JPS6260617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave oven, and its purpose is to detect the state of food preparation and heat it appropriately.

Generally, the heating time for food is determined by the initial temperature of the food,
It is determined by various quantities such as weight, specific heat, and absorbed energy. However, in conventional microwave ovens, the heating time is determined based on the type and amount of food to be dielectrically heated.

Therefore, in this case, among the various quantities that contribute to determining the heating time, the specific heat of the food and the initial temperature of the food are not particularly taken into consideration.Therefore, with this heating time setting, there is a risk of preparation errors. Something happened. In recent years, in order to solve the problems of conventional heating time setting, devices have been put into practical use that determine the dielectric heating time of food by detecting the humidity and gas concentration emitted from the food due to dielectric heating, and have attracted attention. ing. In this device, a heating element for refreshing the sensor from dirt and the like is provided around the sensor, and after refreshing the sensor with this heating element, the high frequency oscillator is energized.

However, since the heating element for the above-mentioned refreshing is separately provided in this device, there is a problem in that extra power is consumed for the heating element.

Therefore, the technical object of the present invention is to enable refreshing of the sensor even without the above-mentioned conventional heating element.

The technical means of the present invention to solve this technical problem is to provide the sensor in the vicinity of the heater that directly receives the radiant heat of the heater that heats the food. Each time food is heated with a heater (for example, to brown the surface of the food), the sensor is sufficiently refreshed with a portion of the heat emitted by the heater, so that the sensor can accurately measure humidity or gas concentration. As a result, optimal dielectric heating control for heated foods can be performed.

In addition, since there is no need to separately provide a heating element for refreshing, the configuration of the sensor section is simplified, and since the power consumption of the heating element is eliminated, power consumption is reduced accordingly, resulting in energy savings. An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is the main body of the microwave oven, 2 is food provided in the heating chamber A, and 3 is a blower fan. 4 is a magnetron used as an example of a high frequency oscillator, and 5 is a sensor for detecting humidity made of metal oxide, which is provided in the exhaust duct A' from the heating chamber A. Further, 6 is a heating element that heats the atmosphere near the sensor 5, and is turned on by closing the switch S, but it is not necessarily necessary. 7 is a humidity amplifier, 8 is a condition detection circuit, and 9 is a control circuit for the heating element 6. Reference numeral 10 denotes a heater (for example, a sheathed heater) provided in the upper part of the heating chamber A, and its current-carrying part is provided in the exhaust duct A', and is connected to a power source (not shown) in the duct A'. In this configuration, food 2 is placed in heating chamber A and a conditioning button (not shown) is pressed. (In this case, it is assumed that the switch S is open and the heating element 6 is not energized, and that the sensor 5 has been refreshed by the previous energization of the heater 10. This refreshing will be discussed in detail later.) The food 2 is dielectrically heated by high-frequency electromagnetic waves radiated into the heating chamber A from the antenna 4a of the magnetron 4, and water vapor is generated from the food 2 by this dielectric heating.

This water vapor is sent from the fan 3, heats up the magnetron 4 after cooling it, and is transported to the main body through the exhaust duct A' as shown by the arrow F' by the cooling hot air (arrow F) that enters the heating chamber A. is discharged outside.

Humidity is detected by the sensor 5 within this exhaust duct A'.

FIG. 2 is a relative humidity graph detected by the sensor ₅ in the state explained in _FIG .
represents time, and H ₀ to _{H 5} represent humidity at each time. Let T ₀ and H ₀ be the time at which the button was pressed and the humidity at that time, then the cooling hot air from the magnetron 4 flows into the heating chamber A, while no water vapor has yet come out from the food 2, so the relative humidity is It decreases like the M line. In other words, as the magnetron 4 is energized and heating continues, the influence of the cooling air volume of the magnetron 4 becomes greater than the increase in the amount of water vapor generated from the food 2, and as a result, the relative humidity gradually decreases. . The point at which the amount of water vapor generated from the food 2 increases and the humidity starts to rise is _T3 , _H3, and the conditioned filling state sensing circuit 8 in FIG. 1 stores the relative humidity at this point. Then, the point at which a change in relative humidity greater than the preset relative humidity is caught
Finish cooking at T ₄ and H ₄ (stop energization to magnetron 4), or T ₂ depending on food 2.
The preparation is completed by further dielectric heating for a time K (T ₄ −T ₂ ) obtained by multiplying the time from T ₄ by a constant K (varies depending on the food 2). In this embodiment, the operations described above are performed.

Next, heater 1 is used to brown the surface of food 2.
When electricity is applied to 0, the surface of the food 2 is browned due to the heat emitted from the heater 10, and at the same time, the sensor 5 is heated to over 400℃ due to the heat generated by the heater 10 in the exhaust guide A', and the sensor 5 is heated to over 400℃. Unwanted materials adhering to the sensor 5 are burned away and refreshed, and therefore the sensor 5 can accurately detect humidity during the dielectric heating.

In this case, a reflector plate 11 is provided on the opposite side of the sensor 5 from the heater 10 to cover the sensor 5 and the heating element 6, so that the heat from the heater 10 is reflected by the reflector plate 11. Being done,
The information is efficiently transmitted to the sensor 5, and refreshing can be performed reliably.

Furthermore, by providing the reflector 11, even though the reflector 11 is provided with holes, the airflow stagnates within the reflector 11, making it easier for the sensor 5 to detect humidity. Control is also ensured.

The opening edge of this reflecting plate 11 is positioned to open downward in the lateral direction of the sensor 5, and the inner surface is also hemispherical, so even if condensation such as water vapor occurs on this inner surface, it will not be generated. Since it does not hit the sensor 5 along the inner surface and falls downward, it does not interfere with the humidity detection by the sensor 5.

Now, in the above explanation, we have talked about the case where the heater 10 is used occasionally, that is, the case where the sensor 5 is refreshed by the heat of the heater 10, but in some households, the heater 10 is rarely used. Some households do not use it,
In this case, the heater 10 cannot refresh the sensor 5, so in this household, the switch S is closed before pressing the adjustment button. Then, the control circuit 9 of the heating element 6 works together with the magnetron 4 and the fan 3, causing the heating element 6 to generate heat and remove dust attached to the sensor 5 and water vapor (absorbed moisture) from the previous use. A skip refresh is performed. Then, when this is completed (in this embodiment, the surface of the sensor 5 has reached a temperature of 400° C. or higher), the power to the heating element 10 is cut off. From then on, the food 2
emits water vapor, and sensor 5 measures the relative humidity at that time.
is detected, and the conditioned condition sensing circuit 8 catches the relative humidity difference with respect to the time at the start of the conditioned condition, thereby controlling the magnetron 4.

In addition, in FIG. 2, in this case, as shown by the N line, the time when the refresh by the heating element 6 is completed, that is, the time when the surface of the sensor 5 reaches 400°C is T ₁ , H ₁
The relative humidity is at its lowest. Then, when the current to the heating element 6 is cut off, the sensor 5 is cooled and the relative humidity rises, becoming similar to the M line from around the _T2 section.

Although the sensor 5 detects the humidity in FIGS. 1 and 2, the sensor 5 may also detect the gas concentration based on the heating of the food.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a microwave oven according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram thereof. A...heating chamber, A'...exhaust guide, 2...food, 4...magnetron (high frequency oscillator), 5...
...Sensor, 6...Heating element, 11...Reflector.

Claims (1)

[Claims] 1. A heating chamber, a high frequency oscillator for dielectrically heating the food in the heating chamber, a sensor for detecting humidity or gas concentration that changes due to the dielectric heating of the food by the high frequency oscillator, and a sensor for detecting the humidity or gas concentration that changes due to the dielectric heating of the food by the high frequency oscillator. What is claimed is: 1. A microwave oven comprising: a heater that performs electric heating; and the sensor is provided near the heater to directly receive radiant heat from the heater. 2. The microwave oven according to claim 1, wherein a reflector is provided on the opposite side of the sensor from the heater.