JP4816673B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that can accurately detect the temperature of a cooking container such as a pan on a top plate.

  In an induction heating cooker that heats an object to be heated such as a pan, as a method of detecting the temperature of the pan, there is a method of detecting the temperature with a thermistor through a top plate on which the pan is placed. In addition, there is an apparatus for detecting the temperature by detecting the infrared ray radiated from the side surface of the pan with an infrared sensor behind the top surface of the top plate. Furthermore, an infrared sensor is arranged on the lower surface of the top plate to detect infrared rays from the pan through the top plate (for example, see Patent Document 1).

  In a conventional induction heating cooker, when the thermistor receives the temperature of the pan through the top plate and detects the temperature, the ceramic top plate has a low heat transfer coefficient. Due to the delay in response, the actual pan temperature and error occur, and the pan temperature cannot be detected accurately.

Further, in the induction heating cooker having the conventional configuration shown in FIG. 6, the infrared sensor 15 behind the top plate 2 is affected by disturbance light such as sunlight or illumination, and cannot accurately detect the temperature. Furthermore, in an induction heating cooker with a configuration in which an infrared sensor is arranged on the bottom of the top plate, the infrared sensor is affected by the magnetic field from the heating coil, and the output voltage drifts when the power is turned on and off, allowing stable temperature measurement. I can't.
Japanese Patent Laid-Open No. 03-184295

  In view of the problems of the prior art, the problem to be solved by the present invention is to provide an induction heating cooker that can accurately detect the temperature of a cooking vessel without being affected by the magnetic field of induction heating.

The present invention includes a heating coil for heating a cooking vessel, a top plate made of glass ceramic that places the cooking vessel above the heating coil and transmits infrared rays in a wavelength range of 2.5 μm or less, and the top plate Infrared detection means composed of a photodiode that outputs a current corresponding to the amount of infrared rays that are placed underneath and radiated from the bottom surface of the cooking container and transmitted through the top plate, and shields the magnetic field from the heating coil. Magnetic shield means for protecting the infrared detection means from the magnetic field, amplification means for IV-converting the output current of the infrared detection means and outputting an amplified voltage, and the bottom temperature of the cooking container from the output of the amplification means Temperature detecting means for detecting the temperature, control means for controlling the power supplied to the heating coil in accordance with the output of the temperature detecting means, and switching means for varying the amplification factor of the amplifying means. The photodiode, with the photodiodes capable of detecting the following infrared wavelength range 2.5 [mu] m, wherein, the slope of the output of said temperature detecting means determines whether more than a predetermined value As an induction heating cooker that switches the switching means so that the amplification factor decreases when the slope of the output of the temperature detection means is equal to or greater than the predetermined value than when the slope of the output of the temperature detection means is less than the predetermined value. It is what.

  The induction cooking device of the present invention can cope with the case where the infrared energy is increased by switching the amplification factor of the amplifying unit with the switching unit.

According to a first aspect of the present invention, there is provided a heating coil for heating a cooking container, a top plate made of glass ceramic that places the cooking container above the heating coil and transmits infrared rays in a wavelength region of 2.5 μm or less, and the ceiling Infrared detecting means composed of a photodiode that is placed under the plate and radiates from the bottom surface of the cooking vessel and passes through the top plate and outputs current corresponding to the amount of incident infrared light, and a magnetic field from the heating coil. Magnetic shield means for shielding and protecting the infrared detection means from the magnetic field, amplification means for converting the output current of the infrared detection means to IV and outputting an amplified voltage, and output of the amplification means from the output of the cooking container Temperature detecting means for detecting the bottom surface temperature, control means for controlling the power supplied to the heating coil in accordance with the output of the temperature detecting means, and switching means for varying the amplification factor of the amplifying means Wherein the photodiode, with the photodiodes capable of detecting the following infrared wavelength range 2.5 [mu] m, the control means determines whether the slope of the output of said temperature detecting means is equal to or higher than a predetermined value When the inclination of the output of the temperature detection means is greater than or equal to the predetermined value, the induction heating cooker that switches the switching means so that the amplification factor is lower than when the inclination of the output of the temperature detection means is less than the predetermined value . It is what you are trying.

In a second aspect based on the first aspect, at the start of heating, the control means switches the switching means so that an amplification factor used when an output slope of the temperature detection means is equal to or greater than the predetermined value. It is what I kept.

Since the object of the present invention can be achieved by using the first and second inventions as the main part of the embodiments, details of the embodiments corresponding to the respective claims will be described below with reference to the drawings. It will be described and the best mode for carrying out the present invention will be described. In addition, this invention is not limited by the following embodiment . Further, in the description of the embodiments, the same reference numerals are assigned to the same configurations and the effects and the same description is not repeated.

( Reference form 1)
FIG. 1 is a block diagram showing a configuration of an induction heating cooker in Reference Embodiment 1. The induction heating cooker supplies a high frequency current to the pan 1, which is a cooking container for cooking the object to be heated, the top plate 2 on which the pan 1 is placed, the heating coil 3, and the heating coil 3. The first high-frequency inverter 4 and the second magnetic-shielding means 7 are the magnetic-shielding means that shields the magnetic field from the heating coil 3 and protects the infrared-detecting means 5 from the magnetic field. And a cylindrical reflecting means 8 for guiding infrared rays from the pan 1 to the infrared detecting means 5 and a first magnetic preventing means 6 for reducing the influence of temperature rise inside the apparatus. The heat insulating means 9 covering the lower opening, the temperature detecting means 10 for detecting the bottom temperature of the pan 1 from the output of the infrared detecting means 5, and the power supplied to the heating coil 3 according to the output of the temperature detecting means 10 are controlled. And control means 11 .

  And the 1st magnetic-shielding means 6 makes | forms the cylinder shape which opened up and down, the upper side fits in the center part of the heating coil 3, and the lower side is arrange | positioned under the heating coil 3. FIG. The 2nd magnetic-shielding means 7 is located in the lower part side of the 1st magnetic-shielding means 6, and is arrange | positioned so that it may cover. Accordingly, the outer periphery is shielded by the first and second magnetic shielding means except that the infrared detection means 5 detects the infrared light incident from the opened upper side of the first magnetic shielding means 6. The first magnetic shield means 6 and the second magnetic shield means 7 are grounded, and the infrared detection means 5 is provided on the substrate 16. The substrate 16 is fixed to the first magnetic shield means 6 with a screw 17, and the first The first and second magnetic shield means 6 and 7 are connected to the zero potential of the infrared detecting means 5.

In this embodiment, when a power supply (not shown) is turned on and a predetermined temperature is set with the operation switch, power is supplied from the high-frequency inverter 4 to the heating coil 3 under the control of the control means 11. When electric power is supplied to the heating coil 3, an induction magnetic field is generated in the heating coil 3, and the pan 1 on the top plate 2 is induction-heated. Due to this induction heating, the temperature of the pan 1 rises and the object to be heated in the pan 1 is cooked.

Here, the operation of the infrared detecting means 5 will be described. When the temperature of the pan 1 rises, infrared rays corresponding to the temperature are emitted from the pan 1. Since the glass ceramic used for the top plate 2 can efficiently transmit infrared rays having a wavelength range of 2.5 μm or less, the infrared detection means 5 is constituted by, for example, a photodiode that can detect wavelengths of 2.5 μm or less. Infrared light of this wavelength range that has passed through the top plate 2 is incident on the photodiode.

  Further, the cylindrical reflecting means 7 having the same diameter has a high mirror surface configuration with an inner surface reflectance of about 0.9 so that more infrared rays can be collected and incident on the photodiode. . Also, the high reflectance means that the emissivity is low, so there is almost no infrared radiation from the reflecting means itself. Further, the reflecting means 8 prevents the temperature of the heating coil 3 and the holding portion of the heating coil 3 from being affected by the temperature from the lateral direction of the infrared detecting means 5.

  Therefore, only the infrared rays from the pan 1 are incident on the infrared detection means 5, and the diode current corresponding to the amount of infrared rays is IV-converted and amplified by the amplification means. Here, since the current of the photodiode is very small and is affected by the magnetic field of the heating coil 3, the magnetic field of the heating coil 3 is blocked by the first magnetic shielding means 6. Further, the magnetic field is interrupted by the second magnetic shielding means 7 because it goes around from the lower part of the substrate 16 provided with the infrared detecting means 5.

  These magnetic shielding means are made of aluminum or the like which is not easily heated by induction. Further, the zero potential (ground) of the circuit of the infrared detecting means 5 and the first and second magnetic shield means 6 and 7 are connected by a screw 17 so that the potential fluctuation is suppressed, and the infrared detection by the on / off of the high frequency inverter 4 is performed. The output drift of the means 5 is reduced.

  With such a configuration, the infrared detection means 5 operates stably, information of the infrared detection means 5 is input to the temperature detection means 10, and the temperature of the pan 1 can be accurately detected. Thereby, the high frequency inverter 4 is controlled by the control means 11 so that the pan 1 is brought to a predetermined temperature, and the object to be heated can be cooked.

  The reflecting means 8 is composed of a copper pipe, an aluminum pipe, or the like. In order to prevent the mirror state of the inner surface from being deteriorated due to oxidation or the like and to reduce the reflectance, an infrared ray of 2.5 microns or less is used. By applying a coating material that is a protective layer with little absorption, such as an epoxy resin, the temperature of the pan 1 can be detected stably and accurately. For aluminum, a bright alumite treatment or the like may be used.

  In addition, the infrared detecting means 5 can be provided with a lens on the window material, thereby increasing the light receiving area, greatly increasing the amount of infrared light incident on the infrared detecting means, improving the S / N ratio, and increasing the sensitivity of the bottom of the pan. The temperature can also be accurately detected.

( Reference form 2)
Figure 2 is a block diagram showing a configuration of the induction cooking device in Reference Embodiment 2. The induction heating cooker of this embodiment is different from the reference embodiment 1 only in the configuration of the reflection means, and the other parts having the same configuration and effects are denoted by the same reference numerals, detailed description thereof is omitted, and is different. However, the explanation will be focused on.

  The reflecting means 12 is formed in the shape of a bowl with the top and bottom open, the lower opening having a small diameter is fitted into the infrared detecting means 5, and the upper opening having a large diameter faces the upper side of the first magnetic shielding means.

In this embodiment , the reflection means 12 has a mortar-like shape with a larger diameter on the upper side. Here, the infrared rays entering the infrared detecting means 5 occupy most from the pan bottom in the range of the direct incident field, but there are some incidents that are incident obliquely and reflected by the reflecting means 12. . FIG. 3A and FIG. 3B are schematic diagrams showing how the infrared rays are incident. The cylindrical reflecting means 8 shown in FIG. 3A is incident on the infrared detecting means 5 after being reflected many times by the reflecting means with respect to the incidence of infrared rays obliquely as indicated by an arrow.

On the other hand, the cone-shaped reflecting means 12 of FIG. 3 (b) in this embodiment is reflected on the top surface of the cone-shaped tube and is radiated to the outside with respect to incident infrared rays as shown by arrows. Therefore, it is not incident on the infrared detecting means 5. Therefore, the temperature at the center of the pan bottom can be detected, and the amount of infrared rays close to the temperature of the heated object in the pan can be detected. In addition, the bottom is not particularly flat, and in the case of a warp pan or the like, it is difficult to be affected by ambient light incident obliquely. As a result, the temperature of the pan 1 can be detected accurately. Thereby, the high-frequency inverter 4 is controlled by the control means 11 so that the pan 1 is brought to a predetermined temperature, and the object to be heated can be cooked.

( Reference form 3)
Figure 4 is a block diagram showing a configuration of the induction cooking device in Reference Embodiment 2. The induction heating cooker of this embodiment is different from the invention of the reference embodiment 1 only in the configuration of the magnetic-shielding means, and other parts having the same configuration and operational effects are denoted by the same reference numerals and detailed description thereof is omitted. The explanation will focus on the differences.

  The first magnetic shielding means 13 has an opening 14 through which cooling air flows on the side surface on the lower side arranged below the heating coil 3. Therefore, as shown by the arrow, the cooling air is made to flow into the first magnetic shield means 13 from the one opening 14 by using the air of the fan provided for other purposes in the induction heating cooker, and the other It becomes the structure discharged | emitted from the opening part 14. FIG.

In this embodiment , the infrared detection means 5 is connected to a wiring by a connector 18 for output to the temperature detection means 10. For this reason, the connector 18 of the first magnetic shield means 6 is opened by the opening 14. The inside of the induction heating cooker is air-cooled by a fan (not shown) or the like to cool the high-frequency inverter 4 or the like, and the cooling air flows into the first magnetic shield means 13 from one opening 14. It is discharged from the other opening 14 and hits the infrared detection means 5, and the temperature of the infrared detection means 5 can be suppressed to a certain temperature or lower.

  Further, since the other opening 14 is provided on the side opposite to the connector 18 side of the first magnetic shielding means 13, the infrared detection means 5 can be cooled more efficiently by creating a path through which cooling air flows. Since the infrared detecting means 5 relatively detects the energy of the difference between its own temperature and the temperature of the object, the temperature difference can be detected more accurately by suppressing its own temperature. If the temperature of the infrared detecting means 5 itself is more constant, the temperature can be detected more accurately. As a result, the pan 1 can be controlled so as to reach a predetermined temperature, and the object to be heated can be cooked smoothly.

( Embodiment )
FIG. 5 is an output diagram of the temperature detection means of the induction heating cooker in the embodiment of the present invention. The configuration of the induction heating cooker in the present embodiment is different from the invention of the reference embodiment 1 only in the control method of the control means 11, and other parts having the same configuration and operational effects are denoted by the same reference numerals. Detailed description will be omitted, and different points will be described with reference to FIG.

In this Embodiment, the infrared detection means 5 detects the infrared rays according to the temperature of the pan bottom, as shown in FIG. 5, and the temperature detection means 10 detects the temperature of the pan bottom. However, the emissivity varies depending on the type of the pan 1, and the absolute value output of the infrared detecting means 5 varies. For example, a black iron pan has an emissivity of about 0.95, whereas a stainless steel pan has an emissivity of about 0.5, and the output varies accordingly.

In the case of boiling water, the bottom of the pan stabilizes at 100 ° C, so it is sufficient to detect this stable point. However, in the case of watering, the temperature at the bottom of the pan rises rapidly and stops before it reaches an abnormal temperature. If you try to control with the absolute value of this output, it will be affected by emissivity. Therefore, when the sensor output changes, that is, when the inclination is equal to or greater than a certain level, it is determined that the sensor is idling and the heating power is reduced. As a result, abnormal temperature rise can be prevented, and cooking can be performed without sacrificing the feeling of heat with a fried food.

  In addition, since the infrared energy is increased when the pan bottom is hot, it can be dealt with by switching the amplification factor of the amplification means (not shown) by the switching means (not shown). For example, it is possible to lower the amplification factor assuming that the heating is started at the time of heating. Further, in accordance with the menu, for example, the control may be performed so that the amplification factor is switched between cooking near 100 ° C. such as cooking rice and boiling water, and otherwise.

  As described above, the induction heating cooker according to the present invention can accurately detect the temperature of the cooking container without being affected by the magnetic field of induction heating, and thus can be applied to temperature detection techniques in cooking and other induction heating.

The block diagram which shows the structure of the induction heating cooking appliance in reference form 1 The block diagram which shows the structure of the induction heating cooking appliance in reference form 2 (A) Schematic diagram of infrared incidence on reflecting means of induction heating cooker to be compared (b) Schematic diagram of infrared incidence on reflecting means of induction heating cooker in Embodiment 2 of the present invention The block diagram which shows the structure of the induction heating cooking appliance in the reference form 3 The output figure of the temperature detection means of the induction heating cooking appliance in embodiment of this invention The block diagram which shows the structure of the induction heating cooking appliance in a prior art example

1 Pot (cooking container)
2 Top plate 3 Heating coil 5 Infrared detector 6, 13 First magnetic shield (magnetic shield)
7 Second magnetic shield (magnetic shield)
8, 12 Reflecting means 10 Temperature detecting means 11 Control means 14 Opening

Claims (2)

A heating coil for heating the cooking vessel, a top plate made of glass ceramic that places the cooking vessel above the heating coil and transmits infrared rays in a wavelength range of 2.5 μm or less, and is placed under the top plate. Infrared detection means composed of a photodiode that outputs a current corresponding to the amount of infrared rays radiated from the bottom surface of the cooking container and transmitted through the top plate, and the infrared detection by shielding the magnetic field from the heating coil Magnetic shielding means for protecting the means from the magnetic field, amplification means for converting the output current of the infrared detection means to IV and outputting an amplified voltage, and temperature for detecting the bottom surface temperature of the cooking container from the output of the amplification means Detection means, control means for controlling the power supplied to the heating coil in accordance with the output of the temperature detection means, and switching means for varying the gain of the amplification means. DOO diode with a photodiode which can detect the following infrared wavelength range 2.5 [mu] m, wherein, the slope of the output of said temperature detecting means determines whether more than a predetermined value, the An induction heating cooker that switches the switching means so that the amplification factor decreases when the slope of the output of the temperature detection means is equal to or greater than the predetermined value than when the slope of the output of the temperature detection means is less than the predetermined value . 2. The induction heating according to claim 1 , wherein at the start of heating, the control means switches the switching means so as to obtain an amplification factor that is used when an output slope of the temperature detection means is equal to or greater than the predetermined value. Cooking device.

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