JPH04147597A - Microwave heating device - Google Patents

Abstract

PURPOSE:To control the drive of a temperature sensor when detecting boiling of water in a subject for heating as temperature detected by the temperature sensor is rapidly raised by causing a large quantity of hot steam to be blown to the wall of a heating room when water in the subject for heating boils so that the wall of the heating room is rapidly heated. CONSTITUTION:Microwaves are fed from a magnetron 2 into a heating room 1 in which foods are stored and microwave heating of foods is carried out. The magnetron 2 is cooled by cooling wind generated by a cooling fan 3. The cooling wind is allowed into the heating room 1 from an inlet portion 4 located at the upper right side of the room 1 and is moved leftward together with steam or the like generated from the foods during heating and is exhausted to the outside from an exhaust portion 5 located at the upper left side of the room 1. A temperature sensor i.e., a thermistor 7 for detecting the temperature of the upper wall 6 of the heating room is mounted on the outer surface of the upper wall 6 of the heating room. When the temperature detected by the thermistor 7 is rapidly raised at a rate of 4 deg.C per second and detection of boiling of the foods is identified, a microcomputer 8 performs control in order to stop the drive of the magnetron 2. Microwave heating is thereby completed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microwave heating device that controls microwave heating by detecting boiling of water in a heated object.

(b) Conventional technology A microwave oven is an example of a microwave heating device.
Many recent microwave ovens have been commercialized that can automatically microwave food using various sensors. Japanese Patent Laid-Open No. 2-10029 discloses that microwave heating is automatically performed by detecting boiling of food using a pressure sensor. However, in this case, it is necessary to provide a bandpass filter or the like to remove unnecessary components from the output of the pressure sensor, making the configuration extremely complicated.

(c) Problems to be Solved by the Invention The present invention seeks to provide a microwave heating device that has a simple configuration and can detect boiling and control microwave heating.

(d) Means for Solving the Problems The present invention provides a heating chamber for storing an object to be heated, a microwave supply means for supplying microwaves for heating the object into the heating chamber, and a heating chamber for heating the object. a temperature sensor that detects the temperature of the wall; and a control section, the control section including a first means for detecting boiling of moisture in the heated object based on a sudden increase in the temperature detected by the temperature sensor; and a second means for controlling the driving of the microwave supply means based on the boiling detection by the first means.

(E) Effect When the water in the object to be heated boils, a large amount of hot steam hits the walls of the heating chamber, which suddenly heats up, causing the temperature detected by the temperature sensor to rise rapidly, which causes boiling to be detected. The microwave supply means is then driven and controlled.

(f) Example FIG. 1 shows the structure of a microwave oven according to an embodiment of the present invention.

Microwaves are supplied from a microwave supply means, that is, a magnetron 2, into a heating chamber 1 in which food is stored, and thereby microwave heating of the food is performed within the heating chamber 1.

Since the magnetron 2 above generates heat when supplying the micro liquid,
Cooling is performed by cooling air generated by the cooling fan 3. This cooling air then enters the heating chamber 1 from the upper right intake section 4, moves to the left along with water vapor etc. generated from the food during heating, and is discharged to the outside from the upper left exhaust section 5. In this case, before this discharge, if there is no cooling air, the water vapor, etc. will rise straight up and hit the center of the heating chamber upper wall 6, but if there is cooling air as described above, it will flow into this cooling air. It hits the upper wall 6 of the heating chamber slightly to the left of the center.

A temperature sensor or thermistor 7 for detecting the temperature of the heating chamber upper wall 6 is mounted on the outer surface of the heating chamber upper wall 6 at a position slightly to the left of the center where water vapor or the like hits.

FIG. 2 shows the change in temperature detected by the thermistor 7 with respect to the microwave heating time.

Referring to the solid line in this diagram, in microwave heating, basically only the temperature of the food rises, but the heating chamber wall gradually heats up due to conduction heat from the food, and the temperature detected by the Thermistough increases. It gradually increases (until T1 time point). When the water in the food boils, a large amount of hot water vapor is generated, and this large amount of water vapor is carried away by the cooling air and concentrated at a location slightly to the left of the center of the upper wall 6 of the heating chamber where the thermistor 7 is located. At this point, the upper wall 6 of the heating chamber near this area suddenly becomes hot, and the temperature detected by the thermistor 7 rises rapidly (Tl~T
between two points in time). Since the upper wall 6 of the heating chamber does not become hotter than water vapor, the temperature detected by the thermistor 7 becomes stable after that (
(after the 12th point).

On the other hand, if the microwave heating is performed for an undesirably long time for some reason and the food ignites, the temperature detected by the thermistor 7 further increases rapidly after time 12 as shown by the broken line.

FIG. 3 shows the circuit of the microwave oven. A microcomputer 8 is provided as a control section that controls the microwave oven. This microcomputer 8 inputs operation information from a keyboard 9 provided on the front side of the microwave oven body, and also inputs the temperature detected by the thermistor 7, and based on these input information, the magnetron 2 and the cooling fan 3 to drive and control.

FIG. 4 shows the flow of the main part of the control program installed in the microcomputer 8. As shown in FIG.

When the key operation information from the keyboard 9 instructs to end the heating when the moisture in the food boils and instructs to start heating, the microcomputer 8 controls the magnetron 2.
Start driving and perform microwave heating.

Then, in step S1 (corresponding to the first means of the present invention), the microcomputer 8 determines whether the temperature detected by the thermistor 7 rises rapidly at a rate of 4°C per second as described above, and whether or not the water in the food has boiled. to judge. Upon detecting and determining that the food has boiled, the microcomputer 8 controls the magnetron 2 to stop driving in step S2 (corresponding to the second means of the present invention). This ends the microwave heating.

If heating is to be performed subsequently after the boiling is detected, the microcomputer 8 controls this heating in step S2. In this case, it would be extremely dangerous if microwave heating was continued for an undesirably long time for some reason and continued to be heated even after the food ignited. In order to avoid such a dangerous situation as much as possible, the microcomputer 8 starts driving the magnetron 2 when the temperature detected by the thermistor 7 suddenly rises to a point on the broken line in FIG. 2 (for example, 160°C). Stop and interrupt microwave heating. This interruption is performed in the same S2 step.

In the above embodiment, boiling of the food is detected when the temperature detected by the thermistor 7 rises rapidly at a rate of 4°C per second. (Fig. 2) may be determined in advance, and boiling may be detected when this temperature S is reached.

(G) Effects of the Invention According to the present invention, in a microwave heating device that detects boiling and controls microwave heating, this boiling detection is performed using a temperature detector that detects the temperature of the heating chamber wall. Therefore, since a conventional pressure sensor is not used, there is no need to provide a bandpass filter or the like associated with this pressure sensor, and the configuration can be simplified.

[Brief explanation of drawings]

The drawings relate to a microwave oven according to an embodiment of the present invention, in which FIG. 1 is a sectional view, FIG. 2 is a diagram of changes in temperature detected by a thermistor, FIG. 3 is a circuit diagram, and FIG. 4 is a flowchart of a control program. DESCRIPTION OF SYMBOLS 1... Heating chamber, 2... Magnetron, 6... Heating chamber earthen wall, 7... Thermistor, 8... Microcomputer.

Claims (1)

[Claims] (1) A heating chamber that stores an object to be heated, a microwave supply means that supplies microwaves for heating the object into the heating chamber, and a temperature detector that detects the temperature of the wall of the heating chamber. , and a control unit, the control unit includes a first means for detecting boiling of water in the heated object based on a sudden increase in the temperature detected by the temperature sensor, and a first means for detecting boiling of water in the heated object based on the boiling detection by the first means. A microwave heating device comprising: second means for controlling driving of the microwave supply means.