JPH0888078A - High frequency heating device - Google Patents

Abstract

PURPOSE: To enable the output of a magnetron to be controlled in response to the amount of food to be heated by letting applied pulses causing the magnetron to generate micro-waves be changed in response to information on temperature from a temperature measurement means measuring the temperature of the magnetron. CONSTITUTION: When the normal amount of food is heated, since the temperature of a magnetron 3 is gradually raised directly after heating is started, small electromotive power at a temperature detecting section 18 is thereby gradually increased. This situation thereby causes the resistant value of a variable resistance element to be decreased, and thereby causes a time constant CR to be decreased. In this case, when the time constant CR is decreased, a wave form is sharply raised up at both the temperature detecting section 18 and the intermediate point (b) of a capacitor C2. a TRIAC 23 is then energized herewith, and the magnetron 3 is controlled to output in response to the normal amount of food. On the other hand, when the amount of food is little, the magnetron 3 is sharply increased in temperature, and the time constant of the temperature detecting section 18 is increased. This situation causes the TRIAC 23 to be energized at a small phase angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating device that radiates microwaves to heat food, and particularly relates to output control of a magnetron that generates microwaves.

[0002]

2. Description of the Related Art A microwave oven, which is an example of a conventional high-frequency heating apparatus, is provided with a magnetron which generates a microwave by an applied pulse, and the microwave generated from the magnetron is applied to food stored in a heating chamber to be absorbed. By doing so, the food is heated.

By the way, since the microwave generated from the magnetron is not completely absorbed by the food, a part of the microwave returns to the magnetron as a reflected wave, and when the microwave returns to the magnetron in this way, it is excessively absorbed by the magnetron. Temperature rise will occur.

Here, when the output of the magnetron is constant, the smaller the amount of food to be heated, the greater the amount of unabsorbed microwaves. Therefore, until now, when the amount of food was small, the magnetron was used. The output of the magnetron is controlled according to the amount of food by turning on and off the energization of the high voltage circuit including it for a certain period of time or by shutting off the power supply with a temperature thermostat or the like to prevent an excessive temperature rise of the magnetron.

[0005]

However, in such a conventional high-frequency heating apparatus, when the energization of the high-voltage circuit is turned on and off for a certain period of time, the life of the magnetron is shortened, and a power source such as a temperature thermostat is used. In the case of shutting off, the operation of the device is stopped during heating and cooking, which causes a distrust of the user.

Therefore, the present invention has been made in order to solve such a problem, and an object thereof is to provide a high-frequency heating device capable of controlling the output of a magnetron according to the amount of food to be heated. It is what

[0007]

According to a first aspect of the present invention, there is provided a high-frequency heating device for heating a food contained in a heating chamber formed inside a main body by radiating a microwave to the food, and applying a pulse to the food. A magnetron that generates microwaves, a temperature measuring unit that measures the temperature of the magnetron, and an output control unit that controls the output of the magnetron by changing the applied pulse according to temperature information from the temperature measuring unit. Be prepared.

According to a second aspect of the present invention, the output control means is
The output pulse of the magnetron is controlled by changing the applied pulse in a relationship inversely proportional to the temperature of the magnetron.

According to a third aspect of the present invention, the temperature measuring means is attached to an appropriate position of the heat dissipation plate of the magnetron.

[0010]

According to the first aspect of the invention, the output control means changes the applied pulse for generating the microwave in the magnetron according to the temperature information from the temperature measuring means for measuring the temperature of the magnetron, thereby outputting the magnetron. To control.

According to the second aspect of the invention, the output control means controls the output of the magnetron by changing the applied pulse in a relation inversely proportional to the temperature of the magnetron.

According to the invention of claim 3, the temperature measuring means is attached to an appropriate position of the heat dissipation plate of the magnetron,
Measure the temperature of the magnetron.

[0013]

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

FIG. 1 is a partial cross-sectional top view of a microwave oven which is an example of a high frequency heating apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is a microwave oven main body (hereinafter referred to as main body), and 2 is a heating chamber 2 formed inside the main body 1. A magnetron 3 and a fan 4 for cooling the magnetron 3 are provided on the side of the heating chamber 2.
A machine room 5 in which is installed is formed. And
The microwave generated from the magnetron 3 is radiated to the food 6 contained in the heating chamber 2 through a waveguide (not shown).

In the figure, 7 is a magnetron 3
A thermocouple 8 having a higher heat resistance than a temperature thermostat such as a thermistor is attached to the leeward side of the heat radiation plate 7, and the thermocouple 8 oscillates the magnetron 3. The temperature inside can be detected. By attaching the thermocouple 8 to the radiator plate 7 in this way, the thermocouple 8 can be easily replaced, and by attaching the thermocouple 8 to the leeward side of the radiator plate 7, The highest temperature of the magnetron 3 can be detected without being affected by the cooling air.

On the other hand, inside the main body 1, as shown in FIG. 2, an illumination 1a provided in a heating chamber or an operation section (not shown).
A normal voltage circuit 9 that lights up and drives the blower motor 1b for the fan, and a high voltage circuit 12 for magnetron oscillation including a high voltage transformer 10, a high voltage capacitor C1, and a high voltage diode 11 are provided.

The normal voltage circuit 9 is provided with a control circuit 13 which is an output control means for controlling the output of the magnetron 3. Here, this control circuit 1
3 is a commercial power supply 15 supplied through a small transformer 14.
And a Zener diode 1 for keeping the voltage level of the commercial power supply 15 rectified by this diode bridge 16 at a reference level.
7 and the output of this Zener diode 17 is divided into 2
It has two resistors R1 and R2. In addition, these 2
The waveform at the midpoint a of the two resistors R1 and R2 is as shown in (1) of FIG.

The control circuit 13 also includes a variable resistor (not shown) that amplifies a small electromotive force generated in the thermocouple 8 due to the temperature change of the magnetron 3 and changes the resistance value according to the magnitude of the small electromotive force. A temperature detector 18 including an element is provided. When the output of the magnetron 3 is constant, the temperature change after the start of heating becomes large as shown by α in FIG. 4 when the amount of food is small,
When the amount of food is normal, it is moderate as shown by β, and when the amount of food is large, it is moderate as shown by γ.

By the way, the temperature detecting section 18 is connected to the capacitor C2. For example, when the amount of food is normal, the temperature change of the magnetron 3 is rather gradual, so that the micro electromotive force is gradual. While increasing.
When the micro electromotive force gradually increases in this way, the resistance value of the variable resistance element decreases and the time constant CR
Is decreasing. Here, when the time constant CR decreases in this way, the temperature detection unit 18 and the capacitor C2
The waveform at the middle point b is as shown in (2) of FIG. 3, which rises sharply as compared with the waveform shown in (2) of FIG. 5, which is a waveform when the amount of food described later is small.

On the other hand, the control circuit 13 has a PUT (programmable) in which the voltage at the midpoint a of the two resistors R1 and R2 is the gate voltage, and the voltage at the midpoint b of the temperature detector 18 and the capacitor C2 is the anode voltage.・ Unijunction ・
(Transistor) element 20 is provided, and a current flows through PUT element 20 when the voltage at midpoint b of temperature detector 18 and capacitor C2 exceeds the reference level, and the photo connected to the cathode accordingly. The triac 23 is shown in FIG. 3 via the diode 21 and the phototriac 22.
Conduction occurs at the phase angle shown in (3).

When the triac 23 conducts at the phase angle shown in (3) of FIG. 3 in this way, the high voltage transformer 1
A pulse P having a magnitude as shown in (4) of FIG. 3 is applied to the magnetron 3 on the secondary side of 0. By the way, the output of the magnetron 3 increases according to the magnitude of the applied pulse, but the commercial power supply 15 used to generate the applied pulse is shown in FIG.
As indicated by (3) in (3) above, the commercial power source 15 is a shaded portion, and not all the commercial power source 15 is used.

Since the shaded area changes steplessly in accordance with the temperature of the magnetron 3, the commercial power supply used by the control circuit 13 to generate the applied pulse in accordance with the temperature of the magnetron 3. The output of the magnetron 3 can be controlled to be an output according to the amount of normal food by changing the ratio of the shaded portion 15 (hereinafter referred to as the conduction ratio).

On the other hand, when the amount of food is small, the temperature of the magnetron 3 rapidly rises and the micro electromotive force greatly increases, and accordingly, the resistance value of the variable resistance element greatly increases and the time constant CR. Is increasing significantly. When the time constant CR is greatly increased in this way, the waveform at the midpoint b of the temperature detector 18 and the capacitor C2 has a gentle rising, as shown in (2) of FIG. As shown in (3) of FIG. 5, the electric conduction occurs at a smaller phase angle than that of (3) of FIG.

Here, when the triac 23 conducts at a small phase angle in this way, the conduction ratio decreases, and the magnetron 3 is smaller than that in (4) of FIG. 3 as shown in (4) of FIG. The pulse P is applied. Then, when the small pulse P is applied to the magnetron 3 in this way, the output of the magnetron 3 is reduced, whereby the temperature of the magnetron 3 is lowered.

As described above, when the temperature of the magnetron 3 suddenly rises when the amount of food is small,
By reducing the conduction ratio to reduce the output of the magnetron 3, it is possible to prevent a rapid temperature rise of the magnetron 3. When the temperature of the magnetron 3 decreases in this way, the time constant CR decreases, and the triac 23 becomes conductive at a large phase angle accordingly, so that the output of the magnetron 3 increases and the food 6 The heating will be resumed.

Then, by configuring in this way,
It is possible to prevent the temperature of the magnetron 3 from rising rapidly without turning on and off the high voltage circuit 12 for a certain period of time, so that the life of the magnetron 3 can be extended. Further, since the power supply is not cut off and the operation of the apparatus is not stopped during the cooking, the user is not made to feel distrust.

When the amount of food is large, the temperature of the magnetron 3 rises more slowly than when the amount of food is normal, so that the micro electromotive force is smaller than when the amount of food is normal. The resistance value of the variable resistance element is reduced accordingly, and the time constant CR is also reduced. When the time constant CR decreases in this way, the temperature detection unit 1
As shown in (2) of FIG. 6, the waveform at the middle point b of 8 and the capacitor C2 has a steeper rise than that of (2) of FIG. 3, and accordingly, the triac changes to (3) of FIG. As shown in the drawing, the conduction is made at a larger phase angle than that in (3) of FIG.

Here, when the triac conducts at a large phase angle in this way, the conduction ratio increases, and as shown in (4) of FIG. 6, the magnetron 3 has a larger pulse than that of (4) of FIG. Is applied. And
By increasing the conduction ratio in this manner, the output of the magnetron 3 is increased when the amount of food is large.

Next, the magnetron output control operation in the thus constructed microwave oven will be described.

First, when heating a normal amount of food,
After the heating is started, the temperature of the magnetron 3 gradually rises, so that the minute electromotive force in the temperature detecting unit 18 also gently increases, whereby the resistance value of the variable resistance element decreases and the time constant CR decreases. Here, when the time constant CR decreases in this way, the waveform at the midpoint b of the temperature detecting unit 18 and the capacitor C2 has a sharp rise as shown in (2) of FIG.

Then, along with this, the triac 23 conducts at the phase angle shown in (3) of FIG. 3, and the magnetron 3 on the secondary side of the high voltage transformer 10 has the power source phase as shown in (4) of FIG. A pulse P having a magnitude proportional to is applied,
The output of the magnetron 3 is controlled so that it will be an output according to the usual amount of food.

On the other hand, when the amount of food is small, the temperature of the magnetron 3 rapidly rises, and along with this, the resistance value of the variable resistance element of the temperature detecting section 18 increases and the time constant CR increases. Then, when the time constant CR increases in this way, the waveform at the midpoint b of the temperature detecting unit 18 and the capacitor C2 has a gentle rising, as shown in (2) of FIG. Conducts at a smaller phase angle than that of (4) of FIG. 3, as shown in (3) of FIG.

When the triac 23 conducts at a small phase angle in this way, the conduction ratio decreases, and a small pulse proportional to the power supply phase shown in (4) of FIG. Output decreases.
Then, when the output of the magnetron 3 decreases in this way, the temperature of the magnetron 3 decreases. When the temperature of the magnetron 3 decreases in this way, the time constant CR decreases, and the triac 23 becomes conductive with a large phase angle accordingly, so that the output of the magnetron 3 increases.
Food heating will be resumed.

When the amount of food is large, the rise of the waveform at the midpoint b of the temperature detecting portion 18 and the capacitor C2 becomes steeper than in the case of the normal amount. As indicated by (3) in (3), conduction is performed at a phase angle larger than that in (3) in FIG. Here, when the triac 23 conducts at a large phase angle in this way, the conduction ratio increases, and a large pulse P proportional to the power source phase shown in (4) of FIG. 6 is applied to the magnetron 3 to output the output of the magnetron 3. To increase.

As described above, the temperature of the magnetron 3 is measured by the thermocouple 8, and the applied pulse for generating the microwave in the magnetron 3 is changed in accordance with the temperature information from the thermocouple 8, whereby the magnetron 3 is heated. The output can be controlled.

[0037]

As described above, according to the present invention, the output of the magnetron can be controlled according to the amount of food to be heated by changing the applied pulse according to the temperature of the magnetron. As a result, it is possible to prevent a rapid temperature rise of the magnetron without turning on / off the high-voltage circuit for a certain period of time, so that the life of the magnetron can be extended. Further, since the operation of the device is not stopped during the cooking by heating the power source, it is possible to prevent the user from feeling distrust.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional top view of a microwave oven as an example of a high-frequency heating apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a magnetron oscillation circuit provided in the microwave oven.

FIG. 3 is a diagram showing various waveforms when the amount of food is normal.

FIG. 4 is a diagram showing a temperature change of the magnetron according to the amount of food.

FIG. 5 is a diagram showing various waveforms when the amount of food is small.

FIG. 6 is a diagram showing various waveforms when the amount of food is large.

[Explanation of symbols]

 1 Microwave Oven Main Body 2 Heating Chamber 3 Magnetron 6 Food 8 Thermocouple 12 High Voltage Circuit 13 Control Circuit 18 Temperature Detector

Claims (3)

[Claims] 1. A high frequency heating device for heating a food contained in a heating chamber formed inside a main body by radiating a microwave to the food, the magnetron generating the microwave by an applied pulse; A high frequency heating apparatus comprising: a temperature measuring unit that measures a temperature; and an output control unit that controls the output of the magnetron by changing the applied pulse according to temperature information from the temperature measuring unit. 2. The high-frequency heating apparatus according to claim 1, wherein the output control means controls the output of the magnetron by changing the applied pulse in a relation inversely proportional to the temperature of the magnetron. 3. The high frequency heating apparatus according to claim 1, wherein the temperature measuring means is attached to an appropriate position of a heat dissipation plate of the magnetron.