JP2010080185A - Microwave heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of causing a change in the frequency at which a reflective wave gets minimum, according to a change during heating of food. <P>SOLUTION: This microwave heating apparatus includes microwave generating sections 3a-3d having output parts 2a-2d connected to a plurality of semiconductor oscillating parts 1a-1d; reflected wave monitoring sections 6a-6d always monitoring a heating chamber 5 and a reflected wave level; a control section 4 receiving the signals and controlling output; and a threshold 10 for not resulting in breakage. When the respective values of signals of the reflected wave monitoring sections 6a-6d exceed the threshold 10, a semiconductor is prevented from breakage by performing negative feedback control so that the output of the semiconductor oscillating parts 1a-1d are the threshold 10 or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microwave heating apparatus that heats an object to be heated, which is an object to be heated, by irradiating microwaves.

  There is a microwave oven as a typical device of a microwave heating device that heats an object by using a microwave. In a microwave oven, microwaves are radiated into a metallic heating chamber in a microwave generator, and an object to be heated in the heating chamber is heated by the radiated microwaves.

Conventionally, as this microwave heating apparatus, a semiconductor oscillating unit, a dividing unit that divides the oscillation output of the semiconductor oscillating unit into a plurality, a divider that amplifies each divided oscillation output, and a synthesis that amplifies each divided oscillation output. And a detecting means for detecting a reflected wave between the synthesizer and the heating chamber, and changing the oscillation state of the oscillator according to the amount of the reflected wave detected by the detecting means. .
JP-A-56-134491

  However, in the conventional configuration, since the semiconductor oscillation units are synthesized by the synthesis unit, the reflected wave related to the oscillation output from one power supply port is always monitored, and the reflected wave becomes larger than a certain level. By stopping the oscillation of the oscillator, changing or stopping the oscillation frequency, or changing and reducing the oscillation output, the semiconductor unit can be reduced without using a protection means for the semiconductor oscillation unit such as an isolator. It was something that could not be destroyed.

  Moreover, even if the oscillation output is changed and reduced, it is unclear how much it is reduced. Also, the control law is very unclear. In addition, although it is said that the detection means for detecting the reflected wave between the heating chamber is detected, how much the reflected wave burden is applied to each semiconductor oscillator when the reflected wave of the synthesis unit is detected. It is unclear whether the semiconductor oscillator can be completely protected.

  In addition, when a plurality of semiconductor oscillating units and subsequent power supply ports are provided and space synthesis is performed in the heating chamber, no mention is made.

  The present invention solves the above-described problem. Even in a configuration in which a plurality of semiconductor oscillation units are provided, each reflected wave load is detected, and no excessive reflected wave is applied to any one of the semiconductor oscillation units. An object of the present invention is to provide a microwave heating apparatus that can irradiate microwaves.

In order to solve the above-described conventional problems, a microwave heating apparatus according to the present invention includes a microwave generation unit having an output unit connected to at least one semiconductor oscillation unit, a heating chamber for storing an object to be heated, and an output. The reflection wave monitor part which is located in the back | latter stage and always monitors a reflected wave level is provided. A threshold value for determining a reflected wave level at which the semiconductor oscillating unit is not destroyed, and the control unit reduces the output of the semiconductor oscillating unit to a threshold value or less when a signal of each of the reflected wave monitoring units exceeds the threshold value; By applying negative feedback control to the oscillation frequency so that excessive reflected wave energy is not applied to the semiconductor oscillation part, microwave heating is performed up to the threshold value that allows the reflected wave. The continuity of heating up to a range not exceeding the value can be maintained.

  Further, the microwave heating apparatus of the present invention includes a threshold value corresponding to each output unit that determines a reflected wave level at which the semiconductor oscillation unit does not break down, and the amount of change to which negative feedback with respect to the oscillation frequency exceeds a predetermined amount. In such a case, it is determined that the oscillation state is such that the amount of reflection from the heating chamber is increased, and the operating frequency is changed by searching for the frequency at which the reflection level detected from the signal of the reflected wave monitoring unit is minimized. Therefore, the frequency at which reflection is minimized can be set again, and negative feedback control is applied to the microwave oscillation frequency, and heating at the optimum frequency that maximizes the output that changes the oscillation frequency of the microwave generator Can be reproduced.

  The microwave heating device of the present invention is located at the rear stage of the output unit, the microwave generation unit having the output unit connected to the plurality of semiconductor oscillation units, the heating chamber for storing the object to be heated, and constantly monitors the reflected wave level. A reflected wave monitor unit; a control unit that receives a signal from the reflected wave monitor unit and controls the output of the output unit; and a threshold value that determines a reflected wave level that the semiconductor oscillation unit does not destroy. When the signal of each reflection monitor part of the signal of the wave monitor part exceeds a threshold value, negative feedback control is performed so that the output of the semiconductor oscillation part becomes equal to or less than the threshold value. Even if the food is overheated or the food wrap swells and the volume of the object to be heated increases, causing the impedance of the heating chamber to change, negative feedback control is applied to the change, and the threshold value The oscillation frequency of the semiconductor oscillating unit is set to an appropriate frequency so as not to exceed the value, and the reflected wave is suppressed to prevent the excessively reflected wave from returning to the semiconductor oscillating unit and destroying the semiconductor element. This makes it possible to always keep the reflected wave level low and maximize the heating concentration on the food.

  A first invention is a microwave generation unit having an output unit connected to a plurality of semiconductor oscillation units, a heating chamber that houses an object to be heated, and a reflected wave monitor that is positioned downstream of the output unit and constantly monitors the level of the reflected wave A control unit that receives a signal from the reflected wave monitor unit and controls the output of the output unit, and a threshold value corresponding to each output unit that determines a reflected wave level that the semiconductor oscillation unit does not destroy. When each reflected wave monitoring unit exceeds a threshold level, the oscillation frequency of the microwave generation unit is changed so that the output of the semiconductor oscillation unit falls below the threshold value.

  By applying negative feedback control and changing the oscillation frequency of the microwave generator, the food being heated is overturned, the food wrap expands, the bulk of the object to be heated increases, and the impedance of the heating chamber changes. Even if the phenomenon occurs, the semiconductor oscillation unit operates so that the oscillation frequency becomes an appropriate frequency, and the reflected wave is suppressed to prevent the excessive reflected wave from returning to the semiconductor oscillation unit and destroying the semiconductor element. This makes it possible to always keep the reflected wave level low and maximize the heating concentration on the food.

  The second invention uses a microcomputer as the control unit. In this application, where digital processing such as various types of processing and storage functions are required for process processing, many microcomputers used in many other home appliances handle many quantities, and process rules are becoming finer. Along with the increase in diameter of wafers, the trend is drastically lowering the price, which is excellent in terms of economy and performance. From this point of view, adopting a microcomputer whose cost performance is expected to evolve in the future can be very economical and performance advantageous for this equipment.

The third invention transplants the microcomputer function of the device of the present invention on the microcomputer that controls the entire device, greatly reduces the redundancy and exerts the economic effect, and combines two parts into one part. From the viewpoint of achieving this, the number of parts can be reduced, and the entire system can be simplified.

  According to a fourth aspect of the present invention, there is provided a microwave generation unit having an output unit connected to a plurality of semiconductor oscillation units, a heating chamber for storing an object to be heated, and a reflected wave monitor that is positioned downstream of the output unit and constantly monitors a reflected wave level. A control unit that receives a signal from the reflected wave monitor unit and controls the output of the output unit, and a threshold threshold value corresponding to each output unit that determines a reflected wave level at which the semiconductor oscillation unit does not break down. When the amount of change to which the feedback exceeds the limit threshold, it is determined that the oscillation state is such that the amount of reflection from the heating chamber is increased, and the control unit quickly decreases the output of the reflected wave monitoring unit.

  As a result, it is possible to realize a highly reliable system in which the semiconductor is not destroyed even by a transient excessive reflected wave. After that, the frequency at which the reflection level detected from the signal of the reflected wave monitor is minimized, the oscillation frequency of the microwave generator is changed, the output is returned to the original high level, and then negative feedback control is applied to generate microwaves. The output frequency is temporarily reduced, but after determining a frequency with less reflected waves, the same high output is obtained as before, so the impedance in the heating chamber changes. In addition, it is possible to provide a device that is quickly recovered to its original output and that is easy to use without extremely increasing the heating time.

  According to a fifth aspect of the present invention, the frequency at which negative feedback is applied is integrated, and when a certain predetermined amount is exceeded, it is determined that the amount of reflection from the heating chamber is in an oscillating state, and the reflected wave monitor signal is used. The frequency at which the detected reflection level is minimized is searched and the oscillation frequency of the microwave generator is changed.The frequency of negative feedback is increased and the deviation of the reflected wave from the minimum frequency is detected to quickly determine the minimum frequency. This is a reset to detect the feedback of the reflected wave to the semiconductor and change the oscillation frequency of the microwave generation part to the optimum frequency with few reflected waves before the semiconductor breaks down, so that the resistance to the reflected wave is remarkably improved. is there.

  In the sixth aspect of the invention, the frequency at which negative feedback is applied is integrated, and if the frequency is less than a predetermined amount, the control unit thins out the monitoring frequency of the reflected wave monitoring unit, and the reflected wave is greatly heated and greatly fluctuated. When there is not, the negative feedback control is configured to extend the monitoring interval, and the job is time-shared with other controls to lower the overall control unit balance and thereby contribute to the control unit cost reduction. It is.

  The seventh invention provides a first threshold value and a second threshold value, the second threshold value is a threshold value larger than the first threshold value, and the control unit is a reflected wave monitor unit Negative feedback control is performed when the output from the generator exceeds the first threshold value and less than the second threshold value. When the output exceeds the second threshold value, the oscillation state is increased in the amount of reflection from the heating chamber. The oscillation frequency of the microwave generator is changed by searching for the frequency at which the reflection level detected from the signal of the reflected wave monitor is minimized.

  In this way, for excessive reflected waves exceeding the second threshold, the frequency at which the reflection level is minimized is quickly found and reset, so that the resistance to the reflected waves is significantly improved, and in normal times, normal Since the negative feedback control is performed, the constant control (stable control) of the reflected wave can be maintained, so that a highly reliable reflected wave protection system can be provided.

  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, the microwave generators 3 a to 3 d of the present invention are output units 2 a to 2 d configured using a semiconductor substrate and reflected wave monitor units 6 a to 6 d that detect reflected power reflected from the inside of the heating chamber 5. It is configured. Basic weak signals that generate microwaves are created by the semiconductor oscillators 1a to 1d. In the case of this embodiment, the semiconductor oscillation units 1a to 1d are provided as described above in order to individually control the frequencies of the microwaves oscillated from the respective power feeding units 7a to 7d. Thereby, the degree of freedom of electromagnetic field distribution in the heating chamber 5 can be increased, and electromagnetic waves can be concentrated on a desired object 9 to be heated arbitrarily arranged. Thus, the feature of the present embodiment is that the microwaves irradiated from the power feeding units 7a to 7d can be freely controlled.

  Further, the microwave processing apparatus of the present invention has a heating chamber 5 having a substantially rectangular parallelepiped structure that accommodates an object 9 to be heated, and the heating chamber 5 has a left wall surface, a right wall surface, a bottom wall surface, an upper wall surface made of a metal material, An open / close door (not shown) that opens and closes to store the inner wall and the object 9 to be heated, and a mounting table on which the object 9 is mounted, and is configured to confine the supplied microwave inside. is doing. And the output of the microwave generation parts 3a-3d is transmitted, and the electric power feeding parts 7a-7d which radiate | emit the microwave into the heating chamber 5 are arrange | positioned at the wall surface which comprises the heating chamber 5. FIG. The arrangement of the power feeding portions 7a to 7d is not limited to the present embodiment, and a plurality of power feeding portions may be provided on any wall surface, and are not opposed surfaces, for example, the right wall surface and the bottom wall surface. You may comprise the electric power feeding part used as a pair by such an adjacent combination.

  The power amplifiers in the output units 2a to 2d are amplified by several tens of dB or more by a cascade amplifier on the printed circuit board. The circuit is formed by a conductor pattern formed on one side of a dielectric substrate made of a low dielectric loss material. The matching circuit is arranged on the input side and the output side of each semiconductor element so that the semiconductor element which is an amplifying element of each amplifying section is operated satisfactorily.

  The microwave transmission path connecting each functional block forms a transmission circuit having a characteristic impedance of about 50Ω by a conductor pattern provided on one surface of the dielectric substrate.

  When the control unit 4 selects a frequency with as few reflected waves as possible, it can maximize the heat transfer power received by the article 9 to be heated, contribute to speed cooking, and reduce the heat loss of the semiconductor element due to the reflected wave power. The heat resistance reliability is improved.

  However, it is inevitable that the object to be heated 9 is affected by the temperature of microwave heating during cooking. For example, it rarely occurs that the article 9 to be heated falls due to thermal expansion during heating or falls. It is also conceivable that the dielectric constant gradually changes as the food temperature rises. Moreover, although the habit of wrapping is often seen in the microwave heating apparatus, it can be seen that this also swells during heating and the volume of the article 9 to be heated increases. At such time, the impedance inside the heating chamber 5 as viewed from the heating chamber 5 changes, and it is predicted that the minimum reflection frequency changes every moment as shown in FIG.

  A point a shown in FIG. 2 is an initial frequency characteristic. When a change in physical properties of the article 9 to be heated appears, a transition is made to a dotted line b curve shown in FIG. Then, when the object to be heated 9 falls down or rolls over during heating, rolls, the dielectric constant changes as the temperature of the food rises, or the wrapped object 9 to be heated becomes enormous, for example, FIG. As shown in FIG. 5, it is predicted that the frequency characteristic changes up to a point c of the alternate long and short dash line. At that time, the reflectance increases by d as shown in FIG. That is, it is used in a state where there are many reflections. This increases the reflection duty of the semiconductor. For example, if the change is larger, the reflection is expected to increase and break down.

Therefore, as a means for avoiding this, it is necessary to always perform negative feedback control so that the frequency becomes a minimum frequency so as not to change the frequency. This will be described with reference to FIG. First, the routine starts from the beginning, and in step 1, the reflection from the reflected wave monitoring unit is monitored. Next, in step 2, each of the reflections of the reflection monitor units 6a to 6d is calculated. Accordingly, each frequency is compared with the acquired data, and the reflected wave is increased, and then in step 3, it is lowered by a predetermined minute frequency fluctuation amount Δf. In the lowered state, the reflections of the reflection monitor units 6a to 6d are calculated.

  Next, in step 5, it is determined by monitoring the reflected wave monitoring units 6a to 6d whether the reflection has increased. If yes, the Δf frequency is increased in step 6. Next, in step 7, each of the reflections of the reflection monitor units 6a to 6d is calculated. Next, in Step 8, it is determined whether or not the reflection has increased. If No, the negative feedback control is completed and the frequency is determined. If yes, go back to step 2. If it repeats in the loop of step 2 to step 8, it counts a predetermined number of times, and if it is satisfied, the frequency is determined.

  On the other hand, if No in Step 5, the Δf frequency is lowered in Step 10. Next, in step 11, each of the reflections of the reflection monitor units 6a to 6d is calculated. In step 12, it is determined whether there is an increase in reflection. If Yes, the frequency is determined. If No, the process jumps to Step 6 and branches to a routine for increasing the Δf frequency. Thereafter, the frequency is determined as described above. The variable range of the frequency is the ISM band (2.45 G ± 0.05 G). According to this sequence, the frequency for negative feedback can be varied freely in the above sequence. This sequence is performed in parallel with respect to the microwaves oscillated from the respective power feeding units 7a to 7d. For example, there is a possibility that the power feeding units 7a to 7d have mutual connectivity and influence each other. Therefore, if one power supply block is changed, another block having connectivity is affected. Because there is a possibility of change. There is a possibility that it will not converge to the best state due to such a mutual interference relationship, but at that time, it is necessary to terminate the execution of the sequence by dividing a predetermined time. For example, if two blocks have a fixed frequency within a predetermined time, the sequence may be terminated or some rule may be necessary.

  In order to simplify the system, there is a microcomputer that controls the entire existing equipment, but by inserting this task into it, the task can be performed in parallel by one microcomputer, and the system is greatly improved. It is also possible to reduce the number of parts and achieve an economic effect.

  However, as described above, it is inevitable that the object to be heated 9 is affected by the temperature of microwave heating during cooking. For example, it rarely occurs that the article 9 to be heated falls due to thermal expansion during heating or falls. It is also conceivable that the dielectric constant gradually changes as the food temperature rises. Moreover, although the habit of wrapping is often seen in the microwave heating apparatus, it can be seen that this also swells in the middle of heating and the volume of the article 9 to be heated increases. In such a case, the impedance in the heating chamber as viewed from the heating chamber 5 changes, and it is predicted that the minimum reflection frequency changes every moment as shown in FIG.

  Moreover, the threshold value according to each output part is provided, and when the variation | change_quantity which a negative feedback applies exceeds a limit threshold value, it will be in the oscillation state which the amount of reflections from the heating chamber 5 increased. Judge. Then, the control unit 4 quickly decreases the outputs of the reflected wave monitoring units 6a to 6d, and then searches for the frequency at which the reflection level detected from the signals of the reflected wave monitoring units 6a to 6d is minimized, and the semiconductor oscillation unit 1a. The oscillation frequency of ˜1d is changed again to a frequency at which reflection becomes the minimum value within the ISM band. Thereafter, the output is returned to the original state, negative feedback control is performed, the process returns to the negative feedback control sequence, and the oscillation frequency of the semiconductor oscillation units 1a to 1d is changed, whereby a highly reliable system can be constructed.

  Further, the frequency of the negative feedback is integrated, and when a certain predetermined amount is exceeded, it is determined that the oscillation state in which the amount of reflection from the heating chamber 5 is increased, and from the signals of the reflected wave monitoring units 6a to 6d. By searching for the frequency at which the detected reflection level is minimized and changing the oscillation frequency of the semiconductor oscillators 1a to 1d, a more reliable system can be constructed.

  Conversely, if a stable state where the frequency of negative feedback is low continues, the monitoring frequency is thinned out, and the control unit 4 can concentrate on processing another task and effectively use the task. The total performance of the control unit 4 can be improved.

  In addition, a first threshold value and a second threshold value are provided, the second threshold value is set to a threshold value larger than the first threshold value, and the control unit 4 includes the reflected wave monitor units 6a to 6a. When the output from 6d exceeds the first threshold value and is less than the second threshold value, the negative feedback control described above is performed, and when the output exceeds the second threshold value, reflection from the heating chamber 5 is performed. A configuration in which it is determined that the oscillation state is increased and the frequency at which the reflection level detected from the signals of the reflected wave monitoring units 6a to 6d is minimized is searched, and the oscillation frequency of the semiconductor oscillation units 1a to 1d is changed. By doing so, it is also possible to construct a more reliable system.

  As described above, the microwave heating device according to the present invention can provide a device that has a plurality of power feeding units and prevents the destruction of the semiconductor from the reflected waves that have returned to the power feeding unit that radiates microwaves. The present invention can also be applied to applications such as a heating device using dielectric heating, a garbage disposal machine, or a microwave power source of a plasma power source that is a semiconductor manufacturing device.

The system block diagram of the microwave heating apparatus in embodiment of this invention The characteristic view which shows the change of the frequency spectrum accompanying the change of the to-be-heated material of this invention The flowchart which shows the flow of the negative feedback control in embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor oscillation part 2 Output part 3 Microwave generation part 4 Control part 5 Heating chamber 6 Reflection monitor part 10 Threshold value

Claims (7)

A plurality of microwave generators having an output unit connected to the semiconductor oscillation unit, a heating chamber for storing an object to be heated, a reflected wave monitor unit that is positioned downstream of the output unit and constantly monitors the reflected wave level; A control unit that receives a signal from the reflected wave monitor unit and controls the output of the output unit; and a threshold value corresponding to each output unit that determines a reflected wave level at which the semiconductor oscillation unit does not break down, and The control unit performs negative feedback control to change the oscillation frequency of the semiconductor oscillation unit so that the output of the semiconductor oscillation unit becomes less than the threshold value when the signal of each reflected wave monitor unit exceeds the threshold value. A microwave heating device configured to be made to operate. The microwave heating apparatus according to claim 1, wherein the control unit is configured to always perform negative feedback control using a microcomputer. The microwave heating apparatus according to claim 1 or 2, wherein the microcomputer is configured to perform processing in combination with a microcomputer that controls the microwave heating apparatus. A plurality of microwave generators having an output unit connected to the semiconductor oscillation unit, a heating chamber for storing an object to be heated, a reflected wave monitor unit that is positioned downstream of the output unit and constantly monitors the reflected wave level; A control unit that receives a signal of the reflected wave monitor unit and controls the output of the output unit; and a threshold threshold value according to each of the output units that determines a reflected wave level at which the semiconductor oscillation unit does not break down, When the amount of change in which negative feedback is applied exceeds the limit threshold, the control unit quickly decreases the output of the reflected wave monitor unit, and then the reflection level detected from the signal of the reflected wave monitor unit is A microwave heating apparatus configured to search for a minimum frequency, change the oscillation frequency of the semiconductor oscillating unit, change the oscillation frequency of the semiconductor oscillating unit by returning the output to the original and performing negative feedback control. The frequency of negative feedback is integrated, and when a certain predetermined amount is exceeded, the frequency at which the reflection level detected from the signal of the reflected wave monitor is minimized is searched, and the oscillation frequency of the microwave generator is changed. The microwave heating device according to any one of claims 1 to 4. The microwave heating device according to any one of claims 1 to 5, wherein the frequency of negative feedback is integrated and the control unit is configured to thin out the monitoring frequency of the reflected wave monitoring unit when the frequency is less than a predetermined amount. A first threshold value and a second threshold value are provided, the second threshold value is a threshold value greater than the first threshold value, and the control unit outputs an output from the reflected wave monitor unit. Negative feedback control is performed when the first threshold value is exceeded and less than the second threshold value, and when the second threshold value is exceeded, the reflection level detected from the signal of the reflected wave monitor unit is The microwave heating device according to any one of claims 1 to 6, wherein a minimum frequency is searched and the oscillation frequency of the microwave generation unit is changed.

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