In this figure, 4A represents reflected power, and 4B represents transmitted power.
As can be seen from these characteristic diagrams, in the variable reactance element 30 described above, when the back plunger distance L1 is set to a position of 10 mm, the transmitted power is reduced by 5% to 95%.

  FIG. 2 shows the variable reactance element 30 provided on the H plane, but the E plane can also be provided in the same manner, and is provided on both the E plane and the H plane to have the same configuration as the EH tuner. You can also

  The microwave application apparatus configured as described above adjusts the EH tuner 16 so that the reflected wave instruction value of the power monitor 15 becomes zero or close to zero.

Therefore, by this adjustment, the reflected wave instruction value becomes zero or close to zero at the place where the power monitor 15 is installed, and the standing wave can be ignored. Therefore, the traveling wave power value indicated by the power monitor 15 is The microwave power oscillated by the microwave oscillator 11 can correctly indicate the microwave power (transmitted power) transmitted through the isolator 14.
And since this transmitted power is irradiated in the applicator 18 after the EH tuner 16, the microwave workpiece 20 is processed by the microwave power that is the transmitted power.

  When adjusting the microwave power, in this state, that is, by adjusting the EH tuner 16 to set the reflected wave indication value to zero or close to zero, the traveling wave indication value of the power monitor 15 is the transmitted power of the isolator 14. When the variable reactance element 30 is adjusted so that the traveling wave instruction value becomes a desired power value.

FIG. 5 is a simplified configuration diagram of the microwave application apparatus shown as the second embodiment.
The microwave application apparatus according to the present embodiment connects the power monitor 33 and the isolator 32 between the variable reactance element 30 and the power monitor 15 of the microwave application apparatus shown in FIG. The microwave reactive attenuator 34 is formed by the type reactance element 30, the power monitor 33, the isolator 32, and the power monitor 15.
Therefore, since the other structure is the same structure as the microwave application apparatus of FIG. 1, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  This microwave application apparatus absorbs the reflected wave from the applicator 18 by the isolator 32 and does not transmit the reflected wave to the microwave oscillator 11 side. Therefore, regardless of the state of the microwave workpiece 20 in the applicator 18. In addition, regardless of the adjustment of the EH tuner 16, only the traveling wave propagates at the place where the power monitor 33 is installed, so the indicated value of the power monitor 33 shows a correct value.

That is, the EH tuner 16 adjusts so that all the transmitted microwave power is absorbed by the EH tuner 16 and later.
That is, the EH tuner 16 is adjusted so that the reflected wave instruction value of the power monitor 15 becomes zero.

  On the other hand, since the microwave variable attenuator 34 can cancel the influence of the reflected wave from the applicator 18 by the isolator 32, the traveling wave instruction value of the power monitor 33 is desired regardless of the adjustment of the EH tuner 16. The variable reactance element 30 can be adjusted independently so that the power value can be adjusted to control the microwave power, and the traveling wave power transmitted through the isolator 32 can be finely adjusted.

Thereby, the microwave power value irradiated into the applicator 18 from the irradiation antenna 17 is delicately controlled, so that the microwave processing accuracy of the microwave workpiece 20 can be increased.
Note that, as described above, the power monitor 33 may be of a specification that can measure only traveling waves, so that an inexpensive power monitor can be used.

  The microwave application apparatus according to the first and second embodiments has been described above. In addition to the control of the power value by the microwave variable attenuators 31, 34, the drive circuit 21 increases or decreases the anode current of the magnetron to increase the power value. By controlling, the microwave power value can be finely adjusted with high accuracy.

  Further, as described above, after setting the microwave power value output from the microwave oscillator by controlling the magnetron anode current to the upper limit of the microwave power required by the microwave application device, By using the wave variable attenuators 31 and 34 to reduce and adjust to the required microwave power value, the generation of reflected waves when adjusting the microwave power value is minimized, which is advantageous for energy saving. It becomes.

  Further, after setting the microwave power value to the upper limit as described above, if the decrease control is performed by the microwave variable attenuators 31, 34, the oscillation frequency of the magnetron and the fundamental oscillation spectrum waveform are maintained constant. The microwave power value can be finely adjusted without being affected by the spectrum.

  In implementing the present invention, an E tuner or an H tuner based on an EH tuner is used as the variable reactance element 30 forming the microwave variable attenuators 31 and 34, but the stub tuner is also a variable reactance. Since this is a kind of element and the reactance can be varied from 0 to ∞, a stub tuner may be provided instead of the EH tuner.

  It can be applied as a microwave power control device that controls the power value of the microwave in preparation for a device that heats and dries using microwave power, a plasma generator that generates plasma by supplying microwave power, etc. it can.

It is a simplified lineblock diagram of a microwave application device shown as a 1st embodiment. It is an expanded sectional view of the variable reactance element with which the microwave application device was equipped. It is the characteristic view which showed the relationship between the plunger distance of the said variable type reactance element, and the reactance amount. It is the characteristic view which showed the relationship of the reflected power coefficient and the transmitted power coefficient with respect to the plunger distance of the said variable reactance element. It is a simplified block diagram of the microwave application apparatus shown as 2nd Embodiment. It is a simplified block diagram of the microwave application apparatus shown as a prior art example. It is a partial expanded sectional view for demonstrating the isolator with which the microwave application apparatus of FIG. 6 is provided. It is an expanded sectional view of the EH tuner with which the microwave application apparatus of FIG. 6 is provided. It is a figure which shows the example of a performance characteristic at the time of driving a magnetron with a DC anode power supply, and a spectrum.

Explanation of symbols

10 Waveguide System 11 Microwave Oscillator 14 Isolator 14a Circulator 14b Dummy Load 15 Power Monitor 16 EH Tuner 18 Applicator 21 Drive Circuit 30 Variable Reactance Element 31 Microwave Variable Attenuator 32 Isolator 33 Power Monitor 34 Microwave Variable Attenuation vessel

Claims (5)

  A microwave circuit consisting of an isolator, a variable reactance element, and a power measurement means that are connected in sequence from the microwave oscillator to the applicator to a waveguide circuit that sends the microwave power output from the microwave oscillator equipped with the magnetron to the applicator. A microwave power control apparatus comprising a variable attenuator and configured to control a power value of a microwave.   Consists of an isolator, a variable reactance element, power measuring means, and an isolator that are sequentially connected from the microwave oscillator to the applicator to a waveguide circuit that sends the microwave power output from the microwave oscillator equipped with the magnetron to the applicator. A microwave power control apparatus comprising a microwave variable attenuator and configured to control a power value of a microwave. In the microwave power control device according to claim 1 or 2,
2. The microwave power control apparatus according to claim 1, wherein the variable reactance element is formed of any one of a stub tuner, an E tuner, an H tuner, and an EH tuner. In the microwave power control device according to claim 1 or 2,
The power measuring means measures the power of both the traveling wave and the reflected wave, or the traveling wave or only the reflected wave, taken out through the directional coupler coupled to the waveguide, and propagates through the waveguide. A microwave power control apparatus formed by a device such as a power monitor that obtains the power value of both a traveling wave and a reflected wave or only a traveling wave or a reflected wave. In the microwave power control device according to claim 1 or 2,
A magnetron anode current control means for controlling the microwave power value is provided, and the microwave power value is controlled by using the anode current control means and the microwave variable attenuator together. Microwave power control device.

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