WO1983001675A1

WO1983001675A1 - High frequency heating device

Info

Publication number: WO1983001675A1
Application number: PCT/JP1982/000165
Authority: WO
Inventors: Ltd. Matsushita Electric Industrial Co.; Kenji Watanabe; Mitsuo Akiyoshi; Kiyoshige Watanabe; Akihiko Ueno
Original assignee: Matsushita Electric Ind Co Ltd
Priority date: 1981-11-06
Filing date: 1982-05-13
Publication date: 1983-05-11
Also published as: JPS5880426A; EP0093173A4; EP0093173A1

Abstract

A high frequency heating device which detects variations in moisture and temperature in the vapor produced by heating food (14) in a heating chamber (13) by using a temperature and relative humidity detector (17), converts them into relative and absolute humidities to determine whether the variation in the absolute humidity has reached a predetermined level, thereby automatically heating or cooling the food. Since this device has a single detector, it produces less error due to detecting errors and changes with time, thereby performing an accurate detection.

Description

• Specification

Title of invention ''

High frequency heating equipment Technical field

5 The present invention relates to a high-frequency heating apparatus for automatically performing cooking by detecting a change in the humidity of the atmosphere in the refrigerator caused by heating of food, in particular, relative humidity and temperature are detected by a single detector. It relates to a high-frequency heating device that performs heating cooking by automatically controlling the heating time by detecting changes in absolute humidity by converting it into humidity.

Background art

In recent years, the development of micro-computers, cost reduction, and various sensors

With the development, microwave ovens that can perform automatic cooking have emerged and are in the limelight. However, if cooking is performed automatically by detecting steam from food, a temperature sensor and a humidity sensor are provided, and the temperature of the atmosphere in the heating cabinet or the exhaust section is detected by the temperature sensor, and the detection signal is output. By controlling the heating heater to keep the temperature of the intake air into the heating chamber constant, the atmosphere in the heating tongue is kept at a constant temperature, and in this state, a humidity sensor is used. A configuration is considered in which the amount of change in 0 is detected and the oscillation output of the magnetron is controlled by the detection signal.

The principle of a general high-frequency heating device that performs automatic cooking in this manner will be described with reference to FIGS. 1 and 2. FIG.

5 In Figures a, b, and c, _Rh 'is the relative humidity change due to heating.

0MPI •, T is the temperature rise, A _h is the change in absolute humidity obtained from and T, and t is the heating time.

Generally, the steam generated by heating food gradually rises with heating. Then, the amount of steam generated after the food reaches ¹ oo ° c is determined by the heating heat. This is for the following reason.

In Fig. 2, O is a heating room, Y is a container, W is water, and Q is air volume.

P is heated heat, Q _E is the latent heat, the Q _c is the heat radiation amount. 'In the figure, a container Y containing water W is placed in a heating chamber O that forcibly sucks and exhausts the air volume Q, and when the heating heat P is added, the water W eventually boils.

The relation of the calorific value at this time is expressed as follows.

Approximately, PQ _E- , water W!]

P. [KWatt] X 860 [teal] = 1 O O "C latent heat [¾ xG [K £ / ti]

G

]

= 86 OXP / 539 X 6 O ¾ Z ¹ ^-]

Is represented by For example, if the heating heat is 700W, 0.0186

, 5 O O W, the amount of steam is 0.0133 U / mi. O If the amount of heat applied is constant, the amount of steam generated per unit time is also constant.

Therefore the absolute humidity of the heating inception converts the relative humidity R _h from the value of the relative humidity sensor and a temperature sensor in the vicinity of the first drawing by] ?, exhaust port absolute humidity A _h

Similarly, the relative humidity is converted into absolute humidity from the relative humidity Rh and temperature ^τ that change with heating, and the difference between the absolute humidity at the start of heating and the temperature at the start of heating depends on the amount of heating heat and food type.

0MPI Detects the time when the set value, which is the change in absolute humidity, is reached. The counting time until the detection of ^ ΑΙ is multiplied by the food-specific heating coefficient Κ, and the product time is continuously heated after the lapse of time. This is because the time is already considered to be approximately proportional to the quantity of food, so it can be heated automatically, regardless of the quantity of food. If the detection of this time "3 ^" is performed only by relative humidity, the detection error will be generated due to the heat generated by the supply of heating heat (magnetron, high pressure, etc. in the electron range).

This is because, as is evident from the psychrometric chart (not shown), the relative humidity rise greatly differs depending on the ambient temperature even with the same increase in the amount of steam.

As described above, according to the principle, automatic heating is performed by detecting the absolute humidity. In this configuration, the accuracy, reliability, and durability of the sensor greatly affect the performance of the device itself, but the following disadvantages arise because the sensor is provided separately.

(1) In order to determine the amount of change between 1 and humidity based on relative humidity and temperature, each sensor is required to be highly accurate and expensive.

(2) Two components with sensors and functions are required. This has led to an increase in the component failure rate of the sensor unit.

(3) The relative humidity sensor and the temperature sensor are not related to the progress of aging at all, and the detection of the absolute humidity after long-term use was inaccurate.

(4) It is considered that the air flow in the exhaust path is turbulent. Therefore, since there is a considerable temperature difference between each part in the exhaust path,

0 PI Since the positions of the temperature sensor and the relative humidity sensor were not the same, an error occurred in the detection of the absolute humidity.

Disclosure of the invention

The present invention detects exhaust gas temperature and humidity and produces water vapor generated from food.

5 It is possible to accurately detect the time required to reach a certain amount of change in air humidity, and to automatically cook and thaw foods.

Another object of the present invention is to reduce the probability of occurrence of a failure by forming a temperature sensor and a humidity sensor with a single element.

Still another object of the present invention is to provide a high-frequency heating apparatus having high cooking performance by eliminating the detection errors by bringing the detection positions of a temperature sensor and a humidity sensor very close to each other. To achieve the above object, the high-frequency heating device of the present invention

1 5 A heating chamber for storing hot food, a high-frequency oscillator for supplying high-frequency power to the heating chamber, a control circuit including a micro-converter for controlling the high-frequency oscillator, and communication with the heating chamber or the heating chamber And a temperature / humidity detector configured with a single sensing element that detects temperature and humidity, and is connected to the heating chamber or the heating chamber by the temperature / 0 humidity detector. In addition to detecting the temperature and relative humidity at the passing position, converting the relative humidity into absolute humidity, measuring the time until the absolute humidity reaches a predetermined constant change amount, and using the time as a function to perform the control. The circuit is configured to control the high-frequency oscillator for automatic cooking.

25 and can be automatically thawed and have excellent cooking performance O

Brief description of drawings

Fig. 1 (a), (b), and (c) are characteristic diagrams of each factor to show the principle of the automatic heating control method based on absolute humidity detection, and Fig. 2 is a cutaway view for explaining the principle. FIG. 3 is an external perspective view of a sensing element used in the high-frequency heating device of the present invention, FIG. 4 is an equivalent circuit diagram of the sensing element, FIG. 5 is a temperature-sensitive characteristic diagram of the sensing element, and FIG. Is a humidity-sensitive characteristic diagram of the sensing element, FIG. 8 is a block diagram of a circuit for measuring temperature and relative humidity from the temperature- and humidity-sensitive characteristics of the sensing element, and FIG. ⁸ is an embodiment of the present invention. An example is a block diagram of the control circuit of the high-frequency heating device, FIGS. 9 (a) to 9 (g) are output waveform diagrams of each block shown in FIG. S, and FIG. 10 is a block diagram of the device. FIG. 11 is an external perspective view of a temperature / relative humidity detector, FIG. 11 is an external perspective view showing another embodiment of the detector, and FIG. 12 is a control circuit of a high-frequency heating device according to another embodiment of the present invention Q. Block diagram, the first 3 view (a) ~ (g) is an output waveform diagram of each block shown in the first 2 FIG. BEST MODE FOR CARRYING OUT THE INVENTION

First, the first embodiment uses a porous dielectric ceramic, which is a metal oxide based on barium titanate π-nitium, as a sensor material. Will be described.

In FIG. 3, the sensing element 1 is a porous dielectric ceramic; electrodes 3 are applied to both sides of the sensing element 1; and a lead wire 4 is bonded to the electrode 3 o

FIG. 4 shows an equivalent circuit of the sensing element 1. C is the capacitance of the bulk of the porous dielectric ceramic 2 at a certain temperature, which occurs in the capacitor 5, and R is the value of the capacitance in an atmosphere with a certain relative humidity.

0MPI This is generated in the resistor 6 by electric resistance generated by moisture adsorption on the surface of the porous dielectric ceramic ² particles. Fig. 5 shows the relationship between temperature and capacitance C, that is, temperature-sensitive characteristics, and Fig. ⁶ shows the relationship between relative humidity and electrical resistance R, that is, the moisture-sensitive characteristics. According to these figures, j? A single sensing element 1 that detects the capacitance C and the electrical resistance R! ) The temperature change in the refrigerator and the relative humidity can be obtained. FIG. 6 is a block diagram showing an example of a temperature and relative humidity detection circuit including a micro computer. A pulse voltage generated from the pulse control unit 8 is applied to a series circuit of the detection element ¹ and the reference resistance element R _s T. This is i? The divided voltage and the time constant are determined. That is, i? Divided voltage is = _{R + R} 'QC

S Series resistance

R Resistance value of sensing element 1

V,

CC applied voltage

Take. Therefore, the resistance value of sensing element 1 is measured.

The time constant is obtained by measuring the time required for the divided voltage to reach a predetermined reference voltage Vref. That is, at the same time that the pulse voltage is applied, the time measurement unit 1O starts counting the clock signal from the clock source oscillation unit 9 and determines whether the divided voltage has reached the base voltage ^ ef. The judgment signal is input to the time measuring unit ¹⁰ by the voltage comparator 11 and the counting is stopped. As a result, the time constant is obtained, and the capacitance C of the detection element 1 can be measured. The minute EE voltage and time constant are input to computing unit 12 and Degree is required.

Figure 8 shows a microwave oven using the above-mentioned temperature and humidity measurement system. 1 3 heating chamber, 1 4 to be heated food, ¹ 5 fan, ^{1 6} Magne collected by filtration down, 1 § temperature and a relative humidity detector, 1 S the first § Figure

Temperature shown in 5Relative humidity measurement part, ¹⁹ is absolute humidity converter, 20 is

Initial values cage 2 1 subtractors, 2 2 setpoint generator, ² 3 ratio較器, 2 4 heating time control circuit, 2 ⁵ magnetic collected by filtration down driving circuit, 2 6 in the exhaust section is there.

9 (a) and 9 (b), the output of the temperature / relative humidity measuring unit 18 is shown as i o, and FIG. 9 (a) shows the temperature and FIG. 9 (b) shows the relative humidity. Also

Figure (c) shows the output of the absolute humidity converter 19, Figure (d) shows the output of the initial value holder SO, Figure (e) shows the output of the subtractor 21, and Figure (f) shows the comparator. The output of 23 and the output of the heating control circuit 24 are shown in FIG.

Next, the operation will be described. When the heating start signal is input, the heating time 5 control circuit 24 operates and starts counting time. This allows

The magnetron drive circuit 25 is operated to oscillate the magnetron 16 to start heating. At the same time, the relative humidity is converted to absolute humidity from the temperature and relative humidity at that time, and the value is held in the initial value holder SO (Fig. 9-d).

0 'The relative humidity changes gradually (Fig. 9-a, b) and the absolute humidity value V _Ah

It is transformed (Fig. 9-σ;). The relationship between relative humidity and temperature and absolute humidity is shown below.

0. 6 2 2 ίό Ρ „

P-P _s 5 Φ; Relative humidity (P _s ; Saturated water vapor pressure at a certain temperature t [1¾])

ΟΛ1ΡΙ il W1P0 ' • P; standard pressure (usually P = 1) [¾ /]

The initial value from the absolute humidity value V _Ah after conversion to the subtracter ^{2 1}

j? is subtracted (Fig. ⁹ e). The output of the subtracter ² 1 V _Ah -? When this o which is compared with the set value V _{A] l} output from the set value generator 2 2, setting the heating amount of heat, such as by the food] multiple number Selected from values. Absolute humidity rise (VAh

) Reaches VAH, the comparator 23 outputs Vf (FIG. 9, 1f).

Receiving the signal of the comparator 23, the heating time control circuit 24 detects the detection time from the start of heating to the output of Vf and the heating time coefficient あらかじめ previously determined according to the type of food and the type of cooking. Multiplied by

Continuously heating Te cowpea to the end (FIG. 9 one g) o T _n time to stop the magnetic collected by filtration down driving circuit 2 5 T. This stops oscillation and ends heating. -

· By the operation as described above, cooking is performed. However, the temperature and humidity detector of the present embodiment has the following functions to accurately detect the temperature.

The temperature / relative humidity detector 17 is always exposed to the steam, oil, and oil fumes generated by the heated food 14 due to heating, so the surface of the detection element 1 becomes dirty. . When these elements are heated to 4 °° C or more, the elements are decomposed and recovered to the initial state. Thus the temperature and relative humidity detector ¹ § in this embodiment is ¾ configuration Remind as to the 1 O FIG. 1 is a sensing element, 2a is a heater, 28 is a heater electrode, and 29 is an electrode of the sensing element 1.

Uni heater 2 7 by surrounding the sensing element ¹ is fixed to the support plate ³ Rei_5 of ¹ 'sheets provided. Another embodiment of this sensing element 1 is shown in FIG.

OMPI _ • Show. 1 is a sensing element, ^{3 1} is a surface heater, ^{3 2} is a heater electrode,

33 is a device electrode of the detection device 1. A surface heater 31 is provided on one surface of the detection element ¹ . Heater electrode ^{3 2} Ru configuration der which is fixed to the support plate 3 4 of one serves likewise the hand electrode sensing element ^1. The support plate ^{3 4} is grounded by the ground terminal ^{3 5.} As described above, the following effects are obtained according to the above embodiment.

(1) Since the temperature and relative humidity detector 17 is composed of a single sensing element ¹ , the measurement error due to the detection position can be almost reduced, and more accurate cooking can be performed. .

(2) By using the porous dielectric ceramic ² , water vapor is adsorbed to the inside of the sensing element 1 through the pores, and an equilibrium state of adsorption / desorption can be obtained in a short time. As a result, the electrical conduction changes very quickly. , ·

(3) If a heater 2 is provided around the sensing element 1 and heated by radiant heat to about 45 O ° C, dirt on the surface of the sensing element 1 is decomposed into carbon dioxide and water. This enables accurate temperature and humidity detection at all times.

(4) By forming the surface heater 31 integrally with the sensing element 1, the sensing element 1 can be heated by conduction heat, and the heating is performed with less power so as to be heated by radiant heat. be able to.

(5) The steam generated from the food 14 to be heated gathers near the exhaust unit 26, so if a temperature and relative humidity detector 1 is placed near this, the relative humidity due to the steam generated from the food 14 to be heated can be reduced. Change positive

• You can catch exactly.

(6) Arrange the temperature and relative humidity detector 1 in the exhaust section 26. • Toyo] can be sufficiently shielded from electromagnetic waves and can be heated

The steam generated from 14 is always exhausted through the exhaust section 26, so that the change in relative humidity due to the steam generated from the food 14 to be heated can be surely catched.

5 (7) The amount of steam generated from the heated food 14

It varies depending on the amount of heating heat controlled according to the type of cooking and the type of cooking. Therefore, the set value V _Ah depends on the type of food to be heated and the type of cooking! ) By changing] ?, yo]? Good cooking can be done.

t o Next, a second embodiment of the present invention will be described with reference to FIGS. 12 and 13 (a) to (g).

This embodiment is different from the above-described embodiment in that the heating chamber is controlled to a predetermined temperature while detecting the amount of change in the absolute humidity and controlling the oscillation output.

1 3 heating chamber at 1 5 first 2 FIG, 1 4 to be heated food, 1 5 fan, ^{1 6} Magne collected by filtration down, ¹ 7 Temperature, Relative Humidity detector 1 8 Temperature, Relative humidity measurement unit 19 is absolute humidity converter, 20 is initial value holder, 21 is subtractor, 22 is set value generator, 23 is comparator, 24 is heating time control circuit, 2 5 is a magnetron drive circuit,

20 26 is an exhaust unit, 38 is an intake unit, 37 is a resistance element, and 36 is a resistance element control unit.

¹³ (a) to ¹³ (g) show the respective output waveforms in FIG. 12 ^ FIGS. ¹³ (a) and 13 (b) show the outputs of the temperature / relative humidity measuring unit 18]. (a) shows the temperature, and (b) shows the relative humidity. Figure (c) shows the absolute humidity change.

25 equipment ^{1 9} output, FIG (d) shows output of the initial value retainer 2 O, force, FIG. (E) is

― 0A1PI The output of the subtracter 21 is shown in FIG. 3 (f), the output of the comparator 23 is shown, and the diagram (g) is the output of the heating time control circuit 24.

Together begin to con preparative π- Le to by connexion resistive element control unit 3-6 resistive element 3 § of O-off controls row heating chamber 1 ³ inside thus set temperature the temperature of the exhaust to the input signal, the initial value storage unit A signal is output to the 2 O and heating time control section 24. Thus, the relative humidity at the start of heating is determined by the absolute humidity converter 19 together with the preset temperature.] The initial absolute humidity is obtained and stored in the initial value holder 2 O (Fig. 13 -d) o Relative temperature gradually changes as heating progresses and is successively converted to absolute temperature value V _Ail (Fig. ^13- c) o Converted absolute humidity value V _All to initial value V _Ail Is subtracted by the subtractor 21. The output of the subtractor ² is compared with a set value V _Ah output from set value generator ^{2 2.} (First 3 Figure - e) ₀ At this time, setting heating heat, food etc. in good more numerical You can choose from When the rise in the absolute humidity (v _Ah- ) reaches J, a signal V _f is output from the comparator 23 (FIG. 13—f). Upon receiving the signal Vf of the comparison 23, the heating time control circuit 24 detects the detection time 1 ^ from the start of heating to the output of the signal and a heating time coefficient determined in advance according to the type of food and the type of cooking. Continue heating the time multiplied by K '^ (Fig. 13-g) o At the end of the ΚΊ ^ time_, stop the magnet opening / closing circuit 25. This stops oscillation and ends automatic heating. .

As described above, the following effects are obtained in the second embodiment.

(1) Absolute humidity is related to temperature and relative humidity as described above. Therefore, to calculate the absolute humidity,

ΟΛ1ΡΙ A function is required to calculate the sum of vapor pressures and the relative humidity in accordance with the formula to determine the sum vapor pressure and to calculate the sum. As described above, to calculate the absolute humidity, it is necessary to find the saturated vapor pressure for each temperature. U To do so, all the saturated vapor pressures for each temperature must be stored. Obviously, this requires a large number of storage elements. Therefore, if the temperature in the vicinity of the temperature and relative humidity detector 17 is controlled at a predetermined constant temperature, the saturated steam E to be stored can be stored at the predetermined temperature. Only saturated steam AE at. Therefore, the number of storage elements is drastically reduced. Therefore, a very simple control circuit configuration can be achieved.

(2) By disposing the resistance element in the intake section 3S], the temperature in the vicinity of the temperature and relative humidity detector 1 is controlled and the temperature in the heating chamber 13 is naturally controlled. Controlled.

On the other hand, if the operating environment of this high-frequency heating device is extremely high and the relative humidity is '95%, for example, the high-frequency heating is used.) No matter how much steam is generated from the food to be heated 14 thereafter, only dew forms on the wall of the heating chamber 13 and the temperature and relative humidity detector 17 catches changes in relative humidity. It is impossible to do it. However, as described above, even if the use environment is at a relative humidity of 95%, the inside of the heating chamber 13 is controlled to a higher temperature, so that the relative humidity decreases. Accordingly, even if steam is generated from the food 14 to be heated, there is a sufficient margin before the plane is flattened, and a change in the relative humidity can be sufficiently caught. Tsuma D

0MPJ A device that is not easily influenced by the

It may be further expanded and to heat the surface of the heated food 1 ⁴ by the radiant heat D directly by the placing the resistive element 3 7 into the heating chamber ¹³ configuration of the second embodiment. This dried the surface of the food to be heated ¹⁴ moderately.], And it could be burnt. In the case of a beef, the cooking performance was the same as that of the heater heating, although high frequency heating was used. Can be

Similarly, a configuration in which the temperature control is performed by an infrared lamp instead of the resistor 3 may be used. This makes the inside of the heating chamber ¹³ sufficiently illuminated.] The lamp for lighting can be omitted. Further, the infrared rays are absorbed by the food, and the food can be heated, so that the same effect can be obtained in the above-mentioned mouth beef or the like.

Further, in the second embodiment, the flow rate of the cooling air from the magnetron ¹⁶ and the flow rate of the air outside the high-frequency heating device were controlled. By adjusting the temperature, it is possible to utilize the energy previously discarded, and it is possible to achieve an energy-saving and low-cost configuration.

Furthermore, in the second embodiment, if the sensing element "!" And the resistance element 3 are arranged close to each other and the temperature is adjusted by controlling the heat generation of the resistance element 37, a small amount of power can be obtained. 'While the temperature can be controlled, it can be shared with a heater that heats and cleans the sensing element 1, resulting in an energy-saving and inexpensive configuration-Industrial applicability

As described above, according to the high-frequency heating device of the present invention, since the temperature and the relative humidity are detected by a single sensing element, the heating chamber

-BU EAU

OMPI • Temperature and relative humidity inside can be measured more accurately. In other words, when measuring temperature and relative humidity with separate sensing elements, the mounting position of each sensing element should be as small as possible]? Even if they are close to each other, there is a limit i), and measurement errors due to the sensing position should be prevented. But the same detection

According to the five elements, the measurement error described above can be almost generated.

Also, when temperature and relative humidity are measured by separate sensing elements, the aging of each sensing element shows its own characteristic. 3) When temperature and relative humidity are measured and converted to absolute humidity Large measurement errors appear. However, according to the same sensing element, the characteristics of the aging over time change with a certain relationship, so that an excellent effect such as a small error is less likely to appear.

OMPI

Claims

• The scope of the claims

1. A heating chamber for accommodating the food to be heated, a high-frequency oscillator for supplying high-frequency power to the heating chamber, a control circuit including a π-computer for controlling the high-frequency oscillator,

5 A temperature / humidity detector, which is provided at a position communicating with the heating chamber and is composed of a single sensing element that detects temperature and humidity, is provided by the aforementioned temperature / humidity detector. In addition to detecting the temperature and relative humidity of the room or the position communicating with the heating room, the relative humidity is converted into absolute humidity, and the time required for the absolute humidity to reach a predetermined amount of change in O is measured. A high-frequency heating device characterized in that the control circuit controls the high-frequency oscillator as a function of this time. -

2. The method according to claim 1, wherein the temperature in the heating chamber is controlled to a predetermined constant temperature by a detection signal of a temperature / humidity detector.

A high-frequency heating device to be referred to as 15.

3. The high-frequency wave according to claim 1, wherein a relative humidity is detected by a resistance value of the detection element, and a temperature is detected by a capacitance and humidity of the detection element. Heating device I. o

04. The high-frequency heating apparatus according to claim ¹ , wherein the detection element of the temperature / humidity detector is made of a metal oxide-based porous dielectric ceramic.

5. The high-frequency heating device according to claim 1, characterized in that a heater for heating the temperature / humidity detector and cleaning the temperature detector is provided nearby or integrally. apparatus.

OMPI • 6. The method according to claim 2, further comprising: a resistance element controlled by a detection signal of a temperature / humidity detector, wherein the temperature in the heating chamber is heated to a predetermined constant temperature by the resistance element. High frequency <Karo heat device.

5 T. High-frequency heating according to claim 1 or 2, characterized in that the temperature / humidity detector is arranged in the exhaust part of the heating chamber.

8. According to claim ¹ or 2, the time required for the difference between the absolute humidity value at the start of heating and the absolute humidity value due to heating to reach a predetermined set value, and High-frequency heating characterized by a configuration in which heating control is performed continuously from the time KT ^ multiplied by the heating time coefficient K determined by the type of food and the type of cooking to the time when the above-mentioned set value is reached. apparatus.

ΟΛ1ΡΙ