JPS6021475B2 - High frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device, which compares an arbitrarily set heating target value with the value of a temperature signal input from a temperature detection element, and the magnitude relationship is reversed from the initial form. It is equipped with a function to turn off the microwave generator when the temperature signal becomes OFF, and is not affected even if the temperature signal changes temporarily due to various noises and the above-mentioned magnitude relationship is temporarily reversed. It is.

As shown in Figure 1, this type of conventional device is equipped with a microwave generator at the top of the heating chamber, and an exhaust temperature detection element on the side. is turned on to heat the food, and a temperature signal T is taken in from the temperature detection element immediately after the start of heating, as shown in FIG.

Here, this value is calculated in the control circuit shown in FIG. 1, and for example, as shown in FIG. 2, this value is multiplied by (10Q) to raise the heating target temperature by ΔT. Furthermore, a value of 8t, which increases the target temperature in proportion to the elapsed time, is added to this value to calculate the value of y2, which is y2 = (10Q)T, 18t,
In order to increase △T by the amount of food increased, △T
=ΔT, 10ΔL corrections are performed. On the other hand, as the temperature of the food rises and the temperature of the air surrounding the food rises, a gradually higher temperature signal y, comes in from the temperature detection element, but since the air flow is uneven, y ，
includes a large size component N as shown in FIG. Therefore, it is actually much shorter than the time when y, > y2 when there is no noise, and the time t2 (; t, - y
), the noise temporarily makes y,>uniform, so
There is a drawback that the control circuit outputs a signal to turn off the microwave generator, and heating ends before the temperature of the food has risen sufficiently. Furthermore, since the timing at which the device turns off is not constant, there is a drawback that even if the same food is heated, it will vary greatly depending on the timing of the noise and the magnitude of the noise. Furthermore, as the amount of food increases and the temperature of the air surrounding the food rises more slowly, the slope of y becomes gentler and gradually approaches the mirror slope of y2. In such a situation, the influence of noise becomes extremely large, and if it is severe, the microwave generator may turn off due to the noise immediately after heating starts. The present invention has been made in view of the above circumstances, and its purpose is to provide a function to successively compare the magnitude relationship between y and y2 every unit time, and to perform arbitrary comparisons starting from the last time of comparison. The microwave generator is turned off when the number of times y, > y2 reaches a predetermined ratio or more when the investigation is traced back a set number of times, and the temperature signal changes temporarily due to various noises. The aim is to provide a high-frequency heating device that is less susceptible to

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, reference numeral 1 denotes an AC power source, and a microwave generator 4 is connected to this power source 1 via an AC control element 2 and a door switch 3. This microwave generator is for supplying microwaves into the heating chamber, and is composed of, for example, a magnetron and a magnetron power source. Further, a one-touch microcomputer (hereinafter referred to as microcomputer) 7 is connected to the power supply 1 via a DC power supply 5 for electronic circuits and a power pulse generation circuit 6 that generates pulses at the frequency of the power supply 1. Furthermore, the microcomputer 7 includes a heating start switch 8-1, and other switches for setting the increase value of the air temperature surrounding the food to determine the temperature rise of the food. For example, in FIG. Whenever the value of Q is determined in advance as in Q3,
A group of operation switches 8 including switches 8-2, 8-3, and 8-4 for setting values such as Q2>Q3, a display device 10 via a buffer amplifier 9 for the display device, and analog and digital temperature values. Through the comparison resistance block 1 1 which compares the value with the value and the temperature detection element 12 which detects the temperature of the air surrounding the food discharged from the heating chamber,
A comparator 13 for comparing the magnitudes of these is connected, and further followed by an ignition circuit 14 for controlling the AC control element. Also, the ROM part of the microcomputer 7 stores the value of Q as high, medium, or low, for example, when the value of Q is set by pressing any of the operation switches 8-2, 8-3, and 8-4.
The button 3 is preset with the function of displaying an indicator lamp as shown in FIG. 4.

Further, the ROM section of the microcomputer 7 is provided with a function to perform the following calculation from the value of Q and a preset value of 8 in order to correct the influence of the difference in the amount of food. That is, in FIG. 2, y2=(1
10 is 2) T, 13t is the function to calculate the value of y2,
As shown in FIG. 5, this average value and the temperature signal y which continues to be input from the temperature detection element. For example, the magnitude 4 relationship is successively compared every second, and when one comparison is completed, the arbitrarily set number of times goes back, for example, 5 times, and when looking at the magnitude relationship, this is the initial state. Reverse y
,>y2, for example, the microwave generator is turned off when the total number of times exceeds 1', that is, 3 times or more.
It has the function of Next, the operation of the present invention configured as described above will be explained.

First, when the AC power source 1 is connected, food is stored in the heating chamber, and the door is closed, the door switch 3 is closed. Furthermore, if you press the appropriate temperature switch 8-3 to set Q=Q2 according to your preference, the medium temperature indicator lamp will light up as shown in Fig. 4, and the microcomputer 7 will calculate the temperature according to the above formula and A function to calculate is prepared. Next, when the heating start switch 8-1 is pressed, the AC control element 2 shown in FIG. 3 is turned on, and the microwave generator 4 connected thereto operates to start heating.

The microcomputer 7 also uses a comparator 13 to compare the voltage obtained through the temperature detection element 12 with the voltage created by the A/○ comparison resistor 11 and the output from the microcomputer, and converts the temperature analog signal into a digital signal. It is converted and measured sequentially. Once the air flow surrounding the food has calmed down after the start of heating, the microcomputer 7 calculates the value of y2 based on the temperature signal T taken in through the temperature detection element 12 and the Q2 and 8. At the same time as calculating the temperature signal y, continuously measuring the subsequent temperature signal y, via the temperature detection element,
Furthermore, as shown in Fig. 5, the magnitude relationship between y and y2 is compared once per second; however, at the beginning of heating, as can be seen from the above calculation results, y. Since <y2, heating continues as is. However, as shown in Figure 5, the value of y obtained by directly measuring the temperature of the air surrounding the food differs from the value y2 calculated by calculation, because the air flow is disturbed. Due to the addition of the generated noise and other electrical external noise, the power fluctuates greatly over time. Therefore, as shown in Figure 5, the actual y,
Even though the value of is lower than y2, temporarily y,>y
2 occasionally appears, but since the value of y is more positive or negative than a virtual value without noise, a state in which y, > y2 occurs three or more times out of the five comparisons does not occur. figure,
The microwave generator continues heating without stopping operation. After that, the temperature of the food increases, and as shown in Fig. 5, the virtual value of y approaches y2, and 5
When y, > y2 is reached three times or more out of the number of comparisons, the operation of the microwave generator 4 is stopped and heating of the food is completed. The heating time t2 at this time is determined by the fact that the value of y is approximately equally positive and negative than the virtual value without noise. The time t. at which y2 intersects the value of t. The time will be very close to. If y. If the waveform of t, does not fluctuate equally in positive and negative directions with respect to a noise-free virtual straight line, but is biased to one side, by changing the number of times y, > y2 accordingly, t, It is possible to complete the heating in a time extremely close to . As explained above, according to the present invention, even if the air flow surrounding the food is disturbed and the detected air temperature varies and temperature noise occurs, the microwave is activated before the food temperature rises to the target value. There are no disadvantages as the generator is turned off and heating stops early.

Therefore, even if noise is introduced into this temperature signal, there is an advantage that highly accurate temperature control can be performed without being affected by the timing or magnitude of the noise. Furthermore, as the amount of food increases, the temperature of the air surrounding the food rises more slowly, and even if the forehead slope of y approaches the mirror slope of uniform, it will not be affected by the noise mentioned above. There is no drawback that heating stops midway. In this example, the comparison is made once every second, and heating is stopped when the magnitude relationship is reversed three or more times out of five comparisons, but if necessary, this time or number of times can be changed to make further comparisons. It is also possible to improve the effect of noise prevention.

It goes without saying that the present invention can also be applied to control methods and circuits different from those of this embodiment.

Although the above embodiment has been described using a one-touch microcomputer, the present invention is not limited to this, and it goes without saying that a control circuit having the above-mentioned functions may also be used.

[Brief explanation of the drawing]

Figure 1 is a principle diagram of a high-frequency heating device with exhaust temperature detection method.
FIG. 2 is a diagram showing a conventional detection temperature comparison method, FIG. 3 is a block diagram showing an embodiment of the control circuit of the high-frequency heating device according to the present invention, and FIG. 4 is a display example of the display device in FIG. 2. , FIG. 5 is a diagram showing a detected temperature comparison method in the present invention. In the drawing, 4 is a microwave generator, 7 is a one-touch microcomputer, 8-2, 8-3, and 8-4 are operation switches for setting the Q values to Q, , 2, and Q3, respectively, and 10
1 is a display device, and 12 is a temperature detection element that detects the temperature of air discharged from the heating chamber. Figure 1 Figure 4 Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] 1. A heating chamber, a microwave generator for irradiating microwaves into the heating chamber, a temperature detection element for detecting the temperature of air discharged from the heating chamber, and an arbitrarily set heating target value. means for comparing the magnitude relationship of the signal values from the temperature detection element successively for each unit time; and a predetermined number of comparison operations each time the comparison operation of the comparison means is completed. control for turning off the microwave generator when the number of times that the magnitude relationship between the heating target value and the signal value of the temperature detection element is reversed from that at the start of heating is equal to or greater than a predetermined percentage of the number of comparisons; A high-frequency heating device characterized by comprising means.