KR950001466B1 - Automatic cooking apparatus for a microwave range - Google Patents

Abstract

The superconductivity sensor, and the automatic heating device of an electronic range using the superconductivity sensor and its method interpret a change of permittivity according to temperature of the superconductivity sensor as a frequency change according to a changing of a capacitance value, to perform the most proper heating control for food. The device includes a first superconductivity sensor and a second superconductivity sensor which are arranged as one pair, and a sensing signal processor for reading the capacitance value change of one pair of superconductivity sensors as a frequency change and for outputting it as a cook progressing information; and a controller for interpreting a sensing signal frequency of the sensing signal processor as the cook progressing information and for controlling the heating for the food through a driving unit.

Description

Pyroelectric sensor and automatic heating device and method of microwave oven using this pyroelectric sensor

1 is a block diagram of a microwave oven heating apparatus using a conventional humidity sensor.

2 is a detailed circuit diagram of a humidity sensing signal processor in a conventional microwave heating apparatus.

3 is a block diagram of a microwave oven using the pyroelectric sensor of the present invention.

4 is a plan view of a pyroelectric sensor applied to the present invention.

5 is a circuit diagram of an embodiment of a detection signal processing means in the automatic heating device of the present invention.

6 is an operational waveform diagram of an embodiment of a detection signal processing means in the automatic heating device of the present invention.

7 is a characteristic diagram showing a change in capacitance value with temperature of the pyroelectric sensor applied to the present invention.

8 is a perspective view of the microwave oven showing the mounting state of the pyroelectric sensor applied to the present invention.

9 is a perspective view showing the duct mounting state of the pyroelectric sensor applied to the present invention.

10 is a flowchart showing a heating control process of the present invention.

Figure 11a is a plan view of a first embodiment of the pyroelectric sensor of the present invention.

b is a sectional view of a first embodiment of a pyroelectric sensor of the present invention;

c is a perspective view of a second embodiment of the pyroelectric sensor of the present invention;

d is a sectional view of a third embodiment of a pyroelectric sensor of the present invention;

* Explanation of symbols for main parts of the drawings

11: heating chamber 12: food

18: magnetron 23A, 23B: pyroelectric sensor

24: detection signal processing means 26: control means

27: first measuring means 28: first recording means

29: second measuring means 30: second recording means

31: detection frequency selection means

The present invention relates to a pyroelectric sensor, an automatic heating apparatus and an automatic heating method of a microwave oven using the pyroelectric sensor, and in particular, the optimum food by interpreting the change in permittivity according to the temperature of the pyroelectric sensor as a change in frequency according to the change in capacitance value. The present invention relates to a heating apparatus and a method for controlling heating.

A microwave oven using a conventional humidity sensor, as shown in Figure 1, the heating control unit (1) for cooking food, the key control unit (2) for cooking operation, the exhaust port for detecting the degree of cooking of food Humidity sensor (2) for detecting the humidity of the exhaust gas in the surroundings, humidity detection signal processing unit (4) for converting the detected humidity into an electrical signal and supplying to the control unit 1, the magnetron under the control of the control unit (1) And a high voltage transformer 6 for oscillation, and an output drive circuit 5 for driving the fan, the turntable 7, the display lamp 8 and the like.

In addition, as shown in FIG. 2, the humidity sensing signal processor 4 is installed around a volleyball in a heating chamber and includes a resistance together with an open thermistor Rth1 and a sealed thermistor Rth2 constituting the humidity sensor 3. A bridge circuit is formed of R5 and R6, and the comparison amplifier 9 senses and amplifies a signal change emitted from the bridge circuit.

In FIG. 2, reference numerals R1, R2, R3, and R4 denote resistors, D1 denotes diodes, and -VCC denotes a power source.

The conventional microwave heating apparatus configured as described above is as follows.

In FIG. 1, when the user puts food into the heating chamber and manipulates the key manipulation unit 2 to cook, the heating control unit 1 drives the high voltage transformer 6 through the output drive circuit 5 to oscillate the magnetron. The fan and turntable 7 are driven while the display lamp 8 is turned on to display the cooking progress.

As air is injected into the heating chamber while cooling the magnetron with the fan's blowing power as the fan and the turntable 7 are driven, steam generated from the food is discharged through the outlet, and the water vapor is discharged from the humidity sensor ( 3) is detected.

That is, as shown in FIG. 2, the internal resistance value of the open-side thermistor Rth1 is changed by water vapor contacting the open thermistor Rth1, and such resistance value change is caused by the bridge circuits Rth1, Rth2, R5, R6. The voltage equilibrium state is changed, and the changed voltage value is compared and amplified by the comparison amplifier 9 and supplied to the heating control unit 1.

The heating control unit 1 determines the cooking progress of the food in accordance with the input humidity detection signal and controls the heating time and the heating end based on the determination result.

However, in this way, the heating control device using the humidity sensor 3 detects the cooking degree by changing the resistance value due to water vapor adsorbed on the surface of the device when the humidity sensor 3 is an absolute humidity sensor. Sensitivity deterioration due to surface contamination of open thermistor (Rth1) is inevitably caused, and it is difficult to rule out the effects of leakage propagation, which increases the detection error.In case of using a relative humidity sensor, the oven cannot be used at high temperature. Automatic cooking after cooking becomes difficult and there is a disadvantage that excessive cooking proceeds because it detects a sudden change in humidity when the food is boiled.

Meanwhile, as a conventional microwave automatic heating device, a separate steam passage is constructed, and a technology for detecting the progress of cooking using a pyroelectric sensor installed therein by suctioning steam by using a suction means through the steam passage (Korean Patent Publication) Publication No. 90-18640 has been proposed, but this technique uses a single pyroelectric sensor, which complicates the microwave structure because a separate passage and steam suction means for inducing steam in the pyroelectric sensor have to be configured. Moreover, since the degree of cooking is interpreted only by steam detection information detected by one pyroelectric sensor, it is difficult to detect and control accurate cooking progress.

In addition, since this technology detects cooking information with one pyroelectric sensor, it has a large detection error and it is difficult to secure precise cooking control because compensation for the detection error is not made.

The present invention eliminates the use of a humidity sensor in order to solve such a conventional disadvantage, and also eliminates the need to establish a separate steam induction means, the existing pyroelectric sensor for sensing the ambient temperature and the pyroelectric sensor for steam detection It is equipped with a pair of sensors to detect food cooking progress information around the outlet and temperature change, and to decode both the temperature and steam detection signal around the outlet detected by the pyroelectric sensor as the information of cooking progress, this temperature and steam detection information The purpose of the present invention is to provide a pyroelectric sensor capable of reducing the detection error and accurately detecting the cooking process by using a frequency change of the oscillation output, and an automatic heating device and an automatic heating method of the microwave oven using the pyroelectric sensor.

A pair of features of the present invention is to install the pyroelectric sensor in the outlet to decode the cooking information from the frequency change according to the change in capacitance value of the ambient temperature as the first sensor, the steam emitted by the second sensor, The present invention is characterized in that the first pyroelectric sensor and the second pyroelectric sensor are used to compensate for the detection error by selecting the detected frequency change value at the time of initial heating as a comparison reference value. The pyroelectric sensor is installed in an enclosed space, and the second pyroelectric sensor is installed in an open structure so as to perform a desired signal detection.

In the microwave oven using the pyroelectric sensor of the present invention having the above-described characteristics and having the above-described features, as shown in FIG. 3, the food 12 is disposed below the heating chamber 11 of the microwave oven 10. The turntable 13 to be placed is installed, the turntable driving motor 14 is installed below the turntable 13, and an air inlet 15 and a microwave waveguide 16 are provided at one side wall of the heating chamber 11, The other side wall is provided with an outlet 17 for air and steam.

In addition, a magnetron 18 is installed around the air inlet 15, and a fan 19 and a fan motor 29 are installed to cool the magnetron 18 and blow air into the heating chamber 11. The turntable driving motor 14, the magnetron 18, the fan motor 20, and the driving means 22 for driving the high voltage transformer 21 for the magnetron oscillation are provided.

In addition, a pair of the first pyroelectric sensor 23A and the second pyroelectric sensor 23B is provided at the discharge port 17, and the cooking progress information is read by changing the capacitance value of the pyroelectric sensors 23A and 23B as a frequency change. The sensing signal processing means 24 for outputting the food 12 through the driving means 22 according to the cooking progress information and the key operation unit 25 operation signal provided by the sensing signal processing means 24 Control means 26 for controlling heating is provided.

On the other hand, the control means 26, the first measuring means 27 for reading the temperature detection signal of the first pyroelectric sensor 23A after the start of heating and measuring the signal frequency, and the data of the first measuring means 27 Storing the data of the first recording means 28 for storing, the second measuring means 29 for measuring the signal frequency by reading the vapor detection signal of the second pyroelectric sensor 23B, and for storing the data of the second measuring means 29 A second recording means 30 and a sensing frequency selecting means 31 for selecting a frequency to be detected through the recording means 28 and 30 are provided.

In FIG. 3, 32 is a food container, 33 is a lamp, 34 is an exhaust port, and 35 is an intake port.

The operation of the automatic microwave oven heating apparatus configured as described above will be described.

In FIG. 3, when the user operates the key operation unit 25 to proceed with cooking, the control unit 26 detects this and the turntable driving motor 14, the magnetron 18, and the fan motor are driven through the driving unit 22. 20), the high pressure transformer 21 is driven to start heating.

Water vapor generated as the food 12 is heated is discharged through the outlet 17 to increase the temperature of the pyroelectric sensors 23A, 23B.

The pyroelectric sensors 23A and 23B change their capacitance value Cp in proportion to the temperature increase, and the change of the capacitance value Cp is read by the detection signal processing means 24 as a change in the output signal frequency of the oscillator. Is detected.

As examples of the pyroelectric sensors 23A and 23B and the sensing signal processing means 24, the pyroelectric sensors and the sensing signal processing circuits shown in FIGS. 4 and 5 are provided. The pyroelectric sensors 23A and 23B have the configuration shown in FIG.

That is, the ceramic plate 36 is in contact with the metal plate 37 so that the dielectric constant increases in proportion to the temperature, and the electrode 38 is connected to the lead wire 39 on the upper surface of the ceramic plate 36 so that the self capacitance according to the increase of the dielectric constant is increased. The change in value Cp is output through the lead wire 39.

A graph of the change in capacitance value according to the temperature of the pyroelectric sensors 23A and 23B is shown in FIG. The configuration of the pyroelectric sensors 23A and 23B and the detection signal processing means 24 having the same characteristics as those of FIG. 7 are the same as those of FIG.

That is, the output terminal of the noah gate G1 is connected to one input terminal of the noah gate G2, the other input terminal of the noah gate G2 is grounded, and the output terminal of the noah gate G2 is pyroelectric sensor 23A. While connecting to the one input terminal of the noah gate (G1) through, the connection point is connected to the connection point of the output terminal of the noah gate (G1) and the one input terminal of the noah gate (G2) through the resistor (R1), The other input terminal of the gate G1 was grounded to constitute the oscillator 24A.

In addition, the oscillator 24B was configured with the noar gates G3 and G4 and the resistor R2 in the same manner as described above for the second pyroelectric sensor 23B. Accordingly, the control means 26 counts the oscillation frequencies of the oscillators 24A and 24B and determines the heating state of the food, and controls the output driving means 22 according to the determined heating state to cook the food. .

In the description of the drawings, reference numeral Vss denotes a power source.

In the sensing signal processing means of the present invention configured as described above, when the potential VI1 applied to one input terminal of the noah gate G1 becomes low in the state where the power supply Vss is applied, the noah gate G1 is shown in FIG. 6A. As shown in FIG. 2, the high potential is output at the time t1 and applied to one input terminal of the noah gate G2. Then, the noah gate G2 outputs a low potential as shown in FIG. 6B at a time t2 at which its constant delay time tpd has elapsed.

Therefore, the high potential output from the noah gate G1 is charged to the pyroelectric sensor 23A through the resistor R1 as shown in FIG. 6C, and the charging potential of the pyroelectric sensor 23A is connected to the noah gate G1. It is applied to one input terminal.

In such a state, when the potential applied to the one input terminal of the noah gate G1 at the time t3 becomes equal to or higher than the threshold hold voltage Vt, the noah gate G1 outputs a low potential at time t4. Noah gate G2 outputs a high potential, the charging potential of pyroelectric sensor 23A is discharged to the output terminal of noah gate G1 through resistor R1, and the charging potential of pyroelectric sensor 23A is noah gate. When discharged below the threshold hold voltage Vt of (G1), the oscillator 24A oscillates by repeating the output of the high potential again by the NOA gate G1.

At this time, the oscillation periods T1 and T2 of the oscillator 24A are as follows.

Here, C1 is the capacitance of the pyroelectric sensor 23A, and In is a natural logarithm.

Then, the full oscillation period T is

(Where K is a constant)

Therefore, oscillation frequency F is as follows.

Therefore, the change in frequency with respect to the change in capacitance of the pyroelectric sensor 23A is as follows.

And the change of frequency with the change of temperature is as follows.

Oscillator 24B also operates in the same manner as the oscillator 24A.

Accordingly, the oscillation frequency of the oscillators 24A and 24B is variable as the pyroelectric sensor detects water vapor generated by heating of the plant as a change in capacitance and the capacitance of the pyroelectric sensor is changed.

On the other hand, in the present invention, the first pyroelectric sensor 23A detects only the temperature around the outlet 17, and the second pyroelectric sensor 23B detects only the water vapor generated from the food 12 at the outlet 17.

That is, as shown in FIGS. 8 and 9, the first and second pyroelectric sensors 23A and 23B are installed as the sensor duct 40 around the outlet 17 and the sensor duct 40 is installed. The duct support 42 is fixed to the range body.

That is, the pyroelectric sensor 23A is installed in the sealed space, and the pyroelectric sensor 23B is installed in the exposed space. Where 41 is a vapor exhaust guide and 43 is a sensor support.

As the pyroelectric sensors 23A and 23B are installed in this manner, the first pyroelectric sensor 23A detects the temperature around the outlet 17 through the hole 17 ', and the second pyroelectric sensor 23B is The blowing of the fan 19 detects that hot air generated from the food 12 is discharged to the outlet 17.

That is, when continuously operating the microwave oven, since the temperature around the outlet 17 maintains a temperature much higher than the temperature during the initial operation, the first pyroelectric sensor 23A senses this temperature and the second pyroelectric sensor 23B is used. Since it is possible to compensate for the initial detection temperature difference by detecting the steam of the food 12, it is possible to perform the optimum cooking control accordingly.

Hereinafter, the operation of the detection signal processing means 23 and the control means 26 according to the frequency will be described with reference to FIG.

After the start of the heating, the first measuring means 27 measures the frequency of the sensing signal of the first pyroelectric sensor 23A supplied from the sensing signal processing means 24 to measure the initial sensing frequency f1 measured by the first recording means ( 28).

Subsequently, as cooking proceeds to the second measuring means 29, the frequency f2 of the sensing signal of the second pyroelectric sensor 23B supplied from the sensing signal processing means 24 is measured, and the measured initial sensing frequency f2 is measured. Is stored in the second recording means (30). Subsequently, the sensing frequency selecting means 31 determines the sensing frequency change value based on the frequency f1 of the first recording means 28 and the frequency f2 of the second recording means 30.

The detection frequency change value is a comparison reference value provided to determine the presence or absence of additional heating and is selected by the calculation of | f1-f2 | Δf. Next, the gimji signal frequency f1 ′ of the first pyroelectric sensor 23A is measured by the first measuring means 27, and the detection signal frequency f2 ′ of the second pyroelectric sensor 23B is measured by the second measuring means 29. ) Is measured and compared with a reference value selected by the detection frequency selecting means (31).

As a result of the comparison, when the absolute value (| f1'-f2 '|) of the difference between the detection signal frequencies f1' and f2 'becomes equal to or more than the reference value, it is determined whether or not the additional heating is performed, and the cooking is finished after the additional heating. The second pyroelectric sensor 23B as the steam sensor for steam detection has its embodiment in the configuration shown in FIG.

First, as the first embodiment, as shown in FIGS. 11A and 11B, the paired electrode plates 44A and 44B are held at regular intervals by the insulator 45 so as to maintain the electrode plates 44A and 44B. The space portion 46 filled with water vapor is formed between the two poles, and is connected to the lead wire 47 to which the capacitance value change between the electrode plates 44A and 44B which changes in correspondence with the amount of water vapor to be filled is output.

That is, since the opposing electrode plates 44A and 44B are maintained at a constant interval d by the insulator 45, the capacitance value Cp between the all electrode plates 44A and 44B is Cp = ε ( S / d). Where? Is the permittivity of air (ε 0 ≒ 1.006) x the dielectric constant of the dielectric deposited in the space portion 46 (E _R ) = ε, and S is the area between the pole plates.

Therefore, the capacitance value Cp is proportional to the area and the dielectric constant and is inversely proportional to the distance between the poles. Therefore, the capacitance of water vapor (dielectric constant of water? 80), which is a dielectric material, is filled in the space portion 46 between the two pole plates 44A and 44B. The capacitance value Cp is changed in proportion to the amount shown in FIG. 7.

In addition, the vapor (pyroelectric) sensor 23B of the present invention has a plurality of electrode plates 44A and 44B having a cylindrical shape so as to increase the capacitance change rate for improving the sensitivity as shown in FIG. 11C as the second embodiment. Construct by overlapping. In this case, the graph slope in FIG. 6 is increased by increasing the area S of the electrode plates 44A and 44B.

As the third embodiment of the present invention, the pyroelectric sensor 23B is laminated with a plurality of electrode plates 44A and 44B as an insulator 45 so that the capacitance change rate is increased for improving sensitivity as shown in FIG. 11D. Configure in series or in parallel.

In this case, it is a case where the slope of the graph in FIG. 6 is increased by expanding the space 46 (increasing the amount of detected water vapor) and increasing or decreasing the combined capacitance value.

In addition, as a fourth embodiment of the pyroelectric sensor 23B of the present invention, a fixed capacitor for reducing stabilization is added and connected to the pyroelectric sensor 23B in series or in parallel.

In this case, the capacitance value of the fixed capacitor acts as the capacitance value and the combined capacitance of the pyroelectric sensor 23B, thereby stabilizing the sensitivity of the pyroelectric sensor 23B. A graph of the change in capacitance value according to the amount of steam of the pyroelectric sensor 23B is shown in FIG.

The configuration of the pyroelectric sensor 23B and the detection signal processing means 24 having the same characteristics as those of FIG. 6 is the same as that of FIG. 5.

5 and 6a and b, the period T and the frequency f of the signal output from the sensing signal processing means 24 are determined by the following equation.

to be.

Where R is the resistance value, C = Cp, Vss is the power supply, and Vt is the threshold voltage of the gate means.

Thus, period T = T1 + T2.

Therefore, it is supplied to the control means 26 as frequency F = 1 / T. Therefore, the period T increases and decreases in proportion to the R value and the C value.

However, since the capacitance value Cp increases with time due to the high temperature water vapor generated from the food 12, the second pyroelectric sensor 23B also increases the period T. In other words, the frequency f is reduced.

However, if the ambient temperature is too high or too low at the beginning of heating, the period T becomes too long or too short to make it difficult for the control means 26 to recognize the period T (ie, error). When a predetermined time has elapsed since the start, the control means 26 causes the period T to be included within a recognizable range.

As described above, according to the waveforms shown in FIGS. 5, 6A, and b, the detection signal processing means 24 follows the capacitance value Cp change of the pyroelectric sensor 23B to the capacitance value Cp. To perform an operation of a square wave oscillation circuit having a variable frequency (period), and the following heating control operation is the same as described above, and thus redundant description thereof will be omitted.

As described above, according to the present invention, the sensor peripheral circuit configuration that detects the cooking degree is simpler than the conventional humidity sensor, which can reduce the cost and reduce the concern about contamination on the sensor surface, thereby reducing the sensitivity deterioration due to contamination. It is possible to provide reliability and precision in cooking control and to provide the optimum cooking state by performing compensation according to ambient temperature during continuous cooking.

In addition, the configuration for steam induction is eliminated, and the detection error is compensated by comparing the degree of cooking progress with a reference value according to the heating start and heating progress, thereby simplifying the configuration of the microwave oven and cooking. It has the effect of highly precise and accurate control.

Claims (7)

A pair of first pyroelectric sensors 23A for detecting only the ambient temperature of the outlet at the outlet 17 of the microwave oven and a second pyroelectric sensor 23B for detecting only steam generated from the food 12 may be provided in pairs. The detection signal processing means 24 which reads the capacitance value change of the pyroelectric sensors 23A and 23B as frequency change and outputs it as cooking progress information, and the detection signal frequency of the detection signal processing means 24 as cooking progress information. Automatic heating device of the microwave oven using a pyroelectric sensor consisting of a control means 26 for analyzing and controlling the heating of food 12 through the drive means (22). The method of claim 1, wherein the first pyroelectric sensor (23A) is sealed in the sensor duct 40 to sense the ambient temperature of the outlet 17, and detects the ambient temperature through the hole 17 'on one side of the duct, 2 pyroelectric sensor 23B is a structure for detecting the steam generated in the food 12 in the heating chamber is opened toward the outlet 17, the sensor duct 40 is fixed to the range body integrally with the duct support 42 Automatic heating device of microwave oven using pyroelectric sensor, The electrode plates 44A and 44B which face each other, the insulator 45 which keeps the electrode plates 44A and 44B at regular intervals, and the electrode plate 44A by the insulator 45 ( A space portion 46 filled with water vapor is formed between 44B), and a lead wire 47 for outputting a change in capacitance value between the electrode plates 44A and 44B which changes in correspondence with the amount of water vapor filled is connected. Pyroelectric sensor, characterized in that. 4. The pyroelectric sensor according to claim 3, wherein the pair of electrode plates (44A) (44B) is formed by stacking a plurality of insulators (46) so as to increase capacitance change rate for improving sensitivity. 4. The pyroelectric sensor according to claim 3, wherein the pair of electrode plates (44A) (44B) are formed in a cylindrical shape so as to increase the capacitance change rate for improving the sensitivity, and overlapping a plurality of electrode plates (44A) (44B). 4. The pyroelectric sensor according to claim 3, wherein a fixed capacitor for sensitivity stabilization is additionally connected to the electrode plates (44A, 44B). After the heating is started, the initial detection signal frequency f1 of the first pyroelectric sensor 23A is measured by the first measuring means 27, stored in the first recording means 28, and the second pyroelectric power is measured by the second measuring means 29. The process of measuring the initial detection signal frequency f2 of the sensor 23B and storing it in the second recording means 30, and comparing the initial detection signal frequency f1 (f2) with or without additional heating for determination. Selecting a detection frequency change value (| f1-f2 | + Δf) by the detection frequency selecting means 31 as a reference value, followed by a first pyroelectric sensor that changes with heating by the first measuring means 27 ( Measuring the detection signal frequency f1 'of 23A and measuring the detection signal frequency f2' of the second pyroelectric sensor 23B, which changes with heating by the second measuring means 29, and then detecting Further heating by comparing the comparison reference value selected by the frequency selecting means 31 and the difference between the detection signal frequencies f1 'and f2' that change with heating. Automatic heating method for a microwave oven using a pyroelectric sensor consisting of a process to determine, radish.