JP6263729B2 - rice cooker - Google Patents

Description

  The present invention relates to a rice cooker used for general household or business use, which includes a heating coil for induction heating a pan.

  Conventionally, this kind of rice cooker has what was comprised so that the resonance sound (pot sound) generated when the pan is induction-heated may be reduced (for example, refer to patent documents 1).

  FIG. 7 shows an inverter of a conventional rice cooker described in Patent Document 1. As shown in FIG. In FIG. 7, a DC power source 35 includes a rectifier 35a and a capacitor 34b, and receives an AC power source 36 to output a DC voltage. The high frequency inverter 32 receives a DC voltage output from the DC power supply 35, and the heating coil 32a and the resonance capacitor 32c resonate due to switching of the semiconductor switching element 32b, thereby generating a high frequency magnetic field in the heating coil 32a. When this high frequency magnetic field is linked to the pan 1, an eddy current flows through the pan 1, and the pan 1 itself generates heat. The current and magnetic field generated at this time cause vibration in the heating coil 32a and the pan 1 itself. When this vibration matches the natural vibration frequency of the pan 1, a strong vibration occurs, and the vibration is heard as a resonance sound (also referred to as a pot sound) from the rice cooker. Here, for convenience, the fact that the pot 1 resonates is also referred to as a pot sound. Furthermore, it has been found that the pan 1 has a strong resonance frequency region in which resonance is strong and a weak resonance frequency region in which the pan 1 weakly resonates.

  In order to reduce this resonance sound (panning sound), the pan 1 having a nonmagnetic metal layer on the outer surface is heated, and the operating frequency of the high-frequency inverter 32 matches the natural vibration frequency or higher order frequency of the pan 1. In order to avoid this, an upper limit is set for the conduction time of the semiconductor switching element 32b.

JP 2001-333856 A

  However, in the conventional configuration, the squealing noise when the oscillation of the inverter 32 is stable is reduced, but the heating output from the start of oscillation to the stable oscillation time is increased from 0 to a predetermined heating output. During this time, a rumbling sound will be generated. When cooking rice, I don't care much about the sound of boiling rice and water in the pot, but the heat retention may move the heating output of a certain period for a long time. Sometimes there is a warming operation at midnight, and it feels quite loud. Moreover, although not as loud as this resonance sound, a beating sound with a natural frequency is generated even when the heating output is stable (when oscillation is stable). There was a problem that it was not solved only by setting the switching frequency at the time of oscillation stabilization so as to prevent these rumbling sounds.

  This invention solves the said conventional subject, and it aims at providing the rice cooker which can maintain a quiet and comfortable environment also at the time of long-time heat retention operation | movement.

In order to solve the conventional problems, rice cooker of the present invention includes a pot to be housed in the body, and pan temperature detector for detecting the temperature of the pan, and a DC power supply, induction heating said pot a heating coil, and a resonant capacitor which resonates with the heating coil, wherein the heating coil supplies current to the heating coil from the DC power source, said heating coil and the resonance capacitor resonates by blocking by conducting a semiconductor switching element resonant current to flow continuously to the heating coil, maintaining a stable heat output heating power by changing the conduction time of the semiconductor switching element by changing the operating frequency of the current flowing through the heating coil including control performs the cook-up process to boil water in the stable heating output and heating the pot as the first stable heating output in the pot to The pot after the completion of the temperature detection portion of the detection result based on controlling the heating output cooking operation and the cooking operation, the stable heating power to heat the pot as the second stable heating output the pan temperature detection unit of a detection result said US executable control unit warmth operation incubating the inside pot based on, and an input unit including a cooking key to start the cooking operation, in advance, the resonance tone by the pot and the resonance current generated The pan that has the stable heating output smaller than the first stable heating output and larger than the second stable heating output is selected, and the control unit starts the heating operation and then the first stable heating output. , said controlled to be greater than the stable heating output, said second stable heating output, control such that the resonance sound is less than the heating power generated to resonance sound due to the pot and the resonance current is generated It is those that.

  As a result, during rice cooking operation and heat retention operation, the operating frequency during stable heating output is prevented from becoming a frequency at which a pot sound is generated, and during warming operation during transient operation until reaching stable heating output. However, it becomes possible to prevent the operating frequency from becoming a frequency at which a pot sound is generated.

  The rice cooker of the present invention can be heated at a stable heating output while avoiding the operating frequency from becoming a frequency at which a pot sound is generated during the rice cooking operation and the heat retaining operation, and at the time of the heat retaining operation, the stable heating output Since the operating frequency can be prevented from becoming a frequency at which a panning sound is generated even during a transient operation until reaching, a quiet and comfortable environment can be maintained even during a long-time warming operation.

The circuit block diagram of the rice cooker in Embodiment 1 of this invention Cutaway sectional view of the main part of the rice cooker Time chart showing the change in heating output during the transient operation of the rice cooker Flow chart showing the operation of the rice cooker The flowchart which shows the heat retention operation | movement of the rice cooker in Embodiment 2 of this invention. Flow chart showing the operation of the rice cooker Circuit block diagram of conventional rice cooker

1st invention is the resonance accommodated in the pan stored in the inside of the main body, the pan temperature detection part which detects the temperature of the pan, a direct-current power supply, the heating coil which induction-heats the pan, and the heating coil By connecting with a capacitor, current is supplied to the heating coil from the DC power supply to the heating coil, and by cutting off, the heating coil and the resonant capacitor resonate and a resonance current continuously flows to the heating coil. The semiconductor switching element to be controlled and the conduction time of the semiconductor switching element are changed to change the operating frequency of the current flowing in the heating coil to control the heating output to be maintained at the stable heating output, and the stable heating output is Based on the detection result of the pan temperature detector, including a cooking step of heating the pan as the first stable heating output and boiling the water in the pan After the completion of the rice cooking operation for controlling the heating output and the rice cooking operation, the heat is maintained by heating the pot with the stable heating output as the second stable heating output and keeping the rice in the pot warm based on the detection result of the pot temperature detecting unit. A control unit capable of performing an operation; and an input unit including a rice cooking key for starting the rice cooking operation, wherein the stable heating output in which a resonance sound is generated by the pan and the resonance current is the first stable The pan that is smaller than the heating output and larger than the second stable heating output is selected, and the controller, after starting the heating operation, uses the first stable heating output as a resonance sound due to the pan and the resonance current. There controlled to be greater than the stable heating output generated, the second stable heating output, in which the resonance sound is configured to control so as to be smaller than the heating output to be generated. Thus, a period is provided in which the first stable heating output is maintained higher than the heating output at which the resonance sound due to the resonance current flowing in the pan and the heating coil is generated, that is, the operating frequency is lower than the operating frequency at which the resonance sound is generated. Heating with a strong heating output necessary for rice cooking operations such as raising can be performed. Furthermore, the heating output that generates the resonance sound by using the second stable heating output that is lower than the heating output that generates the resonance sound due to the pan and the resonance current, that is, the operation frequency that is higher than the operation frequency that generates the resonance sound, during the heat retention operation It is possible to perform a heat insulation operation while avoiding the (operation frequency) region, and it is possible to maintain a quiet and comfortable environment even during a long heat insulation operation.

2nd invention is the resonance accommodated in the pan stored in the inside of the main body, the pan temperature detection part which detects the temperature of the pan, the DC power supply, the heating coil which induction-heats the pan, and the heating coil When connected to a capacitor, current is supplied to the heating coil from the DC power supply to the heating coil, and when the current is cut off, the heating coil and the resonant capacitor resonate, and a resonance current continuously flows to the heating coil. The semiconductor switching element to be controlled and the conduction time of the semiconductor switching element are changed to change the operating frequency of the current flowing in the heating coil to control the heating output to be maintained at the stable heating output, and the stable heating output is Based on the detection result of the pan temperature detection unit, including a cooking step of heating the pan as the first stable heating output and boiling the water in the pan After the rice cooking operation for controlling the heating output and the rice cooking operation, the control unit capable of executing a heat retaining operation for heating the pan and keeping the rice in the pan based on the detection result of the pan temperature detecting unit; An input unit including a rice cooking key for starting a rice cooking operation, wherein the control unit is configured to make the first stable heating output larger than the stable heating output at which resonance sound is generated by the pan and the resonance current. set, from the time of starting the heating of the insulation operation until it reaches the third heating output, performs a transient operation is increased by increasing the amount that is determined in advance for each elapse conduction time a predetermined time, the heating power is 3 When the heating power is reached, the heating power is immediately reduced to zero or low, and then the transient operation is repeated a predetermined number of times, and the third heating power is made smaller than the heating power at which the resonance sound is generated. During the heat insulation operation, the operating frequency is prevented from becoming the frequency at which the resonance sound is generated, and the period during which the heating output is stabilized is reduced to reduce the natural frequency pot sound generated when the heating output is stable. It can be heated while being cooked, and can maintain a quiet and comfortable environment even during long-time warming operation without causing deterioration of rice cooking and warming performance.

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

(Embodiment 1)
FIG. 1 is a circuit block diagram of a rice cooker according to the first embodiment of the present invention, and FIG. 2 is a fragmentary sectional view of the rice cooker.

  In FIG. 2, a pot 1 contains rice and water, and is stored in the main body 9 of the rice cooker. The pan 1 is heated from the bottom and side surfaces by the heating coil 2a. The semiconductor switching element 2b generates a high-frequency current in the heating coil 2a by switching. The pan temperature detection unit 3 detects the temperature of the bottom surface of the pan 1, and the control unit 7 inputs the detection temperature of the pan temperature detection unit 3 and executes the rice cooking operation and the heat retaining operation while controlling the heating output of the heating coil 2a. To do.

  In FIG. 1, a DC power supply 5 includes a rectifier 5a that inputs an AC power supply 6 and performs full-wave rectification, and a capacitor 5b connected between output terminals of the rectifier 5a. The input terminal of the inverter 2 is connected between both ends of the capacitor 5b. The inverter 2 includes a heating coil 2a for induction heating the pan 1, a reverse conduction type semiconductor switching element 2b, and a resonance capacitor 2c. One end of the heating coil 2a is connected to the high potential side of the DC power supply 5, the other end of the heating coil 2a is connected to the high potential side terminal of the semiconductor switching element 2b, and the low potential side terminal of the semiconductor switching element 2b is connected to the DC power supply 5. Is connected to the low potential side output terminal. The resonant capacitor 2c is connected to both ends of the heating coil 2a.

  The display operation unit 4 includes a rice cooking key 4a for inputting a command for starting the rice cooking operation, a heat retaining key 4b for inputting a command for starting the heat retaining operation, and an input unit 4e and a rice cooker including a turn key 4c for inputting the command for stopping the operation. Display unit that displays information and cautions that are occurring inside the rice cooker to the user when an abnormality occurs during operation (such as "Waiting", "Cooking rice", "Cooking completed") 4d.

  The control unit 7 controls the oscillation operation of the inverter 2 by controlling the conduction and interruption of the semiconductor switching element 2 b based on the signal from the display operation unit 4, and the pan temperature detection unit 3 that detects the temperature of the pan 1. Based on the detected temperature, the heating output of the inverter 2 is controlled to perform the rice cooking operation and the heat retaining operation. The rice cooking operation may be executed as soon as the rice cooking key 4a is pressed, or may be executed in accordance with a timer set time. During the rice cooking operation, the heating output at the time of stability becomes the first stable heating output P1 (for example, about 1000 W to 1400 W), and the heating output is operated by ON / OFF duty control to cook rice based on the rice cooking sequence. . At this time, the 1st stable heating output P1 is set to a value smaller than the heating output (for example, 700W to 900W) which a resonance sound generate | occur | produces. After the rice cooking operation is completed, the operation is shifted to the heat retaining operation, and the heat retaining control is performed so that the stable heating output is equal to or lower than the second stable heating output P2 (for example, 500 W) stored in the storage unit 7b. At this time, the second stable heating output P2 is set to a value smaller than the heating output at which the resonance sound is generated.

  A specific configuration of the control unit 7 and operations in the rice cooking operation and the heat retaining operation will be described below with reference to FIG.

  First, the case where the rice cooking operation is started will be described. The control part 7 performs a transient operation | movement until the heating output of the heating coil 2a reaches | attains the 1st stable heating output P1 from the initial heating output Po after starting a heating by rice cooking operation | movement. When the rice cooking key 4a is pressed, the control unit 7 starts the rice cooking operation immediately after that or according to the time set by the timer in response to an instruction from the display operation unit 4. The output control unit 7a reads the first stable heating output P1 from the storage unit 7b, and sends the initial conduction time T1o and the conduction time increase amount ΔT1 stored in the storage unit 7e to the conduction time setting unit 7f. The conduction time setting unit 7f sets the initial conduction time T1o as the timer time in the first timer 7c. Here, the initial conduction time T1o is the conduction time T1 when the heating output is set to the initial heating output Po. The conduction time increase amount ΔT1 is an increment of the conduction time T1 necessary for increasing the heating output by ΔP.

  When the initial conduction time T1o is set, the first timer 7c starts to count the time simultaneously with outputting the drive signal to the drive signal generator 7h, and cuts off the drive signal when the counted time reaches the initial conduction time T1o. To do. The drive signal generator 7h drives the semiconductor switching element 2b based on the drive signal of the first timer 7c, and shuts off the semiconductor switching element 2b when the drive signal is cut off.

  When the semiconductor switching element 2b conducts, the heating coil 2a is supplied with current from the DC power source 5 to the heating coil 2a. When the semiconductor switching element 2b is cut off, the heating coil 2a and the resonance capacitor 2c resonate and the resonance current continues to the heating coil 2a. Then flow. A resonance voltage generated in the heating coil 2a due to the resonance current flowing while the semiconductor switching element 2b is cut off is added to the DC power source 5 and applied to both ends of the semiconductor switching element 2b.

  The conduction timing detector 7i detects a resonance voltage generated in the heating coil 2a, and outputs a drive start signal to the first timer 7c after a predetermined delay time from the time when the detected voltage becomes zero by the resonance operation. The start timing of the drive start signal is set to the predetermined delay time so as to approach the time point when the voltage applied to the semiconductor switching element 2b is minimized or within the period in which a reverse current flows through the semiconductor switching element 2b. Adjusted to set to proper value.

  The first timer 7c outputs a drive signal again based on the drive start signal input from the conduction timing detector 7i and starts counting time. The first timer 7c shuts off the semiconductor switching element 2b again when the counted time reaches the initial conduction time T1o. Thereafter, by repeating this operation, a current continuously flows through the heating coil 2a, and the inverter 2 oscillates. The sum of the initial conduction time T1o of the semiconductor switching element 2b and the cutoff period of the semiconductor switching element 2b is the oscillation period of the high-frequency current flowing through the heating coil 2a.

  The input current detector 7d detects the input current of the AC power source 6 input by the DC power source 5 by inputting the output of the current transformer 8. Therefore, the detection output of the input current detection unit 7d corresponds to the heating output of the heating coil 2a. The zero volt detector 7j detects the time when the voltage of the AC power supply 6 becomes zero volt, that is, detects the zero point of the AC power supply 6, and outputs a pulse corresponding to this zero point. The output control unit 7a receives the zero volt pulse output from the zero volt detection unit 7j, and is currently set by the first timer 7c in synchronization with the zero point (approximately zero phase, approximately 180 degree phase, etc.) of the AC power supply 6. The conduction time increase amount ΔT1 is added to the conduction time T1. As a result, the output control unit 7a performs a transient operation to increase the heating output little by little as time elapses, and the input current detected by the input current detection unit 7d, that is, the heating output becomes the first stable heating output P1. Continue until it reaches.

  The operation after the heating output of the heating coil 2a reaches the stable heating output during the rice cooking operation will be described. The output control unit 7a receives the output signal of the input current detection unit 7d, and the driving time of the semiconductor switching element 2b so that the heating output when the output is stable becomes the first stable heating output P1 stored in the storage unit 7b. To control. 1st stable heating output P1 is set so that it may become larger than the heating output in which the resonance sound by the pan 1 and a resonance current generate | occur | produces, and is ON / OFF based on the temperature detected by the pan temperature detection part 3 which detects the temperature of the pan 1. Combined with output control by OFF duty, rice cooking operation is performed. The rice cooking operation includes a cooking process in which the pot 1 is heated with the stable heating output as the first stable heating output P1 and the water in the pot 1 is boiled, and a relatively large stable heating output is required.

  Next, the case where the heat retaining operation is started will be described. The warming operation may be started by pressing the warming key 4b of the display operation unit 4 or may be started by being automatically switched after the rice cooking operation is finished. Therefore, the heat retention key 4b may be omitted. Since the control in the heat retaining operation of the control unit 7 is basically the same as the control in the rice cooking operation, the difference from the control in the rice cooking operation will be described and the other description will be omitted. When the heat retaining operation is started, the output control unit 7a reads the second stable heating output P2 smaller than the first stable heating output P1 set by the rice cooking operation from the storage unit 7b, and sets it as the stable heating output. And based on the detection result of the pan temperature detection part 3, the heat retention operation | movement which controls the temperature of the rice in the pan 1 to the temperature suitable for heat retention is performed.

  The second stable heating output P2 set in the heat retaining operation is set to be smaller than the heating output at which a resonance sound is generated by the resonance current flowing through the pan 1 and the heating coil 2a. Similarly to the rice cooking operation, the output control unit 7a performs a transient operation of increasing the conduction time T1 by a predetermined increase amount ΔT1 every time a predetermined time elapses.

  About the rice cooker comprised as mentioned above, the operation | movement and an effect | action are demonstrated below, referring FIG. 3 and FIG.

  FIG. 3 shows a time chart showing a change in heating output during a transient operation during a heat retaining operation of the rice cooker in the first embodiment of the present invention. In FIG. 3, the heating output at the time of the heat retention operation | movement of a rice cooker is represented by the continuous line B, the heating output area | region where a pot sound occurs is represented by the oblique line part C, and the heating output at the time of rice cooking operation is represented by the broken line A.

  In FIG. 4, in step 20, presence / absence of key input from the display operation unit 4 is detected. If the rice cooking key 4a is input in step 21, the process proceeds to step 23. If the rice cooking key 4a is not input, the process proceeds to step 22. If it is determined in step 22 that the heat retention key 4b has not been input, the process returns to step 20. As described above, in steps 20 to 22, the process is repeated until there is a key input to the rice cooking key 4a or the heat retention key 4b.

  If the rice cooking key 4a is input, it will progress to step 23 and will set the 1st stable heating output P1 (for example, 1400W) which is the stable heating output for rice cooking operation | movement. Next, in step 24, a rice cooking sequence is executed, and the first stable heating output P1, which is a relatively high heating output, is varied from 1000W to 1400W by ON / OFF duty control, and the rice in the pan 1 is gelatinized. I do. As a result of the gelatinization of the rice in the pan 1 in step 25, it is determined whether or not the detected temperature Temp of the pan temperature detector 3 has reached the rice cooking operation end temperature (for example, 130 ° C.) and the rice cooking operation has been completed. If the rice cooking operation has not been completed, steps 23 to 25 are repeated until the rice cooking operation is completed.

  When the end of the rice cooking operation is determined in step 25 or the heat retention key 4b is input in step 22, the process proceeds to the heat retention operation in step 26 and the second stable heating output P2 that is a stable heating output for the heat retaining operation is ON (heating). An ON / OFF duty (for example, an ON period of 1 second and an OFF period of 32 seconds) that alternately and periodically repeats a period and an OFF (heating stop) period is set. Then, in order to perform ON / OFF duty control, time measurement by an internal timer is started in step 27.

  Next, in step 28, the detection temperature Temp of the pan temperature detection unit 3 is input, and in step 29, it is determined whether or not the detection temperature Temp is lower than the heat retention control temperature Temp1 (for example, 74 ° C.). If the detected temperature Temp is higher than the heat retention control temperature Temp1 in step 29, the process proceeds to step 30 where the heating output is set to 0, and steps 28 to 30 are repeated until the detected temperature Temp falls below the heat retention control temperature Temp1.

  If the detected temperature Temp becomes lower than the heat retention control temperature Temp1 in step 29, the process proceeds to step 31 where an initial heating output Po (for example, 60 W) for the heat retaining operation is set. Next, in step 32, it is determined whether the ON / OFF duty is OFF period. If it is OFF period, the heating output is set to 0 in step 33, and then the process proceeds to step 38. If it is not the OFF period in step 32, the process proceeds to step 34, and it is determined in step 34 whether the second stable heating output P2 has been reached. If the second stable heating output P2 has not been reached, the routine proceeds to step 35, where the current heating output is waited after waiting for a predetermined heating output holding time T2 (for example, 1/2 times the period of the AC power supply 6, 1/120 seconds). Is increased by a heating output increase amount ΔP (for example, 10 W). Steps 34 to 35 are repeated until the second stable heating output is reached. If the second stable heating output is reached, the process proceeds to step 36.

  In step 36, it is determined whether or not an ON / OFF duty ON period (for example, 1 second) has elapsed. If not, the process proceeds to step 37. In step 37, the second stable heating output P2 is maintained, and the process returns to step 36. Steps 36 to 37 are repeated until the ON time elapses. If the ON time elapses in step 36, the process proceeds to step 38. In step 38, the presence / absence of key input is detected, and in step 39, it is determined whether a stop command is input with the cut key 4c. If no stop command is input by the cut key 4c, the process returns to step 28. In this way, the heat retaining operation is performed by executing Step 28 to Step 39. When the cut key 4c is pressed, the process proceeds to Step 40, the heating output is turned off, and the process proceeds to the next process of Step 41.

  When the temperature of the detected temperature Temp is lower than the heat retention control temperature Temp1 in the heat retaining operation from these steps, the heating power is gradually increased from the initial heating power Po (for example, 60 W) in the ON / OFF duty ON cycle. After reaching the second stable heating output (for example, 500 W), this heating output is maintained, and when the ON period ends, the heating output is controlled to be 0 so that the squealing noise starts to occur. The heating output is controlled so as to avoid the region C of the output (for example, 700 W to 900 W). Further, by setting the initial heating output Po in the ON period to 60 W instead of 0, the heating output rises quickly, and the energization time necessary for maintaining the temperature control temperature can be set short. By these operations, it is possible to maintain a quiet and comfortable environment even during long-time heat insulation without causing a decrease in rice cooking and heat retention performance.

(Embodiment 2)
FIG. 5 is a time chart showing a change in heating output during the heat retaining operation of the rice cooker in Embodiment 2 of the present invention, and FIG. 6 is a flowchart illustrating the heat retaining operation of the rice cooker. In FIG. 5, the horizontal axis represents elapsed time, the vertical axis represents the heating output, the heating output in the case of the rice cooking operation is indicated by a broken line A, and the heating output in the case of the heat retaining operation is indicated by a solid line B ′. Further, the range of the heating output in which the resonance sound is generated is indicated by the hatched portion C.

  The control part 7 in 1st Embodiment performs the heat retention operation | movement which heats the pot 1 by setting the stable heating output to the 2nd stable heating output P2, and keeps the rice in the pot 1 based on the detection result of the pot temperature detection part 3. Whereas the second stable heating output P2 is set to be smaller than the heating output C at which the resonance sound is generated, the control unit 7 of the present embodiment is configured to start heating. Until the third heating output is reached, the conduction time T1 is increased by a predetermined increment every time a predetermined time elapses, and immediately after the heating output reaches the third heating output P3, the heating is immediately performed. The first embodiment in that the output is lowered to zero or low, and then the transient operation is repeated a predetermined number of times, and the third heating output P3 is set to be smaller than the heating output at which the resonance sound is generated. Things Different. The description of the same configuration as that of the first embodiment will be omitted, and the operation and action of the difference will be described below with reference to FIGS. 5 and 6.

  In FIG. 6, steps 50 to 55 are the same as steps 20 to 25 in FIG. 4 of the first embodiment, and thus description thereof is omitted.

  When it is determined in step 55 that the rice cooking operation is completed or the heat retention key 4b is input in step 52, the process proceeds to the heat retention operation in step 56, and the third heating output P3 and the number of repetitions (for example, 3) for determining the heat output for heat retention are set. To do. Next, in step 57, time measurement is started by an internal timer for measuring the ON period and the OFF period of the ON / OFF duty. Next, in step 58, the detected temperature Temp of the pan temperature detecting unit 3 is detected, and in step 59, it is determined whether this temperature is lower than the heat retention control temperature Temp1 (for example, 74 ° C.). If the detected temperature Temp is higher than the heat retention control temperature Temp1 in step 59, the process proceeds to step 60, the heating output is set to 0, and steps 58 to 60 are repeated until the detected temperature Temp falls below the heat retention control temperature Temp1. If the temperature is lower than the heat retention control temperature in step 59, the process proceeds to step 61, where the initial heat output Po for heat retention (for example, 60 W) is set. Next, in step 62, it is determined whether the ON / OFF duty is OFF period. If it is OFF period, the heating output is set to 0 in step 63 and the process proceeds to step 64. If it is not the ON / OFF duty ON period in step 64, the process returns to step 63 and steps 63 to 64 are repeated until the OFF period ends and the ON period is reached. In step 64, if the OFF period ends and the ON period is reached, the process proceeds to step 70.

  If it is not the OFF period in step 62, the process proceeds to step 65, and it is determined in step 65 whether the third heating output P3 (for example, 600 W) has been reached. If the third heating output P3 has not been reached, the routine proceeds to step 66, where the heating output increase amount ΔP (for example, 10 W) is added to the current heating output after waiting for the heating output holding time T2 (for example, 1/2 of the power cycle). Only increase. Step 65 to step 66 are repeated until the third heating output P3 is reached, and if the third heating output P3 is reached, the routine proceeds to step 67. After the heating output is set to 0 in step 67, the number of repetitions is increased by 1 to the current number and stored in step 68. Next, it is determined whether the number of repetitions counted in step 69 has exceeded the second time. In step 69, steps 62 to 69 are repeated until the number of repetitions exceeds the second time and reaches the third time. If the number of repetitions reaches the third time in step 69, the process proceeds to step 70. In step 70, key input is performed, and in step 71, it is determined whether a cut key is input. If no stop command is input by the cut key 4c, the process returns to step 58. In this way, the operation during the heat retention is performed by executing Step 58 to Step 71, and when the heating stop command is input with the cut key 4c, the process proceeds to Step 72, the heating is turned off, and the process proceeds to the next process of Step 73.

  When the temperature of the rice is low in the heat insulation operation from these steps, the heating output is increased by a predetermined heating output increase ΔP every time from the initial heating output Po in the ON / OFF duty ON cycle. When the third heating output P3 is reached, the heating is immediately turned off, and the heating output is gradually increased from the initial heating output Po over time. The heating output change pattern as described above is performed three times. When these three ON periods are completed, the heating output is controlled to be 0, and the heat insulation operation is performed while avoiding the heating output region C (for example, 700 W to 900 W) where the squealing noise starts to occur. Can do. In addition, by reducing the heating output stabilization time during which the third heating output P3 is maintained as much as possible, it is possible to reduce the squealing noise of the natural frequency that occurs when the heating output is stabilized. In addition, by setting the initial heating output Po to 60 W instead of 0, it is possible to shorten the energization time required to make the rise of the heating output faster and maintain the detected temperature Temp at the heat retention control temperature Temp1. By these operations, it is possible to maintain a quiet and comfortable environment even during long-time heat insulation without causing a decrease in rice cooking and heat retention performance.

  The heating output region C where the squealing noise starts to occur is determined by the shape of the pan 1 and the oscillation period of the semiconductor switching element 2b. Therefore, it is effective to set the heating output region C where the rumbling sound is generated between the large second stable heating output P2 during the rice cooking operation and the third heating output P3 during the heat retaining operation. Here, the initial heating output Po during the heat retaining operation is set to 60 W, but a thermal power that is stable even when used as the initial heating output (for example, about several tens to several hundreds W) is set as the initial heating output Po. Good.

  As described above, the rice cooker according to the present invention can ensure the heating output necessary for each operation while preventing the generation of resonance sound due to the pan and the resonance current during the heat retaining operation, so that all forms having a rice cooking function and a heat retaining function are provided. It can be applied to other uses such as a heating cooker.

DESCRIPTION OF SYMBOLS 1 Pan 2 Inverter 2a Heating coil 2b Semiconductor switching element 2c Resonance capacitor 3 Pan temperature detection part 4 Display operation part 4a Rice cooking key 4b Heat retention key 4c Cutting key 4d Display part 4e Input part 5 DC power supply 5a Rectifier 5b Capacitor 6 AC power supply 7 Control Unit 7a output control unit 7b storage unit 7c first timer 7e storage unit 7f conduction time setting unit 7h drive signal generation unit 7i conduction timing detection unit 7j zero volt detection unit 8 current transformer 9 main body Po initial heating output P1 first stable heating output P2 Second stable heating output P3 Third heating output T1 conduction time ΔT1 conduction time increase amount T2 heating output holding time Temp detection temperature Temp1 temperature keeping control temperature

Claims (2)

A pan stored inside the main body,
A pan temperature detector for detecting the temperature of the pan;
DC power supply,
A heating coil for induction heating the pan;
A resonant capacitor that resonates with the heating coil;
When the current is supplied, current is supplied to the heating coil from the DC power supply to the heating coil, and when the current is cut off, the heating coil and the resonance capacitor resonate so that the resonance current continuously flows to the heating coil. A semiconductor switching element;
The conduction time of the semiconductor switching element is changed to change the operating frequency of the current flowing in the heating coil so as to maintain the heating output at the stable heating output, and the stable heating output is used as the first stable heating output. A rice cooking operation for controlling the heating output based on the detection result of the pan temperature detection unit and the rice cooking operation after the completion of the rice cooking operation. A control unit capable of performing a heat retaining operation for heating the pot as a heating output and keeping the temperature of the rice in the pot based on the detection result of the pot temperature detecting unit;
An input unit including a rice cooking key for starting the rice cooking operation;
With
In advance, the stable heating output in which the resonance sound due to the resonance current with the pan is generated is selected from the pan that is smaller than the first stable heating output and larger than the second stable heating output,
The control unit, after starting the heating operation, controls the first stable heating output to be larger than the stable heating output at which a resonance sound due to the pan and the resonance current is generated, and the second stable heating output is set. A rice cooker that is controlled to be smaller than the heating output at which the resonance sound is generated. A pan stored inside the main body,
A pan temperature detector for detecting the temperature of the pan;
DC power supply,
A heating coil for induction heating the pan;
A resonant capacitor that resonates with the heating coil;
When the current is supplied, current is supplied to the heating coil from the DC power supply to the heating coil, and when the current is cut off, the heating coil and the resonance capacitor resonate so that the resonance current continuously flows to the heating coil. A semiconductor switching element;
The conduction time of the semiconductor switching element is changed to change the operating frequency of the current flowing in the heating coil so as to maintain the heating output at the stable heating output, and the stable heating output is used as the first stable heating output. A cooking step of boiling the water in the pan and heating the pan based on the detection result of the pan temperature detection unit and controlling the heating output, and heating the pan, and the pan temperature A control unit capable of performing a heat retaining operation for retaining the rice in the pan based on the detection result of the detection unit;
An input unit including a rice cooking key for starting the rice cooking operation;
With
The control unit sets the first stable heating output to be larger than the stable heating output at which resonance sound due to the pan and the resonance current is generated, and the third heating output is started from the start of the heating operation. Until reaching the third heating output, the conduction time is increased by a predetermined increment every time a predetermined time elapses, and immediately after the heating output reaches the third heating output, the heating output is reduced to zero. Or the rice cooker which lowers to a low output and then repeats the transient operation a predetermined number of times and sets the third heating output to be smaller than the heating output at which the resonance sound is generated.

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