KR20000032854A - Method of detecting no-load operation of microwave oven - Google Patents

Abstract

PURPOSE: A detecting method of no-load operation of a microwave oven is provided to prevent overheating of a device and to remove the problem of mis-operation by making the function of detecting no-load state and a fire operated only when a certain time is elapsed. CONSTITUTION: A power supply switch is turned on and operated. An infrared sensor(semiconductor sensor) irradiates a turn table and detects the amount of infrared rays emitted from the turn table and food. The sensor converts the detected amount of the infrared rays to voltage. The voltage is converted to temperature. Herein, the detected temperature compared to the basis of a predetermined set up temperature. If the detected temperature is higher than the predetermined set up temperature, setting delay time is counted. If the detected temperature is lower than the predetermined set up temperature, a microwave oven is operated continually. After a setting time is elapsed, the power supply is turned off.

Description

How to detect no-load operation of microwave oven

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven, and more particularly, to a method of detecting a no-load operation of a microwave oven capable of achieving high reliability and low cost by using a semiconductor sensor module.

In general, a microwave oven refers to a device for cooking food by radio waves.

The operation principle and basic structure of the microwave oven will be briefly described with reference to FIGS. 1 and 2. 1 is an explanatory view for explaining the operation principle of a typical microwave oven, Figure 2 is an exploded perspective view for explaining the structure of a typical microwave oven. In these figures, reference numeral 10 denotes a magnetron that shoots radio waves as a heating source. It usually consists of a special two-pole vacuum tube and generates microwaves. Radio waves generated in the magnetron 10 are concentrated on food through the antenna 12 below. In the center of the microwave oven is a turntable 20 for placing and rotating food to be heated. This is the part that propagates the waves evenly over the food.

One side of the magnetron 10 is provided with a cooling fan 30 and the convection fan 32 to force the flow of air flowing inside the microwave oven. In Fig. 1, reference numeral 22 denotes a transformer, 24 denotes a filter, 40 denotes a door, an arrow indicated by a dashed line indicates a flow of air, and an arrow indicated by a solid line indicates an operation direction of microwaves.

Subsequently, referring to FIG. 2, an operation panel 42 for controlling various switching controls is installed at one side of the door 40, and no food is placed on the turntable 20 inside the microwave oven covered with the case 50. The thermostat 60 is arrange | positioned as a sensor means for stopping operation in an unloaded non-load state. This thermostat 60 is a kind of thermostat, which is a temperature controller as an automatic switch for maintaining a constant temperature. In Fig. 2, reference numeral 52 denotes a lower base for holding the whole microwave oven part.

In the case of no-load during microwave operation, the following two measures are taken. First, even if the microwave oven is running under no load, it can be operated safely mechanically or electrically so as not to damage the product. However, this is undesirable because it requires considerable time, effort and creativity in the product development stage.

Second, as in the conventional description, when the thermostat 60, which is a kind of a temperature sensor set to a predetermined temperature in advance near the magnetron 10, is installed, and the temperature of the magnetron 10 is lower than the load operation. If you go up significantly, the thermostat (60) is the way to cut off the power by detecting the internal temperature.

However, the conventional microwave oven described above has the following problems.

The second method has a fundamental disadvantage that the manufacturing cost is increased because it is forced to employ a thermostat, and the thermostat 60 is fixed because the thermostat 60 is operated by the conduction heat of the contacted part. There is a problem in that there is an error in reliability, such as a temperature difference depending on what the object is.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a no-load operation detecting method for a microwave oven which can achieve high reliability and low cost by using a semiconductor sensor module.

1 is an explanatory diagram for explaining the operation principle of a typical microwave oven

Figure 2 is an exploded perspective view for explaining the structure of a typical microwave oven

Figure 3 is a partially cutaway perspective view showing a state in which the no-load operation detection device of the microwave oven of the present invention is installed

4 is an exploded perspective view showing the structure of a semiconductor sensor adopted in the no-load driving detection method of the microwave oven according to the present invention;

5 and 6 are explanatory views for explaining the operation principle of the semiconductor sensor adopted in the no-load operation detection method of the microwave oven of the present invention.

7 is a plan view showing a sensor PCB of the semiconductor sensor used in the present invention

8 is a graph showing a relationship between a sensing voltage and a temperature for better understanding of the present invention.

9 is a flowchart for explaining a no-load operation detection method of the microwave oven according to the present invention.

<Explanation of symbols for main parts in the drawing>

10: magnetron (oscillator) 12: antenna

20: turntable (glass container) 22: trance

24: filter 30: cooling fan

32: convection fan 40: door

42: operation panel 52: base

60: thermostat 100: semiconductor sensor module

102: sensor PCB 102a: Infrared sensor

102b: op amp 102c: amplification factor adjustment unit

102d: ambient temperature compensator

104: reflector

106: filter 108: case

110: shield wire 120: bracket

122: holder 130: connector

132: sensor connector 134: connector header

136: Sensor Connector Hook

The no-load operation detection method of the microwave oven of the present invention for achieving the above object,

Detecting and measuring the amount of infrared radiation emitted from a turntable or food;

Converting the detected infrared radiation into a voltage;

Converting the voltage into a temperature;

Comparing the preset temperature with the detection temperature;

A delay time count determining step of counting a set delay time when the detection temperature is higher than a set temperature and continuing to operate when the detection temperature is low;

The power is turned off when the set delay time elapses.

In the detection method, if the detection temperature is lower than the set temperature in the delay time count determination step, it is preferable to proceed to the step of continuing operation.

Therefore, the no-load operation detection method of the microwave oven according to the present invention employs an infrared sensor for measuring the amount of infrared radiation emitted from a turntable or food, and thus displays an error message when the temperature is higher than a certain temperature when the voltage is converted into a temperature in the microwave oven. It stops overheating and prevents overheating of the device. At this time, the no-load and fire detection function is operated only when a certain time has elapsed.

EMBODIMENT OF THE INVENTION Hereinafter, the no-load operation detection method of the microwave oven of this invention is demonstrated in detail with reference to an accompanying drawing.

In order to avoid confusion in the description, the same reference numerals are used for the same members having the same function as the conventional description.

Fig. 3 is a partially cutaway perspective view showing a state in which the no-load driving detection device of the microwave oven of the present invention is installed, Fig. 4 is an exploded perspective view showing the structure of a semiconductor sensor adopted in the no-load driving detection method of the microwave oven of the present invention. And FIG. 6 is an explanatory diagram for explaining the operation principle of the semiconductor sensor adopted in the no-load driving detection method of the microwave oven according to the present invention.

Referring to FIG. 3, the sensor 100 of the present invention is installed deep inside the microwave oven main body to sense the turntable 20 at a certain viewing angle.

Referring to FIG. 4, reference numeral 100 denotes a semiconductor sensor module, and the semiconductor sensor module 100 includes a sensor PCB 102 for generating a voltage by infrared rays incident from food, and an infrared ray incident from food. A reflector 104 for concentrating on the filter, a filter 106 that serves to prevent moisture from the food from affecting the sensor or to pass only infrared light from the food and to block the remaining wavelengths; A plated case 108 for enclosing the PCB 102 and not being affected by external noise, and a shield wire 110 for applying DC 5V power to the sensor PCB 102 and transferring the output of the sensor to the microcomputer. And a bracket 120 including a holder 122 to fix the sensor to the microwave side.

In addition, the end of the shield wire 110 is provided with a connector 130 for electrical connection to the device. Reference numeral 132 denotes a sensor connector, 134 a connector header, and 136 a sensor connector hook.

All materials have different infrared radiation according to temperature, and foods also have different infrared radiation according to temperature, and semiconductor sensors sense these infrared rays to generate voltage, and this voltage can be processed by microcomputer to measure the temperature of food.

Next, the operation principle will be described with reference to FIGS. 5 and 6. When infrared rays are incident into the sensor, the temperature rises by heating the black body inside the sensor, and a temperature difference occurs between the hot junction and the cold junction. As such, when different metals are composed of closed circuits and a temperature difference occurs, thermoelectric power is generated by a so-called Seeback effect as shown in FIG. 6. The Seebeck effect refers to a phenomenon in which a thermoelectric power is generated in a circuit when there is a temperature difference at a zero connection point by forming an electric circuit by joining different metals. If two kinds of metals are joined as shown in FIG. 6 and the temperatures of the two contacts P and Q are the same, the potential difference does not occur, but when the temperature is uneven, the electromotive force difference between A and B becomes the thermoelectric power.

The thermistor, heat conduction content, infrared radiation amount inside the sensor also play a very important role, but it is difficult to explain briefly and is omitted below since it does not affect the description of the present invention.

7 is a plan view showing a sensor PCB of the semiconductor sensor used in the present invention.

The sensor PCB 102 is composed of an infra red sensor 102a, an op amp 102b, an amplification factor adjusting unit 102c, an ambient temperature compensating unit 102d, and the like. As described above, the infrared sensor 102a senses infrared rays and generates a voltage. The process of manufacturing the internal thermocouple is the same as the semiconductor device manufacturing process, so it is called a semiconductor sensor, but the official name is a thermopile sensor.

The op amp 102b has a voltage that is generated by several integrated thermocouples in a semiconductor sensor and its value is very small, and the voltage amplification is necessary because the voltage cannot be converted properly by the microcomputer. Element.

The amplification factor adjusting unit 102c is an element adopted because the sensitivity of the semiconductor sensor unit, that is, the voltage generation rate with respect to temperature is different, needs to be adjusted so as to have a constant sensitivity. The amplification factor adjusting unit 102c amplifies the number by cutting the resistance. The rate is different.

The ambient temperature compensator 102d serves to compensate the voltage at a constant rate since the voltage generated by the semiconductor sensor is greatly influenced by the temperature of the sensor itself. For example, if the temperature of the sensor itself is 40 ° C and the temperature of the food to be detected is 20 ° C, a negative voltage is generated because the temperature of the cold junction is higher than that of the hot junction.

In addition, when the microwave oven is operated continuously, the sensor temperature rises, and thus the food temperature cannot be accurately determined. The device is adapted to compensate for these.

Next, the no-load operation detection method of the microwave oven of this invention is demonstrated.

9 is a flowchart for explaining a no-load driving detection method of the microwave oven according to the present invention.

When the microwave oven operates, the sensor detects the temperature of the turntable 20 (glass tray). The amount of infrared radiation emitted from the turntable 20 increases with time as the temperature of the turntable 20 rises. 8 is a graph illustrating a relationship between a sensing voltage and a temperature.

This graph was created using what is actually used in a microwave oven, and is pre-programmed in the microcomputer to determine no load when the temperature reaches 120 ° C. That is, as soon as the temperature reaches 120 ° C., all the operations are stopped while outputting an “Err” message.

Next, the no-load detection method of the microwave oven of this invention is demonstrated with reference to FIG. 9 is a flowchart for explaining a no-load driving detection method of the microwave oven according to the present invention.

First, in the situation where the power switch of the device is turned on and operated, the infrared sensor (semiconductor sensor) of the present invention irradiates the turntable 20 to detect the amount of infrared radiation emitted from the turntable 20 or food Measure The sensor converts the detected infrared radiation amount into a voltage and converts the voltage into a temperature. At this time, it is compared whether the detection temperature detected on the basis of the preset temperature is higher or lower than the preset temperature.

Subsequently, if the detection temperature is higher than the preset temperature, the setting delay time is counted, and if the detection temperature is low, the operation is continued. When the set delay time elapses, the device is turned off.

In more detail with respect to the delay time, the present invention sets a delay time of 10 minutes in order to prevent an error situation occurs in the case of a normal food that rises in a short time in the case of food such as popcorn. In this case, a small load or a food that is rapidly rising in temperature, most of the food is completed within 10 minutes, and more than 10 minutes, there is no food over 120 ℃, so microcomputer will not misjudge.

In addition, this delay time setting has the same effect even when a fire occurs in the heating chamber of the microwave oven, thereby stopping the operation of the microwave oven. In this case, too much food can lead to a fire because at least 10 minutes must pass.

As described above, according to the no-load operation detection method of the microwave oven, since an infrared sensor for measuring the amount of infrared radiation emitted from a turntable or food is employed, an error occurs when the temperature is higher than a certain temperature when the voltage is converted into a temperature in the microwave oven. It stops the operation by displaying a message to prevent overheating of the device. At this time, the no-load and fire detection functions are operated only after a certain period of time, and there is no fear of malfunction.

Claims (2)

Detecting and measuring the amount of infrared radiation emitted from a turntable or food; Converting the detected infrared radiation into a voltage; Converting the voltage into a temperature; Comparing the preset temperature with the detection temperature; A delay time count determining step of counting a set delay time when the detection temperature is higher than a set temperature and continuing to operate when the detection temperature is low; And turning off the power when the set delay time elapses. The method of claim 1, wherein if the detection temperature is lower than a set temperature in the delay time count determination step, the operation continues to the step of continuing operation.