JPH11346924A - Heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating cooker wherein more accurate running control is performed irrespective of a pan to be used by making correction in accordance with a pan material and a gap between the pan and a plate surface, and good handleability is provided. SOLUTION: A heating cooker is provided with a control part 1 for controlling the quantity of heating by a heating circuit part 5 based on a signal from a temperature sensor 8, a heating coefficient detecting circuit 3 for measuring the degree of magnetic connection between a plate 7 and a pan 9 by oscillating a heating coil 6, and the control part 1 performs heating control by correcting the detected temperature of the temperature sensor 8 or a determination parameter based on a heating coefficient measured by the heating coefficient detecting circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for operating a cooking device with higher accuracy and improving the usability of a user.

[0002]

2. Description of the Related Art In a heating cooker for cooking by heating a pot or a frying pan, as a method of detecting a temperature during cooking, a temperature sensor such as a thermistor is brought into contact with the back side of a plate on which the pot is placed, and heat is applied from the bottom of the pot. A temperature detection method of estimating a pot temperature or a temperature of a cooking object by detecting the conducted heat is generally used.

[0003] As an example of such control, in the method of judging boiling of a pot or the like, since the water temperature at the time of boiling saturates around 100 ° C, when the rate of rise of the detected temperature becomes smaller than a predetermined threshold value, A method of judging as boiling and adjusting or stopping the amount of heating was adopted.

[0004]

However, in the conventional temperature detection method, the size of the gap between the temperature sensor and the actually heated pot bottom and the plate, the shape of the pot bottom such as the degree of warping, and the like are different. In some cases, the efficiency of heat conduction from the bottom of the pot to the temperature sensor changes depending on the material and the surface state such as roughness of the bottom of the pot. For this reason, there has been a problem that a difference between the temperature predicted by the temperature sensor and the actual pot temperature occurs.

FIG. 7 shows an example of a case in which a conventional heating cooker determines boiling. In FIG. 7, reference numeral 72a denotes a detection temperature of a temperature sensor when water is boiled in a pot without warping, and reference numeral 71a denotes a detection temperature when water is boiled in a pot with a bottom warp. The wavy lines 71b and 72b are experimentally 71a and 72b.
The result of measuring the water temperature at the same time as a is shown. Generally, the boiling is determined when the rate of change of the temperature rise becomes smaller than a certain threshold value Dth as shown in FIG. However, when determining a pot having no warpage at the bottom with the same threshold value Dth as the optimum threshold value for a warped pot, the temperature curve 7
As shown in 2a, boiling is determined at time t1, and the determination is delayed more than the actual boiling time t0.

As described above, the heating state of the pan varies depending on the shape and material of the bottom of the pan, the size of the gap with the top plate, and the like. The magnetic coupling state with the object,
It is an object of the present invention to solve such a problem by measuring a heating coefficient as an apparent impedance value, selecting an optimum threshold value according to the heating coefficient, and performing control such as boiling determination.

[0007]

According to the present invention, there is provided a plate for placing an object to be heated such as a pot,
A temperature sensor, a heating circuit section including a heating coil for heating an object to be heated and a drive circuit thereof, a control section for controlling the amount of heating by the heating circuit section by a signal from the temperature sensor, A heating coefficient detection circuit for measuring the degree of magnetic coupling between the plate and the object to be heated; and the control unit corrects a temperature detected by the temperature sensor or a determination parameter based on the heating coefficient measured by the heating coefficient detection circuit. To perform heating control.

[0008]

According to the first aspect of the present invention, a change in the degree of heating due to the material of the pot or the gap between the plate and the plate surface is calculated as a heating coefficient from the deviation of the oscillation frequency when the heating coil is oscillated. By correcting the temperature detected by the temperature sensor and the determination parameter, highly accurate operation control can be performed.

According to a second aspect of the present invention, the heating coefficient is
By calculating based on the current and voltage values of the heating circuit, highly accurate operation control is possible.

According to a third aspect of the present invention, a frequency-to-voltage conversion circuit is used as a circuit configuration for detecting a deviation of the oscillation frequency. Operation control is possible.

The invention described in claim 4 adopts a band-pass filter as a circuit configuration for detecting a deviation of the oscillation frequency, thereby achieving a simple circuit configuration using a general-purpose IC or the like with a small number of components. Operation control with higher accuracy is possible.

According to the fifth aspect of the invention, the boiling determination parameter, which is frequently used in the cooking device, can be operated with high accuracy by correcting the boiling determination parameter based on the heating coefficient.

The invention described in claim 6 corrects the boiling determination parameter with reference to the detected temperature at the time of determination in addition to the heating coefficient, thereby coping with variations in cooking conditions such as when the initial water temperature changes. High-precision operation of possible boiling determination is possible.

[0014]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described. FIG. 1 is a block diagram of a cooking device showing the configuration of the present embodiment. Reference numeral 1 denotes a control unit for controlling the operation of the entire cooking device, which includes a microcomputer and its peripheral circuits, and executes a control program for the cooking device stored in the ROM. 9 is a pot for cooking, and 7 is a plate of the main body on which the pot 9 is placed. Reference numeral 6 denotes a heating coil for heating the pan 9 by induction heating. Reference numeral 8 denotes a temperature sensor laid at the lower central portion of the top plate 7. Reference numeral 2 denotes an oscillation circuit unit that oscillates a heating coil to measure a heating coefficient, and reference numeral 3 denotes a heating coefficient detection circuit unit based on a change in resonance frequency oscillated by the oscillation circuit unit 2. It is generally known that in a heating cooker, the better the magnetic coupling between the heating coil 6 and the pan 9 is, the larger the heating input becomes, and the coupling coefficient is an index that reflects the quality of the magnetic coupling state. is there.

The principle and configuration example of the heating coefficient detection circuit section 3 will be described with reference to FIG. FIG. 3A shows the frequency characteristics of the oscillating voltage when a pan with a flat bottom is placed on the plate 7 and oscillated by the oscillation circuit unit 2. Similarly, FIG. 3B and FIG. It is a frequency characteristic in the case of a warped pot and a greatly warped pot. In each case, since the apparent impedance of the heating coil 6 changes depending on the state of the magnetic coupling with the pot, the peak value of the transmission frequency changes to f0 to f2 as shown in FIG.

In this embodiment, the heating coefficient detection circuit section 2
It is constituted by a frequency-voltage conversion circuit for converting the level of the transmission frequency into the magnitude of the voltage.

Each part in FIG. 1 operates as follows according to the flowchart shown in FIG. When the user places the cooking pan 9 on the plate 7 and presses a heating start button, the control unit 1 first causes the oscillation circuit unit 2 to oscillate the heating coil 6. The heating coefficient detecting circuit 2 converts the oscillation frequency into a voltage and inputs the voltage to the controller 1. The control unit 1 reads this voltage value and converts it into a heating coefficient G and a threshold value Dth for performing boiling determination according to the stored correspondence table.

Next, the control unit 1 starts heating the pan by the heating circuit unit 5. The control unit 1 indirectly measures the temperature of the pan 9 by the temperature sensor 8, converts the temperature into a voltage value by the temperature detection circuit unit 4, and inputs the voltage value to the control unit 1. When the time change rate D is large, the boiling determination threshold Dth is large, the control unit 1 continues heating.

When the time rate of change D becomes equal to or less than the determination threshold value Dth, the control unit 1 determines that boiling has occurred, and shifts to control at the time of boiling in which the heating amount is adjusted or heating is stopped.

As described above, according to the present invention, the correction of the temperature required for the temperature control and the determination threshold are measured as a heating coefficient reflecting the magnitude of the heating input to the pan, and the detected temperature is corrected and used as a parameter. By optimizing the threshold value, it is possible to perform an operation with higher temperature control accuracy.

In this embodiment, the case where the present invention is applied to boiling determination is described as an example.
It can also be applied to other controls, such as notification of the completion of residual heat immediately before boiling and operation stoppage when the temperature of the pot rises sharply.

In addition to the frequency-voltage conversion circuit, the heating coefficient detection circuit section 2 extracts only a frequency signal in a specific frequency range (around f0 in FIG. 3) using a band-pass filter, and determines the magnitude of the voltage value. It is also possible to use a circuit configuration that is determined by.

Further, as a method of determining the threshold value Dth in the case of the boiling determination, not only the heating coefficient G but also a method of determining two parameters, the detected temperature Ts of the temperature sensor 8 at the time of the determination and the heating coefficient G, as parameters. It is something. According to our experiments, such a method is particularly effective against variations in cooking conditions such as when the water temperature before cooking is high or when the plate 7 is kept boiling while it is still warm. FIG. 4 shows an example of a table indicating such a method of determining Dth. This table is stored in the control unit 1 in advance, and the heating coefficient G0 detected at the start of operation and the detected temperature Ts during heating are shown. Is converted into an optimum Dth from moment to moment. This table is determined experimentally in advance and stored in the control unit 1.

Finally, in this embodiment, for the sake of simplicity of explanation, the method of comparing the time rate of change D to measure the temperature change for a certain period of time has been described as a method of judging boiling. As a contrivance such as simplification of the microcomputer processing for a minute temperature change, a processing method of performing a boiling determination when the time required for a certain temperature rise becomes larger than a threshold value is also frequently used. It can also be done by a method.

(Embodiment 2) Another embodiment of the present invention will be described below with reference to FIG. This embodiment is different from FIG. 1 only in the configuration for measuring the heating coefficient, and the other configurations can be the same as those in the first embodiment.

In this embodiment, reference numeral 30 denotes a heating coefficient detecting circuit. In this embodiment, the heating coefficient detecting circuit 30 measures the current and voltage in the heating circuit 5 of the heating coil 6 and controls the control unit 1. Circuit configuration.

FIG. 5 shows an example of a table for determining the heating coefficient G from the current and voltage values from the circuit coefficient detecting circuit section 30. The control unit 1 stores such a table in advance, and when heating of the pot is started, the heating coefficient detection circuit unit 3
The current and voltage values input from 0 are converted into heating coefficients G as parameters.

[0028]

As described above, according to the first aspect of the present invention, by performing correction in accordance with the material of the pan and the gap between the plate and the plate surface, operation control with higher accuracy irrespective of the pan used. It is possible to provide an easy-to-use heating cooker capable of performing the above steps.

According to the second aspect of the present invention, there is provided an easy-to-use cooking device which has high merits in commercial terms, does not require a special circuit, enables high-precision operation control, and is easy to use. You can do it.

According to the third aspect of the invention, in particular, by adopting a configuration of a frequency-voltage conversion circuit as a circuit configuration for detecting a deviation of the oscillation frequency, a simple circuit configuration using a general-purpose IC or the like is provided. Therefore, it is possible to provide an easy-to-use heating cooker that can be easily realized, can perform high-precision operation control, and is easy to use.

According to the fourth aspect of the present invention, in particular, by adopting a configuration of a frequency-voltage conversion circuit as a circuit configuration for detecting a deviation of an oscillation frequency, a general-purpose IC or the like can be used with a small number of parts. Further, it is possible to provide an easy-to-use heating cooker which can be easily realized with a simple circuit configuration, can perform highly accurate operation control, and is easy to use.

According to the fifth aspect of the invention, in particular, by correcting the boiling determination parameter based on the heating coefficient, the heating cooker can be operated with high accuracy in boiling determination frequently used in the heating cooker. Can be provided.

[0033] According to the invention of claim 6, in particular, by correcting the boiling determination parameter with reference to the detected temperature at the time of determination in addition to the heating coefficient, the cooking conditions such as when the initial water temperature changes. It is possible to provide a heating cooker that can cope with the variation and that can be operated with high accuracy in the determination of boiling which is frequently used in the heating cooker.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a heating cooker according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a heating cooker according to a second embodiment of the present invention.

FIG. 3 is a diagram showing oscillation frequency characteristics of pots having different levels of warpage at the bottom of the pot.

FIG. 4 is a diagram showing a table for correcting a determination threshold from a detected temperature and a heating coefficient at a determination time;

FIG. 5 is a diagram showing a table for determining a determination threshold from a current-voltage value of a heating circuit unit.

FIG. 6 is a flowchart illustrating an example of a heating operation.

FIG. 7 is a diagram showing a change in temperature when boiling is performed in pots having different degrees of warpage at the bottom of the pot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control part 2 ... Oscillation circuit part 3 ... Heating coefficient detection circuit part 4 ... Temperature detection circuit part 5 ... Heating circuit part 6 ... Heating coil 7 ... Plate 8. ..Temperature sensor 9 ... Pot

Claims (6)

[Claims] 1. A plate on which an object to be heated such as a pot is arranged; a temperature sensor; a heating circuit unit including a heating coil for heating the object to be heated and a drive circuit thereof; and a signal from the temperature sensor. A control unit that controls an amount of heating by a heating circuit unit; and a heating coefficient detection circuit unit that oscillates the heating coil to measure a degree of magnetic coupling between the plate and the object to be heated. A heating cooker in which the control unit corrects a temperature detected by the temperature sensor or a determination parameter based on the heating coefficient measured by the unit to perform heating control. 2. A plate on which an object to be heated such as a pot is arranged; a temperature sensor; a heating circuit unit including a heating coil for heating the object to be heated and a drive circuit thereof; and a signal from the temperature sensor. A control unit that controls the amount of heating by the heating circuit unit; and a heating coefficient detection circuit unit that measures the degree of magnetic coupling between the plate and the object to be heated from current and voltage values of the heating circuit unit. A heating cooker in which the control unit corrects a temperature detected by the temperature sensor or a determination parameter based on a heating coefficient measured by a coefficient detection circuit unit to perform heating control. 3. The heating cooker according to claim 1, wherein the heating coefficient detecting circuit detects a deviation of the transmission frequency based on a voltage value in a certain frequency band, and calculates a heating coefficient from the deviation amount. 4. The heating coefficient detection circuit section detects a deviation of the transmission frequency by a circuit that converts a peak value of the frequency into a voltage, and calculates a heating coefficient from the deviation amount.
The heating cooker as described. 5. The judgment parameter is a judgment threshold value of a temperature change rate for judging boiling, and the control unit corrects the judgment threshold value based on a heating coefficient, and the temperature change rate detected by a temperature sensor is used to judge the corrected judgment value. The heating cooker according to claim 1, wherein the determination of boiling is performed when the temperature falls below a threshold value. 6. A judgment parameter is a judgment threshold value of a temperature change rate for judging boiling, and the control unit corrects the judgment threshold value based on a heating coefficient and a detected temperature at the time of the judgment, and detects the momentarily by a temperature sensor. The heating cooker according to claim 1, wherein the determination of boiling is performed when the temperature change rate falls below the corrected determination threshold.