JPH07119980A - Cooker - Google Patents

Abstract

PURPOSE:To detect a food temperature correctly and permit excellent cooking. CONSTITUTION:A temperature detector, having a narrow field of sight, is formed by collecting infrared rays, emitted out of a food 3, through a light collecting unit 19. An infrared ray detecting element 10 is connected to the light collecting unit 19 thermally through a holder 18 prominent in thermal conductivity to suppress the generation of temperature detecting error due to the affection of the temperature change of ambient air whereby correct detecting of the food temperature and good cooking car be effected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooking apparatus for detecting the temperature of food in a microwave oven, an oven, a grill or the like and performing automatic cooking or the like.

[0002]

2. Description of the Related Art Conventionally, a cooking device of this type (here, a microwave oven) has been constructed as shown in FIG. Reference numeral 1 denotes a heating chamber, on which a food 3 is placed on a cooking table 2 provided at the bottom of the heating chamber 1, and a microwave for heating introduced into the heating chamber 1 is oscillated outside the heating chamber 1. A magnetron 4 is installed. The cooking table 2 rotates to heat the food 3 uniformly and is generally called a turntable. An infrared temperature sensor 5 for detecting the temperature of the food 3 is arranged above the heating chamber 1. In the cooking device configured as described above, when cooking the food 3, the microwave oscillated from the magnetron 4 is introduced into the heating chamber 1, and the microwave is introduced to the food 3
Is heated and cooked, and when the temperature of the food 3 detected by the infrared temperature sensor 5 reaches a predetermined temperature, the cooking is finished. (For example, Japanese Patent Laid-Open No. 4-222321)

[0003]

However, in the above-mentioned conventional configuration, the food temperature may not be accurately detected in some cases.

First, since the infrared temperature sensor can detect only the average surface temperature of food placed near the center of the cooking table in the temperature-sensitive visual field (hereinafter referred to as the visual field), When the shape of the food is small or the food is placed near the end of the cooking table, the temperature of the food cannot be accurately detected because plates, containers, and the cooking table other than the food are in view. Moreover, the temperature of the food cannot be accurately detected because the proportion of the food occupied by the rotation of the cooking table changes.

Further, the ambient temperature is not stable inside or around the heating chamber. During heating and cooking due to the heat generation of the magnetron itself and the temperature rise of the wall surface of the heating chamber 1 caused by the microwaves oscillated from the magnetron, the atmosphere of the infrared temperature sensor constantly rises at about 1 deg / min, which is a general cooking time. It does not stabilize between a minute and a dozen minutes. In this unstable state of the ambient temperature, if there is a difference in the response of the ambient temperature in the vicinity of the infrared temperature sensor, the temperature in the vicinity of the infrared temperature sensor becomes non-uniform and a temperature detection error occurs.

Further, air is sent in the vicinity of the infrared temperature sensor by sending air to cool the magnetron, or sending air to protect the infrared temperature sensor itself when the atmosphere around the infrared temperature sensor rises. In many cases. If used under this condition, the temperature around the infrared temperature sensor becomes non-uniform due to the influence of wind, and a temperature detection error occurs.

In addition, the output signal obtained from the infrared temperature sensor is generally a very small electric signal, whereas the current for driving the magnetron, the current for driving the motor for sending the wind, etc. are relatively large and their switching is performed. The noise due to becomes a temperature detection error. For that reason, it is desirable to provide an electric circuit as close to the infrared temperature sensor as possible for amplification, but in this case there is a problem of heat generation of the electric component, and the heat generation of the electric component causes the temperature near the infrared temperature sensor to become non-uniform, resulting in a temperature detection error. .

All of these temperature detection errors cause undesired cooking for the user, and the present invention solves the above-mentioned problems and accurately detects the temperature of food for good cooking. By doing so, it is an object of the present invention to provide a cooking device that can perform automatic cooking without variations in workmanship.

[0009]

To achieve the above object, the cooking apparatus of the present invention uses a heating means for heating food, a temperature detector for detecting the temperature of the food, and an output signal of the temperature detector for heating. Having control means for controlling the drive of the means,
The temperature detector collects the infrared rays emitted from the food, the infrared detector that detects the infrared rays collected by the condenser, and the thermal conductivity that holds the collector and the infrared detector. And a holder made of an excellent material.

Further, it is made of a material which accommodates the light collecting portion, the infrared detecting element and the holder, has an opening for allowing infrared rays emitted from food to enter the infrared detecting element through the light collecting portion, and does not transmit infrared rays. It is equipped with a case.

A cooking table on which food is placed is provided, and the surface of the cooking table is made of a material having a high emissivity.

A heating chamber for containing food is provided, and the surface of the heating chamber inner wall is made of a material having a high emissivity.

In particular, the condensing part is composed of a thin Fresnel lens which transmits infrared rays. The infrared detection element is a thermopile in which a plurality of star-shaped thermocouple elements are arranged and the hot junction of the thermocouple elements is located near the optical axis of the condensing part.

Particularly, the surface of the holder is made of a material having a high emissivity. Further, the holder and the infrared detecting element or the holder and the light condensing section are thermally coupled by a filler made of a material having excellent thermal conductivity.

The infrared detecting element is provided on a substrate made of a material having excellent thermal conductivity, and the infrared detecting element is thermally coupled to the substrate.

Further, a power supply circuit for supplying power to an amplifier circuit for amplifying the output signal of the infrared detecting element is provided outside the case.

The opening provided in the case has a cylindrical shape,
The inner wall surface of this opening is made of a material having a high emissivity.

The opening provided in the case has a cylindrical shape,
The inner wall surface of the opening has a plurality of protrusions.

Further, the opening provided in the case has a cylindrical shape, and the cross-sectional shape of the opening is substantially the same as the shape of the effective light collecting surface of the light collecting section.

Particularly, a partition plate is provided inside the case for partitioning one side including the opening and the other side including the infrared detecting element.

Alternatively, a heat insulating plate is provided between the case and the holder, the light collecting portion, and the infrared detecting element.

[0022]

According to the present invention, the temperature detector having the narrow field of view is formed without deteriorating the sensitivity because the condensing unit condenses the infrared rays emitted from the food. A part of the infrared rays emitted from food is absorbed in the light condensing part and the temperature of the light condensing part is slightly increased.
A holder made of a material having excellent thermal conductivity, which is thermally coupled to the light collecting portion, quickly conveys the increased temperature to the infrared detecting element.

Further, since the case provided with the opening for allowing the infrared rays emitted from the food to enter the infrared detecting element through the light condensing part, a part of the infrared rays emitted from the food to the case is opened. Is incident on the infrared detecting element through the light condensing part, and the other parts are blocked by the case. On the other hand, when the ambient temperature near the temperature detector fluctuates, this ambient temperature fluctuation amount is moderated by the heat capacity of the case. Regarding the amount of temperature fluctuation inside the case, it is quickly transmitted to the infrared detection element through a holder with excellent thermal conductivity, and the infrared detection element is heated by the control means by an electric signal according to the temperature difference between the reference temperature and the food temperature. To control. Since the temperature detector can be provided as a unit housed in one case, handling such as mounting and replacement becomes easy.

Since the surface of the cooking table on which the food is placed is made of a material having a high emissivity, the temperature of the cooking table as the background can be correctly detected when the food is not placed. This is because most foods or containers have a high emissivity of 0.9 or higher, which eliminates the need to calibrate the emissivity for each measurement.

Further, since the surface of the heating chamber inner wall for accommodating the food is made of a material having a high emissivity, the influence of diffused reflection of infrared rays on the heating chamber inner wall can be minimized. That is, the food temperature detection error is reduced.

Further, since this condensing portion is composed of a thin Fresnel lens, it is easier to mold, is lighter, and can be constructed at a lower cost than a lens which polishes an inorganic material which transmits infrared rays such as silicon. Since the heat capacity of the Fresnel lens is reduced by making it thin, the heat from the food does not stay in the Fresnel lens, but quickly matches the holder temperature and the infrared detection element temperature.

As the infrared detecting element, a plurality of star-shaped thermocouple elements are arranged, and the thermojunction of the thermocouple element is a thermopile located near the optical axis of the light collecting portion. Sensitivity concentrates around. That is, the output of the thermopile has a steep directional characteristic only in a specific part of the food on the optical axis of the condensing part.

In particular, since the surface of the holder is made of a material having a high emissivity, infrared rays (generally referred to as stray light) are not directly incident on the light collecting portion from food but are diffusely reflected on the inner surface of the holder and then are incident on the light collecting portion. Can be minimized. That is, since infrared rays from food can be efficiently focused on the infrared detecting element, the temperature detection error is reduced.

Further, by thermally coupling the holder and the infrared detecting element or the holder and the light collecting portion with a filler made of a material having excellent thermal conductivity, the light collecting portion, the holder,
The temperature of each infrared detection element is always uniform.

Further, since the infrared detecting element is provided on the substrate made of a material having excellent thermal conductivity, and the infrared detecting element is thermally coupled to the substrate, the temperatures of the infrared detecting element and the substrate are always uniform.

Since the power supply circuit is provided outside the case, the power supply circuit provided outside the case supplies power to the inside of the case. Inside the case, the electric signal output from the infrared detection element is output to the outside of the case. Here, the temperature rise due to the heat generation of the power supply circuit is blocked by the case, and the self-heat generation inside the case is reduced.

The opening provided in the case has a cylindrical shape,
Since the inner wall surface of this opening is made of a material having a high emissivity, infrared rays (stray light) that are not directly incident on the light collecting portion from food but are diffusely reflected on the inner wall surface of the opening and then are incident on the light collecting portion Can be kept to a minimum. That is, since infrared rays from food can be efficiently focused on the infrared detecting element, the temperature detection error is reduced. Since the opening has a tubular shape and separates the food from the light collecting unit or the infrared detection element, dirt and vapors scattered from the food hardly adhere to the light collecting unit. Further, the condensing part is not deformed by the heat from the heating means or food. When the heating means is composed of a magnetron, the amount of radio wave leakage is also attenuated and the noise superimposed on the electric signal output by the temperature detector is also reduced.

In particular, since the inner wall surface of the opening has a plurality of protrusions, the plurality of protrusions act as so-called light-shielding screws and prevent stray light.

Furthermore, since the cross-sectional shape of the opening substantially matches the shape of the effective light-collecting surface of the light-collecting portion, the infrared rays radiated from the food into the case by the infrared rays incident on the inside of the case are effectively collected as they are. It is incident on the light section and is efficiently imaged on the light receiving surface of the infrared detection element.

Further, by providing a partition plate for partitioning the inside of the case into one including the opening and the other including the infrared detecting element, the flow of ambient air flowing in through the opening or the like, that is, the wind does not reach the infrared detecting element. It is shut off with a partition plate.

Alternatively, by providing a heat insulating plate between the case and the holder, the condensing unit, and the infrared detecting element, even if the atmosphere temperature fluctuates outside the case or a heating element other than food is present, the heat is directly introduced into the case. Does not affect.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. The same components as those in the conventional example are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, as a cooking device, an example applied to a microwave oven will be described.

In FIG. 1, reference numeral 1 is a heating chamber, on which a food 3 is placed on a cooking table 2 provided at the bottom of the heating chamber 1 and introduced into the heating chamber 1 outside the heating chamber 1. A magnetron 4 that oscillates microwaves for heating is provided. The cooking table 2 rotates to heat the food 3 uniformly and is generally called a turntable.
Further, above the heating chamber 1, a temperature detector for detecting the temperature of the food 3 outputs a non-contact electric signal according to the temperature of the food 3. Reference numeral 7 is a calculation means for processing the electric signal from the temperature detector 5 to calculate the temperature of the food 3. Reference numeral 8 is a control means for performing on / off control or power control of the magnetron 4 according to the temperature of the food 3 obtained from the computing means 7. Reference numeral 9 denotes an operating means for the user to start cooking or set a cooking mode, and this operation information is output to the control means 8.

Here, the inner wall surfaces of the heating chamber 1, including the ceiling surface and the bottom surface, are all painted with a matte black body so that the emissivity is high. As a result, the influence of irregular reflection of infrared rays on the inner wall of the heating chamber 1 can be suppressed to a minimum level, and the temperature error of the food 3 to be detected can be reduced.

The cooking table 2 is provided with a glass dish having a high emissivity of 0.9 or more, and the surface temperature of the food 3 placed on the glass dish is detected by the temperature detector 5. . If the food 3 is not placed on the cooktop 2, or if the food is very small or placed near the corner of the cooktop, the temperature detector 5 detects the surface temperature of the cooktop 2. It will be. It is known that the food 3 generally has a high emissivity of 0.9 or more, which is almost equal to the emissivity of water or ice. The same temperature conversion means can be used for both 3 and the cooking table 2. The emissivity calibration for each measurement is also unnecessary.

Next, the structure of the temperature detector 5 will be described with reference to FIG. Reference numeral 10 denotes an infrared detection element for thermoelectrically converting infrared rays emitted from the food 3, which is called a thermopile type. The amount of infrared rays that changes according to the temperature of the food 3 is set to the hot junction 1
0 A, cold junction 10 due to the voltage generated between cold junction 10B
The temperature difference between B and the food 3 is detected, and the temperature conversion configuration is widely known. (For example, "Transistor technology special edition, temperature / humidity sensor utilization handbook"; Transistor technology editorial department, CQ publisher, 198.
8 years. The hot contact 10A is located in the hole of the heat sink 11, and the cold contact 10B is thermally connected to and held by the heat sink 11, and is housed in the can 12.

The can 12 is usually TO-5 or TO-
The can 12 is made of a highly heat-conductive aluminum package and the can 12 is filled with an inert gas.

A window 13 for passing infrared light is provided on one side of the can 12, a filter 14 made of silicon for transmitting infrared rays having a wavelength of 6 μm to 14 μm is provided, and the output pin 15 is provided on the other side. Are extended and are electrically and thermally connected to the printed circuit board 16. Reference numeral 17 denotes a reference temperature detecting element for detecting the temperature of the cold junction 10B, which is composed of a thermistor or the like, is in close contact with the can 12, and is electrically and thermally connected to the printed circuit board 16.

Reference numeral 18 is a cylindrical holder for holding the can 12 accommodating the infrared detection element 10. Reference numeral 19 is a condenser provided in order to narrow the angle of the infrared light incident on the infrared detection element 10. It is fixed by 18 and a holder cap 20. When the holder 18 receives radiant heat from food, it causes a temperature detection error. Therefore, the holder 18 is housed in the case 21 so that infrared light does not reach the holder 18 directly from the food 3. In addition, the light collecting unit 1
Since 9 is also affected by the radiant heat from the food, the holder 18 is made of a material having excellent thermal conductivity, such as aluminum, in order to quickly conduct heat to the cold junction 10B. The inner surface of the holder 18 is coated with a matte black color to prevent infrared rays from being reflected, and the infrared rays that are not directly incident on the light collecting portion 19 from the food 3 but are diffused on the inner surface of the holder 18 and then are incident on the light collecting portion 19. The effects of (stray light) are minimized.

Further, between the can 12 and the holder 18,
Alternatively, a space between the light collecting unit 19, the holder cap 20 and the holder 18 is filled with a thermal coupling compound used for a radiator. As a result, a part of the infrared rays emitted from the food 3 is absorbed by the light condensing unit 19 and even if the temperature of the light condensing unit 19 is slightly increased, the temperature increase is quickly diffused and made uniform, and thus the can 12 and by extension. Cold junction 1
0B and the reference temperature detection element 17 have the same temperature.

That is, the cold junction 10B of the thermopile has a large heat capacity by being thermally coupled to the can 12, the window 13, the printed circuit board 16, the reference temperature detecting element 17, the holder 18, the holder cap 20, the light condensing portion 19 and the like. The fluctuation is suppressed, and when the condensing part 19 and the like receive heat due to the radiant heat from the food 3, this temperature change is quickly transmitted to the cold junction temperature. This is because when the temperature changes, the heat quickly diffuses and becomes uniform.

The output signal from the infrared detecting element 10 and the output signal from the reference temperature detecting element 17 are transmitted from the printed board 16 through the connector 22 and the lead wire 23 to the outside of the case 21 for signal processing. The case 21 is made of a resin that has a high heat insulating property and does not transmit infrared rays.
1A is provided, and a board supporting portion 21B for fixing the printed board 16 to support the entire holder 18 is provided. Further, a heat insulating air layer is formed between the case 21 and the holder 18 or between the case 21 and the printed circuit board 16. This is to alleviate the effect of ambient temperature fluctuations outside the case 21.

As described above, since the infrared ray radiated from the food 3 is provided with the opening 21A for allowing the infrared ray to enter the infrared detecting element 10 through the light condensing section 19, the infrared ray passes through the light condensing section 19 from the opening 21A. Except for the effective infrared rays incident on the detection element 10, they are blocked by the outer wall of the case 21. Further, since the temperature detector 5 can be provided as a unit housed in one case 21, handling such as mounting and replacement becomes easy.

The inner wall surface of the case 21 including the opening 21A is entirely painted with a matte black body so as to increase the emissivity. The opening 21A has a tubular shape, and a plurality of wavy projections are provided as light-shielding screws on the inner wall surface. As a result, infrared rays (stray light) that are not directly incident on the light condensing portion 19 from the food 3 but are diffusely reflected on the inner wall surface of the opening 21A and then are incident on the light condensing portion 19 can be suppressed to a minimum. That is, since the infrared rays from the food 3 can be efficiently focused on the infrared detection element 10, the temperature detection error is reduced. Further, since the opening 21A is cylindrical and the food 3 is separated from the light condensing unit 19 or the infrared detection element 10, dirt and vapor scattered from the food 3 are less likely to adhere to the light condensing unit 19. Further, the condensing part 19 is not deformed by the heat from the heating means 4 or the food 3. When the heating means 4 is composed of a magnetron, the amount of radio wave leakage is attenuated and the noise superimposed on the electric signal output by the temperature detector is also reduced.

On the contrary, the outer wall surface of the case 21 is resin-plated so as to have a low emissivity. This is to make it difficult for the case 21 to be warmed by the infrared rays radiated from the food 3 or the like to be measured. By resin-plating the outer wall surface of the case 21, there is also an effect of shielding against electromagnetic noise.

Further, the cross-sectional shape of the opening 21A is such that the condensing portion 19
Of the infrared rays radiated from the food 3 to the case 21, the infrared rays that have entered the inside of the case 21 through the opening 21A are effectively incident on the condenser section 19 and refracted as they are. An image is efficiently formed on the light receiving surface of the infrared detecting element 10.

The light condensing portion 19 is composed of a thin (about 0.3 mm thick) Fresnel lens made of polyethylene that transmits infrared rays. The viewing angle β of the temperature detector 5 is narrowed down to 3 ° by a Fresnel lens. The infrared rays from the food 3 collected in the light collecting section 19 are accurately detected by the infrared detecting element 10.
The optical axes are aligned to form an image at. With the method of narrowing the viewing angle β by providing a small hole, at most 20
The temperature detector 5 having a very narrow field of view is formed by providing the light condensing portion 19 made of a Fresnel lens, while the limit is about 0 °. Now, the distance L between the temperature detector 5 (of which the light condensing unit 19) and the food 3 to be temperature-measured is 30c.
Assuming that m is m and the viewing angle β is 3 °, the field of view is a circle having a diameter D of about 1.6 cm according to (Equation 1).

D = 2 * L * tan (β / 2) = 2 * 30 * tan1.5 ° (Equation 1) This is about 0.15 times in diameter D compared to when the viewing angle β was 20 °. Although the field of view area S is about 0.022 times, it is a suitable value as the spatial resolution for detecting the temperature of the food 3. The Fresnel lens is made thinner so that it receives less heat as much as possible.

In particular, as the condensing portion 19, instead of forming a lens that transmits infrared rays with an inorganic material such as silicon, germanium, barium fluoride, or calcium fluoride, polyethylene resin is used, so molding is easy, thin, and light. ,
It can be cheaper. It is easy to mass-produce because it does not require polishing or coating with antireflection film.

FIG. 3 shows a plan view of the main part of the infrared detecting element 10 as seen from the back side (when infrared rays are incident from the front side).
A circular plate-shaped gold black 10D for absorbing infrared rays is disposed on the front side of the organic film 10C, and the thermocouple element 10E is provided on the back side of the organic film 10C at a position corresponding to the gold black 10D.
Is provided. The thermocouple element 10E has electrodes 10F, 1
It is made of a conductive material that connects between 0F, and has 100 pairs of folding parts (only 15 pairs are shown in FIG. 3) so as to surround the center point of the gold black 10D. Two dissimilar metals (eg bismuth and antimony) in each fold
10 in a star-like shape, alternating between the inside and the outside
They are connected in series with 0. This dissimilar metal joint 10
One of A and 10B is located inside the gold black 10D in the vicinity of the center point of the gold black 10D, and is a hot junction 10A for detecting the gold black 10D whose temperature has risen by infrared rays, that is, the amount of infrared light. The other one is located outside of the gold black 10D and has a cold junction 1 that serves as a reference temperature.
It is 0B. Therefore, a voltage value obtained by accumulating the potential difference generated between the hot junction 10A and the cold junction 10B, which is a joint portion of different metals, is generated between the electrodes 10F and 10F at both ends, and the temperature of the hot junction 10A (and thus the food 3 Temperature). The diameter of the gold black 10D is determined based on the focal length f of the light converging portion 19 and the viewing angle β (3 °) based on the image height at which the food 3 is imaged on the gold black 10D via the light converging portion 19. There is also. Gold black 1
The heat capacity of 0D and the hot junction 10A is small, and the heat capacity of the cold junction 10B, which is the reference temperature, is large,
The organic film 10C is made of a heat insulating material so that heat is transferred between the hot junction 10A and the cold junction 10B only by conduction heat transmitted through two dissimilar metals as much as possible.

The output voltage from the infrared detecting element 10 is shown in FIG.
It has directional characteristics as shown in. In FIG. 4, the horizontal axis represents the viewing angle, and the vertical axis represents the output voltage from the thermopile in percentage. The solid line shows the light collecting unit 1.
In the case where 9 is not provided, the directivity characteristic of the thermopile itself in which 100 thermocouple elements are connected in series in a star shape is shown, and the dotted line shows the overall directivity characteristic when the condensing unit 19 is provided and the field of view is narrowed. Shows. Hot junction 10A is gold black 1
It can be seen that the sensitivity on the central axis is maximum because it is close to the center point of 0D. Further, this directional characteristic has a concentric sensitivity distribution centered on the central axis of 0 ° because the arrangement of the thermocouple elements 10E is circular. Here, the light collecting unit 1
It is assumed that the optical axis of 9 and the center point of the gold black 10D in the infrared detection element 10 coincide with each other.

When the condensing portion 19 is provided, not only the viewing angle β becomes smaller, but also it becomes difficult to sense temperature sharply at both ends. That is, the temperature-sensitive area and the non-temperature-sensitive area are clearly separated. That is, since the sensitivity is concentrated around the optical axis of the light collecting section, the temperature detector 5 having a steep directional characteristic can be realized only in a specific portion of the food 3 on the optical axis of the light collecting section 19. Therefore, not the average temperature of the food 3 but the temperature of the specific portion of the food 3 can be accurately detected.

When a Fresnel lens is used as the light condensing unit 19, as the angle of view of the incident light beam increases, the eclipse of the light beam by the rising surface of the Fresnel lens increases, and as a result, the peripheral light amount (image of the incident light beam) increases. It is known that the amount of light from a position with a large angle) decreases, but as a thermopile configuration, a star-shaped multi-coupled thermocouple element 10E is used.
Since the hot junction 10A of the thermocouple element 10E is substantially aligned with the optical axis of the Fresnel lens, the sensitivity on the optical axis of the Fresnel lens is maximized and the output voltage corresponding to the temperature of the food 3 to be measured is You can get well. Since the Fresnel lens also has a larger amount of light as infrared rays passing near the optical axis (central axis), the infrared rays emitted from the food 3 can be efficiently collected by combining with the directional characteristics of the thermopile.

In FIG. 2, the printed circuit board 16 is one in which a resin is uniformly applied to the surface of a metal plate such as a holed aluminum plate, and a conductor pattern is formed on the surface by copper plating. Since the main body of the printed circuit board 16 is made of a metal plate, it is possible to obtain a thermal conductivity higher than that of a printed circuit board such as glass epoxy by one digit or more. Further, as shown in FIG. 5, the copper foil used for the wiring portion 16A on the printed circuit board 16 is thick (for example, about 70 μm) and thick, and the entire surface is covered with the ground pattern 16B, so that the heat dissipation characteristics are improved and the printed circuit board is improved. The temperature of the whole is made uniform. Further, since the printed board 16 is thermally coupled to the infrared detection element 10 and the reference temperature detection element 17, the temperatures of the infrared detection element 10, the reference temperature detection element 17 and the printed board 16 are always uniform.

In the configuration shown in FIG. 2, when the ambient temperature outside the case 21 changes, that is, when the ambient temperature of the heating chamber 1 changes, the ambient temperature affects the hot junction 10A.
1 to the printed circuit board 16 or lead wire 2
3 or the opening of the case 21 for pulling out the lead wire 23 is transmitted to the printed circuit board 16, and the bonding portion of the can 12 with the printed circuit board 16 is affected, and the radiation heat thereof is also affected. On the other hand, the cold junction 10B is affected by the ambient temperature directly from the holder 18 via the can 12 and the heat sink 11. Here, since the holder 18 is made of a material having excellent thermal conductivity such as aluminum, the change in the ambient temperature can be conducted to the cold junction 10B with sufficient response similarly to the hot junction 10A. Therefore, the change in the ambient temperature affects the hot junction 10A and the cold junction 10B with substantially the same response. Further, the reference temperature detecting element 17 is also affected by the ambient temperature with a response equivalent to that of the hot junction 10A and the cold junction 10B, and an output corresponding to the temperature of the cold junction 10B can be obtained from the reference temperature detecting element 17, so that food and An output voltage corresponding to the temperature difference from the contact 10B is generated between the hot contact 10A and the cold contact 10B. The calculation means 7 of FIG. 1 calculates the temperature difference between the cold junction 10B and the food by the infrared detection element 10 based on this output voltage, converts the temperature of the cold junction 10B by the reference temperature detection element 17 and adds it to the food. It calculates the temperature of.

The user puts the food 3 in the heating chamber 1 and the cooking table 2
When placed on the top and instructed to start cooking by the operating means 9, the controlling means 8 drives the magnetron 4 to start heating and cooking the food 3. When the food 3 is heated and its temperature rises, the output signal from the temperature detector 5 changes accordingly, and the calculation means 7 calculates the temperature of the food 3 and outputs it to the control means 8. The control means 8 stops the driving of the magnetron 4 when the temperature of the food 3 obtained from the calculation means 7 reaches a preset temperature.

The set temperature may be set by the user through the operating means 9, and the temperature detector 5 may be used.
Depending on the initial temperature of the food product 3 that can be detected in, for example, if it is the temperature of a frozen food product, it may be determined as an appropriate temperature for thawing, and if the temperature is in the refrigerator, it may be determined as an appropriate temperature for warming milk. Further, the control unit 8 controls the temperature of the food 3 to be uniform by reducing the capacity or intermittently driving the temperature of the food 3 when the temperature of the food 3 reaches another predetermined temperature according to the result of the calculation unit 7. Also do.

Further, as shown in FIG. 2, according to the present invention, a partition plate 24 for shielding the wind is provided. A cross-sectional view taken along the broken line A in FIG. 2 is shown in FIG. As shown in FIG. 6, the partition plate 24 is in close contact with the holder 18 and also in close contact with the cover case 21. That is, the air flowing in from the opening 21A is the infrared detection element 10,
Since it does not flow directly into the can 12, the printed circuit board 16, and the reference temperature detection element 17, it is possible to minimize the occurrence of errors due to the influence of wind. Further, since this configuration can also fix the holder 18, the can 12, the infrared detection element 10, etc. at the same time, it has an effect of preventing the visual field position of the food 3 from being deviated due to vibration and the like, and an error is generated. It also has an effect of preventing a cause of a failure that occurs when, for example, the like adheres to the printed circuit board 16.

FIG. 7 shows an example of a detection circuit for processing the output signals of the infrared detecting element 10 and the reference temperature detecting element 17 to detect the temperature of food. The detection circuit includes an arithmetic means 7 provided outside the case, a power supply circuit 25, and an internal signal processing circuit 26 provided on the printed circuit board 16 inside the case 21. The power supply circuit 25 is a direct current power supply which is full-wave rectified by an AC power supply 26 via a transformer 27 through a bridge circuit composed of diodes 29, 30, 31, 32 and smoothed by a capacitor 33. Further, the DC power source stabilized by the three-terminal regulator 34 and the capacitor 35 is supplied to the arithmetic means 7 and the internal signal processing circuit 26. In the internal signal processing circuit 26, the capacitor 36 again stabilizes the DC power supply. The internal signal processing circuit 26 includes an amplifier circuit 37 that amplifies the output signal of the infrared detection element 10. The amplifier circuit 37 includes operational amplifiers 38 and 39.
And resistors 40, 41, 42 and 43. The DC power supply is divided by resistors 40 and 41, and the midpoint potential is voltage-followered by the operational amplifier 38 to form a reference potential. This reference potential is the cold junction 10B of the infrared detection element 10.
The hot junction 10A is connected to the non-inverting input terminal of the operational amplifier 39.

The inverting input terminal of the operational amplifier 39 is connected to the reference potential via the resistor 42 and to the output terminal via the resistor 43. That is, hot junction 10A and cold junction 10B
The voltage generated between and is amplified by the amplification factor determined by the resistors 42 and 43, and when the temperature of the food is higher than the cold junction 10B, the voltage is higher than the reference potential, and when the temperature of the food is lower than the reference potential, the voltage is lower than the reference potential, and the temperature difference becomes It is possible to obtain an approximately proportional voltage.

Here, the can 12 is connected to the ground of the power source, but this has the effect of removing noise and conducting heat to the can 12 more quickly than the copper foil. Further, the internal signal processing circuit 26 also processes the signal of the reference temperature detecting element 17, and the reference temperature detecting element 17 is composed of a thermistor here and is connected to the power source by forming a series circuit with the resistor 44. . The temperature of the cold junction 10B can be detected by the midpoint potential of the thermistor 17 and the resistor 44. The reference temperature detecting element 17 can be made without using a thermistor, and there is a method of using a semiconductor. The calculation means 7 is composed of an AD conversion circuit 45 and a calculation circuit 46, and the voltage amplified according to the temperature difference between the food and the cold junction 10B and the voltage obtained according to the temperature of the cold junction 10B are A
It is digitized by the D conversion circuit 45, multiplied by an appropriate parameter by an arithmetic circuit 46 including a microcomputer, and added to calculate the temperature of the food 3.

The power supply circuit 25 and the internal signal processing circuit 26 are connected to each other, and the internal signal processing circuit 26 and the arithmetic means 7 are connected to the inside and outside of the case 21 by a lead wire 23. With this configuration, the transformer 28, the diodes 29, 30, 31, 32, and the three-terminal regulator 3 which are components that are particularly prone to generate heat
Since 4 is provided outside the case 21, it is possible to prevent the temperature detection error from occurring due to the influence of heat generation inside the case 21. Here, the AD conversion circuit 45 and the arithmetic circuit 46
The provision of the outside of the case 21 does not restrict the present invention, and it may be inside the case 21.
1 By providing the case 21 outside, there is an effect that the entire case 21 can be downsized.

As a result, power is supplied to the inside of the case 21 by the power supply circuit 25 provided outside the case 21, and inside the case 21, the electric signal thermoelectrically converted and output from the infrared detection element 10 is processed by the amplifier circuit 37. A minute voltage directly output from the infrared detection element 10 does not go out of the case 21, an error due to the influence of noise can be reduced, and an error caused by heat generation of components inside the case 21 can be suppressed. Cooking can be realized.

Next, a second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment is that a heat insulating plate 47 is provided between the case 21, the holder 18, the light condensing unit 19, and the infrared detection element 10 to prevent changes in food temperature, ambient temperature, and the like outside the case 21. The effect was greatly suppressed. As a result, the internal temperature of the heat insulating plate 47 becomes more stable, and the temperature detection accuracy of the food is dramatically improved. The heat insulating plate is made of a conductive metal so as to have a shielding effect against electromagnetic noise from the outside. As a result, the holder 18 and the infrared detection element 10
There is also an effect that the external ambient temperature seen from the above is almost completely equalized. Furthermore, the case 21 is enlarged to make the holder 1
Insulation between the outside of the case 21 and the holder 18 and the like can be realized without increasing the distance to 8 or the like (widening the air insulating layer).

Here, as the structure of the heat insulating plate 47, the case 21 is used.
May have a double structure. Although the above description has been made with the thermopile type infrared detecting element, the same effect can be obtained with the pyroelectric type. In this case, the heat sink 11 and the can 1 are used.
2 may be replaced with a chopper having a driving unit. Further, as the infrared detection element 10, lead sulfide (P
A thermistor / bolometer using a thermal resistance change type such as bS) may be used.

Although the Fresnel lens has been described as the structure of the light collecting unit 19, the light may be collected by using a reflecting mirror such as a Cassegrain mirror.

Between the can 12 and the holder 18,
Alternatively, the compound for thermal coupling used for the radiator between the light collecting unit 19, the holder cap 20 and the holder 18 is used as the filler, but it may also be used as the adhesive.

Further, although the infrared detecting element 10 is explained as one piece, the food temperature is detected at a plurality of points by making a plurality or scanning even one piece, and the food is processed by the maximum temperature, the minimum temperature or the average temperature. You can also improve the finish of 3. It is also possible to shift the field-of-view position measured by the temperature detector 5 from the center point of the cooking table 2 and rotate the cooking table 2 to detect the temperatures of a plurality of portions of the food 3.

The present invention can be applied to other cooking devices such as an oven toaster and a gas table other than the microwave oven.

[0075]

As described above, the present invention has the following effects.

(1) Since the sensitivity of the infrared detecting element is concentrated around the optical axis of the light collecting part, the temperature of a specific part of the food can be accurately detected, and there is no variation in the finished product due to the heating according to the temperature of the food. Good automatic cooking is possible. In particular, the holder made of a material with excellent thermal conductivity that is thermally coupled to the light condensing unit minimizes the effect (transient characteristics) on changes in food temperature and ambient temperature, and dramatically improves food temperature detection accuracy. Improve to.

(2) Since only the infrared rays incident from the opening are effectively focused on the infrared detecting element, even if a heating element exists outside the visual field of the temperature detector, its influence is blocked by the case. Further, when the ambient temperature near the temperature detector fluctuates, this ambient temperature fluctuation amount is alleviated by the heat capacity of the case, etc., so that the temperature detection accuracy of the food is dramatically improved. In particular, since the temperature detector can be provided as a unit housed in one case, handling such as mounting and replacement becomes easy.

(3) The temperature of the cooking table as the background can be correctly detected when food is not placed. Emissivity calibration is not required and temperature conversion can be performed easily.

(4) Since the influence of irregular reflection of infrared rays on the inner wall of the heating chamber can be minimized, the accuracy of detecting the temperature of food can be dramatically improved.

(5) Since the light condensing part is made of a thin Fresnel lens, it can be constructed light and inexpensive. Since the heat capacity of the Fresnel lens is reduced by making it thin, the heat from the food is quickly diffused and uniformized from the Fresnel lens, so that the temperature detection accuracy of the food is improved. Since the transmittance of the Fresnel lens is also improved, the S / N ratio is also improved.

(6) Since the output of the thermopile has a steep directional characteristic only in a specific part of the food on the optical axis of the light condensing part, the temperature of the specific part of the food can be accurately detected. Good heating makes it possible to perform good automatic cooking without variations in the workmanship.

(7) Since the surface of the holder is made of a material having a high emissivity, the influence of stray light can be minimized, and the temperature detection accuracy of food can be improved.

(8) Since the temperature of the condenser, the holder, and the infrared detecting element is always made uniform by the filler made of a material having excellent thermal conductivity, when the ambient temperature near the temperature detector fluctuates. Can detect the temperature of food with high accuracy.

(9) Since the temperature of the infrared detecting element and the substrate are always made uniform by the substrate made of a material having excellent thermal conductivity, the food can be accurately measured even when the ambient temperature near the temperature detector changes. The temperature can be detected. (10) Since the temperature rise due to the heat generation of the power supply circuit is blocked by the case and the self-heat generation inside the case is reduced, the temperature inside the case is always stable and the temperature of the food can be detected accurately.

(11) Since the opening provided in the case has a cylindrical shape and the inner wall surface of this opening is made of a material having a high emissivity, the influence of stray light can be minimized.

(12) In particular, since the inner wall surface of the opening has a plurality of protrusions, the plurality of protrusions act as so-called light-shielding screws and can prevent stray light.

(13) Furthermore, since the cross-sectional shape of the opening substantially matches the shape of the effective light-collecting surface of the light-collecting section, of the infrared rays radiated from the food into the case, the infrared rays that have entered the case through the opening remain unchanged. The light is effectively incident on the light converging portion and is efficiently imaged on the light receiving surface of the infrared detection element, and as a result, the temperature of the food can be detected accurately.

(14) Since the flow of the ambient air flowing in through the opening, that is, the wind, is blocked by the partition plate so as not to reach the infrared detecting element, it is possible to suppress the error generation due to the influence of the wind, which is excellent. Cooking can be realized.

(15) By providing a heat insulating plate between the case, the holder, the light collecting section, and the infrared detecting element, the influence (transient characteristics) on the change of the food temperature and the ambient temperature outside the case is minimized. Therefore, the accuracy of detecting the temperature of food is dramatically improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a cooking device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a temperature detector according to the same embodiment.

FIG. 3 is a plan view showing a main part of the thermopile in the same embodiment.

FIG. 4 is a diagram showing directional characteristics of a temperature detector in the same embodiment.

FIG. 5 is a diagram showing a conductor pattern of a printed circuit board in the example.

FIG. 6 is a sectional view of a main part of a temperature detector according to the same embodiment.

FIG. 7 is an electric circuit diagram of the cooking apparatus of the embodiment.

FIG. 8 is a configuration diagram of a cooking device according to another embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional cooking device.

[Explanation of symbols]

 3 Food 4 Heating Means 5 Temperature Detector 8 Control Means 10 Infrared Detecting Element 18 Holder 19 Focusing Part 21 Case 21A Opening 24 Partition Plate 25 Power Supply Circuit 37 Amplifying Circuit 47 Insulating Plate

Claims (15)

[Claims] 1. A heating means for heating food, a temperature detector for detecting a temperature of the food, and a control means for controlling driving of the heating means by an output signal of the temperature detector,
The temperature detector holds a light collecting unit that collects infrared light emitted from the food, an infrared detecting element that detects the infrared light collected by the light collecting unit, the light collecting unit, and the infrared detecting element. A cooking device provided with a holder made of a material having excellent heat conductivity. 2. A light collecting section, an infrared detecting element, and a holder are housed, and an infrared ray emitted from food has an opening for entering the infrared detecting element through the light collecting section, and does not transmit infrared rays. The cooking apparatus according to claim 1, further comprising a case made of a material. 3. The cooking apparatus according to claim 1, wherein a cooking table on which food is placed is provided, and the surface of the cooking table is made of a material having a high emissivity. 4. A heating chamber for accommodating food is provided, and a surface of the heating chamber inner wall is made of a material having a high emissivity.
The cooking device described. 5. The cooking apparatus according to claim 1, wherein the light condensing unit is a thin Fresnel lens that transmits infrared rays. 6. The cooking apparatus according to claim 1, wherein the infrared detection element is a thermopile in which star-shaped multiple pairs of thermocouple elements are arranged, and the hot junction of the thermocouple element is located near the optical axis of the condensing section. 7. The cooking apparatus according to claim 1, wherein the surface of the holder is made of a material having a high emissivity. 8. The cooking apparatus according to claim 1, wherein the holder and the infrared detecting element or the holder and the light collecting portion are thermally coupled by a filler made of a material having excellent thermal conductivity. 9. The cooking apparatus according to claim 1, wherein the infrared detecting element is provided on a substrate made of a material having excellent thermal conductivity, and the infrared detecting element is thermally coupled to the substrate. 10. The cooking apparatus according to claim 1, wherein a power supply circuit for supplying power to an amplifier circuit for amplifying an output signal of the infrared detection element is provided outside the case. 11. The cooking apparatus according to claim 1, wherein the opening provided in the case has a tubular shape, and the inner wall surface of the opening is made of a material having a high emissivity. 12. The cooking apparatus according to claim 1, wherein the opening provided in the case has a cylindrical shape, and the inner wall surface of the opening has a plurality of protrusions. 13. The method according to claim 1, wherein the opening provided in the case has a cylindrical shape, and the cross-sectional shape of the opening substantially matches the shape of the effective light collecting surface of the light collecting section. The cooking device described. 14. A partition plate for partitioning the inside of the case into one including an opening and the other including an infrared detecting element.
Alternatively, the cooking apparatus according to claim 2. 15. The cooking apparatus according to claim 1, wherein a heat insulating plate is provided between the case and the holder, the light collecting section, and the infrared detecting element.