JPH0564611U - High frequency heating device - Google Patents

Abstract

(57) [Summary] [Purpose] Stable boiling control of food is performed. [Structure] Water vapor generated by boiling food 11 in heating chamber 10 is converged on the surface of temperature sensor 1 together with ventilation air, and the change in temperature detected by temperature sensor 1 is output from output conversion circuit to control circuit 8. Then, heating control is performed. When a fire occurs in the heating chamber 10 and the temperature inside the heating chamber 10 becomes higher than the water vapor temperature, the high temperature exhaust air hits the temperature sensor 1 and an abnormally high voltage VB generated in the temperature sensor 1.
Is output to the control circuit 8. Control circuit 8 is magnetron 1
In addition to stopping the heating operation of No. 3, the fan 14 is also stopped to prevent the inflow of air into the heating chamber 10 and stabilize the food 1.
Not only 1 boiling heating control but also definite safety control is performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a high-frequency heating device that detects boiling of food and automatically controls heating operation.

[0002]

[Prior Art]

 The automation of microwave heating has advanced, and optimal heating can now be performed easily and without hassle.

There are several things, such as one that focuses on infrared rays emitted from the object to be heated, one that focuses on water vapor and gas generated from the object to be heated, and one that focuses on the temperature of the heated room air heated by the object to be heated. Among the automation methods, the method of detecting the temperature of the air in the heating chamber (or the air discharged from the heating chamber) that rises with the heat generation of the object to be heated by the temperature sensor to determine the heating time is compared. Since it can be easily realized by using an inexpensive sensor, it was quickly put into practical use as an automatic microwave oven.

As a method of detecting boiling of food, a technique of detecting water vapor at the time of boiling with a piezoelectric element sensor and controlling heating has been proposed (JP-A-2-44124, etc.) and put into practical use. Came to be.

[0005]

[Problems to be solved by the device]

 Although the above-mentioned piezoelectric element sensor and temperature sensor can control boiling heating accurately, they are not good at heating control that does not generate water vapor, and therefore cannot control when food in the heating chamber burns. There was a problem.

[0006]

[Means for Solving the Problems]

 The present invention was made in order to solve the above-mentioned problems, and not only paying attention to the temperature of the air discharged from the heating chamber, but the steam generated suddenly with the boiling of food from the heating chamber is generated. Focusing on the fact that a large amount of water is mixed into the discharged air, it is considered that the food has boiled when the temperature sensor detects a sudden temperature rise due to the mixing of a large amount of water vapor, and the heating operation is controlled. That is, the amount of heat transferred to the temperature sensor is increased by condensation of water vapor in the exhaust air that is in contact with the temperature sensor, the temperature sensor signal is differentiated to calculate the temperature change, and the change is set to a predetermined value. Control heating operation when reached.

Further, when the temperature inside the heating chamber is high, the heating operation is stopped and the rotation of the fan is stopped when the output voltage of the temperature sensor reaches a predetermined value.

[0008]

[Action]

 With the above configuration, when the food boils to generate water vapor, and the water vapor contained in the ventilation air cools by contact with the cool air from the temperature sensor and the fan, the water vapor condenses The amount of heat transferred to the sensor increases, and the temperature detected by the temperature sensor changes rapidly, and the control circuit identifies boiling of the food accordingly, at which point the control circuit controls the heating operation.

Further, when the food in the heating chamber burns or the temperature rises rapidly, the temperature sensor detects this, so that the control circuit stops heating and also the rotation of the fan to stop the air required for combustion. Prevents inflow and prevents fire spread.

[0010]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS.

In the boiling detection circuit diagram of FIG. 1, 1 is a temperature sensor, 2 is a resistor that is connected in series to the temperature sensor 1 and divides the voltage VE, and the voltage VB changes according to the temperature detected by the temperature sensor 1. Change. This voltage VB is differentiated by a differentiating circuit 9 composed of a capacitor 3 and a resistor 4, then amplified by an amplifying circuit 5, high-frequency noise is removed through an integrating filter composed of a resistor 6 and a capacitor 7, and a voltage is obtained. It is output as V0 to the control circuit 8 including a microcomputer. On the other hand, the above-mentioned voltage VB is directly output to the control circuit 8.

FIG. 2 is a plan sectional view of the high-frequency heating device of the present invention.

Reference numeral 10 is a heating chamber, 11 is a food, and 12 is a turntable on which the food 11 is placed. Reference numeral 13 is a magnetron, and 14 is a fan for cooling the magnetron 13 and for ventilating the air in the heating chamber 10. Reference numeral 15 is an inlet through which the air after cooling the magnetron 13 flows into the heating chamber 10. Reference numerals 16 and 17 denote outlets through which the air flowing in from the inlet 15 flows out of the heating chamber 10. The outlet 17 is connected to an exhaust guide 18 to which the temperature sensor 1 is attached.

Next, the operation of this embodiment will be described.

The steam generated when the food 11 boils and abruptly generated mixes with the ventilation air and flows from the heating chamber 10 through the outlet 17 into the exhaust guide 18 as shown by the white arrow, and reaches the temperature sensor 1 site. Converge. Since the cool air is flowing into the converging part where the temperature sensor 1 is installed by the fan 14 as shown by the black arrow, the ventilation air containing steam flowing from the inside of the heating chamber 10 into the temperature sensor 1 having a low temperature. It is immediately cooled by cold air, becomes saturated steam, is condensed, and the heat of condensation is transmitted to the temperature sensor 1. While the amount of steam generated is small, the temperature detected by the temperature sensor 1 changes relatively slowly. However, if steam condenses on the surface of the temperature sensor 1 after a large amount of steam is generated due to boiling, heat transfer to the temperature sensor 1 will occur. Since the amount increases rapidly, the temperature of the temperature sensor 1 also rises rapidly.

The change in the temperature sensor 1 described above is shown in FIG. 3, and the change in the output voltage V0 of the voltage conversion circuit shown in FIG. 1 is shown. In (a), the voltage V0 once rises and shows a peak due to charging / discharging of the differentiating circuit 9 and then falls to enter the stabilization time. When the steam of the food 11 is rapidly generated by the boiling of the food 11 and the temperature detected by the temperature sensor 1 is rapidly increased, the output voltage V0 of the voltage conversion circuit also changes for a long time (C). Since the fan 14 continues to rotate during this time, the temperature sensor 1 is intermittently exposed to cold air and steam, and the voltage V0 repeats a large change. During this fluctuation time (c), when the voltage change exceeding the set voltage VA is detected, the control circuit 8 detects it and stops the heating operation of the magnetron 13 or lowers the heating output, so that no steam is generated. It decreases and the voltage V0 drops accordingly.

In addition, when an abnormality occurs in the heating chamber 10 during cooking of the food 11 and the temperature inside the heating chamber 10 becomes higher than the steam temperature, for example, when the food 11 burns, high temperature exhaust gas is emitted. When touching the temperature sensor 1, when the voltage VB generated in the temperature sensor 1 changes and exceeds the set voltage, the control circuit 8 stops the heating operation of the magnetron 13. At the same time, the rotation of the fan 14 is also stopped to prevent the inflow of air required for combustion.

Since the measured value used for this control is not the temperature itself detected by the temperature sensor 1 but the change in the detected temperature, the influence of the variation in the constants of the components constituting the voltage conversion circuit is affected. Control accuracy is not likely to appear and stable product manufacturing is possible.

[0019]

[Effect of the device]

 As described above, according to the present invention, accurate boiling detection can be performed, stable boiling heating control can be performed, and food heating control and safety control can be performed with one sensor.

[Brief description of drawings]

FIG. 1 is a temperature sensor output conversion circuit diagram of a high frequency heating apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic plan sectional view of the high-frequency heating device.

FIG. 3 is a diagram showing a change in converted output voltage of the temperature sensor.

[Explanation of symbols]

 1 Temperature Sensor 8 Control Circuit 10 Heating Room 11 Food 13 Magnetron 14 Fan

Claims (1)

[Scope of utility model registration request] 1. A heating chamber (10) for containing a food (11).
A magnetron (13) for generating microwaves for heating food (11), and a temperature sensor (1) for detecting the temperature of ventilation air from the heating chamber (10).
And a fan (14) for blowing air to this temperature sensor (1)
And a differentiating circuit (9) for differentiating the temperature signal detected by the temperature sensor (1) to output a signal corresponding to the amount of change in temperature, and when the output of the differentiating circuit (9) reaches a predetermined value. A control circuit which outputs a signal for controlling heating and outputs a signal for controlling heating and stopping rotation of the fan (14) when the output of the partial pressure due to the change in temperature of the temperature sensor (1) reaches a predetermined value. (8) A high-frequency heating device comprising: