JPH03216990A - automatic heating device - Google Patents

Abstract

PURPOSE:To realize optimum additional heating for various kinds of foods and quantity and to reduce cooking time by a single key operation by providing a sensor for analoguose detecting of the vapor or gas quantity generated from a heated object or the quantity of heat thereof and a control means to control electric power supply to a heating means based on detected signal of the sensor. CONSTITUTION:A control part 5 to control electric power supply to a heating means 9 and a sensor 10 to detect vapor and various kinds of gas generated from a heated object 7 are provided. The control part 5 switches an output of the heating means 9 to a low value when a signal of the sensor 10 reaches a first detection threshold value, determines a second detection threshold value after a specified mask time of the sensor signal, and continues heating at the low output until the sensor signal reaches that value. According to this constitution, an automatic heating device with excellent operability possible to complete heating at an optimum heating state is obtained and cooking is finished efficiently within a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control system for optimally heating an object to be heated in an automatic heating apparatus such as an automatic microwave oven equipped with a sensor and capable of automatic cooking.

Conventional technology The automatic heating device described in Japanese Patent Application Laid-Open No. 62-271 3s3g combines the automatic heating of pre-cooked foods and vegetable preparations, which tend to cause uneven heating, and the automatic heating of general reheated foods using a single key. This realizes automatic heating that is easy to use.

FIG. 8 is a time chart showing this conventional example. This automatic heating device consists of a sensor that detects steam or gas generated from food, a counter that counts the time T until the sensor signal reaches a certain detection threshold, and the amount of change over time in the sensor's detected value. and a control means for controlling the heating means. In the same figure, time H, when the sensor detection value changes by Δh, is defined as the steam generation point, time H2, when the sensor signal changes by a, is defined as the steam detection point, and the time required from the heating start point to H2 is defined as T, Let it be the detection time. Until time H, the maximum heating output is set as P, and at time H, the heating 1 output is switched to a low output P2 intermittently. Then, the rise time t of H, -H2 time is counted by the monitor means, and the slope t of this rise time t and the detection time T
/Calculate the cooking variable k according to T11. After time H2, additional heating is performed at low output P3 for a time determined by multiplication K of kT.

As a result, the K value is automatically increased for foods that require additional heating, so the optimal K value is set regardless of the variety of foods or differences in quantity, and automatic cooking can be consolidated into one key. becomes possible. Furthermore, since the aforementioned gradient t/T is determined using a low output, the dynamic range of this gradient value becomes large, reducing the probability of a judgment error by the monitoring means.

Problems to be Solved by the Invention However, in such conventional automatic heating systems, the output must be lowered to a low level at an early stage in the heating process. Also, the more accurately you try to find the cooking constant k related to additional heating, the lower the P2 output or the larger the a value, increasing the time t and increasing the slope value t/T1 in a larger range. need to exist. For these reasons, it was inevitable that the cooking time would be extended.

Furthermore, as shown in FIG. 8, the sensor of the present invention must have the ability to capture the amount of steam generated at each point in an analog manner, and only then can the gradient value (steam rate of change) be captured. However, with respect to a sensor that is relatively digital, that is, has only the ability to determine whether or not steam has arrived at the sensor, the control method has to be extremely complex and delicate.

For example, an atmosphere sensor using a pyroelectric element described in Japanese Patent Application No. 1-99409 generates an alternating current voltage due to the pyroelectric effect by receiving the heat of steam or gas generated from food. It only has the ability to digitally judge the presence or absence of steam, and does not have the ability to detect subtle changes in the amount of steam. For example, the timing chart when this pyroelectric element is applied to a conventional control system is #c
It is shown in Figure 9. It can be seen that it is extremely difficult to detect differences in the amount of steam, etc., as the signal synchronized with the ON/OFF of heating repeatedly appears and disappears.

Therefore, the present invention provides an automatic heating device equipped with a sensor capable of detecting the amount of steam or gas generated from food.
The primary objective is to achieve optimal additional heating for various foods and quantities with a single key, and to shorten cooking time.

The second purpose is to realize the same one-key aggregation function even with simple sensors that cannot capture the amount of steam generated from food in an analog way, that is, to digitally capture the presence or absence of steam. It is.

Means for Solving the Problems Therefore, in order to achieve the first object, the automatic heating device of the present invention detects in an analog manner the amount of steam or gas generated from the object to be heated, or the amount of heat they have. and a control means that detects a signal from the sensor and controls the supply of electric power to the heating means.

In addition, in order to achieve the second object, the automatic heating device of the present invention includes a sensor that digitally detects the arrival of steam, gas, or heat generated from an object to be heated, and a sensor that digitally detects the arrival of steam or gas generated from an object to be heated. The device is equipped with a heating means that can continuously output and vary the electric power, and a control means that detects a signal from a sensor and controls the supply of electric power to the heating means.

Function: The automatic heating device of the present invention switches the output of the heating means to a low output after the sensor signal reaches the first detection threshold, and after a predetermined sensor signal masking time, the second detection threshold is reached. A value is set and heating is continued at low output until the sensor signal reaches that value, and heating is performed at once at high output without using low output until the first detection. For foods that do not require additional heating, that is, foods that are sufficiently warmed to the inside, steam continues to be emitted even after the output is reduced, and the second detection threshold is immediately reached and cooking ends, so the cooking time is shortened. On the other hand, for food that requires additional heating, that is, food that is only partially warmed, the signal level will drop significantly due to the reduction in output, and the predetermined additional heating will continue until the signal level reaches the second detection threshold again. Finish cooking in the optimum heating state.

In addition, by making the heating means continuously low output, there is no repeated generation and disappearance of a signal that is synchronized with the ON/OFF of heating during intermittent low output, and the signal level is averaged by the second detection. A similar aggregation function can be achieved with a less powerful simple sensor that can be lowered below a threshold and only digitally detect the occurrence of vapor or gas.

EXAMPLE Hereinafter, an automatic heating device showing an example of the present invention will be explained with reference to the drawings.

As shown in FIG. 4, the automatic heating device according to the present invention includes a main body 1 that includes a heating chamber, a door body 2 that can open and close the opening of the heating chamber, and an operation panel 3 that inputs various commands. It consists of a cooking key 4 arranged on top of this.

FIG. 6 is a block diagram showing one embodiment of such an automatic heating device. Commands input from the cooking keys on the operation panel 3 are decoded by the control unit 6.

The control unit 6 then starts heating the object 7 placed in the heating chamber 6 . Heating is performed by supplying power to a magnetron, which is a heating means 9, through a driver 8.

The sensor 1o is realized by a humidity sensor, a gas sensor, or a pyroelectric element that detects the heat of steam or gas.
The point in time when cooking has progressed is detected by reacting to the steam or gas discharged by the fan 11, or the heat thereof. 12 is an exhaust guide, and 13 is a detection circuit for the signal of the sensor 1o.

The mounting plate 14 is rotationally driven by a motor 15, and uneven heating of the object 7 to be heated is improved.

Next, a description will be given of how the control unit 6 determines that steam has been generated, that is, the detection sequence. FIG. 1 is a block diagram showing the internal configuration of the control section 5. As shown in FIG.

Data measuring means 34 measures analog input signals from the sensors. For example, it is composed of an A/D converter and repeats measurements at predetermined time intervals. For example, it may be on the order of several m crowns.

The noise level detection means 36 receives the signal from the data measurement means 34 and detects a representative value such as an average value or a local maximum value within a predetermined time period, that is, a no-signal level (which is a signal level in a static state where no steam (humidity) is generated). noise level). This predetermined time period ranges from several seconds to several tens of seconds, and it is appropriate to start the measurement several seconds after the start of cooking. That is, it is obvious that the heating should be carried out at an earlier stage than when steam is generated when heating the minimum specified food.

The first detection threshold calculation means 36 and the second detection threshold calculation means 37 calculate the first detection threshold and the determining a second detection threshold; 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 specific calculation rule, DI=aDm+b (a, b are constants)...
...(1) may be used, or it may be further expanded using a higher-order equation of Dm. The detection threshold value obtained by such calculation is transferred to the detection threshold holding means 38 and held therein.

The detection judgment means 39 successively compares the held first detection threshold with the instantaneous data measured by the data measurement means 34, and determines that the signal clearly exceeds the detection threshold according to a predetermined judgment rule. When this is recognized, an output reduction command is sent to the power control means 29. One side of the predetermined judgment rule here is that the instantaneous data exceeds the detection threshold value n times, and the n times are defined as the number of times that clearly indicates humidity detection rather than noise false detection.

Furthermore, the detection determination means 39 sends a threshold switching command to the detection threshold holding means 38, then selects the second detection threshold, and executes humidity detection again after a predetermined waiting time. In this case, humidity is detected using the same judgment rule as in the first detection, and when detected, an output stop signal is sent to the power control means 38.

Now, FIG. 2 shows sensor signals and output waveforms when the present heating control method having the configuration shown above is specifically applied to cooking.

Items in parentheses (.) refer to frozen rice among general reheated foods and cooked frozen foods. Sensor output (steam volume,
Fig. 4 is a timing chart of humidity) and heating pattern. 03) is the same timing chart for foods that are relatively prone to uneven ripening when heated by radio waves, such as frozen meat balls and frozen curry among cooked frozen foods.

Now, let me explain about (.). When heating is started, the microwave output is first heated at full power P. Then, when the first detection threshold α is reached at time H, the output is reduced to a low output P2. The food shown here is actually fully heated almost to the inside at this point. Therefore, it has been confirmed that steam continues to come out even if the output is reduced to P2 because steam is emanating from everywhere exposed to the outside. Of course, it is obvious that the P2 output has a limited value.

After that, after a predetermined waiting time, the detection threshold is reset to the second detection threshold a2 and vapor detection is performed.H2
Since the detection threshold value α2 is immediately reached at this point, if heating is stopped at that point, an extremely good heating state will be achieved. The waiting time here is the time required for the steam released at the time of P2 output to escape out of the main body, and is approximately 3 to 4 seconds. Of course, this is not the case if the exhaust capacity of the fan 11 is extremely low.

Here, it takes only about 10 seconds from the output reduction to the end, and the heating time is also extremely short, indicating that the most efficient heating has been carried out for these foods.

Next, (b) will be explained. The process from time H1 to the subsequent waiting time is the same as the example in (.). Then for these foods the output is P2
As a result, the amount of steam released decreases. Of course, this phenomenon is a problem that occurs because these foods are only partially heated. In other words, by reducing the output, the thermal equilibrium state at high output is disrupted, and not only locally heated parts cannot maintain a high temperature state, but also heat flows to unheated parts according to the temperature gradient. There is a rapid transition from a state in which steam is emitted to an equilibrium state at low output, that is, a state in which almost no steam is emitted.

Then, after the predetermined additional heating time has passed, the signal level becomes H2.
At this point, the second detection threshold value α2 is reached and the heating ends.

During these hours H, -H2, local overheating is suppressed and heat conduction from the high temperature area to the low temperature area also works, progressing to a uniform heating state.

Here, the intermittent heating method is used, and the average output is reduced by changing the ratio of operating time and resting time, but the driver 8 is already capable of continuous low output control, which is well known in microwave ovens. By having an inbar evening ceremony,
There is no problem even if the output is continuously low.

In this way, it is possible to automatically terminate the heating in the shortest heating time with the optimum heating pattern depending on the various foods that are undergoing different heating progress.

For example, in JP-A No. 82-27139, which is a conventional example, 240 g of frozen meatballs are heated at low power for nearly 60% of the total cooking time. On the other hand, in this method, the low output ratio is reduced to about 30%, so the time can be dramatically reduced. The same can be said of other conventional examples of frozen curry, frozen rice soup, and frozen shumai.

In addition, in the conventional example, during the heating pause in intermittent heating, the heat from the high temperature area moves to the low temperature area and heating unevenness is eliminated. It is a physical phenomenon that can occur if it exists, and it is not considered that intermittent heating directly eliminates heating unevenness. Therefore, it should be emphasized that in this method, performing heating at high output until the first detection time point (H1 time point) only shortens the heating time and does not lead to any increase in uneven heating.

Furthermore, in order to further shorten the heating time, the time taken to reach the first detection threshold is T1, and if T1 is less than a predetermined short time, the food is considered to be a cooked frozen food and the output is shifted to low output P2. Stop and finish cooking. Even if it is a cooked frozen food, it is known that there is no need for additional heating for food with a small load that generates steam in such a short time because the radio waves penetrate deep into the food and heat it evenly. There is. In this way, it becomes possible to further shorten the cooking time.

Next, FIG. 3 is a timing chart of the sensor output and heating pattern in an embodiment in which a pyroelectric element as disclosed in Japanese Patent Application No. 1-99409 is used as the sensor 10.

The steam or gas that hits the pyroelectric element 1o condenses on the surface of the pyroelectric element 10 and gives the pyroelectric element 10 a large amount of thermal energy mainly consisting of latent heat, so the temperature of the pyroelectric element 10 increases. Pyroelectric voltage is generated. Pyroelectric elements from food 10
Since the heat arriving at the pyroelectric element 10 has temporal fluctuations, the voltage generated from the pyroelectric element 10 also becomes an irregular alternating current voltage.

However, the drawback of this pyroelectric element 10 is that it is inferior in its ability to quantitatively capture the heat of the steam or gas, so it is possible to detect whether steam has arrived or not in a manner similar to a binary judgment. It is.

This problem is not limited to the pyroelectric element shown here, but is a problem that inevitably arises when a sensor with large variations in characteristics is used for such purposes, and the resolution must become coarse.

(.) is a food that is less likely to be heated unevenly, and (b) is a food that is more likely to be heated unevenly. This is the same as the explanation in FIG.

First, (-) will be explained. Initially, heating is performed with high power P1 output and the first detection threshold value a is reached, and a detection search for steam is performed at H, at which point the signal level reaches the first detection threshold value α,
It is determined that this has been reached and the output is reduced to a continuous low output P2.

However, steam continues to come out from food that has been sufficiently heated to the inside, and when a search for steam detection is performed using the second detection threshold a2 after a predetermined waiting time, it is immediately detected at time H2, and heating ends. do.

Next, (b) will be explained. At time H1, the output is reduced to P2, and after a predetermined waiting time, a search for vapor detection is performed using the second detection threshold. At that point, the food is only locally heated and the vapor signal disappears or falls below the second detection threshold. Thereafter, additional heating is extended until time H2, and heating ends in the optimal heating state.

This is possible because the output is continuously low, and when the full power is intermittent to reduce the output, a signal synchronized with the energization and deactivation as shown in Figure 9 appears, extending the additional heating time. It is impossible to do so.

FIG. 6 shows an embodiment of a magnetron drive device that enables continuous low output. In the figure, a commercial power supply 16, a diode bridge 16, an inductor 17 and a capacitor 18
A good filter circuit constitutes the power supply section 19,
Capacitor 21, step-up transformer 22, transistor 23
, diode 24, capacitor 26, diode 26, magnetron 9, and power converter 28. The power conversion m28 includes an inverter made up of a capacitor 21, a step-up transformer 22, a transistor 23, and a diode 24, a high-voltage rectifier circuit made up of a capacitor 25 and a diode 26 that rectifies the output of the step-up transformer 17, and a magnetron 9 that generates high-frequency power. This magnetron 9 radiates high frequency power into the heating chamber as electromagnetic wave energy.

The transistor 23 is controlled by the power control unit 29, for example, from 20 to
It performs a switching operation when given a switching control signal of 200 KHz. Therefore, the primary winding of the step-up transformer #
A high frequency voltage is generated at 12o, and this high frequency voltage is stepped up and supplied to the magnetron 9, causing the magnetron 9 to oscillate. A signal proportional to the input current is sent to the power control unit 29 from the input current detector 3o. This input current detection signal is sent to the operational amplifier 31 in the power control section 29 as shown in FIG. It is configured as follows. Therefore, the conduction time of the transistor 23 is controlled, and the input current is controlled to a predetermined value by so-called pulse width control. As a result, the electromagnetic wave (radio wave) output of the magnetron 9 is controlled to be constant at a predetermined value. The reference voltage generation circuit 32 is configured with a D/A converter or an F/V converter, and can easily vary the power using a power control signal such as a digital signal or a frequency signal sent from the control section 6. The control section 5 can have a much simpler structure if it is composed of a microcomputer.

Effects of the invention As described above, in the automatic heating device of claim 1, the first
After the sensor signal reaches the detection threshold, the output of the heating means is switched to low output, and after a predetermined masking time of the sensor signal, a second detection threshold is set, and the output is kept low until the sensor signal reaches it. This configuration continues heating at 100°C, and the following effects can be achieved.

(1) For reheating food of various types and in different quantities, such as general reheating and reheating of cooked frozen foods that tend to heat unevenly, heat the food in the optimal heating state using a German key. To provide an automatic heating device that is easy to use and can be turned off.

@) It heats at high output all at once until steam is detected, and there is almost no low output period that is wasted during heating progress, which determines the additional heating time in conventional methods, making it possible to finish cooking efficiently and in a short time. becomes.

Furthermore, in the automatic heating device of claim 2, by configuring the heating means so that it can be set to a continuous low output, additional heating is necessary even with a simple sensor that can only judge the presence or absence of steam in a binary manner. In the case of food products, it is possible to reduce the signal level after low output switching to below the second detection threshold, and it is possible to obtain a function equivalent to the aggregation function shown in claim 1.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a heating control unit of an automatic heating device in an embodiment of the present invention, Fig. 2 is a timing chart of the control unit, and Fig. 3 is a control unit when a pyroelectric element is used as a sensor. FIG. 4 is a perspective view of the heating device, FIG. 6 is a block diagram showing the configuration of the heating device, FIG. 6 is a circuit diagram of the driver of the heating means in the heating device, and FIG. 7 is the same. A detailed circuit diagram of the main parts of the driver circuit, FIG. 8 is a timing chart in the control section of a conventional automatic heating device, and FIG. 9 is a timing chart in the control section when a pyroelectric element is used as a sensor in the conventional example. It is. 5...control unit, 8...heating chamber, a...
... Heated object, 9 ... Magnetron, 1o
......Sensor, 34...Data measuring means, 35...Noise level detection means, 36...
...first detection threshold calculation means, 37...
2nd detection threshold calculation means, 38... detection threshold holding means, 39... detection determination means.

Claims (3)

[Claims] (1) A heating chamber that stores an object to be heated, a heating means coupled to the heating chamber, a control unit that controls power supply to the heating means, and detects steam and various gases generated from the object to be heated. The control unit has a first detection threshold and a second detection threshold for a signal from the sensor, and the control unit has a first detection threshold and a second detection threshold for a signal from the sensor, and after heating starts, the signal from the sensor reaches the first detection threshold. an automatic heating device which changes the output of the heating means to a low level substantially synchronously with the reaching of the second threshold value and continues heating until the signal of the sensor reaches a second threshold value after the desired measurement mask time; (2) A heating chamber that stores an object to be heated, a heating means that is coupled to the heating chamber and whose output can be changed continuously, a control unit that controls power supply to the heating chamber, and a heating device that generates heat from the object to be heated. The controller includes a sensor that can digitally detect steam, various gases, or their heat, and the controller has a first detection threshold and a second detection threshold for signals from the sensor, and After starting, the output of the heating means is changed to a continuous low output approximately in synchronization with the signal of the sensor reaching the first detection threshold, and after a predetermined measurement mask time, the signal of the sensor changes to a second detection threshold. Automatic heating device that continues heating until the detection threshold is reached. (3) The time until the sensor signal reaches the first detection threshold is T_1 hour, and if T_1 time is less than a predetermined time, heating ends at that point or desired additional heating is performed and ends. The automatic heating device according to claim 1 or 2.