JPH11225881A - Heating cooking device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a temperature of an object to be heated without being affected by a radiation rate by converting a radiation rate of the object to be heated converted from an output of a light receiving means and converting a temperature of the object to be heated from a light received amount of an infrared ray sensor. SOLUTION: A computing control part 1 gives an instruction to a light emitting control circuit 4 to light a light emitting element, and light reflected in a pan bottom is received by a light receiving sensor 9, is converted into a voltage amount in a reflection detection circuit 6, and is input in the computing control part 1 to calculate a reflectance. The computing equation showing the correlation of a reflectance and an emissivity is set in the computing control part 1 in advance to convert to a emissivity using this computing equation. At the same time, infrared ray radiated from a pan bottom is received by an infrared ray sensor 8, is converted into a voltage amount in a radiation detection circuit 5, and is input in the computing control part 1. Next, temperature calculation equation and temperature calculation equation corresponding to the other emissivity are memorized in the computing control part 1 in advance to calculate a temperature of the pan bottom using this temperature calculation equation. The calculated temperature is compared with a set temperature in a heating control part 2 to increase or decrease a heating amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor for a cooking appliance, and can be applied as a temperature sensor for a cooking pot using an electromagnetic induction system or as a temperature sensor for food in a microwave oven.

[0002]

2. Description of the Related Art Conventionally, in a cooking device, the temperature of a food to be heated or the temperature of a pan is detected by a temperature sensor, thereby detecting the degree of progress of cooking and performing heating control to finish to an optimum cooking condition. And take safety measures such as turning off the power when the temperature of cooked food or cooker suddenly rises.

As a temperature sensor of such a heating cooker, a sensor configuration for detecting an ambient temperature by heat conduction such as a temperature sensor such as a thermistor is generally used. However, as is known as a radiation thermometer, the temperature of an object is measured. There has also been proposed a configuration in which a radiation temperature method using an infrared sensor such as a pyroelectric sensor or a thermopile for measuring a temperature by instantaneously detecting emitted infrared light is applied. In the infrared sensor method, since infrared rays reach the sensor instantaneously, there is an advantage that responsiveness is very good as compared with the case where detection is performed by heat conduction.

The principle of the infrared sensor system is that the object to be heated emits more infrared rays as the temperature rises. Therefore, the amount of infrared rays is converted into a temperature by detecting the amount of the electromotive force or the amount of change in the resistance value by the detecting element.

[0005]

However, in the infrared sensor system, a difference in emissivity indicating the efficiency of infrared radiation from an object is a measurement problem. Generally, even if the temperature of the object to be heated is the same, if the emissivity is high, the amount of emitted infrared light is large, and if the emissivity is small, the amount of infrared light decreases. Therefore, the infrared sensor has no method of determining whether the infrared ray amount is small due to the lower temperature or the infrared ray amount is small because the emissivity is smaller than the reference infrared ray amount.

In an infrared sensor system such as a radiation thermometer,
To solve this problem, the user inputs the emissivity ε that has been checked in advance, corrects it with the amount of infrared rays at the reference temperature of the object, and uses the measured temperature as a relative temperature while the emissivity ε remains constant. And other methods were taken.

[0007] However, such a method can be used in applications such as monitoring where the object to be measured does not change much, but the emissivity changes variously depending on the color, material and surface condition of the object. However, such a method has not been practical in a heating cooker that varies in every way.
However, if the conversion from the amount of infrared rays to the temperature is performed without correcting the emissivity, there arises a problem that the detected temperature is completely shifted.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a heating cooker for measuring the temperature of a heated object such as a cooking object or a pan using an infrared sensor. A light emitting unit that emits light; and a light receiving unit that receives light reflected from the object to be heated. The emissivity of the object to be heated converted from the output of the light receiving unit and the amount of light received by the infrared sensor are used to determine whether the object is heated. It is obtained by converting the temperature of an object.

[0009]

According to the first aspect of the present invention, the reflectance of the temperature measuring portion of the object to be heated is measured by detecting the light reflected by the object to be heated from the light emitting means by the light receiving means. By measuring the emissivity of the object to be heated from time to time using the reflectance and emissivity conversion formula that was programmed, and using this emissivity to correct the detection temperature of the infrared sensor,
This is to perform accurate temperature detection that is not affected by the emissivity of the object to be heated. That is, according to the present invention, when a substance that does not transmit heat, such as a metal oxide surface, a relation of ε = 1−R is established between the emissivity ε and the reflectance R of the substance (reference document “Infrared Engineering”). Haruyoshi Kuno, edited by the Institute of Electronics, Information and Communication Engineers).
In addition, the above-described relationship is used for temperature detection of a portion having a relatively identical shape such as a pan bottom, thereby enabling quick and accurate temperature detection that could not be performed conventionally.

According to the second aspect of the present invention, by using a wavelength of 600 nm to 1000 nm as the wavelength of the reflected light, the influence of the color of the object to be heated and external light can be reduced.
This is a method in which the reflectance can be measured using a light source such as an ED.

According to the third aspect of the invention, the reflected light has a wavelength range of 1000 nm longer than that of the second aspect of the invention.
By utilizing near infrared wavelengths of ~ 2000 nm,
In this method, the influence of the color of the object to be heated and external light can be further reduced, and the reflectance can be measured more accurately.

According to the fourth aspect of the present invention, the wavelength of the infrared light received by the infrared sensor is used as the wavelength of the reflected light by using an infrared wavelength range of 2000 nm or more closer to the wavelength of the infrared sensor than the third invention. It is a method that can perform conversion with a very high correlation with the emissivity of the area.

According to the fifth aspect of the present invention, the spectral range is measured using a light receiving sensitivity wavelength range of the light receiving sensor itself such as a phototransistor as a spectroscopic means of the wavelength for measuring the reflectance, thereby limiting the wavelength range with a simple configuration. It is possible to measure the reflectance.

According to the sixth aspect of the present invention, the wavelength range can be limited with a simple configuration by using a light source having a narrow wavelength range such as an LED or a laser as the light emitting means as the spectral range measuring means for the reflectance measurement wavelength. And the reflectance can be measured.

According to the seventh aspect of the present invention, by using an optical band-pass filter that passes a wavelength in a certain wavelength range as a spectral means for measuring the wavelength of the reflectance, a more accurate wavelength range can be defined. In this case, it is possible to accurately measure the reflectance.

[0016]

An embodiment of the present invention will be described below.
FIG. 1 is a block diagram showing a configuration of one embodiment of the present invention. In this embodiment, an example of a configuration in a case of detecting a pot bottom temperature in an electromagnetic induction type cooking device is shown. Reference numeral 1 in FIG. 1 denotes an arithmetic and control unit for controlling the entire heating cooker and calculating the temperature and the like, and includes a microcomputer and its peripheral circuits. Reference numeral 2 denotes a heating control unit for controlling the amount of heating of the pot in accordance with an instruction from the arithmetic control unit 1. Reference numeral 3 denotes an operation display unit for inputting a temperature setting value or a cooking course from a user and displaying the current pot temperature. It is. Reference numeral 7 denotes a light source for detecting the reflectance of the pot 10, and reference numeral 9 denotes a light receiving sensor that receives light reflected from the bottom of the pot. Reference numeral 4 denotes a light emission control circuit for controlling light emission and extinguishing of the light source 7, and reference numeral 6 denotes a reflection detection circuit for detecting an output of the light receiving sensor 9. Reference numeral 8 denotes an infrared sensor for detecting the amount of infrared radiation emitted from the bottom of the pot, and reference numeral 5 denotes a radiation detection circuit for detecting an output from the infrared sensor 8. Reference numeral 10 denotes a top plate of the heating cooker, which is made of a material that transmits infrared rays or one in which an infrared transmitting material is fitted in a detection unit.

FIG. 2 is a schematic diagram showing an example of the relationship between the total amount W of infrared light received by the infrared sensor 8 and the converted temperature T calculated by the radiation detection circuit 5 and the arithmetic and control unit 1 based on the total amount W. . 2 indicates a relational expression when emissivity ε = 1.0, and similarly, 22 and 23 indicate emissivity ε = 0.5 and ε.
The relational expression when = 0.1 is shown. The lower the emissivity ε, the lower the emissivity at the same temperature. Therefore, if the same total infrared ray W is detected, the lower the emissivity ε, the higher the temperature of the target substance is interpreted as T0 → T1 → T2. You can do it.

FIG. 3 is a schematic diagram showing an example of the correlation between the emissivity ε and the reflectance R at a certain wavelength. Light receiving sensor 9
Strictly, ε = 1−R may not be obtained depending on experimental conditions such as the directivity and sensitivity characteristics of the light emitting element. However, as shown in FIG. The emissivity ε tends to increase as R decreases.

The graphs of FIGS. 2 and 3 are stored in the arithmetic and control unit 1 in the form of an arithmetic expression or a conversion table, and are used for emissivity calculation and temperature calculation.

Using the above description, the schematic operation of the block diagram of FIG. 1 will be described. The arithmetic control unit 1 instructs the light emission control circuit 4 to turn on the light emitting element, receives the light reflected on the bottom of the pot by the light receiving sensor 9, converts it into a voltage amount by the reflection detection circuit 6, and inputs the voltage to the arithmetic control unit 1 for reflection Calculate the rate. The arithmetic control unit 1 has an arithmetic expression 31 showing the correlation between the reflectance and the emissivity in FIG.
Is set in advance, and is converted into the emissivity ε using this equation. At the same time, the infrared sensor 8 receives infrared rays emitted from the bottom of the pot, converts the infrared rays into a voltage amount by the radiation detection circuit 5, and inputs the voltage to the arithmetic and control unit 1. Next, the arithmetic and control unit 1 stores in advance temperature calculation formulas 21 to 23 for converting the infrared ray amount and the emissivity ε into a temperature as shown in FIG. 2 and other temperature calculation formulas corresponding to the emissivity ε. In advance, the pan bottom temperature is calculated using this temperature calculation formula. The calculated temperature T is displayed by the user on the display operation unit 3, or the heating control unit 2 compares the set temperature with the set temperature to increase or decrease the heating amount.

Finally, a method of selecting a wavelength for detecting the reflectance will be described. FIG. 4 is a schematic diagram illustrating an example of the wavelength characteristic of the emissivity indicating the relationship between the emissivity of the substance and the wavelength. As shown in FIG. 4, a substance having a wavelength characteristic whose emissivity largely changes depending on the wavelength is called a selective radiator. When the temperature of the target substance is about several hundred degrees, the infrared radiation of the substance has a large proportion of infrared rays having a wavelength of about 3 micrometers or more, which corresponds to the region indicated by region IV in FIG.
Therefore, in order to correct the emissivity from the reflectance, it is necessary to know the emissivity in the region IV where the infrared sensor actually receives light. That is, even if the emissivity in a wavelength region having completely different wavelength characteristics is examined, the correlation becomes small. Then directly to Region IV
However, since this region receives infrared rays radiated by the target substance, that is, the reflectivity cannot be measured accurately due to the temperature itself of the target substance.

In such a situation, the following means can be considered as means for selecting which wavelength should be selected as the wavelength for measuring the reflectance. One method is to avoid the visible light region I, which is greatly affected by pot color or external light from indoor fluorescent lamps, and to estimate and correct the emissivity from the near-infrared wavelength reflectance corresponding to region II. is there. In the region II, the absorption due to the moisture in the object or the material of the object itself is relatively small, and the factor that causes the reflectance to vary can be reduced. Examples of the light receiving element in the region II include a light receiving element having a silicon composition and a light receiving element having a composition of indium gallium arsenide ingari. In particular, since these light receiving elements and light emitting elements can be diverted to devices widely used as remote controllers for general home appliances and optical communication devices, commercial effects can be expected.

Another method is to use a target area IV
Then, it is a method of correcting from the reflectance of the closer region III. In this region III, it has an emissivity close to that of region IV, and since infrared light in this region is hardly emitted unless it is from a substance of several thousand degrees, it is hardly affected by the amount of infrared light emitted by the object itself, and the reflectance is high. Can be measured accurately.

In this embodiment, the configuration for measuring the temperature of the pot is described. However, the method of the present invention may be a method in which the temperature of the cooked food is detected by installing the device on the microwave oven. Especially,
Since this method calculates emissivity ε almost in real time with temperature measurement, it is particularly effective when ε cannot be set in advance or when temperature detection is performed while moving various objects.

When an influence from the light source 9 for detecting the reflectance is generated, the light emission control circuit modulates the light and emits light in a time-sharing manner such as emitting light during the detection stop time of the infrared sensor. Thus, a method of preventing the influence of the reflection sensor from appearing is also possible.

Further, the configuration of the present invention can be applied not only to the cooking field, but also to temperature control in a painting process in a production line, temperature control of coffee cans of a vending machine, and the like. Is replaceable, and if the shape of the reflection surface of the replaced object to be heated is relatively similar, it is easy to apply the present invention.

[0027]

As described above, the first aspect of the present invention provides
In a heating cooker that measures the temperature of an object to be heated such as a cooking object or a pan by an infrared sensor, a light emitting unit that emits light to the object to be heated and a light receiving unit that receives light reflected from the object to be heated are provided. The emissivity of the object to be heated converted from the output of the light receiving means, and the temperature of the object to be heated is converted from the amount of light received by the infrared sensor, so that the emissivity of the object to be heated is not affected. It is possible to realize a heating cooker provided with a temperature detection sensor capable of accurately detecting temperature.

According to the second aspect of the present invention, by using a wavelength of 600 nm to 1000 nm as the wavelength of the reflected light, it is possible to reduce the influence of the color of the object to be heated and external light, etc. It is a method that can measure the reflectance by using a temperature sensor, and it is possible to realize a heating cooker provided with a temperature detection sensor capable of more accurate temperature detection.

According to a third aspect of the present invention, the wavelength range of the reflected light is 1000, which has a longer wavelength than the second aspect.
The use of near-infrared wavelengths of from nm to 2,000 nm makes it possible to further reduce the influence of the color of the object to be heated and external light, and to measure the reflectance more accurately. It is possible to realize a heating cooker provided with a temperature detection sensor capable of detection.

According to a fourth aspect of the present invention, the infrared light is received by the infrared sensor by using a wavelength region of 2,000 nm or more closer to the wavelength of the infrared sensor than the third invention as the wavelength of the reflected light. It is a method that can convert very high correlation with the emissivity in the infrared wavelength range,
It is possible to realize a cooking device provided with a temperature detection sensor capable of more accurate temperature detection.

According to a fifth aspect of the present invention, the light is spectrally separated by using the light receiving sensitivity wavelength range of the light receiving sensor itself such as a phototransistor as a spectral means for measuring the reflectance measurement wavelength. It is possible to realize a heating cooker provided with a temperature detection sensor capable of being limited and capable of accurately converting reflectance to emissivity.

Further, the invention according to claim 6 uses a light source having a narrow wavelength range, such as an LED or a laser, as a light emitting means as a spectral wavelength measuring means of the reflectance, thereby limiting the wavelength range with a simple configuration. This makes it possible to realize a heating cooker provided with a temperature detection sensor capable of accurately converting reflectance to emissivity.

According to a seventh aspect of the present invention, an optical band-pass filter that passes a wavelength in a certain wavelength range is used as a spectral unit for measuring a wavelength of reflectance.
It is possible to realize a heating cooker provided with a temperature detection sensor capable of more accurately limiting the wavelength range and capable of converting the reflectance into the emissivity more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram of a cooking device showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a received infrared ray amount and a converted temperature T for each emissivity.

FIG. 3 is a characteristic diagram showing a relationship between emissivity and reflectance at a certain wavelength.

FIG. 4 is a characteristic diagram showing a wavelength characteristic of an emissivity of a certain substance.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 arithmetic operation control unit 2 heating control unit 3 display operation unit 4 light emission control circuit 5 radiation detection circuit 6 reflection detection circuit 7 light source 8 infrared sensor 9 light receiving sensor 10 top plate 11 object to be heated

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F24C 7/02 330 F24C 7/02 330A H05B 6/12 335 H05B 6/12 335 6/68 320 6/68 320Q

Claims (11)

[Claims] 1. A heating cooker for measuring the temperature of an object to be heated such as a cooking object or a pan using an infrared sensor, wherein a light emitting means for projecting light onto the object to be heated, and a reflected light from the object to be heated. A heating cooker comprising a light receiving means for receiving light, wherein the temperature of the heated object is converted from the emissivity of the heated object converted from the output of the light receiving means and the amount of light received by the infrared sensor. 2. A light receiving element having a silicon composition can be used as an element of the light receiving means for measuring a reflectance of 600 n.
The cooking device according to claim 1, wherein a wavelength range from m to 1000 nm is used. 3. The wavelength for measuring the reflectance is 1000 nm.
The heating cooker according to claim 1, wherein a wavelength range from 2,000 to 2,000 nm is used. 4. The wavelength for measuring the reflectance is 2000 nm.
The cooking device according to claim 1, wherein the above-mentioned wavelength range is used. 5. The cooking device according to claim 1, wherein the light is spectrally separated using a light-receiving sensitivity wavelength range of the light-receiving element as the spectral means for measuring the reflectance measurement wavelength. 6. The cooking device according to claim 1, wherein the light is dispersed by using a light source having a narrow wavelength range such as an LED or a laser as a light emitting means as the spectral means for measuring the reflectance measurement wavelength. 7. The cooking device according to claim 1, wherein the light is split by using an optical band-pass filter that passes a wavelength in a certain wavelength range as a spectroscopic means for measuring a reflectance measurement wavelength. 8. The cooking device according to claim 1, wherein the infrared sensor is a pyroelectric sensor. 9. The cooking device according to claim 1, wherein the infrared sensor is a thermopile. 10. The cooking device according to claim 1, wherein the cooking device is an electromagnetic induction type cooking device, and the object to be heated is a cooking pot. 11. The cooking device according to claim 1, wherein the cooking device is a microwave oven.