JPH0228767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic heater, and more particularly to a heating cooker that automatically controls cooking using sensor means that is sensitive to water vapor emitted from an object to be heated.

Conventionally, in a microwave oven, as shown in FIG. 1, a relative humidity detection sensor 12 that is sensitive to water vapor emitted from the object to be heated 2 is installed in the heating chamber 1 or inside the exhaust duct 11. The sensor 12 becomes contaminated by emitted droplets, volatile substances, oil smoke, etc., and its initial performance deteriorates as it is used.
There is a problem that sensitivity cannot be obtained. Therefore, a coil heater 14 is provided near the sensor element 13 as shown in FIG.
It has the ability to burn off adhered dirt by heating to a temperature higher than
Cleaning methods that maintain good sensitivity at all times have been devised and implemented for microwave ovens and the like. By the way, after the cleaning of this sensor 12 is completed and the power supply to the coil heater 14 is stopped, the sensor 1
2, it is not possible to immediately obtain stable and good detection performance. The reason for this will be explained based on FIG. 3a. In Figure 3a, the horizontal axis is time t, and the vertical axis is relative humidity.
It shows the change in relative humidity inside the exhaust duct 11 after heating started. Heating starts from point A, but cleaning of the sensor 12 also starts at the same time, so the ambient temperature of the sensor 12 increases rapidly due to the heating of the coil heater 14, and the relative humidity gradually decreases toward point B. It goes on. Point B is the point at which the sensor 12 reaches a predetermined temperature and cleaning is completed. Although there is a slight overshoot because the coil heater 14 is no longer energized at point B, the sensor 12 is now cooled by the exhaust air and the temperature gradually returns to room temperature, so the relative humidity moves toward point C. going up. After reaching point C and returning the sensor 12 to a steady state, the temperature of the exhaust air gradually increases as heating progresses, and therefore decreases toward point D. Point D is the point where the increase in relative humidity due to the water vapor emitted from the heated object 2 exceeds the decrease in relative humidity due to the temperature rise of the exhaust air, and after this the amount of water vapor from the heated object 2 increases, so the relative humidity decreases. increases from point E to point F.

Generally, the relative humidity change amount ΔRH is detected from point D and the output of the magnetron 3 is automatically controlled to control heating.

By the way, this relative humidity change △RH is the change from point B to point C until the cleaning is completed and the steady state is returned.
It is clear from FIG. 3a that this also occurs between the points, but since the change in relative humidity during this period is not due to a large amount of steam emitted from the object to be heated 2, it cannot be used to detect heating. Therefore, it is necessary to wait for the time _tc for detection by the sensor 12.

By the way, if we start heating at high output from the start of heating, if the object to be heated 2 is small, the relative humidity will reach 100% by the time it takes for the sensor 12 to return to a steady state, that is, by the time it reaches time _tc . and when time t _c is reached, the relative humidity change △
It is possible that the condition will become such that RH cannot be obtained. Therefore, as shown in FIG. 3b, there is a method in which the heating output _P0 is set to zero from the start of cooking until time _tc , and then increased to a high output after _tc .

However, in the above method, t _c
Until then, no heating is actually performed at all, so the time required for heating is an additional _tc , which has the disadvantage of poor time efficiency. Therefore, conventionally, as shown in Figure 3c, the time
There was a means to improve time efficiency by starting heating at high output from time t ₁ before reaching t _c (t _c −t ₁ ).
However, when determining t ₁ , care must be taken to ensure that a large amount of water vapor does not come out from the heated object 2 etc. due to high-power heating during the time (t _c - _{t 1} ). Must be decided. Therefore, time (t _c −
_t1 ) is currently only about 10 seconds, and although time efficiency has improved, there has been a problem in that time efficiency has not been significantly improved.

Furthermore, another conventional example is shown in FIG. 3d. Predetermined time
The method is to heat with low output P _L during t ₁ ' and then switch to high output to heat.

There is also a conventional example shown in FIG. 3e. this is,
During a predetermined time t ₁ ″, heating is performed in intermittent operation with the heating on for T ₁ hour and off for T ₂ hours, and after t ₁ ″, the heating is switched to continuous operation at high output. In this case as well, the elements of low power P _L , t ₁ ′, t ₁ ″, T ₁ , and T ₂ must be determined for the object to be heated 2, as in the conventional example described above. The output is determined so that a large amount of steam does not come out from the object 2, but if the energy absorbed by the object 2 from the start of cooking to _tc exceeds a predetermined level, a large amount of steam will be generated. Therefore, the time efficiency can only be improved to the same extent as in the conventional example shown in FIG. 3c.

Therefore, the present invention aims to eliminate the above-mentioned drawbacks and significantly improve time efficiency.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 1 denotes a heating chamber, in which an object to be heated 2 placed therein is heated by high frequency energy oscillated from a magnetron 3. 4 is a fan motor;
While cooling the magnetron 3 and the like, ventilation air 7 is blown into the heating chamber through the ventilation duct 5 and the ventilation opening 6. Exhaust air 9 containing water vapor 8 emitted from the food 2 is discharged into an exhaust duct 11 through an exhaust port 10. Reference numeral 12 is a relative humidity detection sensor that is sensitive to the relative humidity of the exhaust air 9. FIG. 2 shows an enlarged view of the relative humidity detection sensor (hereinafter simply referred to as sensor) 12. 13 is a sensor element, 14 is a coil heater provided near the periphery of the sensor element 13,
Reference numeral 15 denotes a support portion made of ceramic material.

Next, control of heating power, which is a feature of the present invention, will be explained based on FIGS. 4a and 4b.

In the figure, at the same time as cleaning starts, the object to be heated is heated at high output for a predetermined time _t2 , and then the heating of the object is stopped until the time _tc when the relative humidity detection sensor 12 returns to a steady state, and when _tc is reached. After that, heating of the object to be heated is resumed at high output.

That is, the change in the amount of water vapor in the heating chamber 1 is shown in FIG. 4a. The amount of water vapor x ₀ at the start of cooking is determined by the environment in which the microwave oven is placed. The amount of water vapor is reduced by high output heating from the start of cooking to _t2 .
Increase to x ₂ . However, since the output is zero from t ₂ to t _c when the sensor 12 becomes detectable, no steam is generated during this period, and the steam inside the heating chamber 1 is transferred to the outside of the heating chamber 1 by the fan motor 4. Therefore, the amount of water vapor in the heating chamber 1 returns to the initial amount x ₀ of water vapor, so the heating from the start of cooking to t ₂ has no effect on the detection of relative humidity.
Moreover, even if a large amount of water vapor is generated due to heating from the start of cooking to _t2 , it is possible to return to almost _the initial environmental conditions from _t2 to _tc . can add enough energy to Therefore, the heating time is shortened by the time _t2 , improving time efficiency.

FIG. 5 shows an example of such an electric circuit.
16 is a commercial power supply, and 17 is a contact inserted into the main circuit, which is turned ON when cooking starts, and applies voltage to the fan motor 4. 19 is a high voltage transformer, 20 is a high voltage capacitor, 21 is a stack diode,
It serves as the anode power source for magnetron 3. 23
is the contact point of the high voltage reed relay, which turns on and off the anode voltage to magnetron 3. The coil 22 is controlled by a control section 18 including a microcomputer.

Further, FIG. 6 shows another embodiment of the above electric circuit. 25 is a relay, and 24 is its coil, which is controlled by the control unit 18. Further, the relay 25 and its coil 24 can also be implemented as a triax.

After starting cooking using the circuit configuration shown in FIGS. 5 and 6 above, the high voltage reed relay 23 in FIG. 5 and the relay 25 in FIG. 6 are turned on until t ₂ to oscillate the magnetron 3, and after t ₂ It is turned off to stop oscillation, and then turned on again after _tc to oscillate the magnetron 3 and heat it at high output. 6th above
In the circuit shown, relay 25 is connected to 1 of high voltage transformer 19.
Since it is located on the next side, the low pressure side, it can be said that it is economical as there is no need for a special relay switch.

As explained above, according to the present invention, the following effects can be obtained.

(1) According to the present invention, since the sensor element is cleaned at the start of cooking, stable detection performance is always obtained, and since heating is performed without waiting until the sensor returns to a sensing state, it is time efficient.

(2) Immediately before the sensor returns to a detectable state, the environment is configured so that it is almost the same as immediately after cooking starts, so the detection after the sensor returns to a detectable state is different from that shown in the conventional example. It is possible to perform accurate detection similar to that used in conventional methods, and since a large amount of energy can be applied before the sensor returns to a sensing state, it is possible to significantly shorten the cooking time.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of the heating cooker of the present invention, Fig. 2 is an enlarged external perspective view of the sensor section of the same, and Figs. 3 a to e are changes in relative humidity and heating pattern of the conventional heating cooker. FIG. 4a is a characteristic diagram showing changes in the amount of water vapor in the cooking device of the present invention, FIG. 4b is a characteristic diagram showing the heating pattern of the cooking device, and FIG.
The figure is an electric circuit diagram of the heating cooker of the present invention, and FIG. 6 is another electric circuit diagram of the heating cooker. DESCRIPTION OF SYMBOLS 1... Heating chamber, 2... Heated object, 3... Magnetron (heating means), 4... Fan motor (air exhaust means), 11... Exhaust duct (exhaust part), 1
2... Relative humidity detection sensor (sensor means), 13
...Sensor element, 14...Coil heater, 18...
...Control unit (control unit).

Claims (1)

[Claims] 1. A heating chamber for storing an object to be heated, a means for heating the inside of the heating chamber, an air blowing means for ventilating the inside of the heating chamber, an exhaust section communicating with the inside of the heating chamber, and a heating chamber provided in the exhaust section and inside the heating chamber. A method for starting cooking, comprising a sensor means having a sensor element that is sensitive to generated water vapor and a means for cleaning the sensor element, and a control device that controls the heating output of the heating means based on a signal from the sensor element. The heating output is set to be high for a predetermined period of time within the time required for the sensor means to return to the sensing state after the input signal is input, and after the predetermined time has elapsed, the sensor means is in the sensing state. A heating cooker with zero output until it returns to normal.