JPH03216991A - Automatic heating device - Google Patents

Abstract

PURPOSE:To obtain an automatic heating device with high accuracy and reliability without a detection error due to various external thermal disturbance by providing a threshold value determining means which consecutively renews a threshold value after the start of heating and stops the renewal of the threshold value when the value increases or decreases by a predetermined amount from an initial threshold value. CONSTITUTION:A detected threshold value calculating means 19, based on a specified calculating formula, determines a detected threshold value upon receipt of a noise level measured by a noise level detecting means 18. An error deciding means 21 compares the detected threshold value calculated by the detected threshold value calculating means 19 with a first detected threshold value held by an initial detected threshold value holding means and, when an error is within a specified region, transmits the detected threshold value calculated by the calculating means 19 as it is to a detected threshold value holding means 22. In the case where the error exceeds the specified allowable region, on the other hand, the deciding means 21 transmits a detection stop command signal to the noise level detecting means 18 so as to stop the noise level detection thereafter and stops transmission of the detected threshold value to the detected threshold value holding means 22 while stopping its own function. An accurate detection of a vapor signal is performed without influence of external thermal disturbance from ambient heat sources so as to realize an optimum heating state.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is 7lOM: detects the heating state of the food by detecting the steam or hot gas generated from the food inside, and ends the heating process in the optimum 7JOs state. This invention relates to an automatic heating device.

Conventional technology Conventionally, an atmosphere sensor has been used to detect the progress of cooking by detecting the hot air of steam or gas generated from the negative product as the food is heated. Many I71D thermal devices have been devised. For example, patent application ¥1-9940
9 is an example of an automatic η mouth heating system that guides high-temperature gas such as water vapor or gas generated from a product to a pyroelectric element and detects the completion (progress) of heating by changes in the voltage generated in the pyroelectric element. A signal detection method in an automatic heating system using this pyroelectric element is also patented qZ 1-9 9 4 0
7, it is devised more specifically. A conventional example will be explained below based on FIG.

FIG. 6 shows the time course of the voltage (detection signal) generated by the pyroelectric element as heating progresses. (1) Representative value Dm at a predetermined time (T.~τ2) after heating starts as shown in the figure
(for example, a large value, an average value, etc.), and consider that value as the signal level in a static state where no steam has arrived, and its representative value D. A detection threshold value Dli is calculated as a function of .

Thereafter, it is determined based on a predetermined judgment rule that steam has been generated and that the gold detection signal has exceeded the threshold value D1 (steam is detected in one hour. At that point, heating is terminated or after a predetermined additional heating is performed. Whether it ends depends on the nature of the food.

Problems to be Solved by the InventionThe specific configuration of this system is disclosed in Japanese Patent Application No. 19940/1994.
9. In general, microwave ovens are equipped with power components with poor power conversion efficiency, such as a magnetron that is a microwave generating means and a high voltage transformer that generates high voltage 'iILEE for driving the magnetron, so sufficient cooling using a cooling fan or the like is required. Using the pressure of this cooling air, the steam generated from the food in the open storage is guided to the pyroelectric element, which detects a signal. Therefore,
As heating progresses, heat such as the temperature rise of power components and induction loss on the walls of the heating chamber is led to the sensor along with the hot air of the food.

In the case of a short heating time as shown in FIG. 6(a), such heat other than steam does not have an adverse effect on the detection performance. However, when cooking requires a long heating time, such as defrosting frozen food and then reheating it,
As the time from the start of cooking to the detection of the steam signal becomes longer, the effects of heat other than steam become more serious.

FIG. 6(t)) 1 is a specific example. Normally, it should be detected at time tl1' at threshold @D1' (dotted chain line Repe/I/), but it was detected at td because the signal level in a static state increases due to hot air other than steam from food. It ends up. This clearly caused a problem in that the cooking was completed before reaching a sufficient heating state due to false detection.

Similar problems also occur during continuous use.

At the end of the first cooking, the temperature inside the machine room of the set has risen considerably and the cooling fan stops. As a result, the temperature of the atmosphere of the power components rises transiently, and when cooking continues in this state, the accumulated hot air is guided to the sensor, and the detection signal is high immediately after the start, after which the cooling fan cools down the power components and the atmosphere. As a result, a phenomenon occurs in which the detection signal, that is, the signal level in a static state gradually decreases. Therefore, the point that should normally be detected using the dashed-dotted line D1' is the representative value n detected during the period T1 to T2 when the detection signal level is high. There is also the problem that overheating occurs because the steam signal is detected and terminated at the threshold value Di calculated from .

Furthermore, although composite heating conditioners that are also equipped with a heat source other than microwave heating, such as a heater, have been commercialized, even in these devices, the temperature inside the refrigerator is high immediately after heating with the heater. When using the automatic heating function (
0) As shown in the figure, it is easy to imagine that the detection level in the static state will gradually decrease and false detection will occur.

Therefore, the present invention is an automatic boosting device using an atmosphere sensor that detects hot water vapor and gas generated from food, which accurately detects steam signals without being affected by thermal disturbances from surrounding heat sources and optimizes heating. This is to realize termination in the state.

Means for Solving the Problems Therefore, the automatic heating device of the present invention includes an atmosphere sensor that detects hot water vapor or gas generated from an object to be heated, a signal detection means that detects a signal from the atmosphere sensor, and a signal detection means. a threshold determining means for determining a predetermined threshold based on the result of monitoring the signal for a certain period of time; and a control means for detecting the occurrence of the
The threshold value determination means is configured to update the threshold value successively from the start of heating, and stop updating the threshold value when the threshold value increases or decreases by a certain amount from the initial threshold value.

Effects The automatic heating device according to the present invention with the above structure has the following effects.

By continuously updating the threshold value, it is possible to determine the optimal threshold value in response to changes in the signal level in static conditions due to heat from heat sources other than food, vapor from food, Erroneous detection will no longer occur due to fluctuations in signals other than heat caused by gas.

In addition, when the determined threshold value increases or decreases by a certain amount from the initially determined threshold value, updating of the threshold value is stopped, so the increase in signal level due to the original food vapor is statically suppressed. To provide a highly reliable automatic heating device that does not erroneously update a threshold value based on a determination that the signal level has increased in the current state.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. FIG. 3 is a sectional view of essential parts showing the configuration of an automatic heating device according to an embodiment of the present invention, and FIG. 4 is a block diagram showing the basic circuit configuration of the detection system portion thereof.

In FIG. 2, a heated object 3 placed in a heating chamber 1 is dielectrically heated by a magnetron 4. In FIG. The FlO heated object 3 is heated while being rotated by the rotary mounting table 2 in order to improve uneven heating caused by non-uniform electric field strength within the heating chamber 1 .

When the heated object 3 is heated separately and the water content reaches near the boiling point, a lot of high-temperature steam is generated, and this steam is 7111
It rises toward the vent 6 provided in the ceiling of the heat chamber 7. Furthermore, the wind taken in from the set intake port 8 by the cooling fan 7-1L and propeller 7-b provided for cooling power components such as the magnetron 4 enters the heating chamber 1 through the internal intake port 6. Steam generated from the heated object 3 due to wind pressure is discharged to the vent 6. Furthermore, the steam that hits the pyroelectric element 1o condenses on the surface of the pyroelectric element 10 and gives the pyroelectric element 1o a large amount of thermal energy mainly consisting of latent heat, so the temperature of the pyroelectric element 1o increases and the pyroelectric A king arises. At this time, the steam generated from the heated object 3 moves while fluctuating in the air, which is cooler than the steam.
The amount of vapor hitting the pyroelectric element 10 also fluctuates temporally and spatially. Therefore, even if the heated object 3 reaches a certain temperature or higher and steam is generated steadily, the pyroelectric element 1
0 means that at one moment, a large amount of steam causes the temperature to rise, but in the next moment, a small amount of steam hits the object, causing the temperature to drop, and in the next moment, a large amount of steam hits the object again, raising the temperature. While steam continues to be emitted from 411, irregular alternating current electricity EE continues to be generated in response to the temperature fluctuations described above.

FIG. 6 shows the state of electric power generated in this way from the pyroelectric element 10. When the heating time reaches a certain time, a large amplitude AC voltage is generated between the pyroelectric element 10 due to steam from the heated object. (Several 1Qm▼) continues to occur.

Next, in the electronic circuit shown in FIG. 4, the voltage generated in the pyroelectric element 1o is transferred to the DC (direct current) cut circuit 11, L. P. F (low bass filter) 12r then amplifier (amplification circuit) 13
After being amplified by the amplifier circuit, it is read by the microcomputer 14. The pyroelectric element 1o has a high impedance of 1MΩ.
A resistor 16 of about 0.06μ and a capacitor 16 of about 0.06μ
We are attempting to alleviate this by combining these in parallel. Also, microcontroller 14
is controlled by sending control signals to the magnetron 4, cooling fan 7, etc.

Now, when the user sends a heating command to the automatic heating device to reheat the food, the microcomputer 14 receives the command and sends an operation signal to the magnetron 4 and the cooling fan 7 to start heating the object to be heated 3. As the heating progresses, steam is generated from the object to be heated 3, and the high-temperature steam is guided to the pyroelectric element 1o to generate a voltage according to the principle described above. By detecting this, the microcomputer 14 detects that the object to be heated 3 has been sufficiently heated, and ends the heating at that point, or performs predetermined additional heating since the heating may not be sufficient depending on the food. to finish cooking.

Next, a description will be given of how the microcomputer 14 determines that steam has been generated, that is, the detection sequence.

FIG. 1 is a block diagram showing the internal configuration of the microcomputer 14. As shown in FIG.

The data measuring means 1T measures the analog input signal from the seven sensors. For example, it is composed of an A/D converter, etc., and continuously measures data at predetermined time intervals to. time interval t
o is approximately several tens of microseconds.

The noise level detection means 18 receives the signal from the data measurement means 17, and detects the noise level /l/ which is a representative value such as an average value or a local maximum value within a predetermined time period, that is, the i level in a static state where no steam signal has arrived. Measure.

This predetermined time period is set to a value of about several seconds to several t seconds, and the measurement is continuously repeated until a stop command signal is received from the error determining means 21, which will be described later.

The detection threshold calculation means 19 is the noise level detection means 18
The detection threshold value is determined based on a predetermined calculation rule based on the measured noise level. It is obvious that the detection threshold value must be set to a high value with sufficient margin for the noise level. For example, as an example of a concrete operation rule, Di = aDm } b (a- b is a constant) -・- ・- ・- (1), or it can be further expanded with a higher-order expression of Dm. .

The initial detection threshold holding means 20 holds the entire detection threshold of the first measurement. The error determination means 21 compares the detection threshold calculated by the detection threshold calculation means 19 with the first detection threshold held by the initial detection threshold holding means, and If the error of the first detection threshold is within a predetermined range, the detection threshold calculated by the detection threshold calculation hand 19 is sent as is to the detection threshold holding means 22. . On the other hand, if the error deviates from a predetermined tolerance range, a detection stop command signal is sent to the noise level detection means to stop subsequent noise level detection, and
The transmission of the detection threshold value to the detection threshold holding stage 22 is also stopped and its own function is stopped. For example, the limit value α for which the error is positive,
Different limit values may be provided as the negative limit value β.

The detection threshold holding means 22 stores and holds the detection threshold, and the detection judgment means 23 compares the held detection threshold with the instantaneous data measured by the data measuring means 17, and compares the held detection threshold with the instantaneous data measured by the data measuring means 17, according to a predetermined judgment rule. It is recognized that the signal clearly exceeds the detection threshold and informs the power control means 24 that vapor has been detected. As an example of the predetermined judgment rule here, it is assumed that the instantaneous data exceeds the detection threshold value n times, and the n times are the number of times suitable for vapor detection.

The power control means 24 sends a heating control signal to the magnetron 4, and immediately stops or performs a slight additional overheating to complete the heating Mk.

FIG. 2 shows the waveform of the sensor signal input to the microphone. In order to match the voltage level of the microcomputer, the sensor output shown in FIG. 6 is DC-cut and has a waveform similar to f-wave rectification. (&) The figure shows a signal for a very common reheating case. When heating starts and the signal reaches 1 at a predetermined time, the microcomputer 14 reads the signal, repeats measurement at regular intervals until time T2, and calculates the maximum value measured during that time period (TIT2). Representative value Dm
1, and determine the threshold value Di from equation (1). Therefore, the blasphemy threshold D corresponding to 7 is level A/Dull
l+ is determined, and vapor detection is performed based on it in the next time period (r2 to T5). In the time period (T2 to T5), measurements are made continuously at time intervals to as in the previous time period, and at the same time, the maximum value DI12e, which is the noise level, is searched, and at the same time, the measured data is detected at the detection threshold value Dl. The number of times exceeding i is counted, and when a predetermined number of times n is reached, it is determined that a steam signal has been detected.

If there is no vapor detection in a time period (T2~Ts), the detection level Dl2 in the next busy time period is determined by the noise level IvDm2i determined by the noise level search that is running simultaneously in that time period (1
) is determined based on the formula. Thereafter, while updating the noise level and detection threshold in this manner, vapor detection is reached at time td.

The detection level Dl2 at the time limit is determined based on equation (1). Thereafter, while updating the detection threshold in this manner, vapor detection is reached at the td time.

Next, cooking that requires a long time to be detected, such as thawing and warming frozen food, or curry. It has been found that in the case of cooking stew or the like, the noise level before steam detection tends to gradually increase, as shown in Figure (b). This is because hot air is led to the pyroelectric element 1o due to the influence of heat other than the steam from the food, such as heat generated by power components in the machine room or heat due to induction heating generated on the wall inside the oven. In the conventional method of determining the detection level based on the noise level obtained during the initial stage of heating, there were cases where an increase in the noise level due to thermal disturbances could be mistaken for a steam signal, resulting in false detection. , the detection method of the present invention can avoid such problems.

('b) In the figure, DI+. Dl2, Di,5...
..., the detection threshold value rises as the noise level increases, and vapor detection becomes possible at the optimum detection threshold value determined from the noise level immediately before the vapor signal is generated.

Here, the update of the detection threshold value is stopped when Di6i increases by a predetermined update limit value α from the detection level D11 that was initially set, and thereafter, vapor detection is performed using the detection threshold value of Dl5i that was set just before that. Accurate detection thresholds determined by pre-arrival noise levels enable td time vapor detection. Of course, from that point on, the search for the noise level ends.

In addition, by setting the update limit value α in the appropriate increasing direction, an increase in the signal level due to steam is erroneously updated as an increase in the noise level, and a high detection threshold value is all set, resulting in a detection delay. This problem no longer occurs, and highly reliable detection performance can be achieved.

Next, an example of detection during continuous cooking is shown in Figure Cl.As a characteristic of continuous use, due to the influence of the heat remaining in the machine room from the previous use or the heat remaining in the refrigerator,
There is a phenomenon in which the noise level becomes rather high at the beginning of the next use, and then gradually decreases as the vicinity of the pyroelectric element 1o is cooled by the outside air sucked in by the cooling fan. Even in such a situation, according to the detection method of the present invention, since the detection threshold value is updated, detection can be performed at a low noise level Dm1 before the arrival of steam, and steam can be detected accurately at time td.

It is obvious that if steam detection is performed at the first detection threshold value D11 after the start of cooking, the detection time will be delayed and excess Va heat will occur.

Here, as in the example shown in FIG. 3(b), the detection threshold value Di. The updating of the detection threshold value is completed when the detection threshold value Dl5i decreases by more than the update limit value β.

As a result, the increase in the signal level due to the steam signal is reflected in the increase in the noise level and the false detection threshold is updated, and the problem of overheating due to delayed detection as a result of steam detection performed with a high detection threshold occurs. I won't.

In this embodiment, the limit value α. Although β is implemented based on an increase/decrease in the detection threshold, it may also be defined based on an increase/decrease in the noise level.

Effects of the Invention As described above, the automatic heating device of the present invention can provide the following effects.

In other words, since signals are detected continuously, the signal level (noise level) in a static state is updated, and the optimal detection threshold is determined accordingly, the heat generated from power components in the machine room can be reduced. False detections may occur due to thermal disturbances other than the heat of steam emitted from the target cooking object, such as heat due to dielectric heating of the metal heating chamber wall, or residual heat from continuous use. It disappears.

In addition, when updating the detection threshold, there is a limit on the desire to change from the initial threshold, so there is a possibility that the detection level may be set high due to the fact that the original food vapor is mistakenly regarded as an increase in the noise level. It is possible to provide an automatic heating device with higher precision and reliability.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the control system of an automatic heating device according to an embodiment of the present invention, Fig. 2 is an output waveform diagram showing the steam detection method of the device, Fig. 3 is a sectional view of the device, and Fig. 4 FIG. 6 is a block diagram showing the configuration of the detection circuit of the same device, FIG. 6 is an output waveform diagram of a pyroelectric element, and FIG. 6 is an output waveform diagram showing a steam detection method of a conventional automatic 7JO thermal device. 1... Heating chamber, 4... Magnetron, 1
o...Pyroelectric sensor, 14...Microcomputer, 17...Data measurement means, 18...Noise level detection means, 19.
...Detection threshold calculation means, 2o...Initial detection threshold holding means, 21...Error judgment means, 22...Detection threshold holding means Means, 23...
. . . Detection determination means, 24 . . . Power control means. Names and names of the bureau chief, Shigetaka Awano, and one other person No. 1 Figure 24 Ilifu 3 Figure 1 -11 Ka - 1 3 --- Ne Ka 1 - 10 Sodenkazu 4 Zunenkyo 6 Kuchi D7 -- − Noi Prebel DJ −−Ichika 匍し'! 11
1lcノ

Claims (1)

[Claims] a heating chamber, a microwave generating means coupled to the heating chamber for dielectrically heating an object to be heated, an atmosphere sensor for detecting hot air of water vapor or gas generated from the object to be heated, and detecting a signal from the atmosphere sensor. a signal detecting means, a threshold determining means for determining a predetermined threshold based on the result of monitoring the signal of the signal detecting means for a certain period, and a signal level of the signal detecting means exceeding the threshold; control means for detecting that the threshold value has been reached and controlling the supply of power to the microwave generating means, and the threshold value determining means continuously updating the threshold value from the start of heating, An automatic heating device configured to stop updating the threshold value when the threshold value determined at the start of heating increases or decreases by a certain amount.