JP2004327053A - Cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure reflectivity of a pan for precisely measuring a temperature of the pan mounted on a top plate. <P>SOLUTION: A light receiving output of an infra-red ray sensor 5 disposed at a lower face of a top plate 1 is compared with a prescribed value, a light emitting means projects an infra-red ray from a light emitting means when the receiving output is smaller than the prescribed value in a state of mounting a pan 2, and the sensor 5 measures the reflecting light and calculates the reflectivity.By the above, the cooker capable of measuring the reflectivity and a radiation light by one sensor, having a temperature detecting system not influenced by emissivity, is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to an electromagnetic induction heating cooker that can accurately detect the reflectance and temperature of a pot placed on a top plate.
[0002]
[Prior art]
In a heating cooker that heats the food in the pan, as a method of detecting the temperature of the bottom of the pan that is almost equivalent to the temperature of the food, a thermistor of a contact-type temperature sensor through a top plate on which the pan is placed is used. A method of indirectly detecting the pot bottom temperature is generally used. This conventional example will be described with reference to FIG.
[0003]
The top plate 1 is provided on the upper surface of the main body, and the pan 2 is placed. A high-frequency current is supplied to the heating coil 3 by a high-frequency current supply means 4 to heat the pot 2 by induction. A thermistor 5 for detecting a temperature is arranged on the lower surface of the top plate 1, and the temperature of the bottom surface of the pan 2 is indirectly detected from the output of the thermistor 5. The control means 6 controls the power supplied to the heating coil 3 based on the detected temperature. Reference numeral 7 denotes a DC power supply for supplying power to the control means 6, reference numeral 8 denotes a commercial power supply, reference numeral 9 denotes a full-wave rectification means, and reference numeral 10 denotes an inverter including a power supply capacitor 11, a resonance capacitor 12, and a switching element 13.
[0004]
Although not shown, a current transformer 14 for detecting the input current Iin is connected to the input side of the rectifier diode 9, and Vcc detecting means 15 for detecting the collector voltage of the switching element 13 is connected between the collector and the emitter of the switching element 13. , And each detection output is input to the control circuit 6, and the control means 6 performs various protection operations of the inverter 10 based on the input value.
[0005]
As a more responsive detection method, there is also known a method of directly detecting the temperature of the pan bottom by detecting infrared rays emitted from the pan bottom. However, in the induction heating cooker, the top plate 1 is made of crystallized glass (for example, “lithia ceramics”) in which glass having a special composition is reheated to increase the strength and fine crystals are precipitated in the glass. (FIG. 6 shows a graph of an example of the transmission characteristics thereof along with the transmission characteristics of a typical infrared window material.) Infrared rays having a wavelength of 2.6 μm or less are transmitted by 80% or more, and a wavelength of 3 to 4 μm is transmitted. About 30% of the infrared rays, and hardly pass infrared rays having a wavelength longer than 4 μm. Therefore, it is necessary to measure the bottom surface temperature of the pot 2 only at a wavelength component of 4 μm or less. Generally, the bottom surface temperature of the pot 2 at the time of cooking is about 30 ° C. to 230 ° C. Is a wavelength of 6 to 10 microns according to Stefan-Boltzmann's law. (The higher the temperature is, the more the energy is accelerated and radiated as infrared rays. The lower side of the graph in FIG. 6 shows the state at 30 ° C., 100 ° C., and 200 ° C.). With only the components, the infrared energy received by the infrared sensor 5 is weak because it is less than 30% of the total infrared radiation energy even from the bottom of the pot 2 at about 570K (300 ° C.). S / N ratio is poor only by conversion into an electric signal, and measuring the temperature at the time of cooking is not accurate and requires another contrivance.
[0006]
As a solution therefor, a method of integrating the infrared sensor 5 with the amplifier or a method of embedding a window material in the top plate 1 to increase the amount of infrared radiation energy transmitted (for example, see Patent Document 1) have been proposed.
[0007]
Further, a method has been proposed in which emissivity is measured and corrected in order to cope with various kinds of pots having various emissivities and various cooking methods and cooking scenes (for example, see Patent Document 2). This correction method is a method of projecting reference light from an inexpensive light source such as an infrared LED on the bottom surface of the pan 2 and measuring the reflectance of the bottom surface of the pan 2 from the intensity of infrared light reflected from the bottom surface of the pan 2. . Therefore, it is possible to measure in a non-contact manner, and there is no need for a large-scale device or pretreatment such as application of a black body to the bottom of a pot, and it is most suitable for emissivity (≒ 1-reflectance) measurement in a heating cooker. is there.
[0008]
[Patent Document 1]
Japanese Patent No. 2897306 [Patent Document 2]
Japanese Patent Application Laid-Open No. H10-309985
[Problems to be solved by the invention]
However, the infrared sensor system generally has a higher cost than the thermistor system, and therefore can be used only for a high-priced induction heating cooker. In addition, when the mounting angle of the light emitting element and the light receiving element for emissivity measurement is optimized, the mounting area becomes large, which is a restriction on the mechanism design to fit in the center of the heating coil.
[0010]
An object of the present invention is to reduce the size and cost of the object to be heated by using a single light receiving element to receive radiation emitted from the object to be heated at its own temperature and to receive reflected light reflected from the object to be heated. An object of the present invention is to provide a cooking device capable of measuring the temperature of the bottom surface of the pan 2 with high accuracy.
[0011]
[Means for Solving the Problems]
The present invention provides a top plate on which an object to be heated is mounted, electromagnetic induction heating means for heating the object to be heated mounted above the top plate from below the top plate, and the presence or absence of the object to be heated. An object to be heated recognizing means, a light emitting means for projecting light from below the top plate to the object to be heated, light reflected by the light emitting means from the object to be heated, and the object to be heated. A light-receiving means for receiving radiation emitted by the object at its own temperature, and comparing the light-receiving output of the light-receiving means with a predetermined value while the object-to-be-heated recognition means recognizes the presence of the object to be heated; When the output is smaller than a predetermined value, the light receiving amount obtained by subtracting the light receiving amount of the light receiving unit when the light emitting unit is turned off from the light receiving amount of the light receiving unit when the light emitting unit emits light is the amount of the reflected light. And the reflection of the heated object When the received light output is larger than a predetermined value, the output output from the light receiving unit in a state where the light emitting unit is turned off is defined as the amount of the emitted light, and the amount of the emitted light and the reflectance are calculated. Temperature calculating means for calculating the temperature of the object to be heated based on the light receiving element, and the temperature calculating means can receive and receive the radiated light and the reflected light with one light receiving element. It is a heating cooker.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 includes a top plate on which an object to be heated is mounted, electromagnetic induction heating means for heating the object to be heated mounted above the top plate from below the top plate, and Heated object recognition means for recognizing the presence or absence of a heated object, light emitting means for projecting light from below the top plate to the heated object, and light from the light emitting means reflected from the heated object Light receiving means for receiving the reflected light and the radiated light emitted by the object to be heated by its own temperature, and a temperature calculating means for calculating the temperature of the object to be heated based on the output of the light receiving means, The temperature calculating means compares the light receiving output of the light receiving means with a predetermined value in a state where the heated object recognizing means recognizes the presence of the heated object, and when the light receiving output is smaller than the predetermined value, the light emitting means The light reception when the light is emitted When the received light amount obtained by subtracting the received light amount of the light receiving unit when the light emitting unit is turned off from the received light amount of the stage is the amount of the reflected light, the reflectance of the object to be heated is calculated, and when the received light output is larger than a predetermined value. The output from the light receiving means in a state where the light emitting means is turned off is used as the amount of the radiated light, and the temperature of the object to be heated is calculated based on the amount of the radiated light and the reflectance. The temperature calculating means is a heating cooker that can use both a light receiving element and a reflected light element with a single light receiving element, and can measure the temperature of the pot with high accuracy.
[0013]
According to a second aspect of the present invention, in addition to the above, the comparing means of the temperature calculating means continues the calculation of the reflectance even if the received light output exceeds a predetermined value during the calculation of the reflectance, so that the reflectance is initially measured. By preferentially adopting a low value, the reflectance can be measured with a large light emission amount, and the reflectance can be calculated with high accuracy.
[0014]
In the invention according to claim 3, in addition to the above, the inverter has a protection function, and the object-to-be-heated recognition means detects the presence or absence of the object to be heated by the protection function of the inverter. The configuration is simplified by also using the placement detection function provided in the inverter.
[0015]
According to the fourth aspect of the present invention, in addition to the above, it is possible to calculate the reflectance with high accuracy by setting the amount of reflected light when the object to be heated is not placed as a reference value of the reflectance “0”. It is what becomes.
[0016]
According to the fifth aspect of the present invention, in addition to the above, the amount of reflected light in a state where a reflector having a predetermined reflectance is mounted is set as a reference value of the reflectance “1”, so that the reflectance is accurately calculated. It is possible to do.
[0017]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
(Example 1)
FIG. 1 is a block diagram showing the configuration of the cooking device in the present embodiment. The heating cooker according to the present embodiment includes a pot 2 placed on the top plate 1 for heating and cooking the food, a heating coil 3 for heating the pot 2, and a high-frequency current supply unit 4 for supplying a high-frequency current to the heating coil 3. An infrared sensor 5 arranged on the lower surface of the top plate 1 and detecting infrared rays emitted from the bottom surface of the pan 2, a band-pass filter 20 mounted on a light receiving surface of the infrared sensor 5 and transmitting light of a predetermined band wavelength, An amplifier 21 for amplifying the output of the infrared sensor 5, a switching means 22, a reflectance calculating means 24 for calculating the reflectance based on the reflected light, a light emitting means 25, and calculating the temperature of the bottom surface of the pot 2 from the reflectance and the radiated light A temperature calculating means 26, a control means 27 for controlling electric power supplied to the heating coil 3 according to an output of the temperature calculating means 26, and a magnetic shield cylinder 28.
[0019]
Next, the operation of the first embodiment will be described. When a power switch (not shown) is turned on, a predetermined temperature is set with an operation switch, and a heating key is pressed, the control means 27 controls the high-frequency current supply means 4 to supply a minimum power to the heating coil 3 and After the presence of the pan 2 is determined by the protection function (small object detection) of the inverter in the means 27, the supply of the high-frequency current is stopped. This pan presence signal is output from the control circuit 27 to the reflectance calculating means 24 and the temperature calculating means 26, as shown by the dotted line in FIG. The infrared sensor 5 outputs a voltage proportional to the energy of the received infrared light, and uses a bolometer, which is a thermoresponsive detector, a thermopile in which thermocouples are collected at one point, or a pyroelectric element. Therefore, when the temperature of the pan 2 rises and the intensity of infrared radiation from the bottom surface increases, the amount of infrared energy received by the infrared sensor 5 increases, and the output signal voltage of the infrared sensor 5 increases.
[0020]
As described above, the top plate 1 transmits only infrared light having a wavelength of 4 μm or less, and the infrared energy reaching the infrared sensor 5 is weak. An optical filter 20 that transmits light having a wavelength in a predetermined band (for example, a transmission wavelength range of 0.76 μm to 3 μm) for cutting is mounted on the light receiving surface of the infrared sensor 5. By amplifying, the S / N ratio is secured, and practical temperature measurement is possible. The switching means 22 compares the output of the amplifier 21 with a predetermined value. When the output of the amplifier 21 is smaller than the predetermined value (that is, when the bottom surface temperature of the pan 2 is smaller than the predetermined temperature), the output of the amplifier 21 is reflected. The reflectance calculating means 24 is connected to the rate calculating means 24, turns on the light emitting means 25, emits infrared rays having a wavelength of 0.76 to 1.5 μm to the pan 2, and measures an increase in the output of the amplifier 21. Assuming that the increase in the output is due to the reflected light from the pan 2, the reflectance of the pan 2 is calculated. When the calculation of the reflectance is completed (it takes about 0.5 seconds because the infrared sensor is a thermoresponsive type), the control means 27 controls the high-frequency current supply means 4 to supply a predetermined power to the heating coil 3. Then, an induction magnetic field is generated from the heating coil 3 and the pot 2 on the top plate 1 is induction-heated. Due to this heat, the temperature of the pan 2 rises, and heating of the food in the pan 2 is started.
[0021]
Here, when the output of the amplifier 21 becomes larger than a predetermined value (that is, when the bottom surface temperature of the pan 2 is higher than the predetermined temperature), the switching unit 22 connects the output of the amplifier 21 to the temperature calculation unit 26, so that the reflectance is calculated. The temperature calculating means 26 calculates the temperature of the bottom surface of the pot 2 by an approximate expression from the reflectance (≒ 1-emissivity) calculated by the means 24 and the output of the amplifier 21, and inputs this temperature to the control means 27. The high-frequency current supply unit 4 is controlled so that the temperature of the heating coil 3 becomes the set temperature, and the amount of electric power supplied to the heating coil 3 is adjusted. When cooking is completed and the stop key is operated, heating is stopped. Therefore, the temperature calculating means 26 calculates the temperature from the reflectance of the pan 2 and the value obtained by amplifying the detection output of the infrared sensor 5 by the amplifier 21, so that the bottom of the pan 2 can be measured with high accuracy without contact. As a result, it becomes possible to realize an automatic cooking function with delicate heating and automatic adjustment of heating and cooking of a rice cooking sequence.
[0022]
The predetermined value given to the comparison means in the switching means is, for example, the detection value when the temperature of the pot bottom is 45 ° C. in the example shown in the graph showing the relationship between the pot bottom temperature and the detection output (output of the amplifier 21) in FIG. Output is 0.2V. Generally, the temperature information required for cooking is about 50 ° C. to 230 ° C. If the temperature of the pot is 50 ° C. or less, no problem occurs even if the temperature output is zero.
[0023]
Note that a silicon detector such as HgTdTe or IgAS of a quantum type and a pin photodiode have a detection sensitivity of infrared rays which is about two orders of magnitude higher than that of a thermal response type detector, but have a wavelength dependency (that is, a measurement wavelength range is smaller). Therefore, it cannot be used when an infrared sensor having a flat detection sensitivity of 0.76 μm to 3 μm is required as in the present invention.
[0024]
The reflectance calculating means 24 of this embodiment stores the reflectance of a general pot (for example, 0.9) as an initial value, and the output of the amplifier 21 is already output when the heating key is pressed. When the temperature is larger than the predetermined value (that is, when the temperature of the pan 2 is higher than the predetermined temperature), the temperature calculating means 26 inputs the reflectance and the output of the amplifier 21 to calculate the temperature.
[0025]
When cooking is repeatedly performed with the pot 2 placed, the reflectance calculating means 24 stores the reflectance calculated last time.
[0026]
Further, since the reflectance and the increase in the output of the amplifier 21 when the light emitting means 25 is projected have a favorable proportional relationship, the reflectance can be output with a simple conversion circuit.
[0027]
In this embodiment, the presence / absence of a pot is detected by the protection function of the inverter. As long as is less than or equal to a predetermined value, a method of periodically measuring the reflectance may be used.
[0028]
Products that measure the reflectance of the side surface of the pot and correct the temperature measurement value by the infrared sensor have also been put to practical use, but there are various obstacles to measuring the side surface, such as water vapor generated from the pot and cooking materials. There is a case where the measurement is impossible because there are cooking utensils such as balls and the like.Therefore, the method of the present invention for measuring the reflectance of the bottom surface of the pot is superior, and another technique from the viewpoint of the configuration is as follows. ,it is obvious.
[0029]
(Example 2)
In the present embodiment, the basic configuration as a cooker is the same as that of the first embodiment, and a description of the basic configuration will be omitted. The second embodiment is different from the first embodiment in that the switching unit, the reflectance calculating unit, the temperature calculating unit, and the control unit are realized by a microcomputer program. Will be described.
[0030]
FIG. 3 is a block diagram of the present embodiment, and FIG. 4 is a general flowchart. The operation at the time of heating without temperature control will be described based on the flowchart of FIG. When the user turns on a power switch (not shown), a voltage is supplied from the DC power supply 7 to the microcomputer 30 to perform an initialization operation in step 40 (step 40), and waits for a heating key to be pressed in step 41. When the user presses the heating key, the high-frequency current supply means 4 is controlled in step 42 to supply the minimum power to the heating coil 3 for a predetermined time, and a small object detection function (Iin-Vce restriction) which is one of the protection functions of the inverter. , The presence / absence of the pan 2 is determined, and if the pan 2 is not present, small items are intermittently detected while waiting. When the pot 2 is present, the output of the amplifier 21 is compared with a predetermined value in step 43, and when the output of the amplifier 21 is smaller than the predetermined value (that is, when the bottom surface temperature of the pot 2 is smaller than the predetermined temperature), the light emitting means is set in step 44. 25, and the reflectance is calculated. When the output of the amplifier 21 is larger than the predetermined value (that is, when the bottom surface temperature of the pan 2 is higher than the predetermined temperature), the process proceeds to step 45. While the reflectance is measured in step 44, the calculation of the reflectance is continued even if the value of the amplifier 21 exceeds a predetermined value. The temperature of the bottom of the pan 2 is calculated from the reflectance calculated in step 45 or the stored reflectance and the output of the amplifier 21. Here, the infrared energy radiated from the pot 2 itself at about 30 ° C. to 230 ° C. extends over a wavelength range of 6 μm to 55 μm, but the infrared sensor 5 can detect a wavelength range of 0.76 μm to 3 μm. As the energy amount Wd (W / cm ＾ 2) is obtained by partially integrating the equation of Plan over the wavelength range of 0.76 μm to 3 μm, Wd is not proportional to the fourth power of the absolute temperature (Stephan Boltzmann's law).
[0031]
Therefore, in this embodiment, the temperature is calculated by an approximate expression. If the calculated temperature is equal to or lower than the alarm temperature (burn) in step 46, the high-frequency current supply means 4 is controlled to supply a predetermined power to the heating coil 3, and an induction magnetic field is generated from the heating coil 3. Is heated by induction. Due to this heat, the temperature of the pan 2 rises, and heating of the food in the pan 2 is started.
[0032]
At step 47, it is determined whether or not the stop key has been pressed, and if not, the processing at steps 45 to 47 is repeated. When the stop key is pressed, the heating operation ends. By the above operation, during the calculation of the reflectance, the calculation of the reflectance is continued even if the output of the amplifier 21 exceeds a predetermined value. This acts to increase the illuminance of the light emitting means 25 and does not continue as a result. In this case, more accurate reflectance measurement can be performed.
[0033]
Also, in long-term use due to a change in illuminance with time of the light emitting means 25, contamination of the top plate 1, a change in sensitivity of the infrared sensor, etc., an error occurs between the reflectance calculated in step 44 and the actual reflectance. Although there is a danger, a method of solving the above problem by causing the user to perform a calibration operation after a predetermined use time has elapsed can be considered.
[0034]
FIG. 5 is a flowchart of the calibration operation. The operation will be described below. The microcomputer 30 stores the total use time Tw of the heating cooker, the reference value P0 of the reflectance "0", and the reference value P1 of the reflectance "1" in the data EEPROM area, and the user turns on the power switch. After the power is turned on and the initialization operation of step 40 is performed, the user is informed of the necessity of the calibration operation by displaying it on a display (step 51), and the calibration operation is started. The user does not place the pan because it is initially '0' calibration. In step 52, wait for the key defined for calibration of the reflectance “0” to be pressed, and when the “0” key is pressed, measure the amount of reflected light in step 53, and refer to the value of the reflectance “0” reference P0. And
[0035]
Next, in step 54, the "1" calibration is displayed on the display to inform the user. Since the calibration is “1”, the user places a predetermined (reflectance = 1) reflector at a position corresponding to the center of the heating coil 3. In step 55, wait for the key defined for calibration of the reflectance "1" to be pressed, and when the key "1" is pressed, measure the amount of reflected light in step 56, and use that value as the "1" reference P1 for reflectance. And As described above, since the reflectance “0” and the reflectance “1” are calibrated, stable and accurate reflectance measurement can be performed for a longer period.
[0036]
【The invention's effect】
As described above, the present invention provides a top plate on which an object to be heated is mounted, electromagnetic induction heating means for heating the object to be heated mounted above the top plate from below the top plate, and An object to be heated recognizing means for recognizing the presence or absence of an object; a light emitting means for projecting light from below the top plate to the object to be heated; and reflected light in which light from the light emitting means is reflected from the object to be heated. A light-receiving means for receiving the radiated light emitted by the object to be heated according to its own temperature; and a light-receiving output of the light-receiving means being compared with a predetermined value in a state where the object-to-be-heated recognition means recognizes the presence of the object to be heated. When the light receiving output is smaller than a predetermined value, the light receiving amount obtained by subtracting the light receiving amount of the light receiving unit when the light emitting unit is turned off is subtracted from the light receiving amount of the light receiving unit when the light emitting unit emits light. The amount of reflected light Calculate the reflectance of the thermal substance, and when the received light output is larger than a predetermined value, set the output output from the light receiving means in a state where the light emitting means is turned off to the amount of the emitted light, and Temperature calculating means for calculating the temperature of the object to be heated based on the amount and the reflectance, the temperature calculating means can receive the radiated light and the reflected light with one light receiving element. The present invention also realizes a small, low-cost, non-contact, high-precision induction heating cooker capable of non-contact high-precision temperature measurement of a pot.
[0037]
Further, the amount of reflected light when the object to be heated is not mounted is set as the reference value of the reflectance “0”, and the amount of reflected light when the reflector having a predetermined reflectance is mounted is defined as the value of the reflectance “1”. By performing the calibration operation using the reference value, an induction heating cooker capable of performing stable temperature measurement for a long time can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a cooking device according to a first embodiment of the present invention. FIG. 2 is a graph illustrating a relationship between a detected output and a pan bottom temperature according to the first embodiment of the present invention. FIG. 4 is a block diagram showing a configuration of a cooking device according to a second embodiment of the present invention. FIG. 4 is a general flowchart according to a second embodiment of the present invention. FIG. Fig. 7 is a graph showing the configuration of a conventional heating cooker [Description of symbols]
DESCRIPTION OF SYMBOLS 1 Top plate 2 Pot 3 Heating coil 4 High frequency current supply means 5 Infrared sensor 20 Band pass filter 21 Amplifier 22 Switching means 24 Reflectivity calculation means 25 Light emission means 26 Temperature calculation means 27 Control means 28 Magnetic shield cylinder 30 Microcomputer

Claims (5)

A top plate on which the object to be heated is placed; electromagnetic induction heating means for heating the object to be heated placed above the top plate from below the top plate; and recognition of the presence or absence of the object to be heated. Object to be heated, light emitting means for projecting light from below the top plate to the object to be heated, light reflected from the object to be heated by the light emitting means, and the object to be heated Comprises light receiving means for receiving radiation emitted by its own temperature, and temperature calculating means for calculating the temperature of the object to be heated based on the output of the light receiving means, wherein the temperature calculating means comprises: When the object recognizing means recognizes the presence of the object to be heated, the light receiving output of the light receiving means is compared with a predetermined value, and when the light receiving output is smaller than the predetermined value, the light receiving means when the light emitting means emits light From the amount of light received The amount of reflected light obtained by subtracting the amount of light received by the light receiving means when the stage is turned off is used as the amount of reflected light to calculate the reflectance of the object to be heated. A heating cooker for calculating the temperature of the object to be heated based on the amount of the radiated light and the amount of the radiated light, and the output of the light receiving means in the state where the light is received. The cooking device according to claim 1, wherein the temperature calculating unit continues calculating the reflectance even if the received light output exceeds a predetermined value during the reflectance calculation. The heating cooker according to claim 1, wherein the inverter has a protection function, and the object-to-be-heated recognition means detects presence or absence of the object to be heated by the protection function of the inverter. The cooking device according to claim 1, wherein the temperature calculation unit sets the amount of reflected light in a state where the object to be heated is not placed as a reference value of the reflectance “0”. 2. The heating cooker according to claim 1, wherein the temperature calculating means sets the amount of reflected light in a state where a reflector having a predetermined reflectance is placed as a reference value of the reflectance "1".

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