JP4800345B2 - Induction heating cooker - Google Patents

Description

  This invention identifies non-magnetic low resistance pans such as aluminum pans and magnetic pans such as iron pans, and heats each pan at the optimum frequency, and also has multiple cooking modes such as boiling, keeping warm, stewing, fried food, etc. The present invention relates to an induction heating cooker optimally realized in each pan.

  In the case of a conventional non-magnetic pan, the conventional induction heating cooker prohibits transition to a temperature-controlled heating mode (see, for example, Patent Documents 1 to 4).

Japanese Patent Laying-Open No. 2005-26125 (paragraphs 0010, 0054, 0056, FIG. 3) JP 2003-282228 A (paragraphs 0009 to 0011, 0018, FIG. 4) JP 2006-12862 (paragraph 0022, FIG. 4) JP 2006-299024 A (paragraph 0003, FIG. 8)

In the induction cooking device described above, when heating a non-magnetic low resistance pan such as an aluminum pan, the temperature of the temperature sensor cannot be accurately detected due to the influence of heat generated from the heating coil due to an increase in the loss of the heating coil. Alternatively, the repulsive force generated in the heating coil and the aluminum pan raises the pan and the temperature cannot be accurately detected by the temperature sensor, so that temperature control is prohibited.
In this case, the heating coil loss increases or rises only when heating a non-magnetic low resistance pan such as an aluminum pan with a large power. However, the conventional induction heating cooker has a problem that it is inconvenient because temperature control is prohibited during heating of the aluminum pan even when the pan is heated with relatively small power.
The present invention has been made to solve the above-described problems, and aims to ensure usability by performing temperature control even when heating a non-magnetic low-resistance pan such as an aluminum pan.

The induction cooking device according to the present invention includes a heating coil for induction heating of a pan, a resonance capacitor connected in series or in parallel with the heating coil, and changing the resonance frequency by switching the capacity of the resonance capacitor according to the material of the pan. Switching means for detecting, temperature detecting means for detecting the temperature of the pan, an inverter for supplying the heating coil with a high-frequency current in the vicinity of the resonance frequency changed by the switching means, a current detecting means for detecting a current flowing through the inverter, a current Based on the detection results of the detection means, the pan material identification means for identifying whether the pan is a non-magnetic low resistance pan such as an aluminum pan or a magnetic pan such as an iron pan, and a predetermined temperature such as boiling, heat retention, stew, fried food, etc. cooking mode but has multiple cooking modes to be set, the temperature of the pan detected by the temperature detecting means has been selected by the user among a plurality of cooking modes To a predetermined temperature, and a control means for controlling the inverter, the control means, when the identification result of the pot material identifying means determines that the non-magnetic low-resistance pan, maintaining the oil temperature to a specific temperature prohibits control of the cooking mode frying, without disabling at least one control of the cooking mode warmth cooking and stew cooking, based on a detection result of the current detecting means to detect the presence or absence of a pan movement, pan movement Is detected, the electric power supplied to the heating coil is reduced by a predetermined value, and thereafter, the inverter is controlled so that the input electric power is not increased until the cooking mode ends .

  In the induction heating cooker according to the present invention, a non-magnetic low resistance pan like an aluminum pan is used in a cooking mode such as heat insulation and stewing in which a pan is heated with a relatively small power with little heating coil loss and no lifting. However, since temperature control is performed, usability is not impaired.

Embodiment 1 FIG.
1 is a diagram showing a configuration of an induction heating cooker according to Embodiment 1 of the present invention.
In the figure, an inverter 2 converts DC power obtained by converting a commercial AC power source 1 with a diode bridge 2a and a capacitor 2b into high-frequency power and supplies it to the heating coil 5, and includes switching elements 2c and 2d. The resonance capacitors 2e and 2f, the resonance capacitor switching relay 2g, and the current detection resistor 2h are connected to this. The control circuit 3 is connected to the operation panel 4, the heating coil 5, the top plate 6 on which the pan 8 is loaded, and the temperature sensor 7. The operation panel 4 is provided with a start switch 4a, an end switch 4b, a heat retention switch 4c, a water heater switch 4d, a stew switch 4e, a deep-fried food switch 4f, and a heating power adjustment dial 4g.

FIG. 2 is a flowchart showing the operation of the control circuit according to Embodiment 1 of the present invention.
Next, the operation of the first embodiment will be described with reference to FIGS.
When the start switch 4a of the operation panel 4 is pressed in step S01 in FIG. 2, the control circuit 3 performs pan material determination in step S02. At this time, the control circuit 3 turns on the relay 2g, alternately operates the switching elements 2c and 2d, converts the AC power source 1 converted into DC by the diode bridge 2a and the capacitor 2b, and converts it into high frequency power for heating. Supply to coil (half-bridge type). At this time, the switching elements 2c and 2d are driven at a higher frequency while avoiding the resonance frequency determined by the inductance value of the heating coil 5 and the combined capacitance of the resonance capacitors 2e and 2f. Do not. In this state, the control circuit 3 detects the current flowing through the current detection resistor 2h. If a current equal to or greater than a predetermined value flows, the placed pan is a low-resistance non-magnetic pan. Judge as a pan.

  In the case of a magnetic pan, the control circuit 3 performs steps S03 to S18. In this case, the control circuit 3 first determines in step S03 to step S06 whether or not the heat retention switch, stew switch, deep-fried food switch, or water heater switch has been pressed, and if the heat retention switch is pressed, the switch is pressed in step S07. The temperature at the time of being set is set to the target temperature T0. If the stew switch is pressed, the target temperature T0 is set to 60 ° C. in step S08. If the deep-fried food switch is pressed, the target temperature T0 is set to 160 ° C. in step S09. If the water heater switch is pressed, the target temperature T0 is set to 100 ° C. in step S10. If no switch is pressed, the control circuit 3 further checks the heating power adjustment dial in step S11. If the dial is turned in the large heating power direction in step S12, the control circuit 3 increases power (step S13). If the dial is turned in the small direction, the power is reduced (step S14). Further, the control circuit 3 compares the target temperature set in steps S07 to S10 with the current temperature in step S15. If the current temperature is lower than the target temperature, the control coil 3 and the resonance capacitor in step S16. The power is increased by increasing the heating coil current close to the resonance frequency determined by 2e and 2f. If the current temperature is higher than the target temperature, the power is decreased by moving the switching element drive frequency away from the resonance point in step S17. By controlling, the current temperature is controlled to be the target temperature. The control circuit 3 repeatedly executes the control from step S03 to step S17 until the end switch is pressed in step S18.

  When it is determined that the low-resistance nonmagnetic pan is determined in step S02, the control circuit 3 lowers the capacitance value of the resonant capacitor to increase the resonance frequency by opening the relay 2g, and power is supplied at a frequency higher than that of the magnetic pan. Steps S19 to S32 are performed so that the charging can be performed. In this case, the control circuit 3 first determines in step S19 to step S22 whether or not the heat retention switch, the stew switch, the deep-fried food switch, or the water heater switch has been pressed, and if the heat retention switch is pressed, the switch is pressed in step S23. The temperature at the time of being set is set to the target temperature T0. If the stew switch is pressed, the target temperature T0 is set to 60 ° C. in step S24. On the other hand, when the deep-fried food switch is pressed, when the water heater switch is pressed, or when no switch is pressed, the control circuit 3 does not control the temperature and checks the heating power adjustment dial in step S25. In step S26, the power is increased if the dial is turned in the large heating power direction (step S27), and the power is decreased if the dial is turned in the small heating power direction (step S28). Further, the control circuit 3 compares the target temperature set in step S23 to step S24 with the current temperature in step S29. If the current temperature is lower than the target temperature, the control circuit 3 increases the power in step S30. If the temperature is higher than the target temperature, the power is decreased in step S31 to control the current temperature to be the target temperature. The control from step S19 to step S31 is repeatedly executed until the end switch is pressed in step S32.

  According to the first embodiment, even if the type of the pan is a low-resistance nonmagnetic pan, the control circuit 3 performs temperature control at least when the pan is stewed and the heat retention switch is pressed. When the fried food switch is pressed, temperature control is not performed. As a result, the temperature control is performed even in the non-magnetic low-resistance pan such as an aluminum pan in the heat-retaining and stewed cooking mode in which the pan is heated with a relatively small power that causes little heating coil loss and does not lift. Therefore, usability is not impaired.

Embodiment 2. FIG.
In the first embodiment, the rising is prevented by allowing only the stew and heat retention with relatively little input power. In the second embodiment, there will be described the influence of the temperature increase of the heating coil itself due to the loss increase upon heating the low-resistance non-magnetic pan on the temperature sensor, and the method of preventing the pan from being lifted and realizing the temperature control of the fried food and the kettle.
Since the structure of the heating cooker in Embodiment 2 is the same as that of FIG. 1 of the said Embodiment 1, the block diagram and description here are abbreviate | omitted. FIG. 3 is a flowchart showing the operation of the control circuit in the second embodiment of the present invention, and FIG. 4 is a graph showing the relationship between the input power upper limit value and the cooking time in the second embodiment of the present invention.
Next, the operation of the second embodiment will be described based on FIG. 1, FIG. 3, and FIG.
When the start switch is pressed in step S101 in FIG. 3, the control circuit 3 clears the timer T indicating the cooking time to zero as an initial process in step S102. Next, the control circuit 3 determines the pot material in step S103. Since the method for determining the pot material and the process for determining that the pot is a magnetic pot are the same as those in the first embodiment, the flowchart and description of the operation are omitted. When it determines with a nonmagnetic low resistance pan, the control circuit 3 implements the process of step S104-step S123. In this case, the control circuit 3 determines whether or not the heat retention switch, the stew switch, the fried food switch, and the water heater switch are pressed in steps S104 to S107. If the heat retention switch is pressed, the switch is pressed in step S108. The temperature at which this is done is set to the target temperature T0. If the stew switch is pressed, 60 ° C. is set as the target temperature T0 in step S109. If the deep-fried food switch is pressed, the target temperature T0 is set to 160 ° C. in step S110.
If the water heater switch is pressed, the target temperature T0 is set to 100 ° C. in step S111. If none of the switches is pressed in steps S104 to S107, the power is increased if the heating power adjustment dial is turned in the large heating power direction in steps S112 to S116, and the power is decreased if the heating power adjustment dial is turned in the small heating power direction. Control in the direction you want. In step S115, the maximum heating power is limited to 2.5 kW.

In step S117 to step S122, the control circuit 3 counts up the timer T in step S117. In step S118, maximum power Wmax is determined according to the value of timer T. As shown in FIG. 4, the initial value of Wmax is 1.5 kW, and is set to decrease with the value of the timer T, that is, the elapsed cooking time. Specifically, the maximum power Wmax is determined by the following mathematical formula (step S118).
Wmax = W (T)
However, W (T) = 1.5 (0 <T <A),
W (T) = − kT + (kA + 1.5) (A <T <B),
W (T) = n (B <T)
Here, T is a timer value, A and B are different predetermined times, and k and n are constants.
Alternatively, the relationship between the cooking time T and the maximum power Wmax as shown in FIG. 4 is stored in a storage device (not shown) as a table, and Wmax corresponding to the timer T is acquired by referring to this table. Good.
In step S119, the target temperature is compared with the current temperature. If the current temperature is higher than the target temperature, the power is lowered in step S122. If the current temperature is lower than the target temperature, the power is increased in step S121, but if the power has reached the maximum power Wmax in step S120, no further increase is performed. This operation is continued until the end switch is pressed in step S123.

According to the second embodiment, in the case of a non-magnetic low-resistance pan, by the operation as described above, the heating power is reduced during temperature control, so the heating coil loss is small and the influence on the temperature sensor can be suppressed and accurate temperature control is performed. Can do. In addition, by limiting the power to a relatively small power, it is possible to suppress the rise of the pan. Furthermore, in anticipation of the evaporation of moisture and lightening the weight, the upper limit value of the heating power is lowered according to the cooking time, so that even when the pot weight becomes light at the end of cooking, the pan can be prevented from rising and the usability is not impaired.
Although the heating power upper limit value is lowered according to the cooking time, the heating power upper limit value may be lowered according to the integrated value of the input power. In this case, the input power is integrated and, as shown in FIG. 14, the same effect can be obtained by limiting the input power with the input power upper limit value corresponding to the integrated power.

Embodiment 3 FIG.
Since the structure of the heating cooker in Embodiment 3 is the same as that of FIG. 1 of the said Embodiment 1, the block diagram and description here are abbreviate | omitted. FIG. 5 is a flowchart showing the operation of the control circuit in the third embodiment of the present invention, and FIG. 6 is a graph showing the relationship between the target temperature and the cooking time in the third embodiment of the present invention.
Next, the operation of the third embodiment will be described based on FIG. 1, FIG. 5, and FIG.
When the start switch is pressed in step S201 in FIG. 5, the control circuit 3 clears the timer T indicating the cooking time to zero as an initial process in step S202. Next, the control circuit 3 determines the pot material in step S203. Since the method for determining the pot material and the process for determining that the pot is a magnetic pot are the same as those in the first embodiment, the flowchart and description of the operation are omitted. When it determines with a nonmagnetic low resistance pan in step S203, the control circuit 3 implements step S204-step S223. In this case, the control circuit 3 determines whether or not the heat retention switch, the stew switch, the deep-fried food switch, and the water heater switch are pressed in Steps S204 to S207. If it is determined that the control circuit 3 is pressed, the control circuit 3 performs Steps S208 to S211. Set the target temperature corresponding to each switch. Here, the target temperature is changed in accordance with the cooking elapsed time T as shown in the target temperature during frying in FIG. Immediately after the start of cooking, the temperature is lower than the final target temperature, and the final target is gradually reached according to the timer T counted in step S217. Similarly, in the case of heat retention, boiling and boiling, the final target temperature is gradually reached. In step S219, the target temperature is compared with the current temperature. If the current temperature is higher than the target temperature, the power is reduced in step S220. If the current temperature is lower than the target temperature, the power is increased in step S219. Thus, control is performed so that the current temperature becomes the target temperature. In step S221 and step S222, if the final temperature is not reached even after a predetermined time has elapsed from the start of cooking, the process is forcibly terminated. Since the operations in steps S212 to S216 are the same as the processes in steps S25 to S28 in the first embodiment when the heat retention switch, the stew switch, the fried food switch, and the hot water switch are not pressed, the description thereof is omitted. The above operation is continued until the end switch is pressed in step S223.

  According to this third embodiment, as described above, in the case of a low resistance non-magnetic pan, the final target temperature is controlled gradually, so that no large heating power is instantaneously applied. It is possible to hold up and keep the usability. That is, since the target temperature is gradually increased to reach the final target, it is not necessary to increase the thermal power more than necessary, and cooking can be performed with thermal power that does not cause floating.

Embodiment 4 FIG.
Since the structure of the heating cooker in Embodiment 4 is the same as that of FIG. 1 of the said Embodiment 1, the block diagram and description here are abbreviate | omitted. FIG. 7 is a flowchart showing the operation of the control circuit in the fourth embodiment of the present invention.
Next, the operation of the third embodiment will be described based on FIG. 1 and FIG.
When the start switch is pressed in step S301 in FIG. 7, the control circuit 3 clears a counter N indicating the number of retries to zero as an initial process in step S302. Next, the control circuit 3 determines the pot material in step S303. Since the method for determining the pot material and the process for determining that the pot is a magnetic pot are the same as those in the first embodiment, the flowchart and description of the operation are omitted. When it determines with a nonmagnetic low resistance pan in step S303, the control circuit 3 implements step S304-step S325. In this case, the control circuit 3 determines whether or not the heat retention switch, the stew switch, the deep-fried food switch, and the kettle switch are pressed in Steps S304 to S307. If it is determined that the control circuit 3 is pressed, the control circuit 3 performs Steps S308 to S311. Set the target temperature corresponding to each switch. Next, the control circuit 3 detects the movement of the pan in step S317. When the current detected by the current detection resistor 2h changes more than a predetermined value despite the fact that the driving frequency of the switching elements 2c and 2d has not changed, the control circuit 3 determines that the pan has moved due to the pan rising. To do. This is because the current flowing through the heating coil changes because the positional relationship between the heating coil 5 and the pan 8 changes and the impedance viewed from the heating coil 5 changes.

  If it is determined that the pan has moved, the control circuit 3 sets the maximum power to the current power in step S318 and increments the counter N by one. In step S319, the control circuit 3 checks the value of the counter N. When the value of the counter N is equal to or greater than the predetermined value, that is, when the number of times the pan has moved reaches the predetermined number, the control circuit 3 stops the cooking control and stops supplying power to the heating coil. If it is equal to or less than the predetermined number, the control circuit 3 performs the processes of steps S323 to S325. The control circuit 3 compares the target temperature with the current temperature in step S323. If the current temperature is higher than the target temperature, the control circuit 3 lowers the power in step S324, and if the current temperature is lower than the target temperature, the control circuit 3 performs in step S323. By increasing the electric power, the current temperature is controlled to become the target temperature. However, when the power reaches the maximum power Wmax in step S322, no further increase is performed. In addition, since the operation of step S312 to step S316 is the same as the process of step S25 to step S28 of the first embodiment in the case where the heat retention switch, the stew switch, the deep-fried food switch, and the water heater switch are not pressed, description thereof will be omitted. The above operation is continued until the end switch is pressed in step S325.

  According to the fourth embodiment, when it is determined that the pan has moved a predetermined number of times or more by the above operation, the control circuit stops the cooking control and stops the power supply to the heating coil. In addition, since the power is limited below the heating power at which the pan rises, the maximum power can be input to the pan as long as it does not occur, so the usability is not impaired.

Embodiment 5 FIG.
Since the structure of the heating cooker in Embodiment 5 is the same as that of FIG. 1 of the said Embodiment 1, the block diagram and description here are abbreviate | omitted. FIG. 8 is a flowchart showing the operation of the control circuit according to the fifth embodiment of the present invention, and FIGS. 9 and 10 explain the operation of the fifth embodiment. FIG. 9 is a graph showing the relationship between the total weight of the pan and the contents in Embodiment 5 of the present invention and the temperature rise after the predetermined power integrated value is input. When the total weight of the pan and the contents is heavier, the temperature rise of the pan is smaller, and the lighter the temperature is, the larger the temperature rise is. Moreover, FIG. 10 is a graph which shows the relationship between the maximum input electric power in Embodiment 5 of this invention, and the total weight of a pan and the content, and it is a pan of the pan with respect to the total weight of a pan and the content. It shows the maximum power that can be input within the range that does not cause lift.
Next, the operation of the fifth embodiment will be described with reference to FIGS. 1 and 8 to 10.
When the start switch is pressed in step S401 in FIG. 8, the control circuit 3 determines the pan material in step S402. Since the method for determining the pot material and the process for determining that the pot is a magnetic pot are the same as those in the first embodiment, the flowchart and description of the operation are omitted. When it determines with a nonmagnetic low resistance pan in step S402, the control circuit 3 implements step S403-step S422. In this case, in step S403, the control circuit 3 inputs predetermined power for a predetermined time and measures the temperature rise of the temperature sensor. As the total weight of the pan and contents increases, the specific heat also increases, so the relationship between the temperature rise and the weight is as shown in FIG. Therefore, the control circuit 3 estimates the total weight of the pan and the contents by referring to a formula of the relationship shown in FIG. 9 or a table of a storage device (not shown) in which the relationship shown in FIG. 9 is registered from the temperature rise value. Further, in step S404, the control circuit 3 determines the maximum power Wmax from the estimated weight in the same manner as described above based on the graph of FIG.

  Next, in step S405 to step S408, the control circuit 3 determines whether or not the heat retention switch, the stew switch, the deep-fried food switch, or the water heater switch has been pressed. If it is determined that the switch has been pressed, the control circuit 3 proceeds to step S409 to step S412. Set the target temperature corresponding to each switch. Next, the control circuit 3 compares the target temperature T0 with the current temperature in step S413. If the current temperature is higher than the target temperature T0, the power is reduced in step S416, and the current temperature is lower than the target temperature T0. Controls the current temperature to be the target temperature by increasing the power in step S415. However, when the power reaches the maximum power Wmax in step S414, no further power increase is performed. When the heat retention switch, the stew switch, the fried food switch, or the water heater switch is not pressed, the control circuit 3 increases the power if the heating power adjustment dial is turned in the large heating power direction in steps S417 to S421 (step S420). If it is turned in the small direction, the power is controlled to decrease (step S421). Further, the control circuit 3 limits the power (thermal power) so as not to exceed the maximum power Wmax in step S419.

  According to the fifth embodiment, even if a low-resistance non-magnetic pan having a large content and a heavy weight is controlled by the above-described control, even if it is a low-resistance non-magnetic pan having a small content and a light weight, the maximum electric power is within a range in which no lifting occurs. Can be used, so usability is not impaired.

Embodiment 6 FIG.
Since the structure of the heating cooker in Embodiment 6 is the same as that of FIG. 1 of Embodiment 1, the configuration diagram and description here are omitted. In addition, since the weight detection of the pan and the contents in the sixth embodiment is the same as the description of FIG. 9 in the fifth embodiment, the description thereof is omitted. FIG. 11 is a flowchart showing the operation of the control circuit in the sixth embodiment of the present invention, and FIG. 12 shows the relationship between the power reduction amount and the total weight of the pan and the contents in the fifth embodiment of the present invention. It is a graph which shows.
Next, the operation of the sixth embodiment will be described based on FIG. 1, FIG. 9, FIG. 11, and FIG.
When the start switch is pressed in step S501 in FIG. 11, the control circuit 3 determines the pot material in step S502. Since the method for determining the pot material and the process for determining that the pot is a magnetic pot are the same as those in the first embodiment, the flowchart and description of the operation are omitted. When it determines with a nonmagnetic low resistance pan in step S502, the control circuit 3 implements step S503-step S522. In this case, the control circuit 3 inputs a predetermined power for a predetermined time in step S503 and measures the temperature rise of the temperature sensor. As the total weight of the pan and contents increases, the specific heat also increases, so the relationship between the temperature rise and the weight is as shown in FIG. Therefore, the control circuit 3 estimates the total weight of the pan and the contents by referring to a formula representing the relationship of FIG. 9 or a table of a storage device (not shown) in which the relationship of FIG. 9 is registered from the temperature rise value. Further, in step S504, the control circuit 3 determines the power reduction amount ΔW from the estimated weight based on the graph of FIG.

  Next, in step S505 to step S508, the control circuit 3 determines whether or not the heat retention switch, the stew switch, the deep-fried food switch, or the water heater switch has been pressed. If it is determined that the switch has been pressed, the control circuit 3 proceeds to step S509 to step S512. Set the target temperature corresponding to each switch. Next, the control circuit 3 compares the target temperature T0 with the current temperature in step S513. If the current temperature is higher than the target temperature T0, the power is reduced in step S515, and the current temperature is lower than the target temperature T0. Controls the current temperature to be the target temperature T0 by increasing the power in step S414. Next, the control circuit 3 determines whether or not the pan has moved in step S516. The determination method is the same as step S317 in FIG. If it is determined that the pan has moved, the control circuit 3 reduces the power by ΔW. When the heat retention switch, the stew switch, the deep-fried food switch, and the water heater switch are not pressed, the control circuit 3 increases the electric power if the heating power adjustment dial is turned in the large heating power direction in steps S518 to S521 (step S520). If it is turned in the small direction, the power is controlled to decrease (step S521). The above operation is continued until the end switch is pressed in step S522.

  According to the sixth embodiment, since the power when the pan is lifted is lowered according to the weight by the above operation, the width of the pan is minimized, the influence on the power control is suppressed, and the usability is not impaired.

Embodiment 7 FIG.
Since the structure of the heating cooker in Embodiment 7 is the same as that of FIG. 1 of the said Embodiment 1, the block diagram and description here are abbreviate | omitted. Moreover, since the weight detection of the pan + contents in the seventh embodiment is the same as that in the fifth embodiment in FIG. 9, the description thereof is omitted.
Although not shown in FIG. 1, it has a voice output means or a display means, and the control circuit 3 has a function of notifying the user of the estimated weight.

  The user can be urged to confirm the weight, and the usability is not impaired.

  Although the above embodiment has been described on the assumption that the induction heating coil and the resonance capacitor are connected in series, the induction heating coil and the resonance capacitor may be connected in parallel.

Embodiment 8 FIG.
FIG. 13 shows the configuration of the heating cooker in the eighth embodiment. In FIG. 13, a current detection resistor 2i for detecting a current flowing through the switching element 2c is added to FIG. 1 of the first embodiment. Since others are the same, description is abbreviate | omitted. The control circuit 3 performs pan material determination. At this time, the control circuit 3 turns on the relay 2g, operates the switching elements 2c and 2d alternately, converts the AC power source 1 into DC power by the diode bridge 2a and the capacitor 2b, and converts it into high frequency power to heat it. Supply to coil (half-bridge type). When the inductance value of the heating coil 5 is L, the resistance is R, the capacitance of the resonant capacitors 2e and 2f (hereinafter referred to as capacitance) is C1, and the drive frequency of the switching element is f.

Since the current flows most easily at this time, the driving frequency of the switching elements 2c and 2d avoids the resonance frequency and is driven at a frequency higher than that so that no large electric power enters the pan 8. To. In this state, the control circuit 3 detects the current flowing through the current detection resistor 2h. If a current equal to or greater than a predetermined value flows, the placed pan is a low-resistance non-magnetic pan. Judge as a pan. When it determines with a low resistance nonmagnetic pan, the relay 2g is opened and the resonance capacitor 2f is disconnected. As a result, the resonance capacitor is only 2e, and the capacitance C1 portion is reduced. Therefore, the resonance frequency determined by the capacitance of the resonance capacitor 2e and the inductance of the heating coil 5 is increased. The control circuit 3 operates the switching elements 2c and 2d alternately at a frequency higher than the resonance frequency determined by the capacity of the resonance capacitor 2e and the inductance of the heating coil 5, and confirms whether the relay 2g is switched. When the resonance capacitor 2f is not disconnected due to the failure of the relay 2g, the resonance capacitor has a combined capacity of 2e and 2f, the resonance frequency remains low, and the drive frequency and the resonance point are separated. It becomes difficult for current to flow. Therefore, the control circuit 3 determines that the relay 2g has failed when the current flowing through the current detection resistor 2h or 2i is equal to or less than a predetermined value.

の部分がマイナスとなり、スイッチング素子から見たインピーダンスはコンデンサ負荷となり、電流検出用抵抗２ｉにはコンデンサ負荷を充電する大きな突入電流が流れる。よって、制御回路３は、電流検出用抵抗２ｈもしくは２ｉに流れる電流が所定値以上の場合、リレー２ｇが故障したと判定する。 In addition, after the heating of the low-resistance nonmagnetic pan, the control circuit 3 turns on the relay 2g, connects the resonant capacitor 2f to the circuit, and performs pan material determination at the time of reheating. At this time, when the relay 2g fails and the pan determination is performed in a state where the resonance capacitor 2f is not connected to the circuit, the resonance point remains a high resonance point determined by the capacity of the resonance capacitor 2e and the inductance of the heating coil 5. It becomes. If the pan material determination is performed in such a state, since the pan material determination is performed at a frequency closer to the resonance point, a large current flows through the current detection resistor 2h. Moreover, although it is closer to the resonance point, the pan material determination is performed at a frequency lower than the resonance point. in this case,

Is negative, the impedance viewed from the switching element is a capacitor load, and a large inrush current for charging the capacitor load flows through the current detection resistor 2i. Therefore, the control circuit 3 determines that the relay 2g has failed when the current flowing through the current detection resistor 2h or 2i is equal to or greater than a predetermined value.

  As described above, when the failure of the relay 2g is detected, the control circuit 3 has failed to the user with sound, light, display, etc. via notifying means (sound output means, lamp, display means) not shown. This is notified, and the driving of the switching elements 2c and 2d is stopped to stop the heating. As a result, it is possible to prevent the circuit from being abnormally heated by being used in an abnormal state because the circuit constants are not switched normally.

  The control circuit 3 constitutes a pot material determining means for determining whether the pot is a low-resistance nonmagnetic pot or a magnetic pot based on the current flowing through the current detection resistor 2h, and a control means having other functions. The current detection resistors 2h and 2i constitute current detection means.

  As an application example of the present invention, there is an induction heating cooker for heating a non-magnetic low resistance pan such as an aluminum pan.

It is a figure which shows the structure of the induction heating cooking appliance in Embodiment 1-7 of this invention. It is a flowchart which shows operation | movement of the control circuit in Embodiment 1 of this invention. It is a flowchart which shows operation | movement of the control circuit in Embodiment 2 of this invention. It is a graph which shows the relationship between the input electric power upper limit in Embodiment 2 of this invention, and cooking time. It is a flowchart which shows operation | movement of the control circuit in Embodiment 3 of this invention. It is a graph which shows the relationship between target temperature and cooking time in Embodiment 3 of this invention. It is a flowchart which shows operation | movement of the control circuit in Embodiment 4 of this invention. It is a flowchart which shows operation | movement of the control circuit in Embodiment 5 of this invention. It is a graph which shows the relationship between the total weight of the pan and the contents in Embodiments 5-7 of this invention, and the temperature rise after predetermined | prescribed electric power integrated value addition. It is a graph which shows the relationship between the maximum input electric power in Embodiment 5 of this invention, and the total weight of a pan and the contents. It is a flowchart which shows operation | movement of the control circuit in Embodiment 6 of this invention. It is a graph which shows the relationship between the electric power fall amount in Embodiment 5 of this invention, and the total weight of a pan and the contents. It is a figure which shows the structure of the heating cooker in Embodiment 8 of this invention. It is a graph which shows the relationship between the input electric power upper limit in Embodiment 2 of this invention, and integrated power.

Explanation of symbols

  1 commercial AC power supply, 2 inverter, 2a diode bridge, 2b capacitor, 2c, 2d switching element, 2e, 2f resonant capacitor, 2g resonant capacitor switching relay, 2h, 2i current detection resistor, 3 control circuit, 4 operation panel, 4a Start switch, 4b End switch, 4c Insulation button, 4d Water heater button, 4e Stew button, 4f Deep-fried food button, 4g Heating adjustment dial, 5 Heating coil, 6 Top plate, 7 Temperature sensor, 8 Pan.

Claims (11)

A heating coil for induction heating the pan,
A resonant capacitor connected in series or in parallel with this heating coil;
Switching means for changing the resonance frequency by switching the capacity of the resonance capacitor according to the material of the pan,
Temperature detecting means for detecting the temperature of the pan;
An inverter for supplying a high-frequency current in the vicinity of the resonance frequency changed by the switching means to the heating coil;
Current detection means for detecting the current flowing through the inverter;
Based on the detection result of this current detection means, the pan material identification means for identifying whether the pan is a non-magnetic low resistance pan such as an aluminum pan or a magnetic pan such as an iron pan,
Kettle selected, heated, stew, fried, etc., each have a plurality cooking modes of the predetermined temperature is set, the temperature of the pan detected by previous SL temperature detecting means by a user among the plurality of cooking modes Control means for controlling the inverter so that the predetermined temperature of the cooking mode is set,
Wherein, when the identification result of the pot material identifying means determines that the non-magnetic low-resistance pot, prohibits the control of the cooking mode frying to keep the oil temperature to a specific temperature, the heat insulating cooking and the Do not prohibit control of at least one cooking mode of stewed cooking,
Based on the detection result of the current detection means, the presence / absence of pan movement is detected. The induction heating cooker characterized by controlling the said inverter so that it may not be performed .   When the identification result of the pan material identification means is determined to be a non-magnetic low resistance pan, the control means prohibits control of the cooking mode of the fried food cooking and the boiling water,
  The induction heating cooker according to claim 1, wherein control of at least one cooking mode of the heat insulation cooking and the stew cooking is not prohibited. It said control means counts the number of times of detection of the pot moving, if the detected number reaches a predetermined value, the induction heating cooker of claim 1, wherein the stop control of the inverter. Comprising a weight estimation means to estimate the total weight of the pan and contents,
When the identification result of the pan material identification means is a non-magnetic low resistance pan, the control means determines the maximum input power according to the estimated weight estimated by the weight estimation means, regardless of the selected cooking mode. The induction heating cooker according to claim 1 , wherein power supply exceeding the maximum input power is prohibited. Comprising a weight estimation means to estimate the total weight of the pan and contents,
When the identification result of the pan material identification means is a non-magnetic low resistance pan, the control means detects the presence or absence of pan movement based on the detection result of the current detection means. The induction heating cooker according to claim 1, wherein the amount of power reduction is determined from the estimated weight estimated by the estimating means and the integrated input power value. Weight estimation means for estimating the total weight of the pan and contents;
An informing means for performing sound or display,
When the identification result of the pan material identification unit is a non-magnetic low resistance pan, the control unit causes the notification unit to notify by voice or display, and prompts the user to confirm the weight of the pan and the contents. The induction heating cooker according to claim 1 . The induction heating cooker according to any one of claims 4 to 6 , wherein the weight estimating means estimates the total weight of the pan and the contents from the integrated value of the input power and the rate of change of the temperature sensor. Before SL control means, said switching means operates immediately or heating at the start, the inverter is controlled so that the current is reduced to be supplied to the heating coil, the supply to the heating coil which is detected by said current detecting means at this time The induction heating cooker according to claim 1, wherein a failure of the switching means is detected based on a high-frequency current value to be performed. The control means switches the resonance capacitor from non-magnetic low-resistance pot heating to magnetic pot heating, but the switching means fails when the current of the inverter detected by the current detection means exceeds a predetermined value. The induction heating cooker according to claim 8 , wherein the induction heating cooker is determined. The control means has failed when the current of the inverter detected by the current detection means is equal to or less than a predetermined value even though the resonance capacitor is switched from magnetic pot heating to non-magnetic low resistance pot heating. The induction heating cooker according to claim 8 , wherein the induction heating cooker is determined. Providing a notification means,
Wherein the control means when it is determined that the switching means is faulty, claim 8, wherein an inverter is prohibited driving of the heating coil, characterized thereby notifying that it is the failure to the notification means The induction heating cooking appliance in any one of thru | or 10 .

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