JPS5847611B2 - 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, it is not possible to set the heating time without considering not only the item but also the amount of the food.

7 In addition, 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 consideration. The drawback was that mistakes were easily made.

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 with reference to the accompanying drawings.

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 initially there is little steam coming out of the food. To go.

As the amount of steam increases, the relative humidity reaches its lowest point and then starts to rise.

Here, the relative humidity range △ determined from the lowest point of relative humidity
The time at which the temperature rises by h is close to the time at which the food reaches the appropriate temperature, and is the time at which the food exhibits a significant change in cooking status.

This time is close to when most reheated foods reach the appropriate temperature, so for these foods, it is appropriate to set the time T from the start of heating to the above time as the heating time. It gets heated.

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 multiplying this time T by a unique coefficient determined depending on the type of food or cooking type can be added to determine 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 in an exponential characteristic (see Figure 3), the detection voltage obtained with respect to the humidity inside the exhaust port changes over an order of magnitude wider range, ( (See FIG. 4) The amount of change from the minimum value of the detected voltage also varies significantly depending on the seasons such as summer and winter, or the temperature differences depending on the region where it is used.

That is, the detected voltage curve v1 in FIG. 2 is a case where the temperature inside the exhaust port is relatively low and the level of the detected voltage is high.
Furthermore, the amount of change from the minimum value is large, whereas the detected voltage curve (2) is a case where the temperature inside the exhaust port is relatively high, the detected voltage level is extremely low, and the amount of change from the minimum value is also small.

In addition, the voltage width △■(
This corresponds to the above-mentioned relative humidity range Δh).The time at which the relative humidity rises by the above-mentioned relative humidity width Δh occurs earlier in the detected voltage curve 1.

In addition, even in the case of food heating for the first time, unlike the second and subsequent food heating, the temperature rise due to food heating has not progressed yet, so the detected voltage curve is as shown in ■1, unlike the second and subsequent food heating. changes at a higher level than in the case of

Therefore, in the present invention, when heating the food for the first time, or when the temperature inside the exhaust port is relatively low due to differences in temperature, season, region, or day and night, and when heating the same food, the detection voltage is is the change from the minimum value △■
A method is adopted that reduces the time error that occurs.

In Fig. 5, 1 is a microwave oven, 2 is food to be heated, 3 is a blow-in fan, 4 is a magnetron, 5 is a magnetron driver, and 6 is a humidity sensor placed in an exhaust port 7. .

Reference numeral 8 denotes a humidity amplifier that amplifies the humidity measurement voltage obtained by the humidity sensor and outputs it to its output terminal 9 as a detected voltage.

10 is a smoothing circuit that rectifies the negative half cycle of the detected voltage and extracts a smoothed voltage.

11 is a level shift circuit which adds an additional voltage E to the smoothed voltage to turn the negative voltage into a positive voltage.

FIG. 6 shows the waveforms of these detection voltages, smoothed voltages, and level shift voltages.

Furthermore, in FIG. 5, 12 is a maximum value search circuit, one terminal of which is connected to the maximum value holding circuit 13, its input terminal 14 and output point 15, respectively, and the other terminal is connected to output the maximum value search circuit 12. It consists of resistors RA and RB connected to end 16.

A comparator 17 compares the output of the maximum value search circuit 12 with a reference level ΔV, and when this level is exceeded, outputs HDET.
occurs.

18 is a flip-flop circuit whose output OUT controls the madanetron driver 5, and the magnetron 4 is further driven.

Further, reference numeral 19 denotes a heater for heating the vicinity of the humidity sensor 6 to raise the temperature, and is installed in the vicinity of the humidity sensor or is arranged as an integrated unit.

20 is a temperature sensor placed in the passage of the exhaust port 7, for example, one made of a temperature sensitive resistance element such as a thermistor;
Measure the temperature inside the exhaust port.

A voltage converter 21 converts the temperature measured by the temperature sensor 20 into a voltage, and outputs a voltage E.

E is a reference voltage, which is the voltage value of the voltage E1 converted by the voltage converter 21 when the temperature measured by the temperature sensor 20 is the reference temperature.

22 is a heating current generator that supplies current to the heater 19;
The converted voltage E0 is compared with the reference voltage E2, and a current that increases or decreases at O2 is supplied to the heater 19 depending on the magnitude of the difference voltage.

Therefore, in the present invention, when the temperature inside the exhaust port is extremely low compared to the reference temperature, as shown in the detection voltage curve 1 in FIG. Since the voltage E1, which is applied to The humidity decreases extremely, and as a result, the detected voltage curve that changes with the elapse of the heating time changes as shown in 1'.

In addition, even if the temperature inside the exhaust port is much higher than the case of curve 1 above and the relative humidity is extremely low, as shown in the detected voltage curve v2, if the voltage E obtained by converting the temperature into a voltage is lower than the reference voltage E, The heating current increases, the temperature near the humidity sensor increases, and the relative humidity decreases.

However, in the latter case, the amounts of change in heating current, temperature rise, and relative humidity are relatively small compared to the former.

Therefore, in the latter case, the detection voltage curve 2' that changes with the elapse of the heating time is close to the curve 1' in the former case by about an adjacent digit.

Further, in these detected voltage curves, the times at which the voltage increases by the determined voltage width Δ■ from the lowest value are very close to each other as shown in FIG.

In other words, by using such temperature control means, the temperature near the humidity sensor can be leveled, the range of change in relative humidity can be narrowed, and the increase from the lowest value can also be leveled out, so the voltage width △■ can be set appropriately. If such a value is used, when heating the same food, a value that hardly changes as an appropriate value for the heating time can be obtained even when the temperature changes at that time.

Next, the operation of the embodiment of the present invention will be explained.

First, the flip-flop circuit 18 is set to a state of 11" by the heating start signal STARTIN, and this output OUT is used to generate a signal through the magnetron 1 driver 5.
Operate magnetron 4.

This starts heating the food, and the relative humidity near the humidity sensor 6 initially decreases, but then increases as water vapor from the food is generated.

This change in relative humidity is measured by the humidity sensor 6, and the humidity measurement voltage is amplified to obtain a detection voltage.

This detected voltage has an alternating current waveform as shown in FIG. 6, and is rectified and smoothed by the smoothing circuit 10 to obtain a negative smoothed voltage along the envelope of the negative alternating current component of the detected voltage.

The smoothing circuit 10 used here may be a conventional wave amplifier.

Next, this smoothed voltage is level-shifted by adding an additional voltage E in the level shift circuit 11, whereby a positive level-shifted voltage is obtained.

(See FIG. 6) Since this change in level shift voltage has exactly the opposite polarity to the envelope of the detected voltage waveform, the minimum value of the humidity measurement voltage becomes the maximum value of the level shift voltage.

Therefore, this level shift voltage is applied to the maximum value search circuit 12, where the maximum value is detected.

That is, the voltage applied to the input terminal 14 of the maximum value holding circuit is applied to the output terminal 16 through the resistor R and also to the maximum value holding circuit 13, where it is changed to the output terminal 15 of this circuit. Holds and outputs a value with the polarity of the maximum voltage value inverted.

Further, this output is applied to the output end 16 of the maximum value search circuit 12 through the resistor R.

Here, since the resistance values of the resistors R 1 and R 2 are set equal, the voltages passed through each are added.

Therefore, until the voltage applied to the input terminal 14 of the maximum value search circuit 12 reaches the maximum value, the voltage at the output terminal 16 is at zero level, and thereafter becomes a positive voltage and increases as the humidity level increases. .

Here, the maximum value holding circuit 13 may be a circuit commonly used as a peak value holding circuit.

In the voltage level comparator 17 at the output end 16, it is compared with the reference level △V, and the increase from the minimum value of relative humidity △h
Level comparator 17 produces an output when a level corresponding to .

This is because in this case, the reference level Δ■ is set to a level corresponding to Δh.

In this way, it is detected that the relative humidity has increased by the set increment Δh from the minimum value.

Next, since this detection output HDET is applied to the R terminal of the flip-flop 18, the flip-flop 18 returns to the state "O" due to this detection output, and its output OU
Since T disappears, the operation of the magnetron 4 also stops and heating is completed.

In this way, the relative humidity range from the minimum value to the relative humidity range △h
The heating can be performed for the time T, that is, until the time when the temperature rises by T.

However, in the present invention, the temperature sensor 20 measures the temperature inside the exhaust port, and the voltage converter 21 converts the temperature into a voltage and outputs the voltage E.sub.2.

This voltage E1 is compared with a reference voltage E corresponding to a reference temperature in a heating current generator 22, where the voltage E of the voltage E1 is compared with a reference voltage E corresponding to a reference temperature.

Generates an increase in current corresponding to the shortfall.

The heating current generator 22 then adds this current increase to the current flowing through the heater 19.

Due to the increase in the current flowing through the heater 19, the humidity sensor 6
The temperature in the vicinity increases and changes in response to the temperature inside the exhaust port.

Furthermore, as food heating progresses and the temperature inside the exhaust port rises as the temperature inside the oven rises, the converted voltage E0 increases, the increased amount of current flowing through the heater decreases, and the temperature near the humidity sensor 6 becomes equal. If the value is too large, it is kept at a value that does not change.

Therefore, the relative humidity (1
It changes by several percent for a change in °.

) can narrow the range of change.

By narrowing the range of change in relative humidity in this way, the range of change in sensor resistance and detection voltage, which change exponentially with changes in relative humidity, can be narrowed, and therefore the input voltage operating range of the humidity amplifier can be expanded accordingly. There is no need to do so, and the time error that causes the change Δ■ from the minimum value of the detected voltage change curve described above can be reduced.

As can be seen from the above explanation, according to the present invention, it is possible to omit the operation of setting the amount of food in addition to the food name or cooking name as in conventional microwave ovens, and it is also possible to Since it is possible to detect a change in temperature and heat the food for an appropriate time up to that time, there is no need to correct the heating time due to differences in the initial temperature of the food.

Furthermore, there is no need to correct the heating time due to the difference in output capacity of the Magne 1 Ron.

Therefore, compared to conventional microwave ovens, it is easier to operate.
Moreover, a microwave oven capable of accurately heating food can be realized.

Furthermore, since there is no need to correct the heating time depending on the output capacity of the microwave oven, there is no need to prepare a timer according to the output capacity of the microwave oven, and it has the advantage of streamlining production. It is.

Note that the present invention is not limited to the above-mentioned embodiments, but can be easily applied to other general cooking ovens such as electric ovens and gas ovens.

[Brief explanation of drawings]

Figure 1 is a change curve in the relative humidity of the exhaust gas emitted from the oven when food is heated in the oven, and Figure 2 is a detection voltage change curve obtained by detecting the change in relative humidity in Figure 1, as well as the exhaust gas. FIG. 3 is a detection voltage change curve diagram when the temperature control method of the present invention is used to increase the temperature near the humidity sensor in response to mouth temperature; FIG. 3 is a characteristic curve diagram of the humidity sensor;
FIG. 4 is a detected voltage curve diagram, FIG. 5 is a configuration diagram of a control section showing an embodiment of the present invention, and FIG. 6 is a diagram showing voltage waveforms at main points in the diagram. 1... Oven, 2... Food to be heated,
4... Magnetron, 6... Humidity sensor, 7... Exhaust port, 8... Humidity amplifier, 10... Smoothing circuit, 11 ...Level shift circuit, 17...Comparator, 18...
・Flip-flop circuit, 19... Heater.

Claims (1)

[Scope of Claims] 1. A heating means for heating food, a humidity sensor for measuring the relative humidity that changes depending on the water vapor emitted from the food, an exhaust port through which the water vapor emitted from the food passes, and a temperature for measuring the temperature inside the exhaust port. a heater for increasing a heating current in response to a lower temperature measured by the temperature sensor to raise the temperature near the humidity sensor; a detection means for detecting an increase by a predetermined value;
The cooking oven is provided with a circuit for controlling the heating means, with the time from the start of heating by the heating means until receiving a detection signal from the detection means as an appropriate heating time. 2. The cooking oven according to claim 1, wherein the heater is integrated with the humidity sensor or placed near the humidity sensor. 3. A voltage converter that converts the temperature measured by the temperature sensor into voltage, and a current generator that compares the converted voltage with a predetermined reference voltage and generates a current corresponding to the shortfall and flows it to the heater. A cooking oven according to claim 1, comprising: