JPS6220676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heater with a ceiling that has a function of automatically controlling the heating time by detecting water vapor released from the food when the food is high-frequency heated. This provides a reliable humidity detection control method that does not cause malfunctions.

Conventionally, high-frequency heaters have already been invented and commercially available, which control the heating time by detecting the considerable amount of water vapor emitted from the food as a change in relative humidity when the food reaches a predetermined temperature. It's on the market. However, there is no precedent for high-frequency heaters with ceiling lights, and there are new problems.
Therefore, the purpose of the present invention is to solve this problem.

With conventional humidity-sensing high-frequency heaters, as long as the ambient temperature and relative humidity in which the high-frequency heater is used are at room temperature and normal humidity, the relative humidity inside the heating chamber will change from a few percent when heating ordinary foods. The value is up to 100%, and the sensor that should be used for this detection is
It is known that this can be achieved using a metal oxide ceramic material consisting of magnesium spinel (MgCr ₂ O ₄ ) and rutile (TiO ₂ ).

However, in a high-frequency heater with a skylight, the temperature inside the heating chamber immediately after heating with the skylight is 200℃.
In some cases, the relative humidity at that time is very small, 1% or less. In such a case, even if humidity detection type control is attempted, it is difficult to detect because the change in relative humidity due to water vapor released from the food is very small.

The present invention solves these drawbacks and provides a high-frequency heater with a ceiling heater that can reliably detect humidity.

An embodiment of the present invention will be described below with reference to the accompanying drawings. Reference numeral 1 denotes an oven interior, in which foods, etc. 2 placed therein are individually subjected to high-frequency heating by a high-frequency oscillator 3 or a sheathed heater 4, etc. Heater heating can be performed. 5 is a commercial power source, 6 is a power switch, and 7 is a changeover switch for switching between high frequency heating and heater heating. 8 is a control switch for controlling high frequency heating, and is turned ON by a signal from control circuit 9.
-Turn off. 10 is the power supply for the high frequency oscillator 3;
A fan 1 cools the high frequency oscillator 3 and the like, and also ventilates the inside of the oven 1. 12 is an exhaust duct, in which the ventilation air 13 generated by the fan 11 is used to discharge water vapor etc. 1 released from the food 2.
4 is exhausted. 15 is a temperature sensor,
It is installed near the inside of oven 1 and detects the temperature inside the oven. Reference numeral 16 denotes a humidity sensor, which controls heating by detecting changes in relative humidity of ventilation air generated by water vapor 14 emitted from the food 2 during high-frequency heating. That is, when looking at the change in relative humidity (RH) within the exhaust duct 12 with respect to the cooking time t, the characteristics shown in FIG. 2 are shown. In the figure, A is the heating start point, and the relative humidity (RH) initially decreases as the heating progresses. This is because while the temperature of the ventilation air 13 increases by cooling the high frequency oscillator 3 etc., the amount of water vapor 14 released from the food 2 is very small.
The relative humidity is decreasing. Eventually, the food 2 is also heated, and when the temperature rises considerably, the amount of water vapor released suddenly increases, and the relative humidity inside the exhaust duct 12 changes from B→C→D. Detect the relative humidity change (△RH) from B to C at this time to know the temperature state (approximately 80 to 90 degrees Celsius) where a large amount of water vapor starts to be released from food 2, and decide whether to continue heating or stop it. Alternatively, by increasing or decreasing the heating power depending on the type of food 2, good cooking can be achieved. At this time, this B→
The humidity sensor 16 is a sensor for detecting changes in relative humidity (ΔRH) of C, and a MgCr ₂ O ₄ -TiO ₂ based metal oxide ceramic sensor having the characteristics shown by H in Fig. 3 is currently in practical use. has been made into The horizontal axis in FIG. 3 is the relative humidity, and the vertical axis is the electrical resistance of the sensor, and the area generally indicated by I is used. However, immediately after heating cooking using the sheathed heater 4, etc., the humidity sensor 16
When trying to perform automatic cooking using the oven, the temperature inside the oven chamber 1 is very high, so the relative humidity of the ventilation air is very small, so the electrical resistance value of the humidity sensor 16 is as shown in FIG. This is the highest value in the range indicated by the area. Normally, processing such high-impedance signals with an electronic circuit would be very costly, making it difficult to realize the inexpensive high-frequency heating device with a ceiling that we are aiming for.

Therefore, the present invention aims to overcome these problems and automate an inexpensive and highly reliable high-frequency heating device with a ceiling flame by using the following method.

In FIGS. 4a to 4c, t ₀ indicates the point at which automatic cooking by the humidity sensor 16 starts immediately after the heater finishes heating. That is, at time t ₀ , the fourth
When the oven internal temperature T is as high as _t0 as shown in Figure 4-a, the electrical resistance R of the humidity sensor 16 is also high as shown in Figure 4-b, making it difficult to detect. The fan motor 11 is operated to cool the oven interior 1, and the ventilation air 1 is pulled.
3 is also lowered so that the electrical resistance R of the humidity sensor 16 falls within the detectable region I. That point
t ₁ is the temperature detected by the temperature sensor 15.
The point is set as T ₁ , and after the t ₁ point, the high frequency heating operation is started as shown in Fig. 4c (b).

Such a sequence is performed by the control circuit 9. Also, display whether the state of t ₁ point has been reached.
It can also be shown to the user using a display device such as the LED 17. Furthermore, something like an operation button for operating the fan motor 11 is separately provided on the operation section.
A method of cooling the oven interior 1 by operating the fan motor 11 until the display device such as the LED 17 disappears is also possible.

As described above, according to the present invention, the following effects are obtained.

(1) When performing high-frequency heating control using a humidity detection means in a high-temperature condition inside the refrigerator after being heated by a skylight, this can be prohibited in advance by monitoring the temperature inside the refrigerator, so the humidity detection means does not malfunction. enables high-frequency heating control.

(2) By detecting with the temperature detection means that the temperature inside the refrigerator is above a predetermined value and notifying the user using the display means, the user is prohibited from performing high-frequency heating control using the humidity detection means. You can recognize this in advance and accept it.

(3) Detecting the high-temperature condition inside the refrigerator using the temperature sensor means, driving the ventilation means to cool the temperature inside the refrigerator to a predetermined value or less, and enabling high-frequency heating control using the humidity detection means in a short time. I can do it.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit and functional configuration diagram of a high-frequency heater with a skylight showing an embodiment of the present invention, Fig. 2 is also a diagram showing relative humidity changes in the exhaust duct, and Fig. 3 is also a diagram showing the characteristics of the humidity sensor. 4A to 4C are similarly explanatory diagrams of the operation. 1...Oven interior, 3...High frequency oscillator, 4
...Sheathed heater, 7...Selector switch, 8...
Control switch, 11... Fan, 12... Exhaust duct, 15... Temperature sensor, 16... Humidity sensor.

Claims (1)

[Scope of Claims] 1. Temperature detection means for detecting the temperature inside the refrigerator when heated by an open fire, etc., and humidity detection means for detecting humidity changes due to water vapor released when food is heated by high frequency. 1. A high-frequency heater with a headlight, characterized in that the high-frequency heating control by the humidity detecting means is prohibited when the temperature detected by the temperature detecting means is equal to or higher than a predetermined value. 2. The high-frequency heater with a ceiling heater according to claim 1, wherein a display means indicates that prohibition of high-frequency heating control by the humidity detection means is performed. 3. The heating storage has a ventilation means, and the ventilation means is operated until the temperature detected by the temperature detection means falls below a predetermined value, and during that time, the high-frequency heating power is set to zero or low output. A high-frequency heater with a ceiling fire according to claim 1.