microwave processing equipment

Abstract

A microwave processing device according to the present disclosure is provided with a heating chamber, a microwave generating unit, an amplifying unit, a power supply unit, a detecting unit, a control unit, and a storage unit. The microwave generating unit generates microwaves having an arbitrarily defined frequency in a prescribed frequency band. The amplifying unit amplifies an output level of the microwaves. The power supply unit radiates the microwaves amplified by the amplifying unit into the heating chamber as incident electric power. The detecting unit detects reflected electric power returning from the heating chamber to the power supply unit, from among the incident electric power. The control unit controls the microwave generating unit and the amplifying unit. The storage unit stores the microwave frequency and an elapsed time from the start of heating, together with a value of the reflected electric power. The control unit controls the microwave generating unit and the amplifying unit on the basis of a calculated value obtained by calculation with reference to the reflected electric power.

Description

[Technical Field]

[0001] The present disclosure relates to a microwave processing apparatus including a microwave generation unit. [Background technology]

[0002] Some conventional microwave processing devices detect boiling of an object to be heated based on a change over time in the amount of reflected waves, and change the oscillation frequency and oscillation output of a semiconductor oscillator (see, for example, Patent Document 1).

[0003] Boiling of the heated food is detected based on the magnitude of change in the total reflected microwave power or the ratio of the total reflected microwave power to the total incident microwave power. Absolute values, deviations, and standard deviations are used as indicators of the magnitude of change. The conventional microwave processing device described above aims to precisely control the temperature of food by terminating heating or reducing heating output when boiling is detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 125147 [Non-patent literature]

[0005] [Non-Patent Document 1] Kenji Yamanishi, Anomaly Detection by Data Mining, Kyoritsu Shuppan, 2009 [Non-patent document 2] J. Takeuchi and K. Yamanishi. A Unifying framework for detecting outliers and change points from time series. IEEE Transaction on Knowledge and Data Engineering, 18(4):482-492, 2006. [Non-patent document 3] K. Yamanishi and J. Takeuchi. Discovering outlier filtering rules from unlabeled data. In Proceeding of the Seventh ACM SIGKDD International Conference on Knowledge Discovery and Data Mining (KDD01), ACM Press, pp.389-394, 2001 Summary of the Invention

[0006] However, there is still room for improvement in terms of the accuracy of boiling control in the microwave processing apparatus described in Patent Document 1. Therefore, an object of the present disclosure is to provide a microwave processing apparatus that can accurately detect changes in the state of an object to be heated.

[0007] A microwave processing device according to one aspect of the present disclosure includes a heating chamber that accommodates an object to be heated, a heating unit including a microwave generating unit, an amplifier unit, a power supply unit, a detection unit, a control unit, and a memory unit.

[0008] The microwave generating unit generates microwaves having any frequency within a predetermined frequency band. The amplifier unit amplifies the output level of the microwaves. The power feeding unit radiates the microwaves amplified by the amplifier unit into the heating chamber as incident power. The detection unit detects the reflected power of the incident power that returns from the heating chamber to the power feeding unit.

[0009] The control unit controls the microwave generation unit and the amplification unit. The memory unit stores the value of the reflected power along with the microwave frequency and the elapsed time from the start of heating. The control unit controls the microwave generation unit and the amplification unit based on a calculated value obtained by a calculation that references the reflected power.

[0010] The microwave processing device according to the present disclosure can accurately detect changes in the state of an object to be heated, such as changes in the dielectric constant of the object due to heating, such as boiling, swelling, melting, thawing, bursting, and drying, as well as changes in the shape and appearance of the object due to heating. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic configuration diagram of a microwave processing apparatus according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a flowchart showing the overall flow of cooking control in the first embodiment. [Figure 3] FIG. 3 is a flowchart showing details of the reflected power detection process according to the first embodiment. [Figure 4] FIG. 4 is a flowchart showing the flow of score calculation in change finder. [Figure 5] FIG. 5 is a diagram for explaining threshold values ​​used to detect a change in state of the object to be heated in the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining detection of a change in state of an object to be heated in the first embodiment. [Figure 7] FIG. 7 is a conceptual diagram showing boiling detection of an object to be heated in the first embodiment. [Figure 8A] FIG. 8A is a diagram showing heating conditions in a demonstration experiment of boiling detection in the first embodiment. [Figure 8B] FIG. 8B is a first diagram showing experimental results of boiling detection in the first embodiment. [Figure 8C] FIG. 8C is a second diagram showing the experimental results of boiling detection in the first embodiment. [Figure 8D] FIG. 8D is a third diagram showing experimental results of boiling detection in the first embodiment. [Figure 8E] FIG. 8E is a fourth diagram showing experimental results of boiling detection in the first embodiment. [Figure 9]FIG. 9 is a flowchart showing the overall flow of cooking control in the second embodiment. [Figure 10] FIG. 10 is a flowchart showing details of the reflected power detection process according to the second embodiment. [Figure 11] FIG. 11 is a diagram for explaining detection of a change in state of an object to be heated in the second embodiment. [Figure 12] FIG. 12 is a conceptual diagram showing expansion detection of an object to be heated in the second embodiment. [Figure 13] FIG. 13 is a diagram for explaining detection of a change in state of an object to be heated in the third embodiment. [Figure 14] FIG. 14 is a conceptual diagram showing melting detection of an object to be heated in the third embodiment. [Figure 15A] FIG. 15A is a diagram illustrating heating conditions in a demonstration experiment of melting detection in the third embodiment. [Figure 15B] FIG. 15B is a first diagram showing experimental results of melting detection in the third embodiment. [Figure 15C] FIG. 15C is a second diagram showing the experimental results of melting detection in the third embodiment. [Figure 16] FIG. 16 is a conceptual diagram showing detection of thawing of an object to be heated in the fourth embodiment. [Figure 17] FIG. 17 is a conceptual diagram showing the detection of burst of an object to be heated in the fifth embodiment. [Figure 18] FIG. 18 is a conceptual diagram showing dryness detection of an object to be heated in the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Findings that formed the basis of this disclosure) The microwave processing device described in Patent Document 1 detects the boiling state of an object to be heated from changes in reflected power and changes in the ratio of the total reflected power to the total incident power. Hereinafter, the ratio of the total reflected power to the total incident power will be referred to as reflectance.

[0013] However, if the frequency characteristics of microwaves are not taken into consideration, it is difficult to accurately detect changes in the state of the object to be heated. The degree to which the reflected power changes in response to changes in the state of the object to be heated differs depending on the frequency.

[0014] For example, there are frequencies where the change in reflected power is large when the liquid boils, and frequencies where the change is small. Such frequency characteristics depend on the standing wave distribution of the microwaves in the heating chamber, so the frequency characteristics are greatly affected by the type, viscosity, amount, shape, placement position, and shape of the heated object. The frequency characteristics are also affected by the type of state change of the heated object, such as swelling, melting, thawing, bursting, and drying.

[0015] Therefore, in actual cooking of various heated objects, it is difficult to detect state changes using one frequency or frequencies within a narrow band.

[0016] As a result of extensive research, the inventors of the present application have come up with the following invention, which accurately detects changes in the state of an object to be heated based on changes in reflected power taking frequency characteristics into consideration.

[0017] The microwave processing device according to the first aspect of the present disclosure includes a heating chamber that accommodates an object to be heated, a heating unit including a microwave generating unit, an amplifier, a power supply unit, a detection unit, a control unit, and a memory unit.

[0018] The microwave generating unit generates microwaves having any frequency within a predetermined frequency band. The amplifier unit amplifies the output level of the microwaves. The power feeding unit radiates the microwaves amplified by the amplifier unit into the heating chamber as incident power. The detection unit detects the reflected power of the incident power that returns from the heating chamber to the power feeding unit.

[0019] The control unit controls the microwave generation unit and the amplification unit. The memory unit stores the value of the reflected power along with the microwave frequency and the elapsed time from the start of heating. The control unit controls the microwave generation unit and the amplification unit based on a calculated value obtained by a calculation that references the reflected power.

[0020] In the microwave processing device according to the second aspect of the present disclosure, in addition to the first aspect, the control unit may use an average value of values ​​calculated for each microwave frequency as the calculated value. The average value of values ​​calculated for each frequency is, for example, an average value of reflected power values ​​calculated for each frequency.

[0021] In the microwave processing device according to a third aspect of the present disclosure, in addition to the first aspect, the control unit may calculate a calculated value for each microwave frequency, and the control unit may control the microwave generating unit when the calculated values ​​for microwaves of two or more frequencies exceed a threshold.

[0022] In the microwave processing apparatus according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the control unit may obtain the calculated value using a change finder, which is an online change point detection method for time series data.

[0023] In the microwave processing device according to the fifth aspect of the present disclosure, the detection unit may further detect incident power. The storage unit may store the value of the incident power together with the microwave frequency and elapsed time. The control unit may calculate, as a calculated value, a reflectance, which is the ratio of the sum of the reflected power to the sum of the incident power. The control unit may control the microwave generation unit based on the reflectance.

[0024] In a microwave processing apparatus according to a sixth aspect of the present disclosure, in addition to the first aspect, the storage unit may store the calculated value along with elapsed time, and the control unit may control the microwave generation unit when the calculated value exceeds a threshold value that is greater than one time the minimum value of the calculated values ​​stored in the storage unit and less than three times the minimum value.

[0025] In a microwave processing device according to a seventh aspect of the present disclosure, in addition to the sixth aspect, the control unit may not control the microwave generation unit until a predetermined time has elapsed since the start of heating, even if the calculated value exceeds the threshold value.

[0026] In the microwave processing apparatus according to an eighth aspect of the present disclosure, in addition to the sixth aspect, the microwave generating unit may be controlled when the calculated value exceeds the threshold value multiple times within a predetermined time period.

[0027] In the microwave processing apparatus according to a ninth aspect of the present disclosure, in addition to the sixth aspect, the microwave generating unit may be controlled when the calculated value exceeds the threshold value continuously within a predetermined time.

[0028] In a microwave processing apparatus according to a tenth aspect of the present disclosure, in addition to any one of the first to ninth aspects, the control unit detects boiling of the object to be heated as the change in state of the object to be heated.

[0029] In a microwave processing apparatus according to an eleventh aspect of the present disclosure, in addition to any of the first to ninth aspects, the control unit detects expansion of the object to be heated as the change in state of the object to be heated.

[0030] In a microwave processing apparatus according to a twelfth aspect of the present disclosure, in addition to any one of the first to ninth aspects, the control unit detects melting of the object to be heated as the change in state of the object to be heated.

[0031] In a microwave processing apparatus according to a thirteenth aspect of the present disclosure, in addition to any one of the first to ninth aspects, the control unit detects thawing of the object to be heated as the change in state of the object to be heated.

[0032] In a microwave processing apparatus according to a fourteenth aspect of the present disclosure, in addition to any one of the first to ninth aspects, the control unit detects rupture of the object to be heated as the change in state of the object to be heated.

[0033] In a microwave processing apparatus according to a fifteenth aspect of the present disclosure, in addition to any of the first to ninth aspects, the control unit detects drying of the object to be heated as a change in state of the object to be heated.

[0034] In a microwave processing apparatus according to a sixteenth aspect of the present disclosure, in addition to any one of the tenth to fifteenth aspects, the control unit may stop heating after detecting a change in state of the object to be heated.

[0035] In the microwave processing apparatus according to the seventeenth aspect of the present disclosure, the heating conditions in the heating unit may be changed after detecting a change in the state of the object to be heated.

[0036] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0037] (Embodiment 1) <Overall structure> Fig. 1 is a schematic configuration diagram of a microwave processing apparatus according to a first embodiment of the present disclosure. As shown in Fig. 1, the microwave processing apparatus according to the first embodiment includes a heating chamber 1, a microwave generating unit 3, an amplifying unit 4, a power supply unit 5, a detecting unit 6, a control unit 7, and a memory unit 8. In the first embodiment, the microwave generating unit 3 corresponds to the heating unit.

[0038] Heating chamber 1 accommodates load 2, which is an object to be heated, such as food. Microwave generator 3 is composed of a semiconductor element. Microwave generator 3 can generate microwaves of any frequency within a predetermined frequency band, and generates microwaves of a frequency specified by controller 7.

[0039] The amplifier 4 is configured with a semiconductor element. The amplifier 4 amplifies the output level of the microwave generated by the microwave generator 3 in accordance with instructions from the controller 7, and outputs the amplified microwave.

[0040] The power supply unit 5 functions as an antenna and supplies the microwaves amplified by the amplifier unit 4 as incident power to the heating chamber 1. That is, the power supply unit 5 supplies incident power based on the microwaves generated by the microwave generator 3 to the heating chamber 1. Of the incident power, the power that is not consumed by the object to be heated 2 or the like becomes reflected power that returns from the heating chamber 1 to the power supply unit 5.

[0041] The detector 6 is configured by, for example, a directional coupler. The detector 6 detects the value of incident power and the value of reflected power, and notifies the information to the controller 7. In other words, the detector 6 functions as both an incident power detector and a reflected power detector.

[0042] The detector 6 has a coupling factor of, for example, about -40 dB and extracts power that is about 1 / 10,000 of the incident power and reflected power. The extracted incident power is rectified by a detector diode (not shown), smoothed by a capacitor (not shown), and converted into information corresponding to the incident power. The extracted reflected power is similarly converted into information corresponding to the reflected power through rectification and smoothing. The controller 7 receives this information.

[0043] The memory unit 8 is a storage medium such as a semiconductor memory, which stores data from the control unit 7, reads out the stored data, and transmits it to the control unit 7. The control unit 7 is composed of a microprocessor including a CPU (central processing unit). Based on information from the detection unit 6 and the memory unit 8, the control unit 7 controls the microwave generation unit 3 and the amplification unit 4 to perform cooking control in the microwave processing device.

[0044] The control unit 7 stores the value of the reflected power in the memory unit 8 (first memory unit of the memory unit 8) together with the frequency of the microwaves generated by the microwave generation unit 3 and the time elapsed since the start of heating.

[0045] The control unit 7 performs calculations with reference to the values ​​of reflected power stored in the memory unit 8, and controls the microwave generation unit 3 based on the obtained calculated value RF. The control unit 7 stores the calculated value RF in the memory unit 8 (a second memory unit of the memory unit 8). The calculated value RF is, for example, a value indicating the amount of change in reflected power. The value indicating the amount of change in reflected power will be described later.

[0046] The control unit 7 uses the average value of the values ​​calculated for each microwave frequency as the calculated value RF. The average value of the values ​​calculated for each frequency is, for example, the average value of the reflected power calculated for each frequency.

[0047] The control unit 7 uses the value calculated by the change finder as the calculated value RF. The change finder is an online change point detection method for time series data.

[0048] The control unit 7 stores the calculated value RF together with the elapsed time from the start of heating in the memory unit 8 (a second memory unit of the memory unit 8). When the calculated value RF exceeds a threshold value TH, the control unit 7 controls the microwave generation unit 3 to adjust the microwave power. The threshold value TH is a value that is greater than one time the minimum value of the calculated value RF and less than three times the minimum value of the calculated value RF.

[0049] Even if the calculated value RF exceeds the threshold value TH, the control unit 7 does not control the microwave generating unit 3 until a predetermined time has elapsed since the start of heating.

[0050] The storage unit 8 is a single semiconductor memory in which a first storage unit and a second storage unit are configured, but the first storage unit and the second storage unit may be configured as separate semiconductor memories.

[0051] In the first embodiment, the control unit 7 detects boiling of the object to be heated 2 in the heating chamber 1. After detecting boiling, the control unit 7 causes the microwave generation unit 3 to stop generating microwaves.

[0052] <Flowchart> Fig. 2 is a flowchart showing the overall flow of cooking control in embodiment 1. As shown in Fig. 2, when control unit 7 causes microwave generation unit 3 to generate microwaves to start heating (step S1), control unit 7 first performs a process of detecting reflected power (step S2).

[0053] Fig. 3 is a flowchart showing the details of the detection process. As shown in Fig. 3, when the detection process starts (step S11), the microwave generation unit 3 performs frequency sweep (step S12). Frequency sweep is an operation of the microwave generation unit 3 to change the frequency in sequence at predetermined frequency intervals over a predetermined frequency band (for example, 2400 MHz to 2500 MHz).

[0054] During the frequency sweep, the detector 6 detects the reflected power of the microwave at each frequency. The controller 7 measures the frequency characteristics of the reflected power from the detected reflected power (step S13).

[0055] The control unit 7 stores each frequency in the frequency sweep, the value of the reflected power for each frequency obtained in the measurement process, and the elapsed time from the start of heating in the memory unit 8 (first memory unit of the memory unit 8) (step S14). The control unit 7 calculates the calculated value RF to be used for boiling detection based on the frequency characteristics of the obtained reflected power (step S14), and ends the detection process (step S15).

[0056] The control unit 7 returns the process to the flowchart shown in FIG. 2, and heats the object 2 by microwave heating in the heating process (step S3).

[0057] The control unit 7 determines the boiling state of the object to be heated 2 from the information obtained in the detection process (step S4). In the end determination (step S5), the control unit 7 determines whether the object to be heated 2 is in a boiling state.

[0058] If the control unit 7 determines that the object to be heated 2 is in a boiling state, it ends the cooking (step S6). Otherwise, the control unit 7 continues the cooking, determines new heating conditions as necessary (step S7), and proceeds to step S8.

[0059] In step S8, the control unit 7 determines whether or not it is necessary to update the frequency characteristics due to the passage of a certain time since the start of heating, a change in heating conditions, etc. If an update is necessary, the control unit 7 returns the process to the detection process (step S2), and if an update is not necessary, the control unit 7 returns the process to the heating process (step S3).

[0060] <Change Finder> Change Finder is a method for calculating a score that represents the degree of change in time-series data in real time. Representative documents related to Change Finder include, for example, Non-Patent Documents 1 to 3.

[0061] Here, an overview of Change Finder will be given. Figure 4 is a flowchart showing the flow of score calculation in Change Finder. Change Finder uses a method based on two-stage learning of a time series model, and its processing is roughly divided into steps S51 to S56.

[0062] 4, in step S51, time series data is read in. The time series data in the present disclosure includes the microwave frequency, the elapsed time from the start of heating, the incident power, the reflected power, and the reflectance.

[0063] In step S52, a probability distribution function is learned. In step S53, a score is calculated. The processes of steps S52 and S53 are collectively referred to as first-stage learning. An AR model (autoregressive model), which is a probabilistic model of time-series data, is learned using an online forgetting learning algorithm (hereinafter referred to as an SDAR (sequentially discounting AR learning) algorithm). From the obtained probability density function, outliers in the data at each time point are calculated using logarithmic loss or Hellinger score, and a score is calculated.

[0064] In step S54, the scores calculated in step S53 are smoothed. Smoothing involves calculating the average value of the outlier scores calculated in steps S51 and S52 for data within a window whose width is a predetermined integer T. By shifting the window, a new time series of moving average scores is constructed.

[0065] In step S55, a probability distribution function is trained, and in step S56, a score is calculated. The processes in steps S55 and S56 are collectively referred to as second-stage training. The new time series data smoothed in step S54 is modeled using an AR model, and training is again performed using the SDAR algorithm.

[0066] Calculate the data at each time point of the obtained probability model using the Hellinger distance in the same manner as the log loss or steps S52 and S53, and calculate the score. The higher the score, the greater the degree of change at each time point.

[0067] The advantages of the change finder are as follows. In the first-stage learning, only outliers in the time series can be detected. However, after removing the outliers that respond to noise by smoothing the outlier scores, only the essential fluctuations can be detected by the second-stage learning.

[0068] In Embodiment 1 of the present disclosure and Embodiment 3 described later, a predetermined integer T used in the description of step S54 is defined as "smooth".

[0069] In sequentially executing the calculation, the SDAR algorithm updates the parameters or the statistics required for the calculation in the form of a weighted average of the current value and the new value in a ratio of (1 - r):r. Here, "r" is a forgetting parameter with a value in the range of 0 < r < 1. The smaller "r" is, the more the SDAR algorithm is affected by past data. In Embodiment 1 and Embodiment 3, the forgetting parameter is also defined as "r".

[0070] It is also possible to detect the state change of the object to be heated 2 using the score calculated in the first-stage learning shown in FIG. 4. The score calculated in the first-stage learning is the value before performing the smoothing of the score. Therefore, the score calculated in the first-stage learning is effective for detecting a smaller state change of the object to be heated 2.

[0071] However, there is a possibility of detecting noise due to ambient vibration, changes in the dielectric constant in the wall surface and door glass of the heating chamber 1 due to the temperature rise in the heating chamber 1, and minute shape changes. Therefore, it is preferably determined according to the application whether to use the score calculated in the first-stage learning or the score calculated in the second-stage learning for detecting the state change of the object to be heated 2.

[0072] Fig. 5 is a diagram for explaining the threshold value TH used to detect a change in the state of the object to be heated 2 in embodiment 1. The calculated value RF and the threshold value TH are shown on the graph in Fig. 5. In Fig. 5, the horizontal axis represents the elapsed time (minutes) from the start of heating, and the vertical axis represents the calculated value RF.

[0073] The units of the vertical axis in Fig. 5, i.e., the units of the calculated value RF and threshold value TH, are determined by the value used for the calculated value RF. For example, if the calculated value RF is the average value of the reflected power values, the units of the vertical axis in Fig. 5 are power (W). Similarly, if the calculated value RF is the standard deviation of the reflected power values, the units of the vertical axis are also power (W). If the calculated value RF is a value calculated using the Change Finder method, the units of the vertical axis in Fig. 5 are dimensionless.

[0074] As described above, the threshold value TH is a value greater than 1 time the minimum value of the calculated value RF and less than 3 times the minimum value of the calculated value RF. A method for determining the threshold value TH based on the calculated value RF from the start of heating will be described.

[0075] The threshold value TH is calculated by multiplying the minimum value of the calculated value RF since the start of heating by a predetermined magnification factor. In the present disclosure, this magnification factor is greater than 1 and less than 3. When the minimum value of the calculated value RF is updated, the control unit 7 updates the threshold value TH by multiplying the new minimum value by the same magnification factor.

[0076] That is, the minimum value of the calculated value RF is the minimum value of the calculated value RF obtained from the reflected power detected up to that point. Therefore, as shown in Figure 5, if the calculated value RF decreases over time, the threshold value TH decreases along with that change. On the other hand, if the calculated value RF increases over time, the threshold value TH remains unchanged.

[0077] In the first embodiment, the threshold value TH for detection and determination is not set in advance. The control unit 7 determines the threshold value TH for each object to be heated that has a different weight, shape, and container, by referring to the reflected power and incident power stored in the memory unit 8 (first memory unit of the memory unit 8). This allows for flexible detection that takes into account variations in the object to be heated 2 that are expected in actual cooking. As a result, the possibility of false detection can be reduced, enabling highly accurate detection.

[0078] When the calculated value RF is reflectance, the threshold value TH is a value greater than 1 time and less than 3 times the minimum value of reflectance. By using the threshold value TH, it is possible to detect small changes in the state of the heated object 2, such as melting of a small portion of the heated object 2 or partial boiling. As mentioned above, reflectance is the ratio of the total reflected power to the total incident power.

[0079] The optimum value of the multiplying factor by which the minimum value of the calculated value RF is multiplied also changes depending on the weight, viscosity, type, and container of the object to be heated 2. Therefore, the memory unit 8 pre-stores setting conditions suitable for the type, weight, etc. of the object to be heated 2. The control unit 7 reads and uses the optimum setting conditions from the memory unit 8 based on information such as the type and weight of the object to be heated 2 input by the user. This can improve the detection accuracy.

[0080] In the first and third embodiments, the magnification factor by which the minimum value of the calculation value RF is multiplied is called a "threshold."

[0081] Fig. 6 is a diagram for explaining detection of a change in the state of the object to be heated 2 in embodiment 1. In Fig. 6, the horizontal axis represents the time (minutes) elapsed since the start of heating, and the vertical axis represents the calculated value RF. The calculated value RF and threshold value TH are shown on the graph in Fig. 6. The units of the vertical and horizontal axes in Fig. 6 are the same as those in Fig. 5.

[0082] As shown in FIG. 6, even if the calculated value RF obtained by referring to the reflected power exceeds the threshold value TH, the control unit 7 does not detect or determine whether there is a change in the state of the object to be heated 2 until a predetermined time TMa (guard time) has elapsed since the start of heating.

[0083] This reduces the possibility of false detection and enables highly accurate detection in the following cases: For example, when the reflected power changes suddenly and significantly due to a cause other than a phenomenon in which the state of the heated object 2 changes continuously. This also includes cases in which the operation of the detection unit 6 is unstable.

[0084] A phenomenon other than a change in the state of the heated object 2 that causes a large instantaneous change in the reflected power is, for example, deformation of the wall surface of the heating chamber 1 caused by expansion due to a temperature rise. Deformation of the heated object 2, which has an unstable shape, is one such phenomenon.

[0085] In a microwave oven, which is an example of a microwave processing device, these phenomena often occur within 20 minutes of starting heating. This is because it often takes about 20 minutes for the temperature in heating chamber 1 to reach the set temperature. Therefore, in actual cooking, it is appropriate to set the time TMa to a value within the range of 1 second to 20 minutes.

[0086] The optimum value varies depending on the weight, viscosity, type, and container of the object 2. Therefore, the memory unit 8 pre-stores setting conditions suitable for the type, weight, etc. of the object 2. The control unit 7 reads and uses the optimum setting conditions from the memory unit 8 based on information such as the type and weight of the object 2 input by the user. This can improve detection accuracy.

[0087] <Boiling detection> Fig. 7 is a conceptual diagram showing boiling detection of the object to be heated 2 in embodiment 1. In Fig. 7, the object to be heated 2 is a liquid.

[0088] As shown in Figure 7, depending on the fluctuation of the surface during boiling, microwaves may or may not be absorbed by the object to be heated 2. Therefore, when the object to be heated boils, the reflected power fluctuates greatly. In other words, boiling of the object to be heated 2 can be detected by calculating the amount of change in reflected power.

[0089] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, the score calculated by the Change Finder method, and the rate and range of change of the reflected power per given time. The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.

[0090] The frequency average is the average of a number of reflected power values, each of which is obtained for a corresponding one of a number of frequencies.

[0091] When the liquid boils, values ​​indicating the variation in the amount of change in the reflected power, such as the variance, standard deviation, and coefficient of determination, increase. Therefore, by calculating the variation in the amount of change in the reflected power, it is possible to detect the boiling of the object to be heated 2.

[0092] Variance can be either sample variance or unbiased variance. When using sample variance, the variance may be overestimated. For this reason, to evaluate small variances, it may be more appropriate to use the coefficient of determination rather than the sample variance.

[0093] The sample variance is defined by the following formula:

[0094]

number

[0095] Covariance is the average value obtained by multiplying the deviation of one variable by the deviation of another variable. Covariance indicates the tendency of variation between two variables.

[0096] The coefficient of determination is defined by the following formula:

[0097]

number

[0098] The control unit 7 can change the heating conditions or terminate the heating by detecting the boiling of the heated object 2. This makes it possible to prevent overheating or underheating, resulting in optimal cooking.

[0099] Some cooking methods, such as pot-au-feu, require sufficient heating of the ingredients in the object to be heated 2 by boiling continuously for a certain period of time. In such cooking methods, after detecting boiling, a weak boiling state can be maintained by duty controlling the microwave output. This can reduce the risk of ingredients breaking down and the soup becoming cloudy due to overheating.

[0100] Duty control is a control method in which a signal of a constant level is repeatedly output while adjusting the ratio of on and off.

[0101] Cooking that requires duty control of microwave output after boiling detection includes, for example, cooking soups such as pot-au-feu and stew, and heating drinks such as milk and water.

[0102] <Boiling detection demonstration experiment> 8A to 8E are diagrams showing experimental results of boiling detection in Embodiment 1. Fig. 8A shows heating conditions in a demonstration experiment of boiling detection for water, pot-au-feu, and stew.

[0103] 8B to 8E, the horizontal axis represents heating time (minutes) and the vertical axis represents the change finder score. Each graph in Figures 8B to 8E shows the change in the change finder score over time and the change in the threshold value TH over time. Each graph also shows the time when one of the four optical fiber thermometer probes inserted into the object to be heated 2 detects 100°C and the time when all four detect 100°C.

[0104] Figure 8B shows the experimental results of boiling detection for stew under the Change Finder settings of "r" = 0.01, "smooth" = 20, and "threshold" = 1.2. As shown in Figure 8B, under these settings, boiling detection for stew was successful for all five heating conditions, including different weights and containers.

[0105] Figure 8C shows the experimental results of boiling detection for pot-au-feu under the Change Finder settings of "r" = 0.01, "smooth" = 20, and "threshold" = 1.2. As shown in Figure 8C, under these settings, boiling detection for pot-au-feu was successful for all nine heating conditions, which differed in weight, container, etc.

[0106] Figure 8D shows the experimental results of boiling water detection under the Change Finder settings of "r" = 0.01, "smooth" = 20, and "threshold" = 1.2. As shown in Figure 8D, under these settings, boiling water detection was successful for three out of five heating conditions, including different weights and containers.

[0107] Figure 8E shows the experimental results of boiling detection for water under the Change Finder settings of "r" = 0.04, "smooth" = 40, and "threshold" = 1.22. As shown in Figure 8E, under these settings, boiling detection was successful for all five heating conditions, including different weights and containers.

[0108] As described above, the change finder settings for detecting boiling water were used for detecting boiling water in stew and pot-au-feu. As a result, boiling water detection failed under some heating conditions. However, if the change finder settings suitable for detecting boiling water are used, boiling water detection is possible under all heating conditions.

[0109] Depending on the setting conditions of the change finder, it is possible to detect changes in the state of the object to be heated 2 even if the weight, viscosity, type, container, and ratio of water to ingredients of the object to be heated 2 are different.

[0110] The calculated score varies greatly depending on the setting conditions. Therefore, the storage unit 8 stores in advance setting conditions suitable for the type, weight, etc. of the object to be heated 2. The control unit 7 reads out and uses the optimal setting conditions from the storage unit 8 based on information such as the type and weight of the object to be heated 2 input by the user. This can improve the detection accuracy.

[0111] 8A to 8E, cooking was performed in a glass container with a lid on, but similar results could be obtained even if the lid was removed.

[0112] When a metal lid is placed on a metal container that is not transparent to microwaves, boiling causes steam to be released into the heating chamber from between the container and the lid. The steam also condenses, forming water droplets inside the heating chamber 1. This causes a large change in the calculated value RF obtained by referencing the reflected power. This makes it possible to detect boiling of the object to be heated 2.

[0113] 8A to 8E, the dielectric constant of the object to be heated 2 is increased and its viscosity is changed by adding granulated consommé or a commercially available solid stew roux. However, boiling detection is possible even when the dielectric constant and viscosity are changed by something other than consommé or solid roux.

[0114] As described above, according to the first embodiment, accurate boiling detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally completed.

[0115] (Embodiment 2) <Overall structure> The microwave processing device according to the second embodiment of the present disclosure has the same configuration as the microwave processing device according to the first embodiment shown in Fig. 1. Therefore, in the second embodiment, the same or substantially the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0116] In the second embodiment, the control unit 7 performs calculations for each frequency of the microwave by referring to the reflected power stored in the memory unit 8 (first memory unit of the memory unit 8). The control unit 7 determines that a change in the state of the object to be heated 2 has been detected when the calculated value RF obtained for microwaves of two or more frequencies exceeds the threshold value TH.

[0117] In the second embodiment, the control unit 7 stores the incident power value and the reflected power value in the memory unit 8 (first memory unit of the memory unit 8) along with the microwave frequency and the elapsed time from the start of heating. The control unit 7 calculates the reflectance from the incident power and reflected power stored in the memory unit 8, and controls the microwave generation unit 3 based on the reflectance. As described above, the reflectance is the ratio of the sum of the reflected power to the sum of the incident power.

[0118] The control unit 7 further controls the microwave generating unit 3 when the calculated value RF obtained by referring to the reflected power stored in the memory unit 8 (first memory unit of the memory unit 8) exceeds the threshold value TH multiple times within an arbitrary period of time.

[0119] In the second embodiment, the control unit 7 detects expansion of the object 2 to be heated in the heating chamber 1 as a change in the state of the object 2 to be heated.

[0120] In the second embodiment, the microwave processing apparatus includes a radiant heater and a steam generator (neither of which are shown) as a heating unit in addition to the microwave generating unit 3. However, the heating unit may include either or both of the radiant heater and the steam generating unit, and does not necessarily have to include both.

[0121] After detecting the expansion of the object 2, the control unit 7 changes the heating conditions, including changing the heating unit to be used. Changing the heating unit to be used means, for example, changing the heating unit to be used in the heating process from the microwave generating unit 3 to a radiant heater or a steam generating device. The reverse is also possible.

[0122] <Flowchart> Fig. 9 is a flowchart showing the overall flow of cooking control in embodiment 2. As shown in Fig. 9, when control unit 7 controls microwave generation unit 3 to start heating (step S21), control unit 7 first performs a process of detecting reflected power (step S22).

[0123] Fig. 10 is a flowchart showing the details of the detection process. As shown in Fig. 10, when the detection process starts (step S31), the microwave generating unit 3 performs frequency sweep (step S32).

[0124] During the frequency sweep, the detector 6 detects the reflected power and incident power of the microwave at each frequency. The controller 7 measures the frequency characteristics of the reflected power, the frequency characteristics of the incident power, and the reflectance from the detected reflected power and incident power (step S33).

[0125] The control unit 7 stores each frequency in the frequency sweep and the reflected power, incident power, and reflectance for each frequency obtained in the measurement process in the memory unit 8 (first memory unit of the memory unit 8). The control unit 7 also stores the elapsed time from the start of heating in the memory unit 8 (first memory unit of the memory unit 8) (step S34). The control unit 7 calculates the calculated value RF used for expansion detection based on the two obtained frequency characteristics (step S34) and ends the detection process (step S35).

[0126] 9 and starts heating the object 2 by microwave heating in the heating process (step S23). In the heating process, the control unit 7 may use oven heating or radiation heating using a radiation heater, or steam heating using a steam generator, in addition to microwave heating.

[0127] The control unit 7 determines the expansion state of the object to be heated 2 from the information obtained in the detection process (step S24). In the end determination (step S25), the control unit 7 determines whether the object to be heated 2 is in an expansion state.

[0128] If the control unit 7 determines that the object to be heated 2 is in a puffed state, it ends cooking (step S26). Otherwise, the control unit 7 determines whether to maintain the same heating conditions or change the heating conditions, including changing the heating unit to be used, depending on the puffed state of the object to be heated 2 (step S27).

[0129] If the control unit 7 determines that the same heating conditions should be maintained, the process proceeds to step S28. In step S28, the control unit 7 determines whether it is necessary to update the frequency characteristics because a certain time has passed since the start of heating or because the heating conditions have been changed. If an update is necessary, the control unit 7 returns the process to the detection process (step S22), and if an update is not necessary, the control unit 7 returns the process to the heating process (step S23).

[0130] If it is determined in step S27 that the heating conditions should be changed, the control unit 7 determines new heating conditions, including changing the heating unit to be used (step S29), and the process proceeds to step S .

[0131] In the frequency sweep, the microwave generating unit 3 generates microwaves by increasing the frequency in predetermined frequency intervals from the lower limit of a predetermined frequency band. The control unit 7 measures the frequency characteristics of the reflectance and selects the frequency that results in the lowest reflectance based on the obtained frequency characteristics.

[0132] However, the method for selecting the frequency that provides the lowest reflectance is not limited to this. For example, the microwave generation unit 3 may generate microwaves by randomly changing the frequency within a predetermined frequency band. The control unit 7 may calculate the reflectance for each frequency and select the frequency that provides the lowest reflectance.

[0133] FIG. 11 is a diagram for explaining detection of a change in state of the object to be heated 2 in the second embodiment.

[0134] In Fig. 11, the horizontal axis represents the time (minutes) elapsed since the start of heating, and the vertical axis represents the calculated value RF obtained by referring to the reflected power stored in memory unit 8 (first memory unit of memory unit 8). The calculated value RF and threshold value TH are shown on the graph in Fig. 11. The units of the vertical and horizontal axes in Fig. 11 are the same as those in Fig. 5.

[0135] As shown in FIG. 11, when the calculated value RF obtained by referring to the reflected power exceeds the threshold value TH twice within a predetermined time TMb, the control unit 7 determines that a change in the state of the object to be heated 2 has occurred.

[0136] This reduces the possibility of false detection and enables highly accurate detection in the following cases: For example, when the reflected power changes suddenly and significantly due to a cause other than a phenomenon in which the state of the heated object 2 changes continuously. This also includes cases in which the operation of the detection unit 6 is unstable.

[0137] A phenomenon other than a change in the state of the heated object 2 that causes a large instantaneous change in the reflected power is, for example, deformation of the wall surface of the heating chamber 1 caused by expansion due to a temperature rise. Deformation of the heated object 2, which has an unstable shape, is one such phenomenon.

[0138] In actual cooking, it is preferable to set the predetermined time TMb to 1 second or more. This is because it is unlikely that the above-mentioned phenomenon will continue to occur for 1 second or more. Also, as mentioned above, if the threshold value TH is exceeded multiple times within the predetermined time TMb, it is determined that a change in the state of the object to be heated 2 has occurred, thereby improving detection accuracy. In practice, it is preferable to set this number to a value between 2 and 10.

[0139] <Swelling detection> Fig. 12 is a conceptual diagram showing the detection of expansion of the object to be heated 2 in embodiment 2. As shown in Fig. 12, expansion of the object to be heated 2 changes the shape of the object to be heated 2 and dries the object to be heated 2.

[0140] Accordingly, the dielectric constant of the entire object 2 to be heated changes, and the dielectric constant distribution in the object 2 also changes. This also changes the frequency characteristics of the absorbed power. As a result, by calculating the amount of change in the reflected power during heating of the object 2 to be heated, it is possible to detect the expansion of the object 2 to be heated. Absorbed power refers to the microwaves absorbed by the object 2 to be heated.

[0141] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, as well as the score calculated using the Change Finder method, and the rate and range of change of the reflected power per given time.The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.In general, the dielectric constant decreases as the heated object 2 dries.

[0142] The control unit 7 can change the heating conditions or terminate heating by detecting the start and completion of swelling of the heated object 2. This makes it possible to prevent overheating or underheating, resulting in optimal cooking.

[0143] Cooking using rise detection is, for example, baking soufflé and puff pastry and breads.

[0144] As described above, according to the second embodiment, accurate expansion detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally finished.

[0145] (Embodiment 3) <Overall structure> The microwave processing device according to the third embodiment of the present disclosure has the same configuration as the microwave processing device according to the first embodiment shown in Fig. 1. Therefore, in the third embodiment, the same or substantially the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0146] In the third embodiment, the control unit 7 detects the melting of the object 2 to be heated in the heating chamber 1 as a change in the state of the object 2 to be heated.

[0147] FIG. 13 is a diagram for explaining detection of a change in state of the object to be heated 2 in the third embodiment.

[0148] In Fig. 13, the horizontal axis represents the time (minutes) elapsed since the start of heating, and the vertical axis represents the calculated value RF obtained by referring to the reflected power stored in memory unit 8 (first memory unit of memory unit 8). The calculated value RF and threshold value TH are shown on the graph in Fig. 13. The units of the vertical and horizontal axes in Fig. 13 are the same as those in Fig. 5.

[0149] As shown in FIG. 13, when the calculated value RF obtained by referring to the reflected power exceeds the threshold value TH continuously for a predetermined time TMc, the control unit 7 determines that a change in the state of the object to be heated 2 has been detected.

[0150] This reduces the possibility of false detection and enables highly accurate detection in the following cases: For example, when the reflected power changes suddenly and significantly due to a cause other than a phenomenon in which the state of the heated object 2 changes continuously. This also includes cases in which the operation of the detection unit 6 is unstable.

[0151] A phenomenon other than a change in the state of the heated object 2 that causes a large instantaneous change in the reflected power is, for example, deformation of the wall surface of the heating chamber 1 caused by expansion due to a temperature rise. Deformation of the heated object 2, which has an unstable shape, is one such phenomenon.

[0152] In actual cooking, it is preferable to set the predetermined time TMc to 1 second or more, because it is unlikely that the above phenomenon will continue to occur for 1 second or more.

[0153] <Melting detection> Fig. 14 is a conceptual diagram showing detection of melting of the object to be heated 2 in embodiment 3. As shown in Fig. 14, the object to be heated 2 is deformed by melting.

[0154] This changes the dielectric constant of the entire object 2, and also changes the dielectric constant distribution in the object 2. This changes the frequency characteristics of the absorbed power. As a result, by calculating the change in the reflected power during heating of the object 2, it is possible to detect the melting of the object 2.

[0155] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, as well as the score calculated using the Change Finder method, and the rate and range of change of the reflected power per given time.The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.In general, when the heated object 2 melts, the dielectric constant increases.

[0156] The control unit 7 can change the heating conditions or terminate the heating by detecting the start and completion of melting of the object 2 to be heated. This prevents overheating or underheating, resulting in optimal cooking.

[0157] Examples of cooking using melt sensing are melting butter and chocolate.

[0158] <Demonstration experiment of melting detection> 15A to 15C are diagrams showing experimental results of melting detection in embodiment 3. Fig. 15A shows heating conditions in a demonstration experiment of melting detection for butter and chocolate.

[0159] 15B and 15C, the horizontal axis represents heating time (minutes) and the vertical axis represents the change finder score. Each graph in Fig. 15B and 15C shows the change finder score, threshold value TH, and the time when the object to be heated 2 started to melt.

[0160] Figure 15B shows the experimental results of melting detection for butter and chocolate under the Change Finder settings of "r" = 0.01, "smooth" = 5, and "threshold" = 1.5. As shown in Figure 15B, under these settings, melting detection for butter was successful, but melting detection for chocolate failed.

[0161] Figure 15C shows the experimental results of melting detection for butter and chocolate under the Change Finder settings of "r" = 0.02, "smooth" = 50, and "threshold" = 1.08. As shown in Figure 15C, under these settings, melting of butter and chocolate was successfully detected.

[0162] Depending on the setting conditions of the change finder, it is possible to detect a change in the state of the object to be heated 2 even if the weight and type of the object to be heated 2 differs.

[0163] The calculated score varies greatly depending on the setting conditions. Therefore, the storage unit 8 stores in advance setting conditions suitable for the type, weight, etc. of the object to be heated 2. The control unit 7 reads out and uses the optimal setting conditions from the storage unit 8 based on information such as the type and weight of the object to be heated 2 input by the user. This can improve the detection accuracy.

[0164] As described above, according to the third embodiment, accurate melting detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally completed.

[0165] (Fourth embodiment) <Overall structure> The microwave processing apparatus according to the fourth embodiment of the present disclosure has the same configuration as the microwave processing apparatus according to the first embodiment shown in Fig. 1. Therefore, in the fourth embodiment, the same or substantially the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted. In the fourth embodiment, the control unit 7 detects thawing of the object to be heated 2 as a change in the state of the object to be heated 2.

[0166] <Defrosting detection> Fig. 16 is a conceptual diagram showing detection of thawing of the object to be heated 2 in embodiment 4. As shown in Fig. 16, the object to be heated 2 is deformed by thawing.

[0167] This changes the dielectric constant of the entire object 2, and also changes the dielectric constant distribution in the object 2. This changes the frequency characteristics of the absorbed power. As a result, by calculating the change in the reflected power during heating of the object 2, it is possible to detect thawing of the object 2.

[0168] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, as well as the score calculated using the Change Finder method, and the rate and range of change of the reflected power per given time.The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.In general, the dielectric constant increases when the heated object 2 thaws.

[0169] The control unit 7 can change the heating conditions or terminate heating by detecting the start and completion of thawing of the object 2 to be heated. This makes it possible to prevent overheating or underheating. As a result, cooking can be optimally finished.

[0170] Examples of cooking that uses thawing detection include thawing frozen meat, frozen fish, frozen vegetables, and ice.

[0171] As described above, according to the fourth embodiment, accurate thawing detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally completed.

[0172] (Embodiment 5) The microwave processing apparatus according to the fifth embodiment of the present disclosure has the same configuration as the microwave processing apparatus according to the first embodiment shown in Fig. 1. Therefore, in the fifth embodiment, the same or substantially the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted. In the fifth embodiment, the control unit 7 detects the rupture of the object 2 to be heated as a change in the state of the object 2 to be heated.

[0173] <Burst detection> Fig. 17 is a conceptual diagram showing the detection of the rupture of the object 2 to be heated in the fifth embodiment. As shown in Fig. 17, the shape of the object 2 to be heated and the position of the object 2 to be heated in the heating chamber 1 change due to the rupture. These changes cause the frequency characteristics of the absorbed power to change. As a result, the rupture of the object 2 to be heated can be detected by calculating the amount of change in the reflected power during heating of the object 2 to be heated.

[0174] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, the score calculated by the Change Finder method, and the rate and range of change of the reflected power per given time. The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.

[0175] The control unit 7 can change the heating conditions or terminate heating by detecting the rupture of the object to be heated 2. This makes it possible to prevent overheating or underheating, resulting in optimal cooking.

[0176] An example of a cooking technique that uses pop detection is making popcorn.

[0177] As described above, according to the fifth embodiment, accurate burst detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally completed.

[0178] (Embodiment 6) The microwave processing apparatus according to the sixth embodiment of the present disclosure has the same configuration as the microwave processing apparatus according to the first embodiment shown in Fig. 1. Therefore, in the sixth embodiment, the same or substantially the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted. In the sixth embodiment, the control unit 7 detects the drying of the object 2 to be heated as a change in the state of the object 2 to be heated.

[0179] <Dryness detection> Fig. 18 is a conceptual diagram showing detection of dryness of the object to be heated 2 in embodiment 6. As shown in Fig. 18, the object to be heated 2 is deformed by drying.

[0180] This changes the dielectric constant of the entire object 2, and also changes the dielectric constant distribution in the object 2. This changes the frequency characteristics of the absorbed power. As a result, by calculating the change in the reflected power during heating of the object 2, it is possible to detect the drying of the object 2.

[0181] The value indicating the change in reflected power includes the standard deviation, variance, and coefficient of determination of the reflected power value per given time, as well as the score calculated using the Change Finder method, and the rate and range of change of the reflected power per given time.The value indicating the change in reflected power further includes the frequency-averaged reflected power value and the reflected power value for each frequency.In general, the dielectric constant decreases as the heated object 2 dries.

[0182] The control unit 7 can change the heating conditions or terminate heating by detecting the start and completion of drying of the object 2 to be heated. This makes it possible to prevent overheating or underheating. As a result, cooking can be optimally finished.

[0183] Examples of cooking applications using dryness detection include the creation of dried fruits, dried vegetables, and dried meats. Dryness detection can also be used to reduce excess moisture in food. Applications of dryness detection outside of cooking include the use of microwaves to dry wood, clothes, etc.

[0184] As described above, according to the sixth embodiment, accurate dryness detection is possible for objects 2 to be heated that differ in weight, shape, material, placement position, etc., and cooking can be optimally completed. [Industrial Applicability]

[0185] The microwave processing device according to the present disclosure can be applied to heating cookers that dielectrically heat food, as well as microwave heating devices for industrial use such as drying devices, heating devices for pottery, food waste disposal devices, semiconductor manufacturing devices, and chemical reaction devices. [Explanation of symbols]

[0186] 1 Heating chamber 2 Object to be heated 3 Microwave generator 4 Amplification section 5 Power supply unit 6. Detection unit 7 Control Unit 8 Memory section

Claims

1. a heating chamber configured to accommodate an object to be heated; a heating unit including a microwave generating unit configured to generate microwaves having any frequency within a predetermined frequency band; an amplifier configured to amplify an output level of the microwave; a power supply unit configured to radiate the microwaves amplified by the amplifier unit into the heating chamber as incident power; a detection unit configured to detect the incident power and reflected power returning from the heating chamber to the power supply unit, out of the incident power; a control unit that controls the microwave generating unit and the amplifying unit; a memory unit configured to store the values ​​of the reflected power and the incident power together with the frequency of the microwave and the elapsed time from the start of heating, The control unit stores a calculated value, which is the change in the reflected power or the value of the reflectivity obtained by calculation referring to the values ​​of the reflected power and the incident power, in the memory unit along with the elapsed time, determines a threshold based on the minimum value of the calculated value, updates the threshold when the minimum value of the calculated value is updated along with the elapsed time, and detects a change in the state of the heated object and controls the microwave generation unit when the calculated value exceeds the updated predetermined threshold.

2. A heating chamber configured to accommodate an object to be heated; a heating unit including a microwave generating unit configured to generate microwaves having any frequency within a predetermined frequency band; an amplifier configured to amplify an output level of the microwave; a power supply unit configured to radiate the microwaves amplified by the amplifier unit into the heating chamber as incident power; a detection unit configured to detect the incident power and reflected power returning from the heating chamber to the power supply unit, out of the incident power; a control unit that controls the microwave generating unit and the amplifying unit; a memory unit configured to store the values ​​of the reflected power and the incident power together with the frequency of the microwave and the elapsed time from the start of heating, The control unit stores a calculated value, which is the change in the reflected power or the value of the reflectivity obtained by calculation referring to the values ​​of the reflected power and the incident power, in the memory unit along with the elapsed time, and when the calculated value exceeds a threshold value that is greater than one time the minimum value of the calculated value and less than three times the minimum value of the calculated value, detects a change in the state of the object to be heated and controls the microwave generation unit.

3. The microwave processing apparatus according to claim 1 , wherein the control unit is configured to use, as the calculated value, an average value of the reflected power or reflectance calculated for each frequency of the microwave.

4. The control unit calculates the calculated value for each frequency of the microwave, The microwave processing apparatus according to claim 1 , wherein the control unit is configured to control the microwave generation unit when the calculated values ​​for the microwaves of two or more frequencies exceed the threshold value.

5. 5. The microwave processing apparatus according to claim 1, wherein the control unit is configured to obtain the calculated value using a change finder, which is an online change point detection method for time series data.

6. The memory unit is configured to store the value of the incident power together with the frequency and the elapsed time of the microwave, the control unit calculates, as the calculated value, a reflectance that is a ratio of a sum of the reflected power values ​​to a sum of the incident power values; The microwave processing apparatus according to claim 1 , wherein the control unit is configured to control the microwave generation unit based on the reflectance.

7. The microwave processing apparatus according to claim 1 or 2, wherein the control unit is configured not to control the microwave generation unit until a predetermined time has elapsed since the start of the heating even if the calculated value exceeds the threshold value.

8. The microwave processing apparatus according to claim 1 , wherein the control unit is configured to control the microwave generation unit when the calculated value exceeds the threshold value multiple times within a predetermined time period.

9. The microwave processing apparatus according to claim 1 , wherein the control unit is configured to control the microwave generation unit when the calculated value exceeds the threshold value continuously within a predetermined time.

10. 10. The microwave processing apparatus according to claim 1, wherein the control unit is configured to detect boiling of the object to be heated as a change in state of the object to be heated.

11. The microwave processing apparatus according to any one of claims 1 to 9, wherein the control unit is configured to detect expansion of the object to be heated as a change in state of the object to be heated.

12. 10. The microwave processing apparatus according to claim 1, wherein the control unit is configured to detect melting of the object to be heated as the change in state of the object to be heated.

13. The microwave processing apparatus according to any one of claims 1 to 9, wherein the control unit is configured to detect thawing of the object to be heated as a change in state of the object to be heated.

14. 10. The microwave processing apparatus according to claim 1, wherein the control unit is configured to detect a burst of the object to be heated as a change in state of the object to be heated.

15. 10. The microwave processing apparatus according to claim 1, wherein the control unit is configured to detect drying of the object to be heated as a change in state of the object to be heated.

16. The microwave processing apparatus according to any one of claims 10 to 15, wherein the control unit is configured to stop the heating after detecting the change in state of the object to be heated.

17. The microwave processing apparatus according to any one of claims 10 to 15, wherein the control unit is configured to change the heating conditions in the heating unit after detecting the change in state of the object to be heated.

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