JP2010005249A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rice cooker which can assure the reception function of an electric wave clock also during the operation of the rice cooker. <P>SOLUTION: The rice cooker includes a heating coil 2 which induction heats a pan, an inverter circuit 3 which supplies high-frequency electric current to the heating coil 2, a rectification means which rectifies alternating current power supply and supplies electric power to the inverter circuit 3, and a control means 11 which controls the inverter circuit 3 and the transmitted frequency of a standard electric wave. Since the control means 11 controls the inverter circuit 3 so that the operation frequency of the heating coil 2 and the frequency of the second higher harmonic wave may not become the transmitted frequency of a standard electric wave having the present time information and thereby prevents the frequency of the standard electric wave and the frequency of a spurious radiation noise generated from the heating coil from becoming the same, it is possible to assure the reception function of the electric wave clock also during cooking rice and keeping warm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rice cooker or cooker using induction heating used in a general household.

  Conventionally, this type of induction heating cooker is provided with a heating coil for induction heating of a pan, a switching means for turning on / off the heating coil, and a control means for controlling on / off of the switching means, and switching is performed when the heating coil is driven. By providing a difference between the fluctuation range when the on-time of the means increases and the fluctuation range when the means is reduced, the on-time of the switching means varies irregularly, and the operating frequency of the heating coil is fluctuated. Some have reduced radiation noise (see, for example, Patent Document 1).

In recent years, a radio timepiece having a function of receiving a standard radio wave having current time information and automatically correcting an error in the current time has become widespread. In Japan, the standard radio wave has a transmission frequency of 40 kHz (Fukushima Prefecture) and 60 kHz (Fukuoka and Saga Prefecture borders). These two radio stations transmit standard radio waves. The radio clock is receiving radio waves. In addition, cooking appliances using the function of the radio timepiece have been proposed (see, for example, Patent Documents 2 and 3).
JP 2003-36961 A JP 200324211 A JP 2004-16678 A

  However, in the conventional configuration, the frequency region of 20 kHz or more which is the operating frequency band of the heating coil for induction heating the pan overlaps with 40 kHz and 60 kHz which are the transmission frequencies of the standard radio wave having the current time, and the induction heating device If the standard time signal is weak when the time signal is placed nearby, even if unnecessary radiation is reduced, unnecessary radiation noise is superimposed on the standard time signal, making it difficult for the time signal to identify the current time information from the standard time signal. There was a problem.

  Moreover, this invention solves the said conventional subject, and it aims at providing the rice cooker with which a radio timepiece can receive a standard radio wave easily even during cooking rice or during heat retention.

  In order to solve the conventional problems, a rice cooker according to the present invention includes a heating coil for induction heating of a pan, an inverter circuit for supplying a high-frequency current to the heating coil, and a rectifier for an AC power supply to supply power to the inverter circuit. Rectifying means for controlling, and control means for controlling the inverter circuit, the control means so that the operating frequency of the heating coil and the frequency of the second harmonic does not become the transmission frequency of the standard radio wave having the current time information It controls the inverter circuit.

  Since the operating frequency of the heating coil and the frequency of the second harmonic do not become the transmission frequency of the standard radio wave, even if the fundamental wave and the second harmonic, which are large noises among unnecessary radiation noises, are superimposed on the standard radio wave, the radio clock The filter circuit built in the device can discriminate the signal of the standard radio wave, and even when the signal of the standard radio wave is weak, the radio timepiece can receive the standard radio wave and update the current time.

  The rice cooker of the present invention can prevent the radio timepiece from receiving standard radio waves during the rice cooking operation or the heat insulation operation.

  1st invention controls a heating coil which induction-heats a pan, an inverter circuit which supplies a high frequency current to the heating coil, a rectifier which rectifies an AC power source and supplies power to the inverter circuit, and the inverter circuit Control means, and the control means controls the inverter circuit so that the operating frequency of the heating coil and the frequency of the second harmonic do not become the transmission frequency of a standard radio wave having current time information. Since the operating frequency and the second harmonic frequency do not overlap with the standard radio wave transmission frequency, even if the fundamental wave and the second harmonic wave, which are large noises among unnecessary radiation noises, are superimposed on the standard radio wave, they are built into the radio clock. With this filter circuit, it is possible to determine the standard radio signal, and even when the standard radio signal is weak, the radio clock receives the standard radio signal and displays it. It is possible to update the time.

  In the second invention, since the inverter circuit of the rice cooker of the first invention is composed of at least one switching means and a resonant capacitor connected in parallel to the heating coil, the circuit configuration can be simplified. The area can be reduced and a compact rice cooker can be provided.

  According to a third aspect of the invention, in the rice cooker of the first or second aspect of the invention, the input current detection means for detecting the input current supplied from the AC power source to the rectification means is provided, and the control means is detected by the input current detection means. If the input current exceeds the predetermined value, the inverter circuit is controlled so that the fundamental wave and the second harmonic of the operating frequency of the heating coil do not become the transmission frequency of the standard radio wave having the current time information. Even if the power to be supplied increases and the unwanted radiation noise generated from the heating coil increases, the input current from the AC power supply increases due to the increase in the power supplied to the heating coil. If the input current at a level that does not cancel the standard radio signal due to unwanted radiant noise generated from the input current is set to a predetermined value, it will flow to the heating coil when the input current exceeds the predetermined value. The frequency of the current that does not overlap the transmission frequency of the standard radio wave, so even if the fundamental wave and second harmonic, which are large noises among unwanted radiated noise, are superimposed on the standard radio wave, it is standardized by the filter circuit built in the radio clock. The radio wave signal can be discriminated, and the radio timepiece can receive the standard radio wave even when the standard radio wave signal is weak. Further, when the input current is lower than the predetermined value, the radio timepiece can receive the standard radio wave because the unnecessary radiation noise is small even at the same frequency as the standard radio wave transmission frequency. That is, the reception function of the radio clock can be secured even if the rice cooker performs the rice cooking operation or the heat insulation operation.

  According to a fourth aspect of the invention, in the rice cooker of the first or second aspect of the invention, there is provided a coil current detection means for detecting a current flowing in the heating coil, and the control means is configured to detect a current flowing in the heating coil detected by the coil current detection means. When the predetermined value is exceeded, current flows in the heating coil by controlling the inverter circuit so that the fundamental wave and the second harmonic of the operating frequency of the heating coil do not become the transmission frequency of the standard radio wave having the current time information. If the value of the level of the unwanted radiation noise generated by the signal does not cancel the standard radio signal is set to a predetermined value, the frequency of the current flowing in the heating coil when the value exceeds the predetermined value overlaps the transmission frequency of the standard radio signal. Since the operating frequency of the inverter circuit is controlled so that it does not occur, even if the fundamental wave and the second harmonic, which are large noises among unnecessary radiation noises, are superimposed on the standard radio wave A filter circuit built in radio clock it is possible to determine the standard radio signal, even when the standard radio signal is weak, radio clock can receive radio signals. Also, when the current flowing through the heating coil is lower than the predetermined value, even if the transmission frequency of the standard radio wave overlaps with the frequency of the heating coil current, unnecessary radio noise is small, so the radio timepiece receives the standard radio wave signal. be able to.

In the fifth aspect of the invention, in particular, when the control means of the rice cooker of the second aspect of the invention is such that the voltage corresponding to the voltage across the heating coil exceeds a predetermined value, the operating frequency of the heating coil and the frequency of the second harmonic are the current time. By controlling the inverter circuit so that it does not become the transmission frequency of standard radio waves with information, even if the current flowing through the heating coil increases, the magnetic coupling between the heating coil and pan changes, and the leakage flux increases, Since the resonance voltage generated by the heating coil and resonant capacitor increases, the voltage at both ends of the heating coil is detected as a value corresponding to this resonance voltage, and the voltage at both ends when unnecessary radiation noise is at a level that does not cancel the standard radio wave. If this value is exceeded, the operating frequency of the inverter circuit is controlled so that the frequency of the current flowing in the heating coil does not overlap the transmission frequency of the standard radio wave when this predetermined value is exceeded. Therefore, even if the fundamental wave and the second harmonic, which are large noises among unnecessary radiation noises, are superimposed on the standard radio wave, the signal in the frequency band that is not related to the transmission frequency is removed by the filter circuit built in the radio clock, The standard radio wave signal can be discriminated, and the radio timepiece can receive the standard radio wave even when the standard radio signal is weak.

  6th invention has the frequency detection means which detects especially the operating frequency of the heating coil of the rice cooker of 1st or 2nd invention, and a control means of the operating frequency and the second harmonic which the frequency detection means detected By controlling the inverter circuit so that the frequency does not become the transmission frequency of the standard radio wave having the current time information, the operating frequency of the heating coil can be detected reliably, so the operating frequency of the heating coil and the frequency of the second harmonic are standard. It is possible to ensure that the transmission frequency of radio waves is not hit.

  In the seventh aspect of the invention, in particular, the operating frequency of the heating coil of the rice cooker of the first to sixth aspects of the invention is controlled by the ON time of the switching means, so that it is not necessary to add a circuit for detecting the frequency, etc. The configuration can be simplified.

  The eighth invention has power frequency detecting means for detecting the power frequency of the AC power supply of the rice cooker of the first to seventh inventions in particular, and is targeted according to the power frequency detected by the power frequency detecting means. By switching the transmission frequency of the standard radio wave, it is possible to determine the transmission frequency of the standard radio wave included in the frequency area of the AC power supply, and to reduce the frequency range for prohibiting the operating frequency of the heating coil.

  In the ninth aspect of the invention, in particular, the control means of the rice cooker of the first to eighth aspects of the invention sets the current time by receiving the standard radio wave having the current time information, thereby driving the heating coil, Even when heating, the current time information can be updated, and the user can always be provided with the latest information on the time such as the latest current time and the end time of cooking rice.

  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 main part block diagram of a rice cooker according to the first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a pan, which is not particularly illustrated, and is composed of a laminated body using a plurality of magnetic metals and nonmagnetic metals.

  Although not shown in particular, the heating coil 2 includes a first heating coil that faces the center of the bottom surface of the pan 1 and a second heating coil that faces the corner portion of the bottom surface of the pan 1.

  The first heating coil and the second heating coil are electrically connected in series.

Although not particularly illustrated, the first heating coil has a spiral shape and is arranged at a certain distance in the center of the bottom surface of the pan 1. The second heating coil is disposed on the concentric outer side of the first heating coil, and is disposed at a certain distance from the corner portion of the bottom surface of the pan 1.

  The heating coil 2 is constituted by a wire obtained by twisting more than 20 litz wires, each of which is a bundle of a plurality of copper wires, and makes the current distribution uniform when a high-frequency current flows.

  Reference numeral 3 denotes an inverter circuit, which includes a resonance capacitor 4 and switching means 5.

  The resonant capacitor 4 is connected in parallel to the heating coil 2 as shown in FIG. In this embodiment, a polypropylene capacitor is used which has little loss even when a high-frequency current flows.

  The switching means 5 includes a semiconductor element such as a MOSFET or IGBT and a reverse connection diode connected in reverse to the semiconductor element. MOSFETs and IGBTs have high withstand voltage, can be switched at high frequency, and can flow a large current by applying a voltage to the gate terminal. Therefore, there is an advantage that a large current can be flowed with less power than a power transistor. is there. In the present embodiment, an IGBT is used for this semiconductor element.

  Generally, such a configuration of the inverter circuit is called a one-stone voltage resonance type inverter because the heating coil 2 and the resonance capacitor 3 form a parallel resonance circuit.

  6 is an AC power supply for supplying power to the rice cooker. The power supply frequency of the AC power supply 6 is 50 Hz in the eastern Japan region and 60 Hz in the western Japan region.

  Reference numeral 7 denotes a rectifying means, which includes a diode bridge 8, a choke coil 9, and a capacitor 10. Here, the capacity | capacitance of the capacitor | condenser 10 is as small as several micro F, and when an electric current is sent through the bottom heating coil 2, a ripple will arise. In the present embodiment, this ripple voltage waveform is the same as the voltage waveform when the AC power supply 6 is full-wave rectified.

  Reference numeral 11 denotes a control means, which includes an on-time setting means 12, a pulse generation means 13, a synchronization signal generation means 14, and a drive circuit 15.

  The on-time setting means 12 is composed of a ROM or the like inside the microcomputer 18, stores in advance the on-time used in the rice cooking process, the heat retaining process, and the like, and drives the bottom heating coil 2, 8-bit digital data is output to the pulse generating means 13.

  The pulse generating means 13 is composed of a timer circuit having a PWM output function inside the microcomputer 18. The timer circuit constituting the pulse generating means 13 starts counting by the output edge of the synchronizing signal generating means 14, counts the ON time set by the ON time setting means 12, and keeps on the drive circuit 15 until the counting is completed. A high signal is output as an ON signal.

  The synchronization signal generating means 14 is composed of a comparator, a resistance voltage dividing circuit, etc., and the comparator (C2) voltage obtained by dividing the resistance of the terminal by a predetermined ratio and (CE) voltage obtained by dividing the resistance of the terminal by a predetermined ratio. When the divided voltage at the terminal (C2) is higher, a high signal is output to the pulse generator 13. When the divided voltage at the terminal (C2) is lower, a low signal is output to the pulse generator 13. Output to.

The drive circuit 15 is composed of a push-pull circuit composed of an NPN transistor and a PNP transistor (not shown), and applies a voltage to the gate terminal of the IGBT constituting the switching means 5 while the output of the pulse generating means 13 is high. When the IGBT is turned on and the pulse generating means 13 is outputting low, the voltage at the gate terminal of the IGBT is set to 0V, and the IGBT is turned off. Note that this is an example, and the components constituting the push-pull circuit may be constituted by MOSFETs or the like.

  The input means 16 is composed of a plurality of momentary switches. When each switch is pressed by the user, the microcomputer 18 detects that the switch has been pressed, and performs a predetermined operation in accordance with each switch.

  The display means 17 is composed of a plurality of LEDs such as an LCD and red, green and orange. The microcomputer 18 sets the display content of the LCD and the LED to be lit according to the state of the rice cooker, such as during rice cooking or heat insulation.

  As described above, the microcomputer 18 uses some of its functions for the on-time setting means 12 and the pulse generation means 13. The microcomputer 18 operates with a 4 MHz oscillator and a 32.728 kHz oscillator. An LCD display means for controlling the LCD display section, a time measuring means for displaying a clock inside the LCD, a rice cooking process control means for controlling the rice cooking process, and the like are configured.

  Although not particularly illustrated, in the rice cooker of the present embodiment, in addition to that, a function for controlling the display means 17 such as an LCD, an LED, a timekeeping function for displaying a clock inside the LCD, a rice cooking sequence and a heat retention sequence. Has a sequence control function for executing.

  FIG. 2 is a cross-sectional configuration diagram of a main part of the rice cooker of the present embodiment. In order to simplify the drawing, lead wires for electrical connection and screws for fixing components are omitted. In FIG. 2, 21 is a body (main body) of a rice cooker. A lid 22 that covers the upper surface of the body 21 is installed so as to be freely opened and closed. The housing portion 23 of the body 21 has the heating coil 2 disposed on the bottom and side portions thereof, and the ferrite cores 24 are disposed radially on the outer peripheral side of the heating coil 2. The heating coil 2 is a winding having a center substantially directly below the center of the bottom of the pan 1.

  The pan 1 is formed of a magnetic material such as stainless steel, iron, or copper. The pan 1 has a flange 25 protruding outward from the upper end opening, and is placed in the storage portion 23 in a detachable manner by placing the flange 25 in a state of being lifted from the upper end of the storage portion 23. Therefore, the pan 1 has a gap between the storage portion 23 when stored.

  A detachable lid heating plate 26 is set on the lid 22. The lid heating plate 26 is made of a metal such as stainless steel.

  A lid heating coil 27 is built in the lid 22 and heats the lid heating plate 26 by induction.

  A first circuit board 28 is composed of a switch, an LCD, a microcomputer 18 and the like.

  Reference numeral 29 denotes a second circuit board, which is not particularly shown, on which an IGBT constituting the switching means 5, a resonant capacitor 4, a diode bridge 8 constituting the rectifying means 7, a choke coil 9, a capacitor 10 and the like are mounted.

  Reference numeral 30 denotes a retractable power cord storage unit, which is electrically connected to the second circuit board 29 via a lead wire. The power cord storage unit 30 can wind up the power cord using a stopper and a spring.

  Reference numeral 31 denotes a temperature detection means, which is composed of a thermistor, and is arranged at substantially the center of the bottom of the pan 1. Since the resistance value of the thermistor changes with temperature, a voltage dividing circuit is configured with this thermistor and a resistor having a predetermined resistance value, and the resistance value of the thermistor is analogized by supplying a predetermined voltage to both ends of the voltage dividing circuit. Can be converted to voltage. The microcomputer 18 shown in FIG. 1 estimates the temperature from this analog voltage by using a built-in AD converter.

  A cooling means 32 is a fan motor in which a fan is attached to a rotor of a DC brushless motor. This fan motor is on / off controlled by the microcomputer 18 shown in FIG.

  Although not particularly shown, the first circuit board 28 and the second circuit board 29 are electrically connected by lead wires, and are turned on by the on-time setting means 12 and the pulse generation means 13 configured inside the microcomputer 18. The IGBT is turned on and off, and a high-frequency current is passed through the heating coil 2. The heating coil 2 generates an alternating magnetic field when a high-frequency current flows, and an eddy current flows through the pan 1 by the alternating magnetic field, and the pan 1 generates heat.

  As mentioned above, the rice cooker of this Embodiment induction-heats the pan 1, and cooks the food in the pan 1 by heating. Here, the cooked product is rice before cooking rice and water or cooked rice.

  FIG. 3 is a graph showing the relationship between the on-time of the switching means 4 of the rice cooker of the present embodiment, the fundamental wave of the operating frequency of the bottom heating coil 2, and the second harmonic. At this time, the voltage of the AC power supply 6 is 100V. FIG. 3A shows the relationship between the fundamental wave of the operating frequency of the bottom heating coil 2 and the ON time of the switching means 4. FIG. 3B shows the relationship between the second harmonic of the operating frequency of the bottom heating coil 2 and the switching means 4. At this time, the power supply voltage of the AC power supply 7 is constant at 100 VAC.

  As shown in FIG. 3, the on-time, the fundamental wave of the operating frequency of the bottom heating coil 2 and the second harmonic are in a substantially proportional relationship. The second harmonic of the bottom heating coil 2 is twice the fundamental wave. That is, it is possible to set the fundamental wave and the second harmonic of the operating frequency of the bottom heating coil 2 by setting the ON time.

  In FIG. 3, when the on-time is Ton1, the operating frequency of the bottom heating coil 2 is 60 kHz, when the on-time is Ton2, the operating frequency of the bottom heating coil 2 is 40 kHz, and the on-time is Ton3. The second harmonic of the operating frequency of the bottom heating coil 2 is 60 kHz, and when the on-time is Ton4, the second harmonic of the operating frequency of the bottom heating coil 2 is 40 kHz.

  That is, if the on-time is set between Ton2 and Ton3, the fundamental wave and the second harmonic of the operating frequency of the bottom heating coil 2 do not correspond to the transmission frequency of the standard radio wave having the current time information.

  FIG. 4 is a graph showing the relationship between the ON time of the switching means 5 of the rice cooker of the present embodiment and the input current supplied from the AC power source 6. As shown in FIG. 4, the input current increases as the ON time increases. In the rice cooker of the present embodiment, a predetermined on-time is set so as to obtain an optimum input current according to the rice cooking and the heat insulation state.

  FIG. 5 shows operation waveforms of main circuits of the rice cooker according to the present embodiment.

In general, in a rice cooker using induction heating, the on / off frequency of the switching means 6 is 20 kHz or more and 400 times or more of the frequency of the AC power supply 7 (50 Hz or 60 Hz). (A) shows the 8-bit output of the on-time setting means 17. (B) shows the output waveform of the pulse generating means 22. (C) shows a waveform of a current flowing through the switching means 6. (D) shows the voltage waveform at the (CE) terminal and the voltage waveform at the (C2) terminal. (E) shows the output waveform of the synchronizing signal generating means 23, which outputs high when the voltage at the (CE) terminal is smaller than the voltage at the (C2) terminal, and the pulse generating means 22 outputs high after a predetermined time. become. (F) shows a waveform of a current flowing through the heating coil 2.

  The operation waveforms in FIG. 5 will be described with reference to FIG.

  For example, when the rice cooking start switch is pushed by the input means 16 of FIG. 1, the control means 11 detects the signal of the input means 16 and starts the rice cooking process. When the rice cooking process is started, the on-time setting means 12 constituted by the microcomputer 18 sets the on-time Ton of the switching means 5, and the pulse generating means 13 also constituted by the microcomputer 18 is shown in FIG. ), A high pulse having a high pulse width Ton is output to the driving means 15.

  The driving means 15 receives the high signal and applies a voltage of about 20 V to the gate terminal of the IGBT constituting the switching means 5. When a 20 V voltage is applied to the gate terminal of the IGBT, the collector-emitter is turned on, the heating coil 2 is energized, and a current flows through the heating coil 2 as shown in FIG. Since the heating coil 2 has an inductance component, the current flowing through the heating coil 2 has a waveform that rises upward with time.

  When the set on-time Ton elapses at t1, the pulse generating means 13 outputs a low signal to the driving means 15. The driving means 15 receives this low signal, applies 0 V to the gate terminal of the IGBT, opens the collector-emitter of the IGBT, and interrupts the energization path of the heating coil 2. However, since the heating coil 2 has an inductance component, a resonance waveform as shown in the period from t1 to t2 in FIG.

  At this time, the synchronization signal generating means 14 is connected to the collector voltage (voltage at the (CE) terminal) of the switching means 5 shown in FIG. 4 (d) corresponding to the resonance voltage composed of the inductance component of the heating coil 2 and the resonance capacitor 4. The output voltage of the rectifier 7 (the voltage at the (C2) terminal) is compared. When the voltage at the (CE) terminal is higher than the voltage at the (C2) terminal, a low signal is output to the pulse generator 13.

  At t2, when the (CE) terminal voltage becomes lower than the (C2) terminal voltage due to the resonance phenomenon, the synchronization signal generating means 14 outputs a high signal to the pulse generating means 13 as shown in FIG.

  At t3, the pulse signal generation means 13 outputs a high pulse again at the on-time Ton set by the on-time setting means 12 using the edge of the synchronization signal generation means 14 from low to high as a trigger.

  As described above, the pan 1 is induction-heated by flowing a high-frequency current through the heating coil 2 with the period from the point t0 to t3 as one cycle.

  As shown in FIG. 5, in the rice cooker of the present embodiment, when the 8-bit output of the on-time setting unit 17 changes, the high pulse period of the pulse generation unit 22 changes.

As shown in FIG. 5F, the current waveform of the heating coil is approximately a triangular waveform. In addition, since the areas of the current in the positive direction and the negative direction are different, harmonics of the secondary component are included. For this reason, electromagnetic waves having a frequency twice as high as the operating frequency of the heating coil leak as external electromagnetic waves.

  That is, by preventing the basic operating frequency and double frequency of the electromagnetic wave generated by the leakage magnetic field of the heating coil from becoming the transmission frequency of the standard radio wave, it is possible to prevent the standard radio wave transmission signal from being disturbed.

  FIG. 6 shows a time chart of the temperature detection means of the rice cooker of this embodiment and a time chart of the on-time of the switching means. (A) has shown the time chart of the pan bottom temperature which the temperature detection means detected. (B) shows a time chart of the ON time of the switching means.

  In the time chart of the ON time of the switching means in FIG. 6B, the vertical time indicates the ON time of the switching means, and the horizontal axis indicates the period during which the switching means is turned ON / OFF and the high-frequency current flows through the heating coil. ing.

  Operation | movement of the rice cooker of this Embodiment is demonstrated using FIGS.

  At T0 in FIG. 6, among the plurality of momentary switches (input means) mounted on the first circuit board 30 arranged in the lid of the rice cooker shown in FIG. 2, the momentary switch that means the start of rice cooking is pressed. And the microcomputer 18 which comprises the control means 11 shown in FIG. 1 detects the signal of the input means 16, and starts a rice cooking sequence.

  The rice cooking sequence is composed of a plurality of subsequences. In this Embodiment, it is comprised by the pre-cooking process, the rice cooking amount determination process, the boiling maintenance process, and the additional cooking process.

  The period from T0 to T2 corresponds to the pre-cooking process. In the pre-cooking process, the high-frequency current is supplied to the heating coil 1 by setting the on-time of the switching means 5 to Ton5 until the water is easily absorbed by the rice during the period from T0 to T1. The heating coil 1 operates at about 33 kHz in the case of Ton5 as shown in FIG. The conduction ratio at which the heating coil 1 operates at 33 kHz is 10 seconds / 16 seconds. When the temperature detection means 41 shown in FIG. 2 detects 60 degrees at T1, the microcomputer 18 sets the on-time of the switching means 5 to Ton5 according to the preprogrammed contents and sets the conduction ratio at which the heating coil operates at 33 kHz. The temperature is made variable, and a temperature of about 60 degrees is controlled to be maintained for a period until T2.

  The period from T2 to T3 corresponds to the rice cooking amount determination process. In the rice cooking amount determination process, the on-time of the switching means 5 is set to Ton6 and a high frequency current is supplied to the heating coil. Since the on-time is long, the current supplied to the heating coil also increases and the amount of induction heating increases. That is, the temperature of the pan also rises rapidly. In the present embodiment, from the elapsed time (time from T2 to T3) until the temperature detecting means 41 detects 100 degrees after the heating coil 1 driving is started with the ON time of the switching means 5 being set to Ton6, The microcomputer 18 determines the amount of rice cooking, and sets the conduction ratio of the heating coil 1 in the subsequent boiling maintenance process and the conduction ratio of the heating coil 1 drive in the additional cooking process.

The period from T3 to T4 corresponds to the boiling maintenance process. In the boiling maintenance process, the microcomputer 18 sets the ON time of the switching means 5 to Ton5, and drives the heating coil 2 with a conduction ratio of 10 seconds / 16 seconds. If the heating coil 2 is driven to continue induction heating of the pan 1, the water remaining in the pan 1 also evaporates, and the temperature of the pan 1 exceeds 100 degrees and reaches 130 degrees at T4. When the temperature detection means 41 detects 130 degrees, the microcomputer 18 turns off the switching means 5, stops driving the heating coil 1, ends the boiling maintenance process, and shifts to the additional cooking process.

  The period from T4 to T5 corresponds to the additional cooking process. In the reheating process, the microcomputer 18 sets the ON time of the switching means 5 to Ton5, and performs high-frequency switching of the heating coil 2 at a conduction ratio of 2 seconds / 16 seconds. The microcomputer 18 measures the elapsed time from T4, and when T5 is reached, the rice cooking sequence is ended and a buzzer is notified of the end of rice cooking.

  At the same time, at T5, the microcomputer 18 starts a heat retention sequence, sets the ON time of the switching means 5 to Ton7, switches the heating coil 2 at high frequency with a conduction ratio of 1 second / 16 seconds, and heats the pot 1 by induction.

  As described above, in FIG. 6, a plurality of ON times of the switching means 5 are set as Ton5, Ton6, and Ton7.

  As described above, the relationship between the ON time of the switching means 5, the operating frequency of the heating coil 2, and the frequency of the second harmonic is shown in the graph of FIG.

  In the graph of FIG. 3, the operating frequency when the heating coil is switched at high frequency with the ON time of Ton5 is about 33 kHz, and the frequency of the second harmonic is about 66 kHz.

  When the heating coil is switched at high frequency with the Ton6 on time, the operating frequency is about 26 kHz and the frequency of the second harmonic is about 52 kHz.

  When the heating coil is switched at high frequency with the Ton7 on-time, the operating frequency is about 37 kHz and the frequency of the second harmonic is about 74 kHz.

  Even if the heating coil 2 is driven at any ON time, the operating frequency of the heating coil 2 and the frequency of the second harmonic are separated by 1 kHz or more with respect to the transmission frequencies of the standard radio wave of 40 kHz and 60 kHz. The distance between the operating frequency of the heating coil 2 and the frequency of the second harmonic from the transmission frequency of the standard radio wave is not particularly limited, but in this embodiment, 1 kHz is taken into account in consideration of the performance of the noise filter of the radio clock. I try to separate them.

  As described above, in the rice cooker of the present embodiment, the operating frequency of the heating coil 2 and the frequency of the second harmonic are all avoiding the transmission frequencies (40 kHz and 60 kHz) of the standard radio wave, from the start of rice cooking to during the heat retention. Since the transmission frequency of the standard radio wave and the frequency of unnecessary radiation noise generated from the heating coil 2 do not become the same, the radio timepiece can easily receive the standard radio wave signal.

  In this embodiment, the one-stone voltage resonance type inverter has been described. However, the configuration of the inverter circuit is not limited to this, and for example, a two-stone half-bridge type inverter or a four-stone full-bridge type inverter may be used. I do not care.

  Moreover, this Embodiment is an example of Claims 1, 2, and 7 of the rice cooker of this invention.

(Embodiment 2)
FIG. 7 is a main part block diagram of the rice cooker in the second embodiment of the present invention.

In FIG. 7, reference numeral 71 denotes an input current detecting means for detecting the input current supplied from the AC power source 6. Although not specifically illustrated, the input current is converted into a current of several mA at a predetermined ratio using a current transformer, and a direct current voltage is generated using a load resistor, a rectifier diode, and an electrolytic capacitor connected to the secondary side of the current transformer. Has been converted.

  72 is an input current setting means, and sets the input current used in each step of the rice cooking sequence or the heat retention sequence. In the present embodiment, the set value of the input current is stored in advance in a ROM in the microcomputer 73, and the microcomputer 73 outputs a predetermined input current set value to the on-time setting means 74 in a predetermined process.

  The microcomputer 73 uses a part of its functions for the input current setting means 72, the on-time setting means 74, and the pulse generation means 13.

  The on-time setting means 74 compares the output value of the input current detection means 71 with the input current setting value of the input current setting means 72, and the output value of the input current detection means 71 becomes the input current setting value of the input current setting means 72. Thus, the ON time of the switching means 5 is changed.

  Reference numeral 75 denotes a control means, which comprises an input current setting means 72, an on-time setting means 74, a microcomputer 73 constituting the pulse generation means 13, the synchronization signal generation means 14, and the drive circuit 15.

  Reference numeral 76 denotes zero voltage detecting means, which is not particularly shown, but the (u) pole of the AC power source 6 is connected to the base terminal of the transistor through a resistor. The collector terminal of this transistor is connected to a 5V power source generated from the AC power source 6 via a switching power source via a resistor. (U) Low when the potential of the pole is higher than the other pole, low Sometimes high is output to the microcomputer 73.

  Other configurations are the same as those in FIG. 1, and a description thereof will be omitted.

  FIG. 8 is a flowchart showing an example of a method for setting the ON time of the switching means 5 in the rice cooker of the present embodiment.

  The operation effect | action of the rice cooker of this Embodiment is demonstrated using FIG. 7, FIG. 8, FIG. 3, FIG. 4, FIG.

  For example, in the time chart of FIG. 6, when the pre-cooking process of the rice cooking sequence is started, in step 81, the input current setting means 72 sets the input current set value Iin5 used in the pre-cooking process.

  In step 82, the on-time setting means 71 sets Ton1 shown in the graphs of FIGS. 3 and 4 as the initial value of the on-time.

  In step 83, the microcomputer 73 inputs the input current value Iin detected by the input current detecting means 71 after a predetermined time has elapsed since the output value of the zero voltage detecting means 76 becomes a high edge.

  In step 84, it is determined whether the input current value Iin is smaller than the reference value Iin2. At this time, the reference value Iin2 is an upper limit value of the input current that can be adjusted while ignoring the operating frequency of the heating coil 2.

If it is determined in step 84 that Iin <Iin2, the process proceeds to step 85, where the on-time setting unit 74 changes the on-time of the switching unit 5 to Ton = Ton + ΔTon, and then proceeds to step 83. At this time, ΔTon is the amount of change in the on-time, and is a value stored in advance in the ROM inside the microcomputer 73.

  If it is determined in step 84 that Iin <Iin2 is not established, the process proceeds to step 86, where it is determined whether or not the on-time Ton set by the on-time setting means 74 is greater than a predetermined on-time Ton2. At this time, the predetermined on-time Ton2 is an on-time that is assumed that the operating frequency of the heating coil 2 is the same as the transmission frequency of the standard radio wave.

  When Ton <Ton2, the routine proceeds to step 87, where the on-time setting means 74 sets the on-time of the switching means 5 to Ton = Ton8. When the heating coil 2 is driven with the ON time of Ton8, the operating frequency of the heating coil 2 is lower than the transmission frequency of the standard radio wave. As described above, Ton8 is stored in the ROM of the microcomputer 73 as a default value.

  When Ton <Ton2 is not satisfied and after step 87, the routine proceeds to step 88. In step 88, the microcomputer 73 inputs the input current value Iin detected by the input current detection means 71 after a predetermined time has elapsed since the output value of the zero voltage detection means 76 becomes a high edge.

  In step 89, the input current value Iin detected by the input current detection means 71 and the input current setting value Iin5 set by the input current setting means 72 are compared, and it is determined whether or not Iin <Iin5.

  When the input current value Iin <the input current set value Iin5, the routine proceeds to step 90, where the on-time setting means 74 updates the on-time Ton to Ton + ΔTon. Thereafter, the process proceeds to step 88.

  When the input current value Iin <the input current set value Iin5 is not satisfied, the process proceeds to step 91 and the on-time Ton is updated to Ton−ΔTon. Thereafter, the process proceeds to step 88.

  As described above, while the input current value Iin is smaller than the reference value Iin2, the ON time of the switching means 5 is freely set. When the input current value Iin is equal to or greater than the reference value Iin2, Ton8 is set as the lower limit value of the ON time. The operating frequency of 2 is not set to 50 kHz.

  In the present embodiment, the reference value Iin2 is set to a value smaller than Iin used during steady operation. That is, since it is used in a transient state, the operating frequency of the heating coil 2 instantaneously passes the transmission frequency of the standard radio wave, and the influence on the standard radio wave is extremely small. However, this setting method is an example and is not limited.

  As shown in FIG. 4, the input current increases as the ON time of the switching means 5 is increased. An increase in the on-time and input current of the switching means 5 indicates that the high-frequency current flowing in the heating coil 2 also increases. This tendency can be confirmed experimentally, and is also clear from the fact that the ON time of the switching means 5 increases and the energization time to the heating coil 2 becomes longer.

  When the high-frequency current flowing through the heating coil 2 increases, unnecessary radiation noise generated from the heating coil 2 also increases. This has been confirmed experimentally, and it is a general tendency that when current increases and power increases, noise tends to increase even though the ratio is different.

That is, if the high frequency current of the heating coil 2 is small, the unnecessary radiation generated from the heating coil 2 is also small. Therefore, the input current supplied from the AC power source 6 to the rice cooker is detected as a parameter corresponding to the high frequency current of the heating coil 2. By preventing the operating frequency of the heating coil 2 from becoming the transmission frequency of the standard radio wave when a predetermined input current is exceeded, it is not necessary to increase the current supplied to the heating coil 2 from the beginning. An excessive short-circuit current is not caused to flow through the IGBT constituting the switching means 5, and interference with the radio timepiece can be suppressed while maintaining the performance when the heating coil 2 is activated.

  Further, since the zero voltage detection means 76 detects the zero voltage of the AC power supply 6, the power supply frequency of the AC power supply 6 can be detected by measuring the cycle of the zero voltage detection means 76 with the counter of the microcomputer 73. There are 50 Hz and 60 Hz power supply frequencies in Japan. Generally, the eastern Japan region is 50 Hz and the western Japan region is 60 Hz. On the other hand, the transmission frequency of standard radio waves is also transmitted from the prefectural borders of Fukushima Prefecture, Saga Prefecture, and Fukuoka Prefecture, standard radio waves of 40 kHz are transmitted from Fukushima Prefecture, and standard radio waves of 60 kHz are transmitted from the prefectural borders of Saga Prefecture and Fukuoka Prefecture. Has been sent. Therefore, by detecting the power supply frequency of the AC power supply 6, it is possible to estimate the transmission frequency of the standard radio wave that is easier to receive. Even if the second harmonics overlap, the radio timepiece can receive standard radio waves.

  As described above, by detecting the power supply frequency of the AC power supply 6, the transmission frequency of the standard radio wave that is easy to receive is determined, and the transmission frequency and the operating frequency or the second harmonic of the heating coil 2 do not overlap. Thus, the prohibited range of the operating frequency of the heating coil 2 can be minimized.

(Embodiment 3)
FIG. 9 is a main part block diagram of a rice cooker according to the third embodiment of the present invention.

  In FIG. 9, reference numeral 101 denotes a coil current detection unit that detects a high-frequency current flowing through the heating coil 2. Although not specifically illustrated, the current flowing through the heating coil 2 is converted into a current of several mA at a predetermined ratio using a current transformer, and a load resistor, a rectifier diode, and an electrolytic capacitor connected to the secondary side of the current transformer are connected. Used to convert to DC voltage.

  A coil current setting means 102 sets the high-frequency current of the heating coil 2 used in each step of the rice cooking sequence or the heat retention sequence. In the present embodiment, the set value of the high-frequency current of the heating coil 2 is stored in advance in the ROM in the microcomputer 103, and the microcomputer 103 sets the predetermined coil current set value in the predetermined process in the on-time setting means 104. Output to.

  The microcomputer 103 uses some of its functions for the coil current setting means 102, the on-time setting means 104, and the pulse generation means 13.

  The on-time setting means 104 compares the output value of the coil current detection means 101 with the coil current setting value set by the coil current setting means 102, and the output value of the coil current detection means 101 is the coil set by the coil current setting means 102. The ON time of the switching means 5 is changed so as to be the current set value.

  A control unit 105 includes a coil current setting unit 102, an on-time setting unit 104, a microcomputer 103 constituting a pulse generation unit 13, a synchronization signal generation unit 14, and a drive circuit 15.

  Other configurations are the same as those in FIG. 7, and the description in this embodiment is omitted.

As described above, by detecting the high-frequency current flowing through the heating coil 2, the operating frequency of the heating coil 2 does not become the transmission frequency of the standard radio wave when the predetermined coil current is exceeded. It is no longer necessary to increase the current supplied to 2 from the beginning, and an excessive short-circuit current is not allowed to flow through the IGBT constituting the switching means 5 at the time of start-up. Interference can be suppressed.

(Embodiment 4)
FIG. 10: is a principal part block diagram of the rice cooker in the 4th Embodiment of this invention.

  In FIG. 10, reference numeral 111 denotes a both-end voltage detection means for detecting the voltage between the collector and emitter of the IGBT constituting the switching means 5. Although not specifically shown, a resistance voltage dividing circuit configured by connecting a plurality of resistors in series between a collector and an emitter, and a transistor and a capacitor for peak-holding an output voltage divided by the resistance voltage dividing circuit It is composed of an emitter follower circuit using

  Since the voltage at the (CE) terminal in FIG. 10 is obtained by adding the voltage at both ends of the heating coil 2 to the voltage at the (C2) terminal, the voltage between the collector and emitter of the IGBT is detected at both ends of the heating coil 2. It can be said that it corresponds to detecting the voltage.

  Reference numeral 112 denotes a both-end voltage setting unit that sets a voltage value between both ends of the switching unit 5 that is generated when the heating coil 2 is driven in each step of the rice cooking sequence or the heat retention sequence. In the present embodiment, the set value of the both-end voltage of the switching means 5 is stored in advance in the ROM in the microcomputer 113, and the microcomputer 113 sets the predetermined both-end voltage set value in the on-time setting means 114 in a predetermined process. Output to.

  The microcomputer 113 uses a part of its function for the both-end voltage setting means 112, the on-time setting means 114, and the pulse generation means 13.

  The on-time setting unit 114 compares the output value of the both-end voltage detection unit 111 with the both-end voltage setting value set by the both-end voltage setting unit 112, and the output value of the both-end voltage detection unit 111 is compared with the both-end voltage setting unit 112. The on-time of the switching means 5 is changed so that the voltage setting value is obtained.

  Reference numeral 115 denotes control means, which includes a both-end voltage setting means 112, an on-time setting means 114, a microcomputer 113 constituting a pulse generation means 13, a synchronization signal generation means 14, and a drive circuit 15.

  Other configurations are the same as those in FIG. 7, and the description in this embodiment is omitted.

  FIG. 11A shows the relationship between the collector-emitter voltage (both ends voltage) of the IGBT constituting the switching means 5 when the pan 1 is arranged as shown in FIG. Show. FIG. 11B shows the relationship between the collector-emitter voltage (both ends voltage) of the IGBT constituting the switching means 5 and the operating frequency of the heating coil 2 when the pan 1 is arranged as shown in FIG. ing.

As shown in FIG. 11, since there is a correlation between the both-end voltage of the switching means 5, the high-frequency current of the heating coil 2, and the operating frequency, the current flowing through the heating coil 2 is detected by detecting the voltage across the switching means 5. It is possible to estimate, and when the operating voltage of the heating coil 2 does not become the transmission frequency of the standard radio wave when the voltage value exceeds a predetermined both-end voltage value, it is not necessary to increase the current supplied to the heating coil 2 from the beginning. An excessive short-circuit current does not flow through the IGBT that constitutes the switching means 5 at the time of startup, and interference with the radio timepiece can be suppressed while maintaining the performance of the heating coil 2 at the time of startup.

  Further, as shown in FIG. 11, since the operating frequency of the heating coil 2 can be estimated from the detection voltage of the both-end voltage detecting means 111, the both-end voltage detecting means 111 detects the operating frequency of the heating coil 2. It may be used as

  By using it as a frequency detection means, the on-time of the switching means 5 can be controlled so that it does not become the transmission frequency of the standard radio wave, so that the transmission frequency of the standard radio wave and the operating frequency of the heating coil 2 can be reliably shifted. The reception performance of the radio timepiece can be ensured.

  In addition, this Embodiment is corresponded to description of Claim 5 and Claim 6 of the rice cooker of this invention.

(Embodiment 5)
FIG. 12: is a principal part block diagram of the rice cooker in the 5th Embodiment of this invention.

  In FIG. 12, reference numeral 121 denotes a radio wave receiving means, which is not particularly shown, and is composed of an antenna for receiving a standard radio wave and a decoding IC for decoding the received signal. The decoded current time information is converted into a digital signal. It is transmitted to the microcomputer 122. The microcomputer receives this signal and displays the current time on the time display section of the LCD constituting the display means 17.

  A control unit 123 includes an input current setting unit 72, an on-time setting unit 74, a microcomputer 122 constituting the pulse generation unit 13, a synchronization signal generation unit 14, and a drive circuit 15.

  Other configurations are the same as those in FIG. 7, and the description in this embodiment is omitted.

  As described above, even when the function of the radio clock is built in the rice cooker, the operating frequency of the heating coil 2 and the second harmonic frequency are shifted from the transmission frequency of the standard radio wave. A reception function can be secured.

  As described above, the rice cooker according to the present invention controls the inverter circuit so that the operating frequency of the heating coil 2 and the frequency of the second harmonic do not become the transmission frequency of the standard radio wave. Even within, you can secure the reception function of the radio clock. Therefore, it can be applied not only to home use but also to uses such as rice cookers for business use.

Main part block diagram of rice cooker in Embodiment 1 of this invention Sectional drawing of the rice cooker in Embodiment 1 of this invention. The graph which shows the relationship between the ON time of the switching means of the rice cooker in Embodiment 1 of this invention, the operating frequency of a heating coil, and the frequency of a 2nd harmonic. The graph which shows the relationship between the ON time of the switching means of the rice cooker in Embodiment 1 of this invention, and input current The figure which shows the principal part operation | movement waveform of the rice cooker in Embodiment 1 of this invention. The main part time chart of the rice cooker in Embodiment 1 of this invention Main part block diagram of rice cooker in Embodiment 2 of this invention The flowchart which shows the update method of the ON time of the switching means of the rice cooker in Embodiment 2 of this invention. Main part block diagram of rice cooker in Embodiment 3 of this invention Main part block diagram of rice cooker in Embodiment 4 of the present invention The graph which shows the relationship between the both-ends voltage of the switching means of the rice cooker in Embodiment 4 of this invention, the high frequency current which flows into a heating coil, and the operating frequency of a heating coil Main part block diagram of rice cooker in Embodiment 5 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pan 2 Heating coil 3 Inverter circuit 4 Resonance capacitor 5 Switching means 6 AC power supply 11 Control means

Claims (9)

A heating coil for induction heating the pan, an inverter circuit for supplying a high frequency current to the heating coil, a rectifying means for rectifying an AC power source and supplying power to the inverter circuit, and a control means for controlling the inverter circuit, The said control means is a rice cooker which controls the said inverter circuit so that the operating frequency of the said heating coil and the frequency of a 2nd harmonic may not become the transmission frequency of the standard radio wave which has the present time information. The rice cooker according to claim 1, wherein the inverter circuit includes at least one switching means and a resonant capacitor connected in parallel to the heating coil. The control means has an input current detection means for detecting an input current supplied from the AC power source to the rectification means, and when the input current detected by the input current detection means exceeds a predetermined value, the operating frequency of the heating coil and the second The rice cooker according to claim 1 or 2, wherein the inverter circuit is controlled so that a harmonic frequency does not become a transmission frequency of a standard radio wave having current time information. Coil current detection means for detecting the current flowing through the heating coil is provided, and the control means detects the operating frequency of the heating coil and the second harmonic frequency when the current flowing through the heating coil detected by the coil current detection means exceeds a predetermined value. The rice cooker of Claim 1 or 2 which controls an inverter circuit so that it may not become the transmission frequency of the standard radio wave which has present time information. The control means controls the inverter circuit so that when the voltage corresponding to the voltage across the heating coil exceeds a predetermined value, the operating frequency of the heating coil and the frequency of the second harmonic do not become the transmission frequency of the standard radio wave having the current time information. The rice cooker of Claim 2 to do. It has frequency detecting means for detecting the operating frequency of the heating coil, and the control means is an inverter circuit so that the operating frequency detected by the frequency detecting means and the second harmonic frequency do not become the transmission frequency of the standard radio wave having the current time information. The rice cooker of Claim 1 or 2 which controls. The rice cooker according to any one of claims 1 to 6, wherein the operating frequency of the heating coil is controlled by an on-time of the switching means. The power supply frequency detection means for detecting the power supply frequency of the AC power supply is provided, and the transmission frequency of the target standard radio wave is switched according to the power supply frequency detected by the power supply frequency detection means. The described rice cooker. The rice cooker according to any one of claims 1 to 8, wherein the control means sets the current time by receiving a standard radio wave having current time information.

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