JP2003243141A - Cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooker equipped with a temperature detection sensor capable of accurately detecting temperature without being affected by emissivity of a heated object. <P>SOLUTION: There is provided the cooker equipped with a temperature detection system unaffected by emissivity by measuring reflectance as light from a light-emitting means 7 reflected by the heated object 11 is received by a light-receiving means 9 and correcting infrared volume of an infrared sensor 8 with the emissivity converted from the reflectance. <P>COPYRIGHT: (C)2003,JPO

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 heating and cooking equipment, and can be applied to a pan temperature detection of a cooking device by an electromagnetic induction type, or a temperature sensor for a food item in a microwave oven.

[0002]

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

As a temperature sensor for such a heating cooker, a sensor structure such as a temperature sensor such as a thermistor for detecting the ambient temperature by heat conduction is generally used. A configuration applying a radiation temperature method using an infrared sensor such as a pyroelectric sensor or a thermopile that instantaneously senses infrared rays emitted to measure temperature has been proposed. In this infrared sensor method, infrared rays reach the sensor instantaneously, and therefore, there is an advantage that the response is very good as compared with the case where detection is performed by heat conduction.

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

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 03-184295

[Patent Document 2] Japanese Patent Application Laid-Open No. 01-124726

[0006]

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

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 and corrects it with the infrared ray amount at the reference temperature of the target object, or the emissivity ε remains constant and the measured temperature is used as the relative temperature. The method of doing was taken.

However, such a method can be used in applications such as monitoring in which the object to be measured does not change much, but the emissivity changes variously depending on the color, material, surface condition, etc. of the object, so that the object to be heated is cooked each time it is cooked. Such a method could not be put to practical use in a heating cooker in which the number varies depending on the variety.
However, if the amount of infrared rays is converted into temperature without correcting the emissivity, the detected temperature will be completely deviated.

[0009]

In order to solve the above-mentioned problems, the present invention relates to a heating cooker for measuring the temperature of an object to be heated such as a cooking object or a pan by means of an infrared sensor. A light emitting unit that emits light, a light receiving sensor and a reflection detection circuit that receive reflected light from the object to be heated, an infrared sensor and a radiation detection circuit that detect the amount of infrared light emitted from the object to be heated, the light receiving sensor, and An operation control unit that converts the emissivity of the object to be heated converted from the output of the reflection detection circuit and the temperature of the object to be heated from the amount of light received by the infrared sensor, and infrared transmission through a material or detection unit that transmits infrared rays. Equipped with a top plate fitted with wood,
The arithmetic control unit stores the correlation between the emissivity at a certain wavelength and the reflectance in the form of an arithmetic expression or a conversion table, and calculates the emissivity of the object to be heated converted from the outputs of the light receiving sensor and the reflection detection circuit. The temperature is calculated and the temperature of the object to be heated is converted from the amount of light received by the infrared sensor and the emissivity.

[0010]

According to the first aspect of the invention, the reflectance of the temperature measurement portion of the object to be heated is measured in advance by detecting the reflected light reflected by the object to be heated from the light emitting means, and measuring the reflectance in advance. By measuring the emissivity of the object to be heated at any time using the conversion formula of reflectance and emissivity that has been programmed, etc., and by using this emissivity to correct the detection temperature of the infrared sensor,
The temperature is accurately detected without being affected by the emissivity of the object to be heated. That is, according to the present invention, in the case of a substance such as a metal oxide surface that does not allow heat to permeate, the relation of ε = 1-R is established between the emissivity ε and the reflectance R of the substance (reference document “infrared engineering”). Hisashi Harunoyoshi, edited by The Institute of Electronics, Information and Communication Engineers), and is replaceable as the subject of the present invention.
Moreover, the above relationship is used to detect the temperature of a portion having a relatively same shape such as the bottom of the pot, which enables quick and accurate temperature detection which could not be achieved in the past.

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, external light, etc.
It is a system that can measure the reflectance using a light source such as an ED.

According to the third aspect of the invention, the wavelength range of the reflected light is 1000 nm, which has a longer wavelength than that of the second aspect.
By utilizing the near infrared wavelength of ~ 2000 nm,
This is a system that can further reduce the influence of the color of the object to be heated, external light, etc., and can measure the reflectance more accurately.

According to the fourth aspect of the invention, as the wavelength of the reflected light, the infrared wavelength range of 2000 nm or more, which is closer to the wavelength of the infrared sensor than that of the third invention, is utilized, so that the infrared wavelength received by the infrared sensor is It is a method that allows conversion with a very high correlation with the emissivity of the region.

In the fifth aspect of the present invention, the wavelength band is limited with a simple structure by performing the spectral analysis by using the light receiving sensitivity wavelength band of the light receiving sensor itself such as a phototransistor as the spectral measuring unit of the reflectance measurement wavelength. It is possible and the reflectance can be measured.

In a sixth aspect of the present invention, a light source in a narrow wavelength range such as an LED or a laser is used as the light emitting means as the spectral measuring means for measuring the reflectance, whereby the wavelength range can be limited with a simple structure. , The reflectance can be measured.

In the seventh aspect of the present invention, a more accurate wavelength range can be defined by using an optical bandpass filter that passes wavelengths in a fixed wavelength range as the spectral measuring means for measuring the reflectance wavelength. , Which enables accurate measurement of reflectance.

[0017]

EXAMPLES An example of the present invention will be described below.
FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the present embodiment, an example of the configuration in the case of detecting the pot bottom temperature in an electromagnetic induction type cooker is shown. Reference numeral 1 in FIG. 1 is a calculation control unit that controls the entire cooking device and calculates temperature, and is composed of a microcomputer and its peripheral circuits. Reference numeral 2 is a heating control unit for controlling the heating amount of the pan according to an instruction from the arithmetic control unit 1, and 3 is an operation display unit for inputting a temperature set value and a cooking course from the user and displaying the current pan temperature. Is. Reference numeral 7 is a light source for detecting the reflectance of the pot 10, and 9 is a light receiving sensor for receiving the light reflected from the bottom of the pot. Reference numeral 4 is a light emission control circuit for controlling the light emission and extinction of the light source 7, and 6 is a reflection detection circuit for detecting the output of the light receiving sensor 9. Reference numeral 8 is an infrared sensor for detecting the amount of infrared rays radiated from the bottom of the pan, and 5 is a radiation detection circuit for detecting the 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 has an infrared transparent material fitted in the detection portion.

FIG. 2 is a schematic diagram showing an example of the relationship between the total amount W of infrared rays received by the infrared sensor 8 and the converted temperature T calculated by the radiation detection circuit 5 and the arithmetic control unit 1 based on the total amount W. . Reference numeral 21 in FIG. 2 shows a relational expression when the emissivity ε = 1.0, and similarly, 22 and 23 show relational expressions when the emissivity ε = 0.5 and ε = 0.1. The lower the emissivity ε, the smaller the emissivity at the same temperature. Therefore, when the same total infrared radiation amount W is detected, the temperature of the target substance is interpreted to be higher as T0 → T1 → T2 as the emissivity ε is lower. 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 speaking, ε = 1-R may not be obtained due to the experimental conditions such as the directivity and sensitivity characteristics of, but as shown in FIG. 3, the higher the reflectance R, the lower the emissivity ε and the reflectance ε. The lower the R, the higher the emissivity ε.

The graphs of FIGS. 2 and 3 are stored in the arithmetic control unit 1 in the form of arithmetic expressions or conversion tables, and are used for calculating emissivity and temperature.

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

Finally, a method of selecting the wavelength for detecting the reflectance will be described. FIG. 4 is a schematic diagram showing an example of the wavelength characteristic of the emissivity showing the relationship between the emissivity of a substance and the wavelength. As shown in FIG. 4, a substance having wavelength characteristics in which the emissivity largely changes depending on the wavelength is called a selective radiator. In the infrared radiation of a substance, when the temperature of the target substance is about several hundreds of degrees, there is a large proportion of infrared rays having a wavelength of approximately 3 micrometers or more, which corresponds to a region indicated by a region IV in FIG. Therefore, in order to correct the emissivity from the reflectance, it is necessary to know the emissivity in the area IV actually received by the infrared sensor. In other words, the correlation becomes small even if the emissivity in the wavelength region having completely different wavelength characteristics is examined. In that case, the reflectance can be directly measured by the reflectance of the region IV, but this region receives infrared rays emitted from the target substance, that is, the reflectance cannot be accurately measured due to the influence of 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 reflectance measurement wavelength. One is a method of avoiding the visible light region I that is greatly affected by the pot color or the outside light from the indoor fluorescent lamp, and estimating the emissivity from the reflectance of the near infrared wavelength corresponding to the region II, and correcting it. is there. In the area II, the absorption of water in the object and the material of the object itself is relatively small, and the factor of variation in reflectance can be reduced. As the light receiving element in the region II, there are a light receiving element having a silicon composition and a light receiving element having a composition of indium gallium arsenide. In particular, these light-receiving elements and light-emitting elements can be used as remote controls for general household appliances and devices that are widely used as devices for optical communication, and therefore commercial effects can be expected.

Another method is the region I which is the target region.
In V, it is a method of correcting from the reflectance of the closer region III. The region III has an emissivity close to that of the region IV, and the infrared rays in this region are hardly emitted unless the substance is at a temperature of several thousand degrees. Can be measured accurately.

In this embodiment, the structure for measuring the pot temperature is shown, but the method of the present invention may be installed in the upper part of the microwave oven to detect the temperature of the cooked food. In particular,
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 the influence from the light source 9 for detecting the reflectance occurs, the light emission control circuit modulates and emits light in a time division manner such as emitting light during the detection stop time of the infrared sensor. Therefore, a method of preventing the influence of the reflection sensor is also possible.

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

[0028]

As described above, the invention according to claim 1 is
In a heating cooker that measures the temperature of an object to be heated such as a cooking object or a pan with an infrared sensor, a light emitting means for projecting light on the object to be heated, a light receiving sensor for receiving reflected light from the object to be heated, and A reflection detection circuit, an infrared sensor and an emission detection circuit for detecting the amount of infrared rays emitted from the object to be heated, the emissivity of the object to be heated converted from the outputs of the light receiving sensor and the reflection detection circuit, and the infrared ray. An arithmetic and control unit for converting the temperature of the object to be heated from the amount of light received by the sensor, and a top plate in which an infrared transmitting material is fitted to a material or a detecting unit that transmits infrared rays, the arithmetic and control unit is provided at a certain wavelength. The correlation between the emissivity and the reflectance is stored in the form of an arithmetic expression or a conversion table, and the emissivity of the heated object converted from the outputs of the light receiving sensor and the reflection detection circuit is calculated, and the red value is calculated. A heating cooker equipped with a temperature detection sensor capable of accurate temperature detection without being affected by the emissivity of the object to be heated by converting the temperature of the object to be heated from the amount of light received by the line sensor and the emissivity. It can be realized.

Further, according to the second aspect of the present invention, by utilizing 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, external light, etc., and to use a light source such as an LED. It is a system in which the reflectance can be measured by using it, and it becomes possible to realize a heating cooker equipped with a temperature detection sensor capable of more accurate temperature detection.

In the invention according to claim 3, the wavelength range of the reflected light is 1000, which has a wavelength longer than that of the second invention.
By using the near-infrared wavelength of nm to 2000 nm, it is possible to further reduce the influence of the color of the object to be heated, external light, etc., and it becomes a method that can measure the reflectance more accurately. It is possible to realize a heating cooker including a temperature detection sensor capable of detecting.

Further, according to the invention of claim 4, as the wavelength of the reflected light, the infrared ray wavelength region of 2000 nm or more, which is closer to the wavelength of the infrared ray sensor than that of the third aspect of the invention, is used so that the infrared ray sensor receives the light. It is a system that can be converted with a very high correlation with the emissivity in the infrared wavelength range,
It is possible to realize a heating cooker including a temperature detection sensor capable of more accurate temperature detection.

Further, according to the fifth aspect of the present invention, as the spectral measuring means of the reflectance measurement wavelength, the light receiving sensitivity wavelength range of the light receiving sensor itself such as a phototransistor is used to perform the spectral analysis. It is possible to realize a heating cooker including a temperature detection sensor that can be limited and that can accurately convert reflectance to emissivity.

Further, according to the present invention, the light source in the narrow wavelength range such as LED or laser is used as the light emitting means as the spectroscopic means for measuring the wavelength of the reflectance, so that the wavelength range can be limited with a simple structure. Therefore, it is possible to realize a heating cooker equipped with a temperature detection sensor capable of performing accurate conversion from reflectance to emissivity.

The invention according to claim 7 uses an optical band-pass filter for passing a wavelength in a fixed wavelength range as a spectroscopic unit for measuring the reflectance wavelength.
It is possible to realize a heating cooker equipped with a temperature detection sensor that can more accurately limit the wavelength range and can more accurately convert reflectance to emissivity.

[Brief description of drawings]

FIG. 1 is a block diagram of a heating cooker showing an embodiment of the present invention.

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

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

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

[Explanation of symbols]

1 Arithmetic control unit 2 Heating control section 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 Heated object

Claims (9)

[Claims] 1. A heating cooker for measuring the temperature of an object to be heated such as a cooking object or a pan by an infrared sensor, and a light emitting means for projecting light on the object to be heated and reflected light from the object to be heated. A light receiving sensor and a reflection detecting circuit for receiving light, an infrared sensor and a radiation detecting circuit for detecting the amount of infrared rays emitted from the object to be heated, and radiation of the object to be heated converted from outputs of the light receiving sensor and the reflection detecting circuit. rate,
And an arithmetic control unit that converts the temperature of the object to be heated from the amount of light received by the infrared sensor, and a top plate in which an infrared transmitting material is fitted to a material or a detecting unit that transmits infrared, and the arithmetic control unit is The correlation between the emissivity at the wavelength and the reflectance is stored in the form of an arithmetic expression or a conversion table, and the emissivity of the heated object converted from the outputs of the light receiving sensor and the reflection detection circuit is calculated, and the infrared sensor An electromagnetic induction heating cooker in which the temperature of the object to be heated is converted from the amount of received light and the emissivity. 2. A light receiving element having a silicon composition can be used as a light receiving sensor element for the reflectance measurement wavelength.
The cooking device according to claim 1, which uses a wavelength range from nm to 1000 nm. 3. The reflectance measurement wavelength is 1000 nm.
2. The cooking device according to claim 1, which uses a wavelength range from 1 to 2000 nm. 4. The measurement wavelength of the reflectance is 2000 nm.
The heating cooker according to claim 1, which uses the above wavelength range. 5. The cooking device according to claim 1, wherein the spectroscopic means for measuring the reflectance wavelength uses the wavelength range of the light-receiving sensitivity of the light-receiving sensor to perform the spectrum. 6. The heating cooker according to claim 1, wherein a light source in a narrow wavelength range such as an LED or a laser is used as the light emitting means as the spectral measuring means for measuring the reflectance wavelength. 7. The heating cooker according to claim 1, wherein an optical bandpass filter that passes a wavelength in a fixed wavelength range is used as a spectroscopic unit for measuring the 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.