JPS5858565B2 - cooking oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a configuration for detecting the cooking state of food and automatically determining the heating time in a cooking oven such as a microwave oven.

For example, in a microwave oven, the heating time is determined by various quantities such as the initial temperature, quantity, final temperature, specific heat, and microwave absorption energy of the food to be heated.

Conventionally, the heating time of a microwave oven has been set to a time determined based on the type and amount of food to be heated.

The relationship between heating time for each item and amount is determined in advance based on the results of heating experiments.

Therefore, when heating any food, the heating time cannot be set unless information about not only the item but also the amount of the food is taken into consideration.

Furthermore, among the various quantities that contribute to determining the heating time, the specific heat of the food, the initial temperature of the food, and the final temperature of the food are not particularly taken into account, so this method of setting the heating time is prone to cooking mistakes and heating mistakes. There were some drawbacks that could easily occur.

The present invention solves the problems of the conventional heating time setting method and provides means for realizing a cooking oven that is easy to operate.

An embodiment of the present invention will be described below.

As shown in Figure 1, the relative humidity inside the oven exhaust port, which generally changes when food is heated in the oven, decreases as the temperature inside the oven rises because there is little steam coming out of the food at first. .

Then, as the amount of steam increases, the relative humidity reaches its lowest point, and then begins to rise.

Here, the relative humidity range J determined from the lowest point of relative temperature
The time at which the food rises by
0° C.), and is the time when the cooking state of the food shows a significant change.

For most reheated foods, this time is close to when the food reaches its appropriate temperature, so for these foods, setting the time T from the start of heating to the above time as the heating time is the appropriate heating time. .

Note that this time T is a value that already includes the influence of the amount of food and the initial temperature.

Therefore, there is no need to newly consider the amount of food and the initial temperature.

Further, the time obtained by adding the time obtained by multiplying this time T by a unique coefficient determined depending on the type of food or cooking type can be determined as the appropriate value of the total cooking time.

However, the relative humidity inside the exhaust port differs significantly depending on the ambient temperature.

Since the resistance value of the humidity detection sensor changes with respect to humidity as a logarithmic function (see Figure 3), the detection voltage obtained with respect to the humidity inside the exhaust port varies over an order of magnitude wider range, and the detection voltage The amount of change from the minimum value also varies significantly depending on seasons such as summer and winter, and temperature differences depending on the region where it is used.

In other words, the detected voltage curve V1 in Fig. 2 indicates that the temperature inside the exhaust port is relatively low, that is, the room temperature is low (the level of the detected voltage is high when the inside of the exhaust port and the room temperature are the same temperature, and the amount of change from the minimum value is low). On the other hand, the detected voltage curve V2 is a case where the temperature inside the exhaust port is relatively higher than the room temperature due to the influence of previous heating, and the detected voltage level is extremely low, and the amount of change from the minimum value is also small.

In addition, the voltage width determined from the minimum value of the detected voltage curve, (V
(This corresponds to the above-mentioned relative humidity width JhK) However, the time when the detected voltage curve V1 rises is earlier.

Note that, unlike the first time of food heating and the second and subsequent food heating, from the second time onwards, the temperature rise due to food heating progresses and the detection voltage curve changes from Vl to V2, and the JV detection time changes.

Therefore, in the present invention, the temperature of the humidity sensor is measured by an electric heater near the sensor, so that the temperature of the humidity sensor is adjusted to T, as shown in the room air diagram in FIG.
At an indoor temperature of
Heat to.

Similarly, at other room temperatures, the relative humidity value RH1 at the room temperature T1' is heated to the temperature T2' at the relative humidity value RH2 indicated by the same absolute humidity value.

Furthermore, the temperature of the temperature sensor is always controlled to a predetermined temperature value (T2 at T1. It is designed to reduce the effects of temperature rise.

Next, FIG. 5 shows a block diagram of the present invention.

1 is the food to be heated, 6 is a humidity sensor, and the food to be heated 1
The air flow 5 containing water vapor sent by the air blower 4 by the fan 3 is detected to detect the change in humidity caused by the humidity change, and the humidity change is detected by the amplifier 7.
amplify by.

Since the signal source applied to the humidity sensor is generally an alternating current, a rectification and smoothing circuit 8 is provided to rectify and smooth the humidity signal.

9 is a signal comparison circuit, which compares the level of humidity change and a preset reference value V8f, and
The control signal h2 is output to the power control circuit 10 of.

The power control circuit 10 has a function of supplying power to the magnetron 2 from the start of cooking and stopping the power supply in response to a control signal h2.

Although the above configuration is the principle of the heating control method using the humidity detection means, the present invention further includes the following temperature control circuit for the humidity sensor.

15 is a temperature sensor for indoor temperature detection, and an amplifier 16
The temperature detection signal is amplified by a set coefficient (power from Ul to T2 shown in FIG. 4).

Reference numeral 11 denotes a temperature sensor that detects a temperature change within the exhaust port, and the temperature sensor 11 amplifies the temperature change within the exhaust port.

13 is a differential amplifier, which amplifies the difference between the output [eb] of the amplifier 12 and the output KeO of the amplifier 160 (Kea eb); 14 is a drive circuit for the electric heater 11;
The temperature of the humidity sensor is controlled by supplying power matching the input signal of (Kea-eb) to the electric heater 11 and dissipating heat from the electric heater 11.

FIG. 6 shows a timing chart of the block diagram shown in FIG.

hl is a humidity detection signal, which is the output of the rectifier and smoothing circuit 8.

Th indicates the temperature inside the exhaust port and is the output of the amplifier 12, and the humidity signal is affected by the heat of the food and the temperature rise of the magnetron, as shown in e5, and the temperature increases.

T is the temperature of the sensor, T1 indicates the room temperature, and the temperature sensor 6 is heated by the electric heater 17 when the room temperature is T1.
Let Ke be the temperature signal of

It is assumed that the temperature signal Ke of the controlled humidity sensor is sufficiently larger than the temperature rise eb of the exhaust port.

From this, as food heating progresses, eb rises, but the temperature of the humidity sensor decreases due to (Kea-"b), the power supplied to the electric heater decreases, and the specified temperature at room temperature T1 Leaning on T2.

Assuming that the heating progresses and the humidity detection signal reaches the reference value vef, a signal h2 is obtained from the comparator 9, and from the h2 signal,
Controls the power of the magnetron to perform power and thermal shutdown.

As described above, according to the present invention, it is possible to eliminate the detection time error in relative humidity detection due to seasonal differences such as summer and winter, temperature due to regional differences, and temperature rise of the humidity sensor due to heating, and to use a relative humidity sensor. The cooking oven can be automatically stopped and controlled.

This eliminates the need to set the amount of food in addition to the food name or cooking salt as in conventional microwave ovens, and also eliminates the need to correct the heating time due to differences in the initial humidity of the food.

Therefore, it is possible to realize a microwave oven that is easier to operate than conventional microwave ovens and that can heat food accurately.

[Brief explanation of drawings]

Figures 1 and 2 are timing charts of humidity detection using the conventional method, Figure 3 is a resistance-relative humidity characteristic diagram of a humidity sensor, Figure 4 is a room air diagram, and Figure 5 is an embodiment of the present invention. FIG. 6 is a timing chart of each part of the block diagram shown in FIG. 2... Magnetron, 3... Fan,
6...humidity sensor, 7...amplifier, 9
... Signal comparison circuit, 10 ... Power control circuit, 11 ... Temperature sensor, 12 ...
Amplifier, 13...Differential amplifier.

Claims (1)

[Claims] 1. In an oven that controls the heating time by detecting changes in humidity caused by heating food using a humidity sensor and processing the signals to determine the heating time of the food, a room temperature detection means and a humidity sensor are installed. A means for detecting the temperature inside the exhaust port, a means for heating the temperature of the humidity sensor to a value set according to the room temperature using an electric heater installed near the temperature sensor, and a temperature increase inside the exhaust port due to food heating. and temperature control means for the humidity sensor, the temperature control means having means for subtracting the temperature of the humidity sensor from the set value.