JPH0268885A - High frequency heating device - Google Patents

Abstract

PURPOSE:To achieve the automatization of thawing and heating by only a single sensor by detecting the weight of a heated material to calculate the heating time at the time of thawing, and detecting the weight change during heating to control the feed to a heating means at the time of heating. CONSTITUTION:Various heating instructions inputted from a key board 4 on an operation panel are decoded by a control part 7 and displayed in determined manners. In a heating chamber 8, a heated material 10 is placed on a table 9 and a magnetron 11 controls the feed by the control part 7 through a driver 12. A weight detecting means 14 is mechanically engaged with the top end of the driving shaft of a driving source 13 of the table 9. The control part 7 detects the total weight of the heated material prior to thawing to calculate the thawing time. In the case of heating, it detects the weight reduction of the heated material accompanied by the progress of heating to control the feed to the heating means. Hence, both the thawing and the heating can be automatized with only a single weight detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device such as a microwave oven that is equipped with a weight sensor and configured to automatically control the end of heating.

BACKGROUND OF THE INVENTION High-frequency heating devices equipped with conventional technology sensors to automatically control heating time have already been widely put into practical use.

In order to automate various types of heating, for example, microwave ovens that combine humidity sensors, gas sensors, and weight sensors are most commonly commercialized.

The reason why high-frequency heating devices equipped with composite sensors are in widespread use is that each sensor has a different area of expertise in automation, and by combining them, it has become possible to cover a wide range of areas. It is.

The first humidity sensors and gas sensors that were put into practical use were able to detect various gases and vapors emitted from food and control the finish of the food. Therefore, even if the amount of the heated object is the same, it has been possible to automate various foods whose heating times vary greatly depending on the type of the heated object.

However, such humidity sensors and gas sensors are difficult to detect when thawing objects that are below freezing point, such as when thawing frozen foods, because the amount of gas or steam generated from the food is very small. It did not have the same sensitivity.

On the other hand, the dielectric constant of ice is constant, so whether it is meat or vegetables,
The heating time in a frozen state is determined only by the amount of food, regardless of the type of food. For this reason, weight sensors have been widely used to detect the amount of food and calculate the thawing time based on this.

Humidity sensors and gas sensors are good at heating objects to high temperatures, and weight sensors are resistant to defrosting.
They have been widely used in microwave ovens and other high-frequency heating devices as a ``compatible'' combination that takes advantage of each other's strengths and covers each other's weaknesses.

Problems to be Solved by the Invention However, since the automated high-frequency heating device with such a conventional configuration must be equipped with two sensors, the control system is naturally expensive. Since the configuration is complex, it is disadvantageous in terms of reliability, and of course, the probability of failure increases accordingly. Even when a microcomputer is used as the control unit, a program must be prepared to support the two sensors, which requires a large amount of ROM capacity.

In view of this background, the present invention attempts to automate both thawing and heating using only a single sensor.

Means for Solving the Problems In order to solve the above problems, the present invention provides a heating chamber for heating an object to be heated, a heating means coupled to this heating chamber, and a control for controlling power supply to this heating means. a storage stand on which the object to be heated is placed; a weight detection means for detecting the weight of the object to be heated on the placing stand; It consists of a defrost key to set the temperature, and a heating key to instruct the object to be heated to a certain temperature.

Function: When the control unit detects the pressing of the defrost key, the high-frequency heating device of the present invention detects the weight of the object to be heated before and after starting power supply to the heating means via the weight detection means, and also detects the weight of the object to be heated before and after starting power supply to the heating means. The heating time is then calculated, and if the pressing of the heating key is detected, the weight of the object to be heated is repeatedly measured via the weight detection means while supplying power to the heating means, and changes in weight during heating are detected. and is configured to control power supply to the heating means.

With this configuration and operation, thawing and heating can be automated using only a single weight sensor.

EXAMPLE Hereinafter, a heating device according to the present invention will be explained with reference to the drawings.

FIG. 2 is a perspective view of the main body of a high-frequency heating device such as a microwave oven according to the present invention.

A door body 2 is provided on the front surface of the main body 1 so as to be openable and closable, and an operation panel 3 is disposed thereon. A keyboard 4 is arranged on the operation panel 3. On this keyboard, there is a defrost key 5 that instructs to automatically defrost the frozen object to be heated.
and a heating key 6 that instructs to automatically heat an object to be heated that has been frozen, refrigerated, or stored at room temperature to a certain temperature. Furthermore, the heating keys include a reheating key for reheating the object to be heated in the heating method, a thawing cooking key for heating already cooked frozen foods, a cooking key for heating raw materials, and the like.

FIG. 3 is an embodiment of a block diagram showing the system configuration of the heating device according to the present invention.

Various heating commands inputted from the keyboard 4 on the operation panel 3 are decoded by the control unit 7 and a predetermined display is performed.

In heating chamber 8! The object to be heated 10 is placed on the 11 stand 9,
Heating means 1 is also heated by a magnetron. Power supply to the magnetron 11 is controlled by the control unit 7 via the driver 12 .

The mounting table 9 is rotationally driven by a drive source 13 during heating in order to improve uneven heating of the object 10 to be heated. A weight detection means 14 is mechanically engaged with the tip of the drive shaft of the drive source 13 that freely moves in the thrust direction.

As such a weight detection means, a strain gauge, a capacitance type pressure sensor, a displacement sensor, etc. can be used. 1
5 is a detection circuit.

FIG. 4 shows an example of a specific circuit configuration of such a system.The control section 7 is realized by a microcomputer, and the weight sensor 14 is a capacitance type pressure sensor. An oscillation circuit is used as the detection circuit 15, and is formed by a combination of a sawtooth wave generation circuit and a waveform shaping circuit of an operational amplifier.

The output pulse of the oscillation circuit 15 is connected to the input terminal TC of the built-in counter of the microcomputer 7.

Weight measurement is performed by a built-in counter connected to the TC terminal, and by counting the number of output pulses of the oscillation circuit 15, the pressure applied to the sensor, that is, the weight can be detected.

Reference numeral 16 denotes a level shift circuit for voltage conversion and waveform shaping, which may be added as appropriate.

For example, the operational amplifier is TLO82, and the microcontroller is MB88.
515, but it goes without saying that any device with equivalent functionality can also be used.

Next, the operation of the control section, which is the main point of the present invention, will be explained.

FIG. 5 is a flowchart showing a control program of the microcomputer which is the control section 7. As shown in FIG.

First, the entered key is decrypted. As a result, if it is detected that the defrosting key has been pressed (a), the total weight W0 of the object to be heated is detected prior to heating (c).

During thawing, a predetermined net made of plastic is usually used to allow drips from the heated object to drip onto the mounting table and prevent the heated object from boiling.

By subtracting the net weight WH from the detected total weight W0, the net weight WF of the heated object can be obtained (C)
.

w, = w, -wN -...-...- (1) Based on this, calculate the thawing time T. (d) The thawing time T is a function of the net weight WF of the object to be heated. However, it is calculated as shown in the following equation, for example.

To-T, +T2 +T3 +T4 ・・・-・-(
2) Here, T+ is a short heating stage at high power that is carried out at the beginning of heating, and T is a continuation (pause stage).
, respectively, represent a thawing stage at medium output, and T4 represent a finishing stage at low output, and each T7 time is expressed, for example, by the following linear equation.

T, 1=AnWF +B, ・ ・(3) However, A
,,B,: constant (n-1 to 4) The thawing time is determined as a function depending on the weight, thus gradually reducing the output.6 Once the time is determined, the power supply to the heating means is started (e), the heating time T7 of each stage and the high frequency output at that time are controlled (f), and when the total heating time T has elapsed, the heating is automatically terminated (no smell).

FIG. 1 is a time chart showing such an operation, and (A
) Im shows how power is supplied to the heating means during the above thawing.

Now, returning to FIG. 5 again, the operation of the heating key will be explained.

Now, if the pressing of the heating key is detected, a decrease in the weight of the object to be heated as the heating progresses is detected, and the power supply to the heating means is controlled. However, simply detecting the weight change from the start of heating causes the output value of the weight detection means to fluctuate depending on the temperature characteristics of the circuit and sensor element, and the amount is generally so large that it cannot be ignored. In order to detect weight changes, it is necessary to devise a method that is not affected by such temperature characteristics. Furthermore, since the weight sensor collects data through a mechanical system, the main body is often subject to noise from external vibrations, such as the effects of opening and closing a door.

Therefore, in the present invention, if the pressing of the heating key is detected,
First, start heating i), then the initial form of the object to be heated! t
wi is detected (j), and then the weight of the object to be heated ff1W1 is continued to be detected at certain time intervals (b) by counting for a predetermined time (1), and then the previous measured value and The difference DW is obtained by the following formula (2).

DW=Wfi −W, , , −−−−−−−−−−
- (4) Initially, the weight of the object to be heated hardly changes.

Therefore, only output fluctuations due to temperature characteristics of circuits and elements are detected as DW values.

As the heating progresses and steam and the like begin to be generated from the object to be heated, the weight of the object to be heated becomes lighter, and by detecting changes in this weight, it is possible to control the point at which heating is completed.

Since such a difference DW is based on weights measured at a certain predetermined time interval, it can be considered as a time change rate of weight change, that is, a time differential value. Therefore, such a difference DW is larger than a certain value C3 and a certain value C2
By determining (n) whether the difference in weight is smaller than the above, it can be determined whether the obtained weight difference value is a normal decrease in the weight N of the object to be heated.

C,<DW<Cz −−1−・−(5) However, CI,
Cz: Constant, that is, if the difference value DW is larger than a certain value C2, it indicates that it includes not only the temperature characteristics of the circuit or sensor but also the weight reduction of the heated object. Another value C
If it is smaller than t, it can be seen that the weight 1 of the object to be heated is normally reduced, rather than noise coming in from the outside due to the influence of vibrations or the like. Therefore, such difference values are added (O),
Through this process, the differential IDW, which is the time differential value of weight change, is
can be integrated again to indicate the weight change amount ΔW.

ΔW=ΣDW ・−・・−・−・(6) If the difference value is smaller than a certain value C8, it is assumed that it is an output fluctuation due to the temperature characteristics of the circuit and sensor, and such value is not subjected to integration processing. Similarly, if the difference value is larger than a certain value C2, it is considered to be noise and is discarded without being processed as data.

Through the above procedure, the differential integral weight ΔW can accurately detect only the weight change of the heated object, and if this is compared with a certain threshold value W□ (p), the weight change has reached a predetermined value. It can be determined whether the If this threshold value W, 14 is exceeded, the heating of the object to be heated has progressed to a predetermined point, and the power supply to the heating means is changed or terminated (9), so that the heating is automatically terminated. Ru.

(B) of Fig. 1 is a time chart showing the operation of such a heating key, in which the time T until reaching a certain threshold value Wi,l is counted, and here the output is switched to low,
An example is shown in which heating is continued for a time KT multiplied by a certain constant K as the remaining time.

This is a technology that has been widely used in humidity sensors, gas sensors, etc.

Now, returning to Figure 5 again, when the command key is neither a defrost key nor a heating key, the decoding of that key proceeds,
Control appropriate to that key will be performed (r)
.

Effects of the Invention As described above, the high-frequency heating device of the present invention can automate both thawing and heating using only a single weight detection means.

This simplifies the control system configuration, improves reliability, and, of course, reduces the probability of failure.

In addition, when using a microcomputer in the control section, the basic part of the control of the weight sensor can be used for the first 2111 weight measurement and weight change detection, and the ROM capacity of the microcomputer can be reduced compared to the conventional composite sensor method. can.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing one embodiment of the control method of the present invention. FIG. 2 is a perspective view of the main body of a high-frequency heating device such as a microwave oven according to the present invention, and FIG. 3 is a block diagram showing the system configuration! , FIG. 4 is a circuit diagram showing a specific example of the present invention, and FIG. 5 is a flowchart showing the structure of a control program showing an example of the present invention. 7...control unit, 8-heating chamber, 9...river...i!
Placement stand 10...Heated object, 11...Heating means, 14
・−・−・i amount detection means. Name of agent: Patent attorney Shige Takashi Awano and one other person Figure 1 Figure 2? Figure 14 top

Claims (1)

[Claims] A heating chamber that heats an object to be heated, a heating means coupled to this heating chamber, a control unit that controls power supply to this heating means, a mounting table on which the object to be heated is placed, and a heating device on this mounting table. a weight detection means for detecting the weight of the object to be heated; a thawing key for instructing the control section to defrost the object when the temperature is below freezing point; and a thawing key for instructing the control section to thaw the object to be heated to a certain temperature. and a heating key for detecting the decompression key, and when the pressing of the defrosting key is detected, the control section detects the weight of the object to be heated before and after starting power supply to the heating means via the weight detection means, and detects the weight of the object to be heated before and after starting power supply to the heating means. The heating time is calculated based on the heating time, and if the pressing of the heating key is detected, the weight of the object to be heated is repeatedly measured via the weight detection means while supplying power to the heating means, and the heating time is calculated based on the heating time. A high frequency heating device configured to control power supply to the heating means by detecting a weight change.