JP2000323271A - High frequency heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a high frequency heater from exceeding a prescribed current by just changing a program of a microcomputer and to provide a high output by controlling the irradiation level of a high frequency magnetic wave to be changed elapsing after a prescribed time. SOLUTION: In a high frequency heater, when a food is put in a heating chamber 5 and a high output cooking selection key is selected from an operation panel 9 to be started, a signal for oscillating magnetron 1 is transmitted from a microcomputer substrate 3 which receives the signal from the operation panel 9 to an inverter 2. The emission level of the magnetron 1 is set to some setting value (Lb1) so that the input current is prevented from exceeding 15A. When proceeding the cooking, the temperature of the magnet of the magnetron 1 is raised so that the input current is reduced by gradual reduction characteristic. When a certain time is elapsed without completing the cooking, it is so set that the magnetron 1 is actuated at the emission level of the setting value (Lb2) formed by correcting the reduced portion of the input current. Then, it is so set as to Lb1<Lb2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to output control of a high-frequency heating device.

[0002]

2. Description of the Related Art When a high-frequency heating apparatus is operated, as the operation proceeds, the temperature of the magnet of the magnetron rises, the cutoff voltage decreases, and the input current gradually decreases until the temperature is saturated. This gradually decreasing characteristic is a control that reduces the input current and derates when the temperature rises to reduce the temperature duty of each electric component, so it can be said that it is a power control method that is very light for equipment. .

However, due to the gradual decrease characteristic of the input current, 1.5 to 2 A is required until the temperature is saturated after the device starts operating from a cold state in which the temperature is sufficiently adjusted to the atmosphere.
Has also been found to decrease. Further, according to the Electrical Appliance and Material Control Law, the timing of measuring the high-frequency output is the temperature saturation state.

On the other hand, current breakers installed in indoor wiring generally have a lower limit of 15 A in Japan. It is a fact that many users still use the 15A breaker. When a fuse having a rating of 15 A is used, the input current is not allowed to exceed 15 A. Therefore, it is an indispensable restriction to use an input current within 15 A in electrical equipment in Japan.

[0005] Considering such a high-frequency heating apparatus having a large high-frequency output, if the high-frequency output is determined at the time (b) as shown in FIG. As shown in the above, the current exceeds 15 A, and the above-mentioned restriction on the input current in the market cannot be observed.

In other words, there is a constraint that the design must be made slightly lower than 15 A at the start of heating. Unless a power supply, a magnetron, and a food supply system with high efficiency for converting an input current into a high-frequency output is achieved, the maximum high-frequency output is limited to 700 W at most, which is an obstacle to increasing the output of a high-frequency heating device.

In order to solve the above-mentioned problem, a current input to a magnetron driving power supply is detected, and the value of the current is detected as D.
Prior to the present invention, a method was considered in which the output of the input current detection circuit for converting to the C voltage is controlled to be constant by negative feedback control.

In the present invention, as shown in FIG. 6, an input current detection circuit 4 is provided between a magnetron 1, a driving power supply (inverter) 2 and a microcomputer board 3, as shown in FIG. According to this method, when the high-frequency output is high and the input current may exceed 15 A, the input current is controlled by controlling the output of the input current detection circuit 4 to a value not exceeding 15 A by negative feedback control. It was possible to comply with the restriction of 15 A and to achieve high output of the high-frequency heating device.

[0009]

However, in order to realize an output of 800 W in the above technique, it is necessary to provide an input current detection circuit 4 separately, so that the circuit board is costly and the layout of the board is small. This was one of the factors that made the design difficult.

[0010]

According to the present invention, there is provided a heating chamber for heating an object to be heated, a magnetron for radiating high-frequency electromagnetic waves to the heating chamber, and a drive for operating the magnetron. An apparatus control circuit having a power supply and control means for controlling the radiation level of the high-frequency electromagnetic wave is provided. The apparatus control circuit is a control method for changing the irradiation level of the high-frequency electromagnetic wave by the control means after a lapse of a predetermined time.

According to the above invention, when high output and high frequency output are required, the magnetron is controlled at a level where the input current does not exceed 15 A in a cold state, and a gradually decreasing characteristic of the magnetron in a warm state when the operation is advanced. The magnetron can be controlled at a level corrected for the decreasing current value, and high output can be maintained. According to this method, even if the input current detection circuit is not provided, it is possible to increase the output without exceeding 15 A only by changing the program of the microcomputer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a heating chamber for heating an object to be heated in a main body, a magnetron for emitting high-frequency electromagnetic waves to the heating chamber, a power supply for driving the magnetron, and a power supply for driving the high-frequency electromagnetic waves. A device control circuit having control means for controlling a radiation level, wherein the device control circuit changes the irradiation level of the high-frequency electromagnetic wave by the control means after a lapse of a predetermined time. As the high-frequency heating cooking progresses, the magnetron temperature rises and the input current decreases, so the output value also decreases, but after a certain period of time, the control method is to increase the radiation level of the magnetron by the amount that the input current decreases. Therefore, the initial output value can be maintained.

The present invention also has a short-time high-output function,
At least when the high-frequency output value is set, the control is such that the radiation level of the magnetron is changed over time. Therefore, the total input current is 15
When the magnetron is operated at a level that does not exceed A and the input current decreases as the operation proceeds, the magnetron can be operated at a level corrected by the reduced amount, and high output can be maintained.

Further, according to the present invention, the radiation level can be changed two or more times during one cooking operation. Correction is performed at a point in time when the decrease value of the input current is small, and by increasing the number of times, the input current constant control is approached without limit. With this method, higher output with higher accuracy can be achieved.

Further, in the present invention, the radiation level of the magnetron is changed by utilizing the detection level of a thermistor for temperature detection provided in the refrigerator. As the magnetron operates and cooking progresses, the temperature of the non-heated material and the inner wall surface increases.
By detecting these temperatures, the radiation level of the magnetron can be changed to achieve high-power operation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) In FIG.
A turntable 7 which rotates with the object 6 to be heated placed thereon is disposed at the bottom of the table. Reference numeral 8 denotes a door for taking in and out the object 6 to be heated, and 9 denotes an operation panel for selecting a cooking method and a cooking time. Reference numeral 2 denotes a driving power supply (inverter) for operating the magnetron. Reference numeral 3 denotes a microcomputer board, which controls the inverter 2 and other components from options on the operation panel 9. Reference numeral 10 denotes a thermistor for detecting the temperature inside the refrigerator. The components having the same reference numerals as those of the conventional example indicate the components having the same functions.

Next, the operation and operation will be described with reference to FIG. When the food is put into the heating chamber 5 and a high-power heating cooking selection is made from the operation panel 9, for example, a “warm” key is selected and started, the magnetron 1 oscillates from the microcomputer board 3 which received the signal of the operation panel 9 to the inverter 2. A signal is sent to the user. The inverter 2 receives this signal and causes the magnetron 1 to oscillate. At this time, the radiation level Vref of the magnetron 1 is one set value Lb
Since it is set to 1, the input current does not exceed 15A. As cooking progresses, the temperature of the magnet of the magnetron 1 increases, and the input current decreases due to the gradually decreasing characteristic. Here, when the cooking is not completed and a certain time T has passed, control is performed to operate the magnetron 1 with a Vref value of a set value Lb2 corrected for the decrease in the input current. At this time, if Lb1 <Lb2 is set, the input current increases, but the value of Lb2 may be set at a level not exceeding 15 A because it is a correction for the decrease. As the input current increases, the high frequency output also increases. FIG. 2 shows the relationship between the input current and the set value.

(Embodiment 2) Recently, as a control method for extracting the features of the inverter power supply, a boost in which components are sufficiently cooled (when there is no previous use history), the high-frequency output is increased to a rating or more, and cooking is completed in a short time. Has functions. For example, if the boost function is used for 90 seconds after the operation is started, cooking that requires a relatively short time such as reheating can be mostly benefited from this function.

However, it is difficult for a model without the input current detection circuit 4 to maintain a high output while maintaining the restriction of 15 A as shown in the conventional example of FIG. Therefore, a certain time T is set in advance, and a control method of changing the radiation level of the magnetron 1 after T has elapsed is adopted. When the set is cold, the radiation level of the magnetron 1 is set to Lb1, so that the input current does not exceed 15A and operates with high output. As the temperature of the magnetron 1 rises during operation, the input current decreases due to the gradually decreasing characteristic, and the output level also decreases. However, the input current increases and the output level increases because the radiation level is increased to Lb2 after the elapse of the time T.

As described above, when the short-time high-output function (boost function) is operating, high output can be realized by changing the radiation level of the magnetron 1 with the passage of time at an input current not exceeding 15 A. it can.

(Embodiment 3) Embodiment 3 will be described with reference to a timing chart shown in FIG. In the third embodiment, the timing of changing the magnetron radiation level described in the first or second embodiment is subdivided. By doing so, the correction can be made at a point in time when the decrease in the input current due to the gradual decrease characteristic of the magnetron 1 is small, so that the input current changes at a level close to 15 A and a high output can be maintained.

(Embodiment 4) In Embodiment 4, the change of the magnetron radiation level described in Embodiments 1 to 3 utilizes the signal of the thermistor 10 as a temperature detecting means for detecting not the lapse of time but the inside temperature. As the cooking progresses, the temperature of the heated object 6 rises. When the high-frequency electromagnetic wave radiated from the magnetron 1 is reflected on the wall surface of the heating chamber 5, some loss occurs, and the temperature of the wall surface rises. If the correlation between the thermistor signal level that changes due to the temperature rise and the input current decrease due to the gradually decreasing characteristics of the magnetron 1 is measured in advance, the timing of changing the radiation level of the magnetron 1 can be determined using the signal level of the thermistor 10. It is possible to maintain high output.

According to the above method, the radiation level of the magnetron 1 can be controlled without changing the input current detection circuit 4 by changing the program of the microcomputer so as not to exceed 15 A.
Moreover, a high-output high-frequency heating device can be provided.

[0025]

As is apparent from the above description, according to the present invention, a high-frequency high-frequency heating apparatus whose input current does not exceed 15 A and whose output is high can be realized by changing the program of the microcomputer. Since the input current detection circuit can be omitted only by changing the program, it can contribute to cost reduction of the product. Also, since parts can be omitted, this is an effective means for saving space in product development.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating the operation of a high-frequency heating device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of changes in input current and Vref of the high-frequency heating device according to the first embodiment of the present invention.

FIG. 3 is a front sectional view of a main part of the high-frequency heating device according to the first embodiment of the present invention.

FIG. 4 is a timing chart of changes in input current and Vref of a high-frequency heating device according to a third embodiment of the present invention.

FIG. 5 shows the input current and Vref of a conventional high-frequency heating device.
Change timing chart

FIG. 6 is a front sectional view of a main part of a conventional high-frequency heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetron 5 Heating chamber 6 Heated object 10 Thermistor (temperature detecting means)

Claims (4)

[Claims] 1. A heating chamber for heating an object to be heated in a main body, a magnetron for emitting high-frequency electromagnetic waves to the heating chamber, an inverter power supply for driving the magnetron, and control means for controlling a radiation level of the high-frequency electromagnetic waves. And a device control circuit having a control method for changing the radiation level of the high-frequency electromagnetic wave by the control means after a lapse of a predetermined time. 2. A high-frequency heating apparatus according to claim 1, further comprising a short-time high-output function, wherein the control method changes the radiation level of the high-frequency electromagnetic wave after a lapse of a predetermined time when at least setting the high-frequency output value. 3. The high-frequency heating apparatus according to claim 1, wherein the radiation level of the high-frequency electromagnetic wave is changed in two or more stages. 4. The high-frequency heating apparatus according to claim 1, wherein a radiation level of the high-frequency electromagnetic wave is changed by a signal from a temperature detecting means provided in the heating chamber.