JPS5930964B2 - cooking oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for detecting humidity in a method of automatically cooking food by detecting the humidity value generated by heating the food.

FIG. 1 shows the principle of an automatic heating control method using humidity detection. In FIG. 1, h is the humidity change accompanying heating, and t is the heating time.

In general, the change in relative humidity caused by heating food using a microwave oven is that the temperature of the food is 80 to 90% on average.
h shows a tendency to decrease for a while until it is heated to 0° C. or higher and the amount of water vapor increases rapidly.

This is because the relative humidity decreases because the temperature increase due to heat generated by the magnetron, transformer, etc. accompanying heating has a greater influence than the humidity value that increases due to heating.

When the amount of water vapor rapidly increases as described above, the relative humidity rises at a steep slope from the lowest value h m1n7).

At this time, the temperature of the food reaches an average of 80 to 90° C. or higher, so this point in time when the temperature rises rapidly can be considered as a singular point in the heating state.

This point in time can be taken as the time T when the set value Δh has increased from "h min f)".

Although some foods may be heated to an appropriate temperature within this time period T, they are generally heated automatically by the following method.

In other words, count the time T until h min rises by Δh from 7:)・, and when T is reached, multiply the counted value T by the heating coefficient k unique to the food, and for the resulting time kT, T If the principle of continuous heating is used, the time until T is considered to be approximately proportional to the amount of food, so it has the advantage of being able to automatically heat the food regardless of the amount of food.

The minimum value of relative humidity h min
The method of holding it is complicated, and it also has the disadvantage that errors tend to occur when holding it for a long time.

Therefore, in order to eliminate this drawback, the present invention detects changes in relative humidity without providing a holding means.

FIG. 2 shows an embodiment in which the present invention is applied to a microwave oven.

In FIG. 2, 1 is a humidity sensor provided at the exhaust port, 2 is a humidity sensor provided at the intake port, 3 is food to be heated, 4 is a heating chamber, 5 is a magnetron, and 6 is a fan.

7 and 8 are amplifiers that receive the signals from the humidity sensors 1 and 2 and amplify them to a predetermined value; 9 is a comparator that compares the difference between the amplifiers 1 and 8 with a threshold value ΔV; 10 receives the heating start signal 5TRT and starts counting. Then, the magnetron drive circuit 11 is driven continuously for the time it takes to receive the signal from the comparator 9 and the time equal to this time multiplied by the heating time coefficient set for the resistance/tightening. This is the heating time control circuit that operates.

3 shows the output waveform of each circuit in FIG. 2, a is the output waveform of the amplifier 7, b is the output waveform of the amplifier 8, d is the input waveform of the comparator 9, and e
is the output waveform of the comparator 9, f is the heating time control circuit, the operating time of 10 is shown, and C is the temperature near the temperature sensor 2.

In FIGS. 2 and 3, a heating time control circuit 10 is operated in response to a heating start signal 5TRT, and this circuit 10 operates a magnetron drive circuit 11.

Therefore, a voltage is applied to the magnetron 5, and the heated food 3
Start heating.

At the same time, the fan 6 is also operated to blow air.

As heating progresses, the temperatures at the intake and exhaust ports rise due to self-heating of the magnetron 5, high-voltage transformer, and other circuit components.

(Waveform c) Therefore, as the temperature rises, the humidity values of the relative humidity sensors 1 and 2 decrease.

The average humidity of the heated object is 80 to 90℃ (local temperature of food 1
00° C.), the humidity value of the humidity sensor 2 at the exhaust port rapidly increases, and the difference between the humidity values of the intake port and exhaust port sensors becomes large.

Similarly, the voltage difference between the amplifier outputs of the amplifiers 7 and 8 becomes sharper (waveform a y b ).

The threshold value ΔV of the comparator 9 is reached and a detection signal (waveform e) is output.

Upon receiving the detection signal, the heating time control circuit 10 calculates the time until detection T, (waveform f), and the time K multiplied by the heating time coefficient K determined by the type of food cooking that has been set for roughness and tightening.
Continue heating the TI.

After the time KT1 ends, the heating time control circuit 10 stops, and therefore the magnetron drive circuit 11 also stops applying voltage to the magnetron, and heating ends.

As described above, according to the present invention, humidity can be detected without requiring a minimum value holding means.

Furthermore, the humidity value generated from the food can be measured more accurately by providing humidity detection means at the intake port and the exhaust port, respectively.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a humidity detection system, FIG. 2 is a schematic diagram of a cooking oven showing an embodiment of the present invention, and FIG. 3 is an output waveform diagram of each circuit in FIG. 2. 1.2... Humidity sensor, 4... Heating chamber, 5... Magnetron, 6... Fan.

Claims (1)

[Claims] 1. In a cooking oven that detects the humidity value that changes as food is heated and controls and stops the heating time of the food, a humidity detection means is provided at the intake and exhaust ports of the oven, This cooking open device is characterized by being provided with means for comparing the difference between both humidity values and a humidity value set as a roughness/tightening, and a heating time control means for receiving a signal from the comparing means and controlling the heating means. 2. The time required for the difference in the humidity values of the temperature detection means installed at the exhaust port and the intake port to reach the humidity value set for the strain/tightening is multiplied by the heating time coefficient determined by the type of food and type of cooking. 2. The cooking opener according to claim 1, further comprising a heating time control circuit that controls the heating time so that the heating continues until the humidity value reaches the set humidity value.