JP5089728B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that uses an infrared sensor to accurately detect the temperature of a pan without detection delay.

  Conventionally, the detection value of the temperature detecting means is corrected according to the material of the heated object detected by the pot material detecting means, the temperature detecting means for detecting the temperature by the amount of radiant energy of the heated object, and the pot material detecting means. There is an induction heating cooker that performs output control (see, for example, Patent Documents 1 and 2).

  In patent document 1, the infrared sensor is installed in the side of the pan, infrared rays are received directly from the side of the pan without using the top plate, and the pan temperature is calculated by the emissivity of the pan according to the material. In Patent Document 2, an infrared sensor is attached under the top plate, and the pan temperature is detected through the top plate.

JP 2003-264055 A (7th page, FIG. 4) Japanese Patent Laying-Open No. 2005-078993 (page 5, FIG. 1)

  In Patent Document 1, since an infrared sensor is arranged in an installation part protruding from the top plate so as to directly receive infrared rays radiated from the side surface of the pan, an object is placed between the pan and the infrared sensor. The temperature cannot be detected correctly if it is touched. In addition, in order to receive infrared rays emitted from the side of the pan, it is necessary to provide an installation portion for installing an infrared sensor on the top plate, which causes a problem in design.

  In Patent Document 2, since an infrared sensor is attached under the top plate, an induction heating cooker having a design without a protrusion can be obtained. However, since temperature detection is performed via the top plate, there is a problem that the temperature cannot be accurately detected. Specifically, since the pan and the top plate are in contact with each other, the temperature at the bottom of the pan and the temperature of the top plate are substantially equal. At this time, infrared rays received by the infrared sensor under the top plate are radiated from the pan and those radiated from the top plate. However, Patent Document 2 does not consider the point where there is radiation from two places, such as radiation from the pan and radiation from the top plate, and uniformly converts the temperature using infrared emissivity according to the pan material. Therefore, there is a problem that temperature cannot be detected with high accuracy. In addition, the temperature calculated using the infrared emissivity according to the pan material is corrected with a fixed value of +10 degrees and −10 degrees according to the material, but the temperature of the pot is the fourth power of the infrared radiation amount. Since it changes depending on the root, there is a problem that temperature cannot be detected with high accuracy when it is corrected with a fixed value.

  This invention is made in view of such a point, and provides the induction heating cooking appliance which can perform the accurate temperature detection which considered the infrared rays radiated | emitted from a top plate with the infrared sensor arrange | positioned under a top plate. With the goal.

An induction heating cooker according to the present invention includes a top plate on which an object to be heated is placed, a heating coil that is provided under the top plate and heats the object to be heated, and converts an AC voltage into a high-frequency voltage for heating. A drive circuit for supplying a high-frequency current to the coil, an infrared sensor that is provided under the top plate and receives infrared rays radiated from the bottom surface of the heated object, and detects the infrared emissivity of the heated object. The emissivity detection means, the infrared emissivity detected by the emissivity detection means, and the infrared emissivity of the top plate stored in advance are compared, and the temperature conversion emissivity is determined according to the comparison result Emissivity determining means, temperature converting means for calculating the temperature of the object to be heated based on the temperature converting emissivity determined by the temperature converting emissivity determining means and the output of the infrared sensor, And a drive circuit control means for controlling the drive circuit based on the temperature obtained by the conversion means, temperature conversion for emissivity determination unit, when the infrared emissivity of the object to be heated is smaller than the infrared emissivity of the top plate of the temperature conversion for emissivity, an infrared emissivity of the infrared emissivity and the top plate of the heated object detected by the emissivity detecting means, by adding at a predetermined ratio set larger top plate side, the the size rather and than infrared emissivity of the heated object is to determine a value smaller than the infrared emissivity of the top plate.

  According to the present invention, when using an object to be heated having an infrared emissivity smaller than that of the top plate, an emissivity for temperature conversion larger than the infrared emissivity of the object to be heated is determined, and the determined emissivity for temperature conversion is determined. Since the temperature of the object to be heated is calculated using, temperature calculation can be performed in consideration of infrared rays emitted from the top plate, and the pan bottom temperature can be detected with high accuracy.

It is a block diagram which shows the structure of the induction heating cooking appliance which concerns on Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the induction heating cooking appliance which concerns on Embodiment 1 of this invention. It is the figure which showed the relationship between the material of a pan, its surface state, and emissivity. It is a flowchart which shows operation | movement of the induction heating cooking appliance which concerns on Embodiment 2 of this invention. It is a figure which shows an example of the pan temperature table used with the induction heating cooking appliance of Embodiment 2 of this invention. It is a block diagram which shows the structure of the induction heating cooking appliance which concerns on Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the induction heating cooking appliance which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the induction heating cooking appliance which concerns on Embodiment 4 of this invention. It is a flowchart which shows operation | movement of the induction heating cooking appliance which concerns on Embodiment 4 of this invention.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an induction heating cooker according to Embodiment 1 of the present invention.
The induction heating cooker has a top plate 2 on which a pan 1 that is an object to be heated is placed, a heating coil 3 disposed under the top plate 2, and infrared rays that receive infrared rays emitted from the pan bottom and the top plate 2. And a sensor 4. The infrared sensor 4 includes a temperature sensor (not shown) that detects the temperature of the infrared sensor 4 itself. In addition, the induction heating cooker converts the commercial power supplied from the commercial AC power source 5 into high-frequency power and causes a high-frequency current to flow through the heating coil 3, an input current detection unit 7, and an input voltage detection unit 8. And the heating coil electric current detection part 9 and the control part 10 which controls the whole induction heating cooking appliance are provided. The detection values of the infrared sensor 4, the temperature sensor built in the infrared sensor 4, the input current detection unit 7, and the input voltage detection unit 8 are input to the control unit 10. In FIG. 1, A and B represent infrared radiation. A represents infrared rays from the pan 1, and B represents infrared rays radiated from the top plate 2 heated by the heat of the pan 1.

  The control unit 10 includes a microcomputer, and includes a CPU, a RAM, a ROM, and the like. The ROM stores a control program and a program corresponding to a flowchart described later. The control unit 10 calculates the pan temperature based on the amount of light received from the infrared sensor 4 and controls the drive circuit 6 based on the pan temperature. Further, the control unit 10 functionally configures emissivity detection means, temperature conversion emissivity determination means, temperature conversion means, and drive circuit control means.

FIG. 2 is a flowchart showing the operation of the induction heating cooker according to Embodiment 1 of the present invention. The operation will be described with reference to FIGS.
When the start of a heating operation is input from an operation input unit (not shown) and the heating power level is set, the control unit 10 starts driving the drive circuit 6 and starts induction heating by supplying current to the heating coil 3. The process of FIG. 2 is entered. First, the controller 10 reads the input current and input voltage of the drive circuit 6 and calculates the input power W (S1). Subsequently, the control unit 10 reads the heating coil current Ic (S2). Then, the control unit 10 with a heating coil current Ic and the input power is W, the load impedance Z pot 1 as seen from the heating coil 3 side calculated by ^{Z = W / Ic 2 (S3} ). Although the input power W of the drive circuit 6 is used here, the load impedance Z may be obtained using the output power of the drive circuit 6. Then, the control unit 10 reads the infrared sensor output P and the temperature To of the infrared sensor 4 itself from a temperature sensor (not shown) built in the infrared sensor 4 (S4). Then, the control part 10 reads the infrared emissivity 0.9 of the top plate 2 memorize | stored previously (S5).

  And the control part 10 judges whether the load impedance Z is larger than the preset threshold value (alpha), and judges whether the pot 1 in use is iron or stainless steel (S6). Since the magnetic stainless steel material has the largest pan impedance viewed from the heating coil 3, if the load impedance Z is larger than the threshold value α, it is determined as a magnetic stainless steel pan, and the process proceeds to step S7, and if the load impedance Z is less than the threshold value α. It determines with an iron pan and transfers to step S8.

Prior to explaining the processing of steps S7 and S8, the infrared emissivity according to the material of the pan and its surface state will be explained.
FIG. 3 is a diagram showing the relationship between the material of the pan, its surface state, and the infrared emissivity. As shown in FIG. 3, the infrared emissivity of the pan 1 varies depending on the material and the coating condition of the surface. Since magnetic stainless steel is resistant to rusting, it is not painted when processed as a pan 1. For this reason, the infrared emissivity of the magnetic stainless steel pan 1 is 0.16 of stainless steel (polished) based on FIG. On the other hand, in the case of an iron pan, the iron pan is painted with lacquer or paint to prevent rust. The infrared emissivity of lacquer and paint takes values from 0.92 to 0.97 as shown in FIG. For this reason, the infrared emissivity of the iron pan is 0.94, which is approximately halfway between 0.92 and 0.97. The infrared emissivity corresponding to the material of the pan 1 is stored in the control unit 10 and used for calculating the temperature conversion emissivity ε in steps S7 and S8.

  Next, infrared rays received by the infrared sensor 4 will be described. The infrared sensor 4 receives both infrared rays emitted from the pan 1 and infrared rays emitted from the top plate 2. Since the top plate 2 is in contact with the pan 1, the upper surface of the top plate 2 is heated to the same temperature as the pan 1 by receiving heat from the pan 1. Therefore, infrared rays corresponding to the pan temperature are also emitted from the top plate 2, and the infrared rays are received by the infrared sensor 4. Therefore, the infrared sensor 4 receives infrared rays from two places having different emissivities.

  Here, the received light amount (output) of the infrared sensor 4 is P (= P0 + P1), the received light amount (output) based on infrared rays from the top plate 2 is P0, and the received light amount (output) based on infrared rays from the pan 1 is P1. And In practice, P0 and P1 cannot be distinguished from each other, but here, P0 and P1 are assumed to be assumed.

  In calculating the pan temperature based on the output of the infrared sensor 4, the output P0 of the infrared sensor 4 should be converted to the temperature using the infrared emissivity 0.9 of the top plate 2, but in reality P0 and P1 Cannot be distinguished. For this reason, when the temperature is simply converted using the infrared emissivity of the pan 1 itself and the output P of the infrared sensor 4, the output P0 of the top plate 2 is more than the top plate 2 when the pan 1 is a stainless steel pan. Since the temperature is converted using a small infrared emissivity, the calculation result is higher than the actual temperature. Therefore, when performing the temperature conversion in consideration of the infrared rays radiated from the top plate 2, when the infrared emissivity of the pan 1 is smaller than that of the top plate 2, the infrared emissivity of the pan 1 used for temperature conversion is It is necessary to correct to a value larger than the infrared emissivity of the pan 1 itself and smaller than the infrared emissivity of the top plate 2 and perform temperature conversion using the new infrared emissivity after the correction. The new infrared emissivity after this correction is hereinafter referred to as temperature converted emissivity.

  On the other hand, in the case of an iron pan, since the temperature conversion of the output P0 of the top plate 2 is performed using an infrared emissivity of 0.94 that is larger than that of the top plate 2, the actual temperature is contrary to the case of the stainless pan. Results in a low calculation result. Therefore, when performing temperature conversion in consideration of infrared rays radiated from the top plate 2, when the pan 1 has an infrared emissivity greater than that of the top plate 2, the temperature conversion emissivity is greater than the infrared emissivity of the pan 1 itself. Correction is made to a value that is smaller and larger than the infrared emissivity of the top plate 2, and temperature conversion is performed using the new infrared emissivity after the correction.

  Next, a method for calculating the temperature conversion emissivity will be described. Considering the behavior of the infrared rays emitted from the pan 1, the infrared rays emitted from the pan 1 are attenuated when passing through the top plate 2 and then received by the infrared sensor 4. On the other hand, the infrared rays radiated from the upper surface of the top plate 2 due to the heat transmitted from the pan 1 to the top plate 2 are attenuated in the same manner as the infrared rays of the pan 1, but are directly received by the infrared sensor 4, so the attenuation amount is Smaller than the infrared rays emitted from the pan 1. That is, the infrared rays received by the infrared sensor 4 are more often attributed to the top plate 2 side than the pan 1. Therefore, the temperature conversion emissivity is obtained using a predetermined ratio determined in consideration of this point, the infrared emissivity of the pan 1, and the infrared emissivity of the top plate 2.

Here, the ratio for obtaining the temperature conversion emissivity is set to: pan: top plate = 0.2: 0.8. Using this ratio, the temperature conversion emissivity is calculated by the following equation (1).
ε = 0.2 × infrared emissivity of pan + 0.8 × infrared emissivity of top plate (1)

  Therefore, in step S7, the temperature conversion emissivity ε = 0.2 × 0.16 + 0.8 × 0.9 can be calculated as 0.752, and in step S8, the temperature conversion emissivity ε = 0.2 × 0. 0.994 + 0.8 × 0.9 can be calculated as 0.908.

  In this way, the ratio of the top plate 2 is increased to calculate the temperature conversion emissivity ε, and the pan temperature Ta is calculated by the following equation (2) using the temperature conversion emissivity ε (S9).

ここで、σ：ステファン・ボルツマン定数

Where σ: Stefan-Boltzmann constant

  The pan temperature Ta calculated as described above is compared with the target temperature Tobj corresponding to the set thermal power (S10). If the target temperature Tobj is higher than the pan temperature Ta, the heating coil current is increased (S11), If the pan temperature Ta is equal to or lower than the target temperature Tobj, the heating coil current is stopped (S12), and the heating coil current is controlled so that the pan temperature becomes the target temperature. Moreover, although not described in the flowchart, if the pan temperature Ta is equal to or higher than the abnormal temperature (for example, 250 ° C.) value, the heating coil current is also cut off and stopped.

  As described above, in the first embodiment, when a pan having an infrared emissivity smaller than that of the top plate 2 such as a stainless steel pan is used, it is larger than the infrared emissivity (here 0.16) of the pan 1 itself. Further, a temperature conversion emissivity ε having a value smaller than the infrared emissivity (0.9 in this case) of the top plate 2 is calculated. Then, the temperature is converted based on the temperature conversion emissivity ε. For this reason, it is possible to calculate the pan temperature in consideration of the infrared radiation from the top plate 2 and to accurately measure the pan bottom temperature.

  In addition, when using a pan with an infrared emissivity larger than that of the top plate 2 such as an iron pan, the temperature is converted to a value that is larger than the infrared emissivity of the top plate 2 and smaller than the infrared emissivity of the pan 1 itself. The emissivity ε is calculated. Then, the temperature is converted based on the temperature conversion emissivity ε. For this reason, it is possible to calculate the pan temperature in consideration of the infrared radiation from the top plate 2 and to accurately measure the pan bottom temperature.

  In this way, since the pan bottom temperature can be detected with high accuracy, it is possible to prevent erroneous detection of a temperature higher than the actual temperature, unnecessarily power control, and cooking failure due to insufficient heating. Thus, since it can prevent that the protective function by electric power control works unnecessary, an easy-to-use induction heating cooker can be provided.

  Moreover, when calculating | requiring the emissivity (epsilon) for temperature conversion, it can obtain | require easily by calculating using the preset ratio. Here, the ratio is set to pan: top plate = 0.2: 0.8, but the ratio on the side of the top plate 2 only needs to be high and is not limited to this value.

  Moreover, since an infrared sensor is attached under the top plate 2, it can be an induction heating cooker having a design with no protrusion.

Embodiment 2. FIG.
In the first embodiment, when the temperature is calculated in step S9 in FIG. 2, the fourth root is calculated, and a microcomputer (not shown) in the control unit 10 is burdened. A method for reducing this will be described in the second embodiment. The configuration of the induction heating cooker of the second embodiment is the same as that of FIG. 1 of the first embodiment, and the pot temperature calculation method is different from that of the first embodiment.

  FIG. 4 is a flowchart showing the operation of the induction heating cooker according to Embodiment 2 of the present invention. In FIG. 4, the same steps as those in the flowchart shown in FIG. The second embodiment is the same as the flowchart of the first embodiment except for steps S21 to S27 in the flowchart of FIG. In the following, the second embodiment will be described focusing on the differences from the first embodiment.

  In step S4, the control unit 10 reads the infrared sensor output P and the infrared sensor temperature To, and then determines an infrared sensor temperature correction coefficient K1 (hereinafter referred to as a correction coefficient K1) corresponding to the infrared sensor temperature To (S21). . The control unit 10 stores in advance a function f1 indicating the relationship between the infrared sensor temperature To and the correction coefficient K1, and the correction coefficient K1 is determined using this function f1. The function f1 is created such that the correction coefficient K1 increases as the temperature To increases, and conversely the correction coefficient K1 decreases as the temperature To decreases. Here, the function f1 is used to determine the correction coefficient K1 from the infrared sensor temperature To, but it may be determined using a table.

  Then, the control part 10 calculates | requires the pan temperature Ta1 with reference to the pan temperature table TB based on the infrared sensor output P (S22). As shown in FIG. 5, the pan temperature table TB is a table in which the infrared sensor output P and the pan temperature Ta <b> 1 are stored in association with each other. The pan temperature table TB is created based on experiments and stored in the control unit 10 in advance. The pan temperature table TB is a table created based on an equation obtained by temporarily setting the infrared sensor temperature To as 25 ° C. and the emissivity as 1, and substituting these temporarily set values into the above equation (2). As the infrared sensor output P increases, the pan temperature Ta1 also increases. Since the pan temperature Ta1 of the pan temperature table TB is a temporary temperature obtained after temporarily setting the infrared sensor temperature To and the infrared emissivity of the pan 1, the infrared sensor temperature obtained in step S21 is the temporary temperature. It is necessary to perform correction using the correction coefficient K1 for correction and the correction coefficient for emissivity correction according to the pan material.

  As the correction coefficient for emissivity correction, the correction coefficient Ks for the magnetic stainless steel pan and the correction coefficient Kt for the iron pan are calculated in advance through experiments and stored in the control unit 10. A method for calculating the correction coefficients Ks and Kt will be described later.

  In calculating the corrected pot temperature Ta from the temporary pot temperature Ta1, the control unit 10 first determines the material of the pot 1 in step S23. When the load impedance Z is greater than the threshold value α, the control unit 10 determines that the stainless steel is magnetic. And the correction coefficient Ks of magnetic stainless steel for correct | amending temporary pan temperature Ta1 is read (S24). And the temporary pan temperature Ta1 calculated | required in step S22 uses the correction coefficient K1 for infrared sensor temperature correction | amendment calculated | required in step S21, and the correction coefficient Ks for emissivity correction | amendment in the case of magnetic stainless steel, It correct | amends by Ta = K1xKsxTa1, and calculates the pan temperature Ta after correction | amendment (S25).

  On the other hand, when it determines with an iron pan in step S23, the control part 10 reads the correction coefficient Kt of the iron pan for correct | amending temporary pan temperature Ta1 (S26). And the temporary pan temperature Ta1 calculated | required in step S22 uses the correction coefficient K1 for infrared sensor temperature correction | amendment calculated | required in step S21, and the correction coefficient Kt for emissivity correction | amendment in the case of an iron pan, It correct | amends by Ta = K1 * Kt * Ta1 and calculates the corrected pan temperature Ta (S27). The operation after calculating the pan temperature Ta is the same as that in the first embodiment.

  Next, a method for calculating the correction coefficients Ks and Kt will be described. Here, the correction coefficient is experimentally obtained so that the temperature is matched in the temperature range around 200 ° C. often used for fried foods and fried foods. When calculating the correction coefficient Ks for stainless steel, first, a 200 ° C. stainless steel pan is placed on the top plate 2 and the amount of received infrared light P is measured at an ambient temperature of 25 ° C. Based on the amount of received light P, the pan temperature table TB is referred to, and when 150 ° C., for example, Ks is obtained as 1.33 from 200 = 150 × Ks.

  Similarly, when calculating the correction coefficient Ks for the iron pan, a 200 ° C. iron pan is placed on the top plate 2 and the amount of received infrared light P is measured at an ambient temperature of 25 ° C. Based on the amount of received light P, the pan temperature table TB is referred to, and when 190 ° C., for example, Kt is obtained as 1.05 from 200 = 150 × Kt.

  By the way, even if it is the same 200 degreeC pan 1, the light-receiving amount of the infrared sensor 4 was different by the case where the top plate 2 was interposed between the pan 1 and the infrared sensor 4, and the case where it was not interposed. It will be a thing. As described in the first embodiment, the infrared ray received by the infrared sensor 4 is more dominant than the top plate 2 because the infrared ray from the top plate 2 is more dominant than the pan 1. In the case of low magnetic stainless steel, the amount of received light is smaller when the top plate 2 is not interposed and when the top plate 2 is not interposed. Therefore, when the correction coefficient is obtained in the same manner as above based on the amount of infrared light received without the top plate 2, the amount of infrared light received is smaller than when the top plate 2 is present. The pot temperature is lowered. For this reason, the correction coefficient without the top plate 2 is larger than the correction coefficient with the top plate 2. In other words, the correction coefficient Ks when the top plate 2 is present is a smaller value than the correction coefficient obtained when the top plate 2 is not present.

  On the other hand, when the pan 1 is an iron pan having an infrared emissivity higher than that of the top plate 2, the amount of received light is greater when the top plate 2 is not interposed and when the top plate 2 is not interposed. Therefore, when the correction coefficient is obtained in the same manner as described above, the correction coefficient has a larger amount of infrared rays received than when the top plate 2 is provided, and therefore the pot temperature obtained with reference to the pot temperature table TB is higher. . For this reason, the correction coefficient when there is no top plate 2 is smaller than that when there is a top plate 2. In other words, the correction coefficient Kt when the top plate 2 is present is a larger value than the correction coefficient obtained when the top plate 2 is not present.

  As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and the temperature can be calculated without calculating the fourth root by using the table and the correction coefficient.

  Further, the correction coefficient for correcting the infrared emissivity of the pan 1 is made smaller than the correction coefficient when the infrared ray from the pan bottom is directly received without passing through the top plate 2 in the case of a stainless steel pan having a small infrared emissivity. Therefore, the calculation result is not higher than the actual temperature, and the pan temperature can be calculated with high accuracy. Similarly, when the infrared emissivity of the pan 1 is as large as that of a painted iron pan, it is larger than the correction coefficient when the infrared rays from the pan bottom are directly received without passing through the top plate 2, so that the actual temperature is higher than the actual temperature. The pan temperature can be accurately calculated without a low calculation result.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing a configuration of an induction heating cooker according to Embodiment 3 of the present invention. In FIG. 6, the same parts as those in FIG.
The induction heating cooker according to the third embodiment is a new thermistor 11 that detects the temperature of the top plate 2 in contact with the lower surface of the top plate 2 in addition to the induction heating cooker according to the first embodiment shown in FIG. Other configurations are the same as those of the first embodiment.

  FIG. 7 is a flowchart showing the operation of the induction heating cooker according to Embodiment 3 of the present invention. 7, the same step numbers are assigned to the same parts as those in the flowchart of the first embodiment shown in FIG. In the third embodiment, the processes of steps S31 to S34 are newly added to the flowchart of FIG. 2 of the first embodiment. In the following, the third embodiment will be described focusing on the differences from the first embodiment.

  In step S31, the control unit 10 reads the temperature Tb of the top plate 2 detected by the thermistor 11. Then, the control unit 10 compares the temperature Tb of the top plate 2 with the pan temperature Ta calculated based on the infrared sensor output, adopts the higher temperature as the temperature Ts of the pan 1 (S33 and S34), and step The temperature control after S10 is performed.

  By performing such control, when the infrared sensor 4 becomes dirty and the amount of received infrared light decreases and is calculated to be lower than the actual temperature, the control by the thermistor 11 can be switched. Therefore, even when the infrared sensor 4 becomes dirty, cooking can be continued safely. Also, because the higher temperature is adopted, the stainless steel pan is misjudged as an iron pan, and even though the actual temperature is high, it is calculated as a low temperature, and the control temperature is abnormal with respect to the target temperature. Can be prevented.

  As described above, according to the third embodiment, the same effect as in the first embodiment can be obtained, and even if the infrared sensor 4 is contaminated, the cooking is safely performed by switching to the control by the thermistor 11. It is possible to continue.

  In addition, although the example which newly added the process of step S31-S34 to the flowchart of Embodiment 1 shown in FIG. 2 was shown here, you may add to the flowchart of Embodiment 2 shown in FIG. .

Embodiment 4 FIG.
FIG. 8 is a block diagram showing a configuration of an induction heating cooker according to Embodiment 4 of the present invention. In FIG. 8, the same parts as those in FIG.
The induction heating cooker according to the fourth embodiment has a configuration in which a light emitting element 12 and a light receiving element 13 are newly added to the induction heating cooker according to the first embodiment shown in FIG. Same as 1.

  FIG. 9 is a flowchart showing the operation of the induction heating cooker according to Embodiment 4 of the present invention. 9, the same step numbers are assigned to the same parts as those in the flowchart of the first embodiment shown in FIG. Hereinafter, the difference between the fourth embodiment and the first embodiment will be mainly described.

  First, the control unit 10 reads the infrared sensor output P and the temperature To of the infrared sensor 4 itself from a temperature sensor (not shown) built in the infrared sensor 4 (S4). Subsequently, the control unit 10 reads the infrared emissivity εt of the top plate 2 stored in advance (S5), and then directly detects the infrared emissivity of the pan 1 (S41). That is, light is emitted from the light emitting element 12 toward the pot 1 as indicated by the arrow C, and the light reflected by the pot 1 (arrow D) is received by the light receiving element 13. The controller 10 stores in advance a relational expression or table for determining the infrared emissivity of the pan 1 from the amount of received light, and the infrared emissivity of the pot 1 is determined from the amount of received light using the relational expression or table. decide. Then, the control unit 10 converts the temperature by 0.2 × ε + 0.8 × εt using the determined infrared emissivity, the predetermined ratio similar to the first embodiment, and the infrared emissivity εt of the top plate 2. The emissivity ε for use is obtained (S42). The subsequent processing is the same as in the first embodiment.

  In addition, although the control example combined with Embodiment 1 shown in FIG. 2 was shown here, it is good also as control combined with Embodiment 3. FIG.

  As described above, in the fourth embodiment, the same effects as those of the first and third embodiments can be obtained, and the infrared emissivity is not estimated from the material of the pan 1, but the light emitting element 12 and the light receiving element are received. Since the surface state of the pan 1 is directly identified by the element 13 and the infrared emissivity of the pan 1 is determined, the pan temperature can be detected with higher accuracy. Therefore, temperature control with few false detections of pan temperature can be realized.

  1 pan, 2 top plate, 3 heating coil, 4 infrared sensor, 5 commercial AC power supply, 6 drive circuit, 7 input current detection unit, 8 input voltage detection unit, 9 heating coil current detection unit, 10 control unit, 11 thermistor, 12 Light emitting element, 13 Light receiving element.

Claims (5)

A top plate for placing an object to be heated;
A heating coil provided under the top plate for heating the object to be heated;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
An infrared sensor that is provided under the top plate and receives infrared rays emitted from the bottom surface of the object to be heated via the top plate;
Emissivity detection means for detecting the infrared emissivity of the heated object;
A temperature conversion emissivity determining means for comparing the infrared emissivity detected by the emissivity detection means with the infrared emissivity of the top plate stored in advance and determining the temperature conversion emissivity according to the comparison result; ,
Temperature conversion means for calculating the temperature of the object to be heated based on the temperature conversion emissivity determined by the temperature conversion emissivity determination means and the output of the infrared sensor;
Drive circuit control means for controlling the drive circuit based on the temperature obtained by the temperature conversion means,
The temperature conversion for emissivity determination means, the infrared emissivity of the object to be heated is a pre SL temperature conversion for emissivity is smaller than the infrared emissivity of the top plate, is detected by the emissivity detecting means infrared emissivity of heated and the infrared emissivity of the top plate, the top plate side by adding at a predetermined ratio set large, the size rather and said top plate than the infrared emissivity of the object to be heated An induction heating cooker characterized in that it is determined to have a value smaller than the infrared emissivity . A top plate for placing an object to be heated;
A heating coil provided under the top plate for heating the object to be heated;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
An infrared sensor that is provided under the top plate and receives infrared rays emitted from the bottom surface of the object to be heated via the top plate;
Emissivity detection means for detecting the infrared emissivity of the heated object;
A temperature conversion emissivity determining means for comparing the infrared emissivity detected by the emissivity detection means with the infrared emissivity of the top plate stored in advance and determining the temperature conversion emissivity according to the comparison result; ,
Temperature conversion means for calculating the temperature of the object to be heated based on the temperature conversion emissivity determined by the temperature conversion emissivity determination means and the output of the infrared sensor;
Drive circuit control means for controlling the drive circuit based on the temperature obtained by the temperature conversion means,
The temperature conversion for emissivity determination means, the infrared emissivity of the object to be heated is a pre SL temperature conversion for emissivity of greater than infrared emissivity of the top plate, is detected by the emissivity detecting means By adding the infrared emissivity of the heated object and the infrared emissivity of the top plate at a predetermined ratio that is set large on the top plate side, the infrared emissivity of the object to be heated is smaller than the infrared emissivity of the object to be heated. An induction heating cooker characterized by being determined to have a value larger than the infrared emissivity . A thermistor is provided under the top plate and detects the bottom surface temperature of the pan via the top plate, and the drive circuit control means includes a temperature calculated by the temperature conversion means and a temperature detected by the thermistor. The induction heating cooker according to claim 1 or 2 , wherein the higher one is used as the temperature of the object to be heated for control. A means for measuring input or output power of the drive circuit and a heating coil current measuring means, wherein the emissivity detecting means determines the pot material from the ratio of input or output power and output current at the start of heating, The induction heating cooker according to any one of claims 1 to 3 , wherein an infrared emissivity of an object to be heated is estimated based on a material. The emissivity detecting means has light emitting means for emitting light toward the pan bottom of the object to be heated through the top plate, and light receiving means for receiving light emitted by the light emitting element reflected by the pan bottom, The induction heating cooker according to any one of claims 1 to 4 , wherein an infrared emissivity of an object to be heated is estimated based on an amount of light received by the light receiving means.

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