JP5062013B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that induction-heats an object to be heated such as a pan or a frying pan using an electromagnetic induction heating coil.

In recent years, induction heating cookers that inductively heat an object to be heated such as a pan with a heating coil have been widely recognized because of their excellent features of safety, cleanliness, and high efficiency. In order to detect the temperature of an object to be heated, an induction heating cooker of this type has been proposed that includes an infrared sensor that detects infrared energy emitted from the object to be heated. The infrared sensor is provided below the top plate, and receives infrared rays emitted from an object to be heated that are incident on an infrared ray incident area formed so that infrared rays can pass through the top plate, and the temperature of the object to be heated. The signal which changes according to is output. The cooking devices described in Patent Literature 1 and Patent Literature 2 detect the temperature of an object to be heated using an infrared sensor, and perform heating control of the heating coil based on the detected temperature.
Japanese Patent Laid-Open No. 11-225881 JP 2007-115420 A JP 10-125457 A

  FIG. 11 is a diagram illustrating the relationship between the temperature of the object to be heated and the amount of radiant energy generated. A solid line 47 indicates a case where the object to be heated is a black body (reflectance = 1), and a broken line 48 indicates a case where the object to be heated is magnetic stainless steel (reflectance = 0.4). According to the figure, the radiant energy when the temperature of the black body is 300 ° C. and the radiant energy when the temperature of the magnetic stainless steel is 447 ° C. are substantially equal. Thus, the absolute value of the amount of energy received by the infrared sensor varies greatly depending on the difference in reflectance of the object to be heated. For this reason, when the absolute temperature of the object to be heated is obtained based on the absolute value of the amount of energy received by the infrared sensor, there is a problem that a large error occurs.

  In the heating cooker described in Patent Document 1, the temperature of the object to be heated is converted from the amount of light received by the infrared sensor and the reflectance of the object to be heated, and the temperature of the object to be heated is controlled based on the converted absolute temperature information. ing. Since such a method measures the reflectance, the configuration becomes complicated, and there is a possibility that the reflectance cannot be measured accurately due to contamination of the infrared incident region or the object to be heated.

  In Patent Document 2, using an infrared detection element composed of two Si photodiodes having peak sensitivities of 1 μm or less and different wavelength ranges, the output ratio of each infrared detection element is calculated to calculate the heating object. There has been proposed a cooking device provided with an infrared detecting means for measuring the temperature of an object to be heated without being affected by the difference in emissivity. However, there are problems that two infrared detecting elements are required and the configuration is complicated, and that it is easily affected by ambient light.

In patent document 3, the induction heating part which has a heating coil and a switching means, the load pan mounted on the said heating coil via a plate, the temperature element which detects the temperature of the said load pan, and the said temperature element Input means for selecting a control temperature controlled based on the detected temperature detected by the control means, display means for displaying a state determined by the input means, detected temperature by the temperature element, and control selected by the input means Thermal power adjusting means for adjusting the heating power to the load pan according to temperature, induction heating part control means for controlling the output to the induction heating part according to the output of the thermal power adjusting means, and the induction heating part control means A drive means for driving the switching means in the induction heating unit in response to a control signal from the temperature sensor, a temperature change detected by the temperature element, a change time and a differential rate. The heating power adjusting means includes a detecting means, and when the temperature detected by the temperature element is higher than the control temperature, the heating power adjusting means performs heating with a weak heating power (hereinafter referred to as “heating power weak”), and from the control temperature When the temperature is lower, the thermal power switching means for heating with a thermal power stronger than the thermal power weakness (hereinafter referred to as “thermal power strong”), the thermal power weakness corresponding to each of a plurality of control temperatures, and the thermal power strength are selected. It is the structure which has a thermal-power selection means. When trying to heat oil for deep-fried food with such a configuration, as the amount of oil increases, the temperature of the bottom of the load pan rises faster than the temperature of the oil in the load pan and detects that the temperature element has reached the control temperature. When the above control is performed, there is a problem that the temperature of the oil is controlled to be lower than the target temperature, and the deep-fried food cannot be made well.

  The present invention solves the above-mentioned problems, and is an induction heating cooker capable of controlling the temperature of an object to be heated by an infrared sensor with a simple configuration that is not easily affected by ambient light, dirt on the top plate or the object to be heated. The purpose is to provide.

  An induction heating cooker according to the present invention includes a top plate for placing an object to be heated, a heating coil for induction heating the object to be heated placed on the top plate, and an inverter for supplying a high-frequency current to the heating coil. A circuit; an infrared detection element that is provided below the top plate and detects an amount of infrared radiation emitted from the object to be heated; and an amplification unit that amplifies a signal detected by the infrared detection element, and the object to be heated An infrared sensor that outputs a detection signal having a magnitude corresponding to the temperature of the sensor, and a control unit that controls the output of the inverter circuit based on the output of the infrared sensor, wherein the infrared sensor is configured to perform the induction heating by the control unit. The higher the temperature of the object to be heated in the vicinity of the control temperature range in which the temperature of the object to be heated is controlled by controlling the output of the coil, the greater the size and the rate of increase. When the increase amount of the output value of the infrared sensor with respect to the initial detection value that is the output value of the infrared sensor immediately after the start of heating becomes a first predetermined value or more, the induction heating coil Or the heating is stopped, and when the amount of increase in the output value of the infrared sensor becomes less than a second predetermined value smaller than the first predetermined value, the output of the induction heating coil is increased to start heating. Immediately after, the first or / and second predetermined value is corrected so that the differential value of the output value of the infrared sensor increases as the differential value increases.

  As a result, when the temperature T of the object to be heated rises, the infrared sensor outputs a detection signal X whose inclination increases. For this reason, the temperature T of the object to be heated when the predetermined increase amount ΔX is obtained depends on the temperature TS at the start of heating the object to be heated. However, the higher the temperature T of the object to be heated, the steeper the change in the temperature T of the object to be heated in the detection signal, and the smaller the temperature change ΔT of the object to be heated corresponding to the predetermined increase ΔX. . Therefore, as the temperature T of the object to be heated becomes higher, the predetermined increase ΔX can be obtained with a slight temperature change ΔT. Therefore, the temperature change is detected and the output is suppressed with good responsiveness or the heating is stopped. Temperature rise can be suppressed.

  Further, even when disturbance light is steadily incident on the infrared sensor, the detection signal X of the infrared sensor moves in parallel, so that the temperature suppression control operation of the temperature T of the object to be heated is hardly affected. Can do.

  Further, the influence of the difference in emissivity can be significantly reduced as compared with the case where the output of the infrared sensor is converted into the temperature of the object to be heated and the absolute value is obtained.

Also, when heating oil for fried foods, the differential value of the infrared sensor output value decreases as the oil amount increases, while the oil temperature in the load pan increases to the temperature at the bottom of the load pan as the oil amount increases. Therefore, when the differential value of the infrared sensor output value is large, the predetermined amount of correction is reduced, and when the differential value of the infrared sensor output value is small, the predetermined value is increased. It becomes possible to quickly raise the temperature of the oil in the pan to the target temperature.

  The induction cooking device of the present invention can accurately control the temperature of an object to be heated with an infrared sensor with a simple configuration.

  The first invention includes a top plate for placing an object to be heated, a heating coil for induction heating the object to be heated placed on the top plate, an inverter circuit for supplying a high-frequency current to the heating coil, An infrared detection element provided below the top plate for detecting the amount of infrared radiation emitted from the object to be heated; and an amplifying unit for amplifying a signal detected by the infrared detection element; An infrared sensor that outputs a detection signal having a magnitude corresponding thereto, and a control unit that controls the output of the inverter circuit based on the output of the infrared sensor, wherein the infrared sensor outputs the output of the induction heating coil by the control unit. The temperature and the rate of increase increase as the temperature of the heated object increases in the vicinity of the control temperature range in which the temperature of the heated object is controlled by controlling the temperature of the heated object. A signal is output, and the control unit outputs an output of the induction heating coil when an increase amount of the output value of the infrared sensor with respect to an initial detection value which is an output value of the infrared sensor immediately after the start of heating becomes a first predetermined value or more. Or when heating is stopped and the amount of increase in the output value of the infrared sensor is less than a second predetermined value smaller than the first predetermined value, the output of the induction heating coil is increased and immediately after the start of heating. By correcting the first or / and second predetermined value so that the differential value of the output value of the infrared sensor increases, the oil amount is increased when oil is heated for fried food. The differential value of the infrared sensor output value becomes smaller as the oil amount increases, while the oil temperature in the load pan becomes lower than the temperature at the bottom of the load pan as the oil amount increases. When the differential value is large, the correction value of the predetermined value is decreased, and when the differential value of the infrared sensor output value is small, the correction value of the predetermined value is increased, so that the temperature of the oil in the load pan is set to the target temperature. It is possible to start up quickly.

  The second invention is the infrared sensor according to the first invention, particularly when the temperature of the object to be heated is less than the detection lower limit temperature, and the detection signal is substantially constant with respect to the temperature of the object to be heated. When the temperature of the object to be heated is equal to or higher than the detection lower limit temperature, the higher the temperature of the object to be heated, the higher the size and the increase rate. When the temperature TS at the start of heating the object is lower than the detection lower limit temperature T0, the magnitude of the detection signal of the infrared sensor output is substantially constant. For this reason, the temperature T of the object to be heated when the predetermined increase amount ΔX with respect to the initial output value X0 of the infrared sensor output during heating is obtained is a value that does not depend on the temperature TS at the start of heating. When the temperature TS at the start of heating of the heated object is equal to or higher than the detection lower limit temperature T0, when the temperature T of the heated object rises, the infrared sensor outputs a detection signal X whose inclination increases. In this case, the above-described effects can be obtained. If the detection lower limit temperature T0 is set in the vicinity of the control temperature range in which the control unit controls the output of the induction heating coil to control the temperature of the object to be heated, it is not affected by the temperature of the object to be heated at the start of heating. The temperature range of the object to be heated at the start of heating, which can control the temperature of the object to be heated, is widened.

  Further, even when disturbance light is incident on the infrared sensor constantly, the output X of the infrared sensor is translated in the same manner as described above so that the suppression control operation of the temperature T of the heated object is hardly affected. can do.

  In the third invention, in particular, the initial detection value of the first or second invention is changed immediately after the start of heating, and is the output value of the infrared sensor at the same time as the start of heating or immediately before the start of heating. The initial detection value can be detected without being affected by the temperature rise of the heated object from the start of heating until the initial value is stored.

  In particular, the fourth aspect of the invention has a storage unit that stores the output value of the infrared sensor immediately after the start of heating as an initial detection value, and the output of the infrared sensor after the start of heating. When the value is smaller than the initial detection value, the initial detection value is changed to the reduced output value of the infrared sensor, and when the output value of the infrared sensor becomes small after the heating starts, the heating starts. It is assumed that the ambient light incident on the infrared sensor sometimes disappeared, that water or a cooked food was introduced. If heating is continued in this state until the predetermined increase ΔX is obtained, the temperature of the object to be heated that suppresses or stops the output becomes higher than the set temperature. Therefore, when the initial output value decreases after the start of heating, the heated object can be prevented from being heated more than expected by changing the initial output value to a value after the decrease. Thereby, it becomes possible to implement | achieve high-heat-power cooking safely so that the temperature suppression control of the to-be-heated object by an infrared sensor may become difficult to be influenced by disturbance light.

  In particular, the fifth aspect of the present invention includes a storage unit that stores the output value of the infrared sensor at the same time as the start of heating or immediately before the start of heating as an initial detection value. When the output value of the infrared sensor is smaller than the initial detection value, the output value of the infrared sensor is reduced after heating is started by changing the initial detection value to the output value of the reduced infrared sensor. In such a case, it is assumed that the disturbance light that has been incident on the infrared sensor at the start of heating has disappeared, that water or a cooked product has been introduced, and the like. If heating is continued in this state until the predetermined increase ΔX is obtained, the temperature of the object to be heated that suppresses or stops the output becomes higher than the set temperature. Therefore, when the initial output value decreases after the start of heating, the heated object can be prevented from being heated more than expected by changing the initial output value to a value after the decrease. Thereby, it becomes possible to implement | achieve high-heat-power cooking safely so that the temperature suppression control of the to-be-heated object by an infrared sensor may become difficult to be influenced by disturbance light.

  In the sixth aspect of the invention, in particular, the first or infrared detecting element is formed of a photodiode using InGaAs, so that an output can be obtained at a temperature of approximately 120 ° C. or higher and oil suitable for fried foods. The temperature can be controlled, and an inexpensive infrared detection element having a simple configuration can be used. Therefore, the configuration can be simplified and the cost can be reduced.

  In a seventh aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, an operation switch is provided that sends a signal to the control unit and instructs the heating coil to heat the heated portion. It is possible, and by roughly controlling the heated object to a temperature set temperature, it becomes possible to roughly set the heated object to a temperature set by an operation switch. Since an object to be heated can be controlled to an optimum temperature according to cooking such as grilled meat suitable for about 250 ° C., an induction heating cooker with few failures can be realized.

  Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
[Configuration of induction heating cooker]
FIG. 1 is a perspective view of an induction heating cooker according to an embodiment of the present invention. The induction heating cooker according to the present embodiment includes an outer case 1 and a top plate 2 provided on the upper portion of the outer case 1 and covered with a top frame 2a. A left induction heating burner 3 and a right induction heating burner 4 that are heated using heating coils are provided on the left and right of the top surface of the top plate 2, and the heating range corresponding to each heating coil is printed and displayed on the top surface of the top plate 2. Yes. A heated object such as a pot is induction-heated at a portion placed on the display unit indicating the heating range of the left induction heating burner 3 and the right induction heating burner 4.

  On the front side of the left induction heating burner 3 and the right induction heating burner 4, a left induction heating burner display unit 5 for displaying the heating output of the left induction heating burner 3 and the right induction heating burner 4 and a right induction heating burner display unit. 6 is provided. Further on the front side are a left induction heating burner operation switch (operation unit) 7 and a right induction heating burner operation switch (operation unit) 8 for the user to control the heating of the left induction heating burner 3 and the right induction heating burner 4 respectively. Are provided in a line in the left-right direction. On the front surface of the outer case 1, a power switch 9 is provided on the right.

  FIG. 2 is a configuration diagram of the induction heating cooker according to the embodiment of the present invention. Although there are two induction heating burners in FIG. 1, only one opening is shown in FIG. 2 for convenience of explanation. Below the top plate 2, an AC magnetic field is generated at a position corresponding to the circular displays 3a and 4a indicating the heating range of the induction heating burners 3 and 4 shown in FIG. A heating coil is provided. In the present embodiment, the heating coil has a split winding configuration with an inner coil 21a and an outer coil 21b. Hereinafter, the inner coil 21a and the outer coil 21b are collectively referred to as a heating coil 21. The heating coil 21 does not need to have a split winding configuration. The heating coil 21 is placed on a heating coil support 22 provided below the top plate 2. The lower surface of the heating coil support 22 is provided with a ferrite 23 that is a magnetic body that concentrates the magnetic flux toward the back side of the heating coil 21 in the vicinity of the heating coil 21.

  In the top plate 2, a portion facing the space portion between the inner coil 21 a and the outer coil 21 b is an infrared incident region 24, which is formed so that infrared rays can be transmitted. The top plate 2 is entirely formed of a heat-resistant ceramic that can transmit infrared rays, and the lower surface other than the infrared incident region 24 is covered with, for example, a black printing film 2b that hardly transmits infrared rays and has a low reflectance (see FIG. 3). . The configuration of the infrared incident region 24 is not limited to this. A portion of the top plate 2 other than the infrared incident region 24 may be made of a material that does not transmit infrared rays, and a portion of the infrared incident region 24 may be formed of a material that can transmit infrared rays. Moreover, you may comprise the circumference | surroundings of the infrared incident area | region 24 with the printed film whose infrared transmittance is not zero. A cylindrical light guide tube 25 having upper and lower openings perpendicular to the upper and lower surfaces of the heating coil 21 between the inner coil 21 a and the outer coil 21 b below the infrared incident region 24 is formed integrally with the heating coil support 22. And provided. The infrared sensor 26 is provided to face the lower opening of the light guide tube 25. Infrared radiation radiated from the bottom surface of the article to be heated 20 increases in radiant energy as the temperature of the article to be heated 20 increases. This infrared light is incident from an infrared incident region 24 provided on the top plate 2, passes through the light guide tube 25, and is received by the infrared sensor 26. The infrared sensor 26 outputs a detection signal based on the amount of infrared energy received.

  In addition, when the heating coil 21 is not a division | segmentation winding structure, the infrared rays incident area | region 24 can be provided in opening of the center part of the heating coil 21. FIG. In this case, when the infrared incident region 24 is as close as possible to the winding of the heating coil 21, the temperature of a higher temperature portion of the object to be heated 20 can be detected by the infrared sensor 26.

The display LED 27 is provided in the vicinity of the infrared sensor 26 and is attached to the heating coil support base 22 together with the infrared sensor 26. That is, the display LED 27 is provided in the vicinity of the heating coil 21 and the infrared sensor 26 below the top plate 2. The display LED 27 is arranged so that the user can visually recognize the light emission state near the infrared incident region 24 through the top plate 2 from above the device. For example, the light emitted from the display LED 27 provided below the heating coil 21 is guided to the vicinity of the back surface of the top plate 2 by the light guide 27b to emit light. Therefore, the display LED 27 has a function of allowing the user to recognize the position where the infrared incident region 24 exists. As shown in FIG. 1 when viewed from the top of the device, the light emitting region 27a where the light of the display LED 27 can be visually recognized is formed in the vicinity of the infrared incident region 24, and on the outer peripheral side of the heating coil 21 with respect to the infrared incident region 24 It is provided on the near side from the center of the heating coil 21. By setting the positional relationship between the infrared incident region 24 and the light emitting region 27a in this manner, it is possible to increase the probability of covering the infrared incident region 24 by covering the light emitting region 27a with the bottom surface of the article 20 to be heated. In order to further increase the probability that the infrared incident region 24 is covered with the bottom surface of the object to be heated 20, the infrared incident region 24 and the light emitting region 27 a are on or near a straight line that passes through the approximate center of the heating coil 21 and is perpendicular to the front surface of the body. It is desirable that the light emitting region 27a is provided in front of the infrared incident region 24.

  An inverter circuit 28 that supplies a high-frequency current to the heating coil 21 and a control unit 29 that controls the operation of the inverter circuit 28 are provided below or around the heating coil 21. The operation unit 7 is provided on the front surface or the upper surface of the device, and includes a heating off / on key 7a for starting or stopping a heating operation, a down key 7b for reducing output, and an up key 7c for increasing output. . Further, the heating operation section 7 is provided with a temperature setting cooking off / on key 7d for starting or stopping the heating operation for controlling the temperature of the cooking container or the food / oil in the cooking container to a set temperature, and outputs it. The set temperature can be raised or lowered using the down key 7b for reducing the output and the up key 7c for increasing the output, and the set temperature is displayed on the temperature display portion 7e. The control unit 29 includes a storage unit 29 a, and starts and stops the supply of the high-frequency current to the heating coil 21 and the high frequency supplied to the heating coil 21 based on the output signal of the operation unit 7 and the output signal of the infrared sensor 26. The magnitude of the current is controlled, and other overall induction heating cookers are controlled. The power switch 9 is provided on the front or top surface of the device.

  Furthermore, the induction heating cooker of this Embodiment has the temperature sensor 30 which is provided in the vicinity of the display LED 27 and detects the ambient temperature around the display LED 27. The temperature sensor 30 is a temperature detection unit, and includes a temperature detection element such as a thermistor. The control unit 29 determines whether or not the temperature detected by the temperature sensor 30 is equal to or higher than a predetermined temperature. When the control unit 29 determines that the temperature is equal to or higher than the predetermined temperature, the control unit 29 suppresses a decrease in the life of the display LED 27, The output of the display LED 27 can be reduced or its driving can be stopped as compared with the case of.

[Operation of induction heating cooker]
Hereinafter, the basic operation of the induction heating cooker will be described. When the power switch 9 is turned on by the user, the control unit 29 enters a standby mode. In the standby mode, when a temperature setting cooking start command is input from the temperature setting cooking OFF / ON key 7d of the operation unit 7, the set temperature is displayed on the display unit 7e, and the control unit 29 enters the heating mode. In the heating mode, when the temperature setting cooking off / on key 7d is operated (for example, pressed) and a temperature setting cooking stop command is input, the control unit 29 enters a standby mode and stops heating. In the heating mode, when the temperature setting up / down key 7b, 7c is operated (for example, pressed) and a temperature up / down command is input, the control unit 29 controls the switching element of the inverter circuit 28 based on the input command. Then, the amount of high-frequency current supplied to the heating coil 21 is controlled. When a high-frequency current is supplied to the heating coil 21, a high-frequency magnetic field is generated from the heating coil 21, the object to be heated 20 placed on the top plate 2 is induction-heated, and the object to be heated reaches a set temperature. Thus, the high frequency current is controlled.

  After the power switch 9 is turned on and before the heating off / on key 7a of the operation unit 7 is operated, that is, in a standby state, the control unit 29 recognizes the display LED 27 and the position of the infrared incident region 24 to the user. In addition, a drive signal is output to urge the infrared incident region 24 to be properly covered with the object to be heated 20 to emit light. In addition, the user is instructed by an instruction manual or the like so as to cover the object to be heated 20 before starting the heating, or a precaution to that effect is displayed on the top plate 2, or It is instructed by notification or display by voice or text. The user places the object to be heated 20 above the display LED 27 to cover and hide the display LED 27, and then operates the heating off / on switch 7a to start heating.

  As shown in FIG. 3, the infrared sensor 26 includes a photodiode 26a using InGaAs as an infrared detection element and an amplifier 26b for amplifying an output signal of the photodiode 26a as components. A filter 31 for removing the influence of visible light is provided between the lower opening of the light guide tube 25 and the infrared detection element 26 a of the infrared sensor 26. The filter 31 is formed so as to cover the side and upper side of the infrared detection element 26a. A condensing lens 31a is integrally formed with the filter 31 above the infrared detection element 26a.

  FIG. 6 is a diagram showing the transmittance of the filter 31 of the induction heating cooker according to the embodiment of the present invention. A filter 31 is used such that the transmittance of light having a wavelength of less than about 0.9 μm is zero. FIG. 4 is a spectral sensitivity characteristic diagram of the photodiode 26a of the induction heating cooker according to the embodiment of the present invention. The photodiode 26a of the present embodiment is set so that the peak sensitivity is about 1.5 μm (1.55 μm) in the spectral sensitivity characteristic, and can detect light having a wavelength of about 0.9 to 1.7 μm. . FIG. 5 is a diagram showing the relationship between the spectral radiance and wavelength of a black body. Infrared radiation energy (radiance) increases as the temperature of the object to be heated 20 increases.

The infrared sensor 26 of the present embodiment uses the indium gallium arsenide photodiode as described above as the infrared detection element 26a and adjusts the amplification factor of the amplifier 26b, thereby obtaining a detection signal as shown in FIG. It is configured as follows. In FIG. 7, the horizontal axis represents the temperature of the bottom surface portion of the object to be heated 20 facing the infrared incident region 24, and the vertical axis represents the output voltage of the infrared sensor 26, that is, the magnitude of the detection signal. A solid line 41 is a case where there is no disturbance, and a broken line 42 is a case where there is a disturbance. First, a case where there is no disturbance due to visible light or the like will be described. In the present embodiment, as shown in FIG. 7, the detection signal of the infrared sensor 26 has a magnitude of substantially zero when the temperature of the object to be heated 20 is lower than the detection lower limit temperature T0 (about 125 ° C.) (this embodiment When the temperature of the object to be heated 20 reaches the detection lower limit temperature T0 (about 125 ° C.), the output starts to be generated. The higher the temperature of the object to be heated, the larger the detection signal of the infrared sensor 26 In order to increase the inclination of the increase, that is, the characteristic is such that the increase rate is large. Note that the resolution of the microcomputer that measures the output voltage of the infrared sensor 26 used in the control unit 29 is 20 mV, and a value less than that value is measured as zero. An electromagnetic wave including infrared rays is radiated from the surface of an object whose absolute temperature is T (K). The total amount of radiant energy E (W / m ² ) per unit of time is theoretically E = represented by εσT ^4. Here, ε is an emissivity, and σ is a Stefan-Boltzmann constant. Accordingly, by selecting, as the detection element 26a, a sensor having a peak sensitivity characteristic at a necessary wavelength from among various elements capable of detecting infrared rays, and configured as shown in FIGS. 2 and 3, the detection voltage is amplified by the amplifier 26b. The characteristics having desired characteristics as shown in FIG. 7 can be obtained.

  FIG. 8 shows a flowchart of temperature control of the object to be heated 20 by the infrared sensor 26 of the control unit 29. When the power switch 9 is turned on (S1) and the temperature setting cook-off / on key 7d is turned on (S2), the control unit 29 inputs the output voltage of the infrared sensor 26 and outputs the output voltage X0 (initially) immediately after the start of heating. Detected as (detected value) (S3). The temperature setting is preset to 180 ° C. by default and is displayed on the temperature display portion 7e. When the set temperature is changed, it is changed using the down key 7b and the up key 7c (not shown in the flowchart). The detected output voltage X0 immediately after the start of heating is stored in the storage unit 29a (S4). The output voltage of the infrared sensor 26 is input again and detected as the current output voltage X (S5). A differential value of the current output voltage X is calculated (S6). The differential value may be a method of calculating a difference from the output voltage X before a predetermined time. A threshold for determining whether or not the temperature of the object to be heated has reached the set temperature is set (S7). A difference (increase amount ΔX) between the output voltage X0 immediately after the start of heating stored in the storage unit 29a and the current output voltage X is calculated, and it is determined whether or not the calculated increase amount ΔX is equal to or greater than a threshold value (S8). ).

  For example, in FIG. 7, the predetermined value is set to 0.4 V for the increase amount ΔX. If the temperature of the object to be heated 20 is T1 (for example, 30 ° C.) immediately after the start of heating (for example, immediately after the operation of the temperature setting cooking off / on key 7d), the object to be heated 20 when the increase amount ΔX becomes a predetermined value. The temperature is T3 (for example, 180 ° C.). Further, if the temperature of the object to be heated 20 is T2 (for example, about 152 ° C.) immediately after the start of heating, the temperature of the object to be heated 20 when the increase amount ΔX becomes a predetermined value becomes T4 (for example, about 185 ° C.). . Further, if the temperature of the object to be heated 20 is T4 (for example, about 185 ° C.) immediately after the start of heating, the temperature of the object to be heated 20 when the increase amount ΔX becomes a predetermined value becomes T5 (for example, about 200 ° C.). .

  When the control unit 29 determines that the increase amount ΔX is equal to or greater than the predetermined value (Yes in S8), the control unit 29 calculates a correction value based on the immediately preceding differential value δ (S9). The correction value can be calculated by a method of storing the relationship between δ and the correction value in advance and reading out the correction value corresponding to δ. A correction value is added to the threshold for the set temperature (threshold for the set temperature + correction value) as a new threshold (S10). If it is determined that the increase amount ΔX is equal to or greater than the threshold value (Yes in S11), the operation of the inverter circuit 28 is stopped or the heating output is reduced to suppress the temperature rise of the article to be heated 20 (S12). Even if the temperature decreases, while the increase amount ΔX is equal to or greater than the predetermined value, the heating output suppression operation or stop is continued (No in S13), and when the increase amount ΔX becomes less than the predetermined value (Yes in S13), ΔX0 Determines whether or not the elapsed time after reaching the threshold value (the value before correction) corresponding to the set temperature is t1 or more (S14), and if it is before the elapse of t1 time, the output is increased again or stopped. Heating output return control is performed such as resuming the heating operation of the heating coil 21 (S15), and the process returns to S11. The threshold value used for this heating output return control may be the same as the value for suppressing the heating output, or may be set to a different value such as providing a hysteresis lower than the value for suppressing the heating output. Good. If the elapsed time after ΔX0 reaches the threshold value (the value before correction) corresponding to the set temperature in S14 is t1 or more, the correction value is subtracted from the threshold value, and the threshold value is set to the set temperature. Returning to the threshold value (S16), heating output return control is performed such as increasing the output again or restarting the heating operation of the heating coil 21 that has been stopped (S15), and the process returns to S11. The magnitude of the heating output when returning can be selected as appropriate. In particular, as the temperature of the object to be heated 20 becomes higher, the change of the increase ΔX with respect to the temperature change of the object to be heated 20 changes more rapidly, and the temperature change of the smaller object to be heated 20 can be detected with higher sensitivity. For example, even if the object to be heated 20 is heated with a high heating output such as 3 kW, the temperature of the object to be heated 20 can be maintained at a high temperature with high responsiveness and can be prevented from excessively rising. For example, it can detect the high temperature before oil ignition, can distinguish between heating in an empty pan and stir-fry state, and can heat up to a temperature suitable for stir-fry with high heating power, so quickly raise the temperature Can do. Needless to say, the combination with other temperature control methods is not excluded.

  When determining that the increase amount ΔX is less than the predetermined value (No in S8), the control unit 29 determines whether or not the current output voltage X is equal to or higher than the output voltage X0 immediately after the start of heating stored in the storage unit 29a. When the current output voltage X is equal to or higher than the output voltage X0 immediately after the start of heating stored in the storage unit 29a (Yes in S17), the process returns to S8. When the current output voltage X is less than the heating start output voltage X0 stored in the storage unit 29a (No in S17), the output voltage X0 immediately after the start of heating stored in the storage unit 29a is set to the current output voltage X. Change (S18) and return to S8.

During heating, the output voltage usually increases. However, the infrared incident region 24 is not properly covered with the object to be heated 20 immediately after the start of heating, and when the object to be heated 20 is moved to an appropriate position during the heating, the output voltage X0 immediately after the start of heating. Is affected by a disturbance and is larger than that when not receiving a disturbance, and thus a phenomenon occurs in which the output voltage decreases despite heating. In this case (No in S17), the output voltage X0 immediately after the start of heating stored in the storage unit 29a is changed to the current output voltage X that is less likely to be affected by disturbance (S8). Thereafter, output control processing is performed based on the newly stored output voltage.

  As described above, when the temperature TS immediately after the heating of the object to be heated 20 is less than the detection lower limit temperature T0, the detection signal (output voltage) of the infrared sensor 26 is large even if the temperature of the object to be heated 20 changes. Zero and almost constant. Therefore, by heating, the temperature T of the article to be heated 20 exceeds the detection lower limit temperature T0, and the amount of increase ΔX of the current detection signal with respect to the detection signal immediately after the start of heating becomes a predetermined value. . At this time, the suppression temperature T3 of the article to be heated 20 does not depend on the temperature TS immediately after the start of heating, and is the suppression temperature T3 = T0 + ΔT3 corresponding to the point where the detection signal of the infrared sensor 26 increases by ΔX from zero. The controller 29 stops the operation of the inverter circuit 28 at the suppression temperature T3 or reduces the heating output to suppress the temperature rise of the article 20 to be heated.

  Further, when the temperature TS immediately after the heating of the article to be heated 20 is equal to or higher than the detection lower limit temperature T0, when the temperature T of the article to be heated 20 rises, the detection signal of the infrared sensor 26 increases and the increase rate gradually increases. . The temperature of the object to be heated when the increase amount ΔX becomes a predetermined value depends on the temperature TS immediately after the heating of the object to be heated is started. However, the higher the temperature T of the article to be heated 20, the greater the rate of increase of the detection signal, and the temperature change ΔT of the article to be heated corresponding to the predetermined increase ΔX becomes smaller. In the case of FIG. 7, ΔT3 (about 55 ° C.)> ΔT4 (about 38 ° C.)> ΔT5 (about 18 ° C.). Therefore, as the temperature T of the article to be heated 20 becomes higher, the predetermined increase amount ΔX can be obtained with a slight temperature increase ΔT. Therefore, the output is suppressed with good responsiveness or the heating is stopped to suppress the temperature increase. can do.

  Next, a case where there is a static disturbance due to visible light or the like will be described. The disturbance light does not depend on the temperature of the object to be heated 20. Therefore, as shown in FIG. 7, when there is a disturbance (broken line 42), the level is almost parallel to the level W of the disturbance light in the axial direction of the detection signal of the infrared sensor as compared with the case where there is no disturbance (solid line 41). Then it gets bigger. When the temperature TS immediately after the heating of the article to be heated 20 is lower than the detection lower limit temperature T0, the detection signal of the infrared sensor 26 is W and is substantially constant. FIG. 9 is a diagram illustrating a change with time of the output voltage of the infrared sensor 26 after the start of heating (t0). A solid line 43 is a case where there is no disturbance, and a broken line 44 is a case where there is a disturbance. In any case, the heating output is suppressed or the heating is stopped when the article to be heated 20 reaches the predetermined control temperature (t1). Therefore, the influence of static disturbance light can be removed by the configuration of the present embodiment.

  In this way, by controlling the temperature rise of the object to be heated 20 by the infrared sensor 26 and the control unit 29 having the above-described configuration, the temperature difference immediately after the start of heating or the influence of disturbance light such as visible light that is constantly input. The bottom surface temperature of the object to be heated 20 can be suppressed below the temperature around the set temperature, and the temperature increase of the object to be heated 20 can be controlled with high accuracy.

  Next, the influence of the reflectance of the object to be heated 20 on the detection signal of the infrared sensor 26 will be described with reference to FIG. In FIG. 10, a solid line 45 is an actual measurement result showing a relationship between the temperature of the object to be heated and the magnitude of the detection signal of the infrared sensor 26 when the object to be heated is a black body (reflectance = 1), and a broken line 46 is the broken line 46. It is the result of having calculated the characteristic in case heating material is magnetic stainless steel (reflectivity = 0.4) by multiplying the solid line 45 by the reflectivity 0.4. According to the figure, the output value of the infrared sensor 26 when the temperature of the black body is 180 ° C. is substantially equal to the output value of the infrared sensor 26 when the temperature of the magnetic stainless steel is 202 ° C., and the temperature difference is 22 ° C. It is. As described above, in FIG. 11, the radiant energy when the temperature of the black body is 180 ° C. and the radiant energy when the temperature of the magnetic stainless steel is 300 ° C. are substantially equal, and the temperature difference is 120 ° C. Thus, the influence of the difference in emissivity can be significantly suppressed as compared with the conventional control method.

When the temperature of the object to be heated is less than the detection lower limit temperature, the induction heating cooker of the present embodiment outputs a detection signal having a substantially constant magnitude with respect to the temperature of the object to be heated. When the temperature is equal to or higher than the detection lower limit temperature, the higher the temperature of the object to be heated, the larger the size and the rate of increase. Using the infrared sensor that outputs the detection signal, the output voltage X0 immediately after the start of heating. When the increase amount ΔX with respect to the (initial detection value) becomes a predetermined value or more, the output of the induction heating coil is reduced or the heating is stopped. Accordingly, when the temperature TS immediately after the heating of the heated object is less than the detection lower limit temperature T0, the induction is performed when the temperature T of the heated object becomes a certain temperature independent of the temperature TS immediately after the heating is started. The output of the heating coil can be reduced or the heating can be stopped. Even if the temperature TS immediately after the heating of the object to be heated is equal to or higher than the detection lower limit temperature T0, the temperature T of the object to be heated reduces the output of the induction heating coil or heats the oil before it smokes. Can be stopped. Furthermore, it is possible to hardly be affected by stationary disturbance light.

  In the induction heating cooker of the present embodiment, the control unit 29 stores the output voltage X0 (initial detection value) immediately after the start of heating in the storage unit 29a, and the current output voltage X is stored after the start of heating. When the output voltage X0 becomes smaller than the immediately following output voltage X0, the stored output voltage X0 immediately after the start of heating is changed to the current output voltage X. As a result, the infrared incident region 24 is not properly covered with the object to be heated 20 immediately after the start of heating, and when the object to be heated 20 is moved to an appropriate position during heating, the object to be heated 20 has a high temperature. Even when a food item such as water or vegetables is put into the object 20 to be heated, the object to be heated is prevented from being heated more than expected, and high-heat cooking can be realized safely.

  In the present embodiment, the output voltage X0 (initial detection value) of the infrared sensor immediately after the start of heating is used as a reference for measuring the increase ΔX, but the present invention is not limited to this. Instead of immediately after the start of heating, it may be simultaneously with the start of heating, or may be immediately before the start of heating, and the same effect can be obtained by selecting as appropriate. Further, the timing immediately after or immediately before the start of heating may be changed to such an extent that the gist of the invention is not changed. For example, a predetermined time may be delayed after detecting the heating start operation by the cut-off key 7a. Further, in the embodiment, the heating output is suppressed or the heating operation is stopped when the increase ΔX of the detection signal of the infrared sensor 26 with respect to the output value immediately after the start of heating becomes a predetermined value or more. In response to the increase in the amount of increase ΔX being greater than or equal to a predetermined value by an audible alarm device such as an alarm sound or a notification sound, the temperature of the object to be heated becomes a low temperature state or a high temperature state that reaches a predetermined temperature. (For example, indicating the preheating state of the frying pan) may be displayed or notified.

  The induction heating cooker according to the present invention can detect the temperature of an object to be heated with a simple configuration by detecting infrared rays emitted from the object to be heated, and can detect the temperature of the object to be heated in the vicinity of the temperature of the object to be heated. Because the output can be controlled with high responsiveness, it has the effect of improving the controllability of the object to be heated by the induction heating cooker and enhancing the cooking performance, and is used for general household and business use. Useful for heating cookers.

The perspective view of the induction heating cooking appliance by embodiment of this invention The block diagram of the induction heating cooking appliance by embodiment of this invention The partial expanded sectional view of the induction heating cooking appliance by embodiment of this invention Sensitivity characteristic diagram of infrared detection element of induction heating cooker according to an embodiment of the present invention The figure which shows the case where a to-be-heated material is a black body by the amount of infrared radiation energy which the infrared rays detection element of the induction heating cooking appliance by embodiment of this invention detects The figure which shows the transmittance | permeability of the filter arrange | positioned around the infrared sensor of the induction heating cooking appliance by embodiment of this invention The output characteristic figure of the infrared sensor with respect to the temperature of the to-be-heated object of the induction heating cooking appliance by embodiment of this invention The flowchart which shows the output control process based on the output of the infrared sensor of the control part by the induction heating cooking appliance of embodiment of this invention The output characteristic figure of an infrared sensor with respect to the elapsed time after the heating start of the induction heating cooking appliance by embodiment of this invention The output characteristic figure of the infrared sensor with respect to the temperature of the to-be-heated object from which the reflectance of the induction cooking appliance by embodiment of this invention differs Characteristics diagram of infrared sensor with respect to the temperature of an object to be heated in a conventional induction heating cooker

Explanation of symbols

1 outer case 2 top plate 3 left induction heating burner 4 right induction heating burner 5 left induction heating burner display section 6 right induction heating burner display section 7 left induction heating burner operation switch (operation section)
8 Right induction heating burner operation switch (operation unit)
9 Power switch 20 Heated object 21 Heating coil 21a Inner coil 21b Outer coil 22 Heating coil support base 23 Ferrite 24 Infrared incident area 25 Light guide tube 26 Infrared sensor 26a Photo diode (infrared detecting element)
26b Amplifier 27 Indicator LED
27a Light emitting area 27b Light guide 28 Inverter circuit 29 Control unit 29a Storage unit 30 Temperature sensor 31 Filter 31a Condensing lens

Claims (7)

A top plate for placing an object to be heated; a heating coil for inductively heating the object to be heated placed on the top plate; an inverter circuit for supplying a high-frequency current to the heating coil; and a lower part of the top plate. An infrared detector provided to detect the amount of infrared rays emitted from the heated object, and an amplifying unit for amplifying a signal detected by the infrared detecting element, and detecting a size corresponding to the temperature of the heated object An infrared sensor that outputs a signal, and a control unit that controls the output of the inverter circuit based on the output of the infrared sensor, and the infrared sensor controls the output of the induction heating coil by the control unit. As the temperature of the object to be heated increases in the vicinity of the control temperature range in which the temperature control of the heated object is performed, the detection signal whose magnitude and increase rate increase is output. The control unit reduces the output of the induction heating coil when an increase amount of the output value of the infrared sensor with respect to an initial detection value that is an output value of the infrared sensor immediately after the start of heating becomes a first predetermined value or more, or When the heating is stopped and the increase amount of the output value of the infrared sensor becomes less than a second predetermined value that is smaller than the first predetermined value, the output of the induction heating coil is increased. The induction heating cooker, wherein the first or / and second predetermined value is corrected so as to decrease as the differential value of increases. The infrared sensor outputs a detection signal whose magnitude is substantially constant with respect to the temperature of the heated object when the temperature of the heated object is less than the detection lower limit temperature, and the temperature of the heated object is the detection lower limit temperature. 2. The induction heating cooker according to claim 1, wherein when the temperature is equal to or higher than the temperature, the detection signal increases in size and rate of increase as the temperature of the object to be heated increases. 3. The induction heating cooker according to claim 1, wherein the initial detection value is an output value of the infrared sensor at the same time as the start of heating or immediately before the start of heating instead of immediately after the start of heating. The control unit includes a storage unit that stores an output value of the infrared sensor immediately after the start of heating as an initial detection value. When the output value of the infrared sensor becomes smaller than the initial detection value after the start of heating, the control unit The induction heating cooker according to claim 1 or 2, wherein a detection value is changed to an output value of the reduced infrared sensor. The control unit has a storage unit that stores the output value of the infrared sensor at the same time as the start of heating or immediately before the start of heating as an initial detection value, and the output value of the infrared sensor becomes smaller than the initial detection value after the start of heating. The induction heating cooker according to claim 3, wherein the initial detection value is changed to the output value of the reduced infrared sensor when the value is detected. The induction heating cooker according to claim 1 or 5, wherein the infrared detection element is formed of a photodiode using InGaAs. An operation switch for sending a signal to the control unit and instructing the heating coil to heat the heated part, wherein the operation switch is capable of temperature setting, and is configured to roughly control the heated object to a temperature set temperature. Item 7. The induction heating cooker according to any one of items 1 to 6.