JP4915081B2 - rice cooker - Google Patents

Description

  The present invention relates to a rice cooker having a function of detecting disconnection of a heating means for heating a pan.

  Conventionally, in this type of rice cooker, an induction heating coil or heater using high-frequency induction heating is used as a heating means for heating a pan, and for example, an induction heating coil is driven as a means for driving these heating means. Sometimes a semiconductor switching element is used, and when a heater is driven, a relay or a semiconductor switching element is used.

Here, in the conventional rice cooker, the disconnection of a heating means (an induction heating coil, a heater, etc.) is determined as follows. First, current detection means for detecting an input current to the heating means is provided to detect an input current when the semiconductor switching element or the relay is turned on, and when it is lower than a predetermined value, it is determined that the circuit is disconnected (for example, Patent Documents) 1 and 2).
JP 2004-275645 A JP 2001-95683 A

  However, in such a conventional configuration, since an input current is once passed through the heating means, there is a problem that it is not possible to immediately determine that a disconnection occurs when the power outlet is turned on or when waiting for reservation. It was.

  The present invention solves the above-mentioned conventional problems, and aims to provide a safe rice cooker by reliably detecting a disconnection of the heating means at an early stage without passing an electric current to the heating means and notifying the user. It is said.

In order to achieve the above object, the present invention provides a heating means for heating a pan, a capacitor constituting a parallel resonance circuit with the heating means, and a series connection to the heating means, and interrupts the current path of the heating means. Switching means for controlling, control means for turning on and off the switching means, first disconnection determining means for determining disconnection of the heating means, abnormality notifying means for notifying disconnection of the heating means, and rectification for rectifying AC current Power supply voltage detection means for detecting a voltage obtained by dividing the power supply voltage of the AC power supply, and a both-end voltage detection means for detecting a voltage obtained by dividing the voltage at the connection between the heating means and the switching means, and determining disconnection. The means compares the output of the power supply voltage detection means with the output of the both-end voltage detection means, and determines that the heating means is disconnected when the output value of the power supply voltage detection means is larger. The abnormality notification unit performs the abnormality notification corresponding to disconnection, the rectifying means comprises a low-frequency magnetic field cancellation means constituted by the winding having the same frequency component as the low-frequency component of the current flowing through the heating coil, The low-frequency magnetic field canceling means is disposed in the vicinity of the heating coil so that the low-frequency magnetic field of the low-frequency magnetic field canceling means and the low-frequency magnetic field generated by the heating coil cancel each other, and the output of the power supply voltage detecting means Comparing the voltage with the output voltage of the rectifying means, and when the output voltage of the power supply voltage detecting means is large, it has second disconnection determining means for determining disconnection of the low frequency magnetic field canceling means. To do .

As a result , disconnection can be detected without passing current through the heating means, and disconnection can be determined by the voltage across the switching means. Therefore, disconnection can be detected when the switching means is turned off. It is possible to detect disconnection before starting rice cooking, and to notify the user.

  The rice cooker of this invention can detect the disconnection of a heating means early and reliably without supplying an electric current to a heating means, can alert | report to a user, and can provide a safe rice cooker.

The present invention includes a heating means for heating the pot, and a capacitor that constitute a parallel resonant circuit and the heating means, and a switching means and said series connected to the heating means, interrupting the current path of the heating means, for energizing the switching Control means for turning on / off means, first disconnection determining means for determining disconnection of the heating means, abnormality notifying means for notifying disconnection of the heating means, rectifying means for rectifying AC current, and power source of AC power supply A power supply voltage detecting means for detecting a voltage obtained by dividing the voltage; and a both-end voltage detecting means for detecting a voltage obtained by dividing the voltage at the connecting portion between the heating means and the switching means. The output of the means is compared with the output of the both-end voltage detection means, and when the output value of the power supply voltage detection means is larger, the heating means is determined to be disconnected, and the abnormality notification means is Performs the corresponding abnormality notifying to said rectifying means comprises a low-frequency magnetic field cancellation means constituted by the winding having the same frequency component as the low-frequency component of the current flowing through the heating coil, the low-frequency magnetic field cancellation means Is arranged in the vicinity of the heating coil so that the low frequency magnetic field of the low frequency magnetic field canceling means and the low frequency magnetic field generated by the heating coil cancel each other, and the output voltage of the power supply voltage detecting means and the output of the rectifying means When the output voltage of the power supply voltage detection means is large by comparing the voltages, there is provided a second disconnection determining means for determining disconnection of the low frequency magnetic field canceling means. For this reason, the disconnection of the low-frequency magnetic field canceling means or the disconnection of the heating means can be detected without passing an electric current to the heating means, and the disconnection can be determined by the voltage across the switching means. Disconnection can be detected at the same time, disconnection can be detected before starting cooking, such as during standby or reservation, can be notified to the user, and an abnormal stop can be detected early.

  Furthermore, the disconnection of the induction heating coil through which a large current flows compared to the heater can be detected without passing the current, can be notified to the user, and an abnormal stop can be found early.

Furthermore, the output of the existing power supply voltage detection means can be used, and an increase in mounting area and an increase in cost can be suppressed.

Further, it is possible to recognize whether the heating coil is disconnected or the low-frequency magnetic field canceling means is disconnected, and repair can be performed at an early stage.

  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 in Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the rice cooker. In FIG. 2, lead wires for electrical connection and screws for fixing components are omitted to simplify the drawing.

  As shown in FIG. 1, the heater 1 constitutes a heating means, is configured in a spiral shape, and is configured to heat the pan 25 (see FIG. 2). The pan is composed of a laminated body using a plurality of metals.

  The switching means 2 is connected in series to the heater 1 so that the current path of the heater 1 is cut off and energized. In the present embodiment, the switching means 2 is configured by a relay, but is not limited thereto, and may be configured by a semiconductor element such as a bidirectional thyristor.

The control means 3 turns on and off the switching means 2 and is composed of a microcomputer and a peripheral circuit. The rice cooking process and the heat retention process specific to the rice cooker are stored in the ROM, and switching is performed according to the rice cooking process and the heat insulation process. A signal for turning on / off means 2 is output.

  The voltage detection means 4 detects a voltage obtained by dividing the voltage across the heater 1, and includes a first voltage dividing circuit including resistors 5 and 6, a second voltage dividing circuit including resistors 7 and 8, and The output of the first voltage dividing circuit is compared with the output of the second voltage dividing circuit, and the comparator 9 is configured to output high or low. In the present embodiment, the first voltage dividing circuit is connected to one terminal of the heater 1, and the second voltage dividing circuit is connected to the other terminal of the heater 1.

  In this embodiment, when the switching means 2 is off, the voltage dividing ratio is adjusted so that the output voltage of the first voltage dividing circuit is lower than the output voltage of the second voltage dividing circuit when the heater 1 is normal. Therefore, the output of the comparison circuit 9 is high during normal operation. On the other hand, when the heater 1 is disconnected, when the switching means 2 is off, the output voltage of the second voltage dividing circuit becomes 0 V through the resistor 8, and the output voltage of the first voltage dividing circuit becomes larger. The output of the comparison circuit 9 changes to low. That is, the output of the comparison circuit 9 changes without disconnection.

  The disconnection determining means 10 determines disconnection of the heater 1 and is configured using the same microcomputer as the control means 3. The disconnection determination means 10 inputs the signal of the voltage detection means 4 when the control means 3 is turning off the heater 1, and determines that the disconnection occurs when the output of the voltage detection means 4 is low.

  The abnormality notifying means 11 notifies the disconnection of the heater 1 and is composed of a buzzer and a liquid crystal. When the disconnection determination means 10 determines that the disconnection has occurred, the abnormality notification means 11 outputs a buzzer sound and switches the content of the liquid crystal display from a normal display to a display at the time of abnormality. For example, in the present embodiment, the liquid crystal has a time display unit that displays the current time, and the time display unit is used to perform display indicating the disconnection of the heater 1. In this embodiment, “U30” is displayed.

  The AC power supply 12 supplies power to the rice cooker. The power supply frequency of the AC power supply 12 is 50 Hz or 60 Hz in Japan, and the power supply voltage is 100V.

  Next, as shown in FIG. 2, the rice cooker body 21 is provided with a cover 22 that can be opened and closed on its upper surface, and is a heating means on the bottom and side portions of the storage portion 23 provided inside, as shown in FIG. 1. A bottom heater 24 constituting the heater 1 is provided.

  The pan 25 is made of a laminated body of metal such as aluminum, has a flange 26 protruding outward from the upper end opening, and is placed in a state where the flange 26 is lifted from the upper end of the storage unit 23. 23 is detachably stored. A detachable lid heating plate 27 is attached to the lid 22, and the lid heating plate 27 is made of a metal such as stainless steel. A lid heater 28 is built in the lid 22 to heat the lid heating plate 27.

  The first circuit board 29 is mounted with a switch, an LCD constituting the abnormality notifying means 11, a microcomputer constituting the control means 3, and the like. Although not particularly illustrated, the second circuit board 30 is mounted with a relay that constitutes the switching means 2, a buzzer that constitutes the abnormality notification means 11, and the like.

  The wind-up type power cord storage unit 31 is electrically connected to the second circuit board 30 via a lead wire. The power cord storage portion 31 is configured to wind up the power cord using a stopper and a spring.

The temperature detection means 32 is composed of a thermistor and is arranged at the approximate center of the bottom of the pan 25. 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.

  Although not particularly shown, the first circuit board 29 and the second circuit board 30 are electrically connected by lead wires. The block diagram of FIG. 1 shows the peripheral circuit block of the bottom heater 24, and the lid heater 28 is omitted, but the lid heater 28 is similarly provided with voltage detection means and disconnection judgment means. By providing, disconnection determination can be performed. At this time, the abnormality notifying means makes it easy to repair the failure by enabling the disconnection of the bottom heater 24 and the disconnection of the lid heater 27 to be distinguished.

  In this way, the two heating means of the bottom heater 24 and the lid heater 28 are controlled by the microcomputer (control means) mounted on the first circuit board 29, and the rice cooking process stored in advance is executed.

  Here, when the heater 1 is turned off, the disconnection determination means 10 turns off the heater 1 when the output of the voltage detection means 4 that detects a voltage obtained by dividing the voltage across the heater 1 becomes low (exceeds a predetermined value). It is determined that there is a disconnection, and the abnormality notification means 11 is configured to perform an abnormality notification corresponding to the disconnection.

  The operation in the above configuration will be described. When the switching means 2 is off and the heater 1 is normal, the output voltage of the first voltage dividing circuit constituting the voltage detecting means is lower than the output voltage of the second voltage dividing circuit. The output of is high. On the other hand, when the heater 1 is disconnected, when the switching means 2 is off, the output voltage of the second voltage dividing circuit becomes 0 V through the resistor 8, and the output voltage of the first voltage dividing circuit becomes larger. The output of the comparison circuit 9 changes to low.

  The disconnection determination means 10 receives the signal of the voltage detection means 4 and determines that the disconnection occurs when the output of the comparison circuit 9 is low. When the disconnection determination means 10 determines that the disconnection has occurred, the abnormality notification means 11 outputs a buzzer sound and switches the content of the liquid crystal display from a normal display to a display at the time of abnormality.

  As described above, in the present embodiment, when the heater 1 is turned off, the disconnection determination unit 10 outputs a low output from the voltage detection unit 4 that detects a voltage obtained by dividing the voltage across the heater 1 (a predetermined value). The heater 1 is determined to be disconnected, and the abnormality notification unit 11 is configured to perform abnormality notification corresponding to the disconnection. Therefore, since the disconnection can be detected without passing a current through the heater 1, the switching unit 2 is Disconnection can be detected when it is off, disconnection can be detected before starting cooking, such as during standby or reservation, and can be notified to the user, and an abnormal stop can be detected early.

(Embodiment 2)
FIG. 3 is a principal block diagram of the rice cooker in the second embodiment of the present invention.

  As shown in FIG. 3, the voltage detection means 41 detects a voltage obtained by dividing the voltage across the heater 1, and includes a parallel circuit of resistors 42 and 43 connected to both ends of the heater 1, and the parallel circuit and the resistance. The voltage dividing circuit is divided by 44 and 45, and an emitter follower circuit including a resistor 46, an NPN transistor 47, a capacitor 48, and a resistor 49 for peak-holding the output voltage of the voltage dividing circuit. The voltage detection means 41 outputs an analog voltage, and the disconnection determination means 50 inputs this analog voltage, and determines that it is disconnected if it is lower than a predetermined value. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

The operation in the above configuration will be described. If the heater 1 is disconnected when the switching means 2 is off, the terminal of the resistor 43 on the heater 1 side is opened, and the parallel circuit of the resistors 42 and 43 is only the resistor 42. Therefore, the voltage dividing circuit is also composed of the resistors 42, 44 and 45, and the output voltage of the emitter follower circuit becomes smaller than that when the heating means 1 is normal.

In this embodiment, when the resistance values of the resistors 42 and 43 are 96R and the resistance values of 44 and 45 are R, the output voltage when the heater 1 is not disconnected is
100V × R / (96R / 2 + R + R) = 2V
The output voltage when the heater 1 is disconnected is
100V × R / (96R + R + R) = 1.02V
It becomes. Therefore, disconnection of the heater 1 can be determined by setting 1.5V as a threshold value.

  As described above, if the analog voltage is directly input, the mounting area of the comparison circuit can be omitted.

(Embodiment 3)
FIG. 4 is a principal block diagram of the rice cooker in Embodiment 3 of the present invention.

  As shown in FIG. 4, the heating coil 51 generates a high-frequency magnetic field and constitutes a heating means for induction heating the pan. Although not particularly shown, the heating coil 51 has a spiral shape and is fixed to the bottom of the pan. They are arranged at a distance and are magnetically coupled to the bottom of the pan. The heating coil 51 is composed of a wire obtained by twisting more than 20 litz wires in which a plurality of copper wires are bundled, and makes the current distribution uniform when a high-frequency current flows. The resonant capacitor 52 is connected in parallel to the heating coil 51. In the present embodiment, a polypropylene capacitor having a small loss even when a high-frequency current flows is used.

  The switching means 53 is constituted by a semiconductor element called IGBT and a diode reversely connected to the IGBT. The IGBT has a high withstand voltage, can switch at a high frequency, can flow a large current by applying a voltage to the gate terminal, and has an advantage that a large current can be flowed with less power than a power transistor.

  The rectifying means 54 includes a diode bridge 55, a choke coil 56, and a smoothing capacitor 57. Here, the capacity of the smoothing capacitor 57 is as small as several μF, and ripple occurs when a current is passed through the heating coil 51. In the present embodiment, this ripple voltage waveform is the same as the voltage waveform of the AC power supply 12.

  The power supply voltage detecting means 58 detects a voltage obtained by dividing the power supply voltage of the AC power supply 12, and includes a resistor 59 connected to the (u) pole of the AC power supply 12 and a resistor connected to the (v) pole of the AC power supply. 60, a resistance voltage dividing circuit composed of a resistor 61 connected to the ground, and a first emitter follower circuit 62 for peak-holding the output voltage of this resistance voltage dividing circuit.

  The both-end voltage detection means 63 detects a voltage obtained by dividing the voltage at the connection portion between the heating coil 51 and the switching means 53, and includes a resistor 64 connected to the connection portion (c) between the heating coil 51 and the switching means 53; A resistor voltage divider circuit composed of a resistor 65 connected to the ground and a second emitter follower circuit 66 for peak-holding the output voltage of the resistor voltage divider circuit.

The control means 67 is constituted by a microcomputer 68 and its peripheral circuits, and a rice cooking process and a heat retention process are stored in advance in a ROM in the microcomputer 68. The control means 67 performs on / off control of the switching means 53 according to this process. Further, the control means 67 inputs the output voltage of the power supply voltage detection means 58 and the output voltage of the both-end voltage detection means 63 via the AD input port 69 of the microcomputer 68, and the energization ratio of the switching means 3 is determined according to these values. It is adjusted.

  The disconnection determining means 70 determines disconnection of the heating coil 51 and is configured using the microcomputer 68. The output voltage of the power supply voltage detection means 58 and the output voltage of the both-end voltage detection means 63 are determined by the microcomputer 68. When the output value of the power supply voltage detection means 58 is larger, the heating coil 51 is determined to be disconnected.

  The abnormality notifying means 71 is composed of a liquid crystal and a buzzer. When the disconnection determining means 70 determines that the heating coil 51 is disconnected, a liquid crystal display indicating a disconnection and a buzzer notification are performed. Although not specifically shown, the drive circuit 72 is constituted by a push-pull circuit constituted by an NPN transistor and a PNP transistor, and supplies power to the IGBT constituting the switching means 3 while the output of the control means 67 is high, Turn on the IGBT.

  Here, the disconnection determination means 70 compares the output of the power supply voltage detection means 48 with the output of the both-end voltage detection means 63, and when the output value of the power supply voltage detection means 58 is larger, the heating coil path 51 is determined to be disconnected. It is configured to determine.

  The operation of the above configuration will be described with reference to FIG. FIG. 5 shows a flowchart of disconnection determination in the rice cooker of the present embodiment. First, when the state of the rice cooker is a standby process, that is, a state in which nothing is connected to the AC power source 12 or a reservation standby process, disconnection determination as shown in FIG. 5 is performed.

  In step S 1, the output voltage of the power supply voltage detection means 58 is converted into a digital value via the AD input port 69 and temporarily stored in the microcomputer 68. The digital value input at this time is set to V58. In step S2, the first predetermined value Vs1 preset in the ROM of the microcomputer 68 is compared with the digital value V58. If the digital value V58 is large, it is determined that the AC power supply 12 is normal, and the process proceeds to step S3. If value V58 is small, it will progress to step S8, it determines with the power supply voltage of AC power supply 12 being abnormal, and disconnection determination is stopped.

  In step S3, the control means 67 turns off the switching means 53 and confirms whether the heating coil 51 is turned off. When the heating coil 51 is turned on, the disconnection determination is stopped. If the heating coil 51 is off, the process proceeds to step S4. In step S 4, the output voltage of the both-end voltage detection means 63 is converted into a digital value via the AD input port 69 and temporarily stored in the microcomputer 68. The digital value input at this time is set to V63.

  In step S5, the digital value V58 is compared with the digital value V63. If the digital value V58 is large, it is determined that the heating coil 51 is disconnected, and the process proceeds to step S6. If the digital value V58 is small, disconnection determination is stopped.

  In step S6, since it is determined that the heating coil 51 is disconnected, the abnormality notifying means 71 outputs a display indicating that the heating coil 51 is disconnected and a buzzer sound that notifies the abnormality. In this embodiment, the buzzer sound is output for a certain period, but the display continues to be displayed until the user recognizes it and performs an operation such as turning off the power or pressing the off switch.

  The power supply voltage detection means 58 used in the present embodiment is for detecting a power supply voltage abnormality even during the rice cooking operation, or for reducing the energization ratio of the switching means 53 and making the input power substantially constant when the power supply voltage is high. Used for voltage detection. The both-end voltage detection means 63 is used for voltage detection so that the voltage at both ends of the switching means 53 becomes high during the rice cooking operation so that the maximum rating is not exceeded.

  As described above, in the present embodiment, the disconnection determination means 70 compares the output of the power supply voltage detection means 58 with the output of the both-end voltage detection means 63, and the output value of the power supply voltage detection means 58 is larger. Since the heating coil 51 is determined to be disconnected, the disconnection of the heating coil 51 can be determined using the power supply voltage detection means 58 and the both-end voltage detection means 63 that are used even during the rice cooking operation. It becomes unnecessary, and the effect that the cost and the mounting area are not increased can be obtained.

  In addition, since the heating means includes the heating coil 51 that generates a high-frequency magnetic field, it is possible to detect disconnection of the heating coil 51 in which a large current flows compared to the heater without flowing current, and to notify the user, An abnormal stop can be detected early.

(Embodiment 4)
FIG. 6 is a principal block diagram of the rice cooker in the fourth embodiment of the present invention. Note that the same components as those in the third embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 6, the synchronization signal generating unit 81 compares the output voltage of the rectifying unit 54 with the voltage obtained by dividing the voltage of the connection portion of the heating coil 51 and the switching unit 53, and determines when the switching unit 53 is turned on. A first voltage dividing circuit in which the output of the rectifying means 54 is divided by resistors 82 and 83; and a second voltage in which the voltage at the connection between the heating coil 51 and the switching means 53 is divided by resistors 84 and 85. And a comparison circuit 86 that compares the output voltages of the first voltage dividing circuit and the second voltage dividing circuit, and outputs high or low.

  The voltage dividing ratios of the first voltage dividing circuit and the second voltage dividing circuit are different, and the output voltage of the first voltage dividing circuit is set to be lower when the heating coil 51 is off. Therefore, when the heating coil 51 is normal and not driven, the synchronization signal output means 81 outputs low, and when the heating coil 51 is disconnected, the synchronization signal output means 81 outputs high.

  The control means 87 is configured using a microcomputer 88, and when the heating coil 51 is turned on in the rice cooking process, the switching means 53 is turned on by using an edge when the output signal of the synchronization signal generating means 81 becomes low to high as a trigger. The signal is output to the drive circuit 72. In the microcomputer 88, a standby process, a reservation standby process, a rice cooking process, and a heat retention process are stored in advance, and although not particularly illustrated in FIG. 6, by pressing a reservation switch, a rice cooking switch, a heat retention switch, and a switch off, , Transition to each step. Note that a state where the AC power supply 12 is connected and nothing is performed is a standby process.

  The disconnection determination means 89 is configured by using the microcomputer 88, and confirms the output of the synchronization signal generation means 81 during the standby process or the reservation standby process. When the disconnection determining means 89 determines that the disconnection has occurred, the abnormality notifying means 71 outputs a display meaning disconnection and a buzzer meaning abnormality.

As described above, in the present embodiment, the output voltage of the rectifying unit 54 is compared with the voltage obtained by dividing the voltage of the connection portion of the heating coil 51 and the switching unit 53, and the switching unit 53 is turned on. Since the synchronization signal generation means 81 is provided, and the disconnection determination means 89 determines the disconnection of the heating coil 51 based on the output of the synchronization signal generation means 81 when the heating coil 51 is off, the existing synchronization signal generation means 81 is provided. This eliminates the need for new circuits and components, and prevents an increase in mounting area and cost.

(Embodiment 5)
FIG. 7 is a main block diagram of a rice cooker according to Embodiment 5 of the present invention.

  As shown in FIG. 7, the rectifying unit 91 includes a diode bridge 55, a choke coil 56, a low-frequency magnetic field canceling unit 92, and a smoothing capacitor 57.

  The low-frequency canceling means 92 is composed of a winding having the same frequency component as the low-frequency component of the current flowing through the heating coil 51, and a side portion of the rice cooker, for example, the storage portion 23 for storing the pan 25 (both shown in FIG. 2)), the heating coil 51 and the winding wound several turns concentrically. At this time, the coil is wound such that the direction of the current flowing through the low frequency magnetic field canceling unit 92 is opposite to the direction of the current flowing through the heating coil 51. Here, the heating coil 51 is composed of a bottom heating coil disposed on the bottom and side portions of the storage portion 23 and a lid heating coil for heating a lid heating plate (none of which is shown) built in the lid. ing.

  A voltage dividing circuit including resistors 93 and 94 divides the output voltage of the diode bridge 55. The comparison circuit 95 is constituted by an IC, and compares the output voltage of the voltage dividing circuit composed of the resistors 93 and 94 with the output voltage of the voltage dividing circuit composed of the resistors 82 and 83, and outputs high or low. The voltage dividing ratio of the resistors 93 and 94 is different from the voltage dividing ratio of the resistors 82 and 83. When the low frequency magnetic field canceling means 92 is connected, the output voltage of the voltage dividing circuit composed of the resistors 93 and 94 is used. Is set to be larger. Therefore, when the low-frequency magnetic field canceling means 92 is not disconnected, the comparison circuit 95 outputs low, and when the low-frequency magnetic field canceling means 92 is disconnected, the comparison circuit 95 is composed of resistors 82 and 83. Since the output voltage becomes 0, the comparison circuit 95 outputs high.

  Since the resistors 82 and 83 constitute the synchronization signal generating means 81 as in the fourth embodiment, description thereof is omitted here.

  The microcomputer 96 is used to realize the control means 87, the first disconnection determination means 97, and the second disconnection determination means 98. As in the fourth embodiment, the microcomputer 96 stores a rice cooking process, a heat retaining process, a standby process, and a reservation standby process in the ROM.

  Similar to the fourth embodiment, the first disconnection determination means 97 detects the output of the synchronization signal generation means 81 during the standby process or the reservation standby process, and determines whether the heating coil 51 is disconnected. The second disconnection determining means 98 detects the output of the comparison circuit 95 during the standby process or the reservation standby process, and determines whether the low frequency magnetic field canceling means 92 is disconnected.

  The abnormality notification means 99 is composed of a liquid crystal and a buzzer. When the first disconnection determination means 97 determines disconnection, the abnormality notification means 99 outputs a display indicating that the heating coil 51 is disconnected and a buzzer sound indicating abnormality. When the second disconnection determining means 98 determines the disconnection, a display indicating that the low-frequency magnetic field canceling means 92 is disconnected and a buzzer sound indicating an abnormality are output.

  The operation of the above configuration will be described with reference to FIG. FIG. 8 is a flowchart for determining disconnection of the rice cooker according to the present embodiment. The rice cooker of embodiment performs the disconnection determination shown in FIG. 8 at the time of a standby process or a reservation standby process.

  In step S81, the second disconnection determination means 98 determines whether the output of the comparison circuit 95 is high or low. If it is high, it is determined that the low frequency magnetic field canceling means 92 is disconnected, and the process proceeds to step S82. If it is low, it is determined that the low frequency magnetic field canceling means 92 is not disconnected, and the process proceeds to step S83.

  In step S82, the abnormality notifying means 99 receives the output of the microcomputer 96, outputs a display indicating the disconnection of the low frequency magnetic field canceling means 92, and outputs a buzzer sound indicating an abnormality to notify the disconnection, thereby determining disconnection. Exit. In the present embodiment, as in the first embodiment, “U31” is displayed using the time display unit of the liquid crystal.

  In step S83, the first disconnection determining means 97 determines whether the output of the synchronization signal generating means 81 is high or low. If it is high, it is determined that the heating coil 51 is disconnected, and the process proceeds to step S84. If it is, it will determine with the heating coil 51 not having disconnected, and a disconnection determination will be complete | finished.

  In step S84, the abnormality notification means 99 receives the output of the microcomputer 99, outputs a display indicating the disconnection of the heating coil 51 and a buzzer sound indicating an abnormality, notifies the disconnection, and ends the disconnection determination. In the present embodiment, as in the first embodiment, “U30” is displayed using the time display unit of the liquid crystal.

  Thus, the rice cooker of this Embodiment can reduce the low frequency magnetic field generated from the bottom heating coil and the lid heating coil by providing the low frequency magnetic field canceling means 102. In addition, since the disconnection of the low-frequency magnetic field canceling means 102 can be determined, the failure location can be determined immediately and repaired.

  As described above, in the present embodiment, the rectifying unit 91 includes the low-frequency magnetic field canceling unit 92 configured by the winding having the same frequency component as the low-frequency component of the current flowing through the heating coil 51. The frequency magnetic field canceling means 92 is disposed in the vicinity of the heating coil 51 so that the low frequency magnetic field of the low frequency magnetic field canceling means 92 and the low frequency magnetic field generated by the heating coil 51 are in the direction to cancel each other. The second disconnection determining means 98 for comparing the output voltage of the power supply voltage detecting means and the output voltage of the rectifying means 91 to determine the disconnection of the low frequency magnetic field canceling means 92 can be reduced. Therefore, it is possible to recognize whether the heating coil 51 is disconnected or the low-frequency magnetic field canceling unit 92 is disconnected, and repair can be performed at an early stage.

  In addition, the abnormality notifying means 99 changes the display contents in accordance with the determination results of the first disconnection determining means 97 and the second disconnection determining means 98, so that the fault location is clarified and repaired at an early stage. can do.

  As described above, the rice cooker according to the present invention can detect the disconnection of the heating means early and reliably without passing an electric current to the heating means, and can notify the user, and provides a safe rice cooker. Therefore, it is useful as a rice cooker having a function of detecting disconnection of the heating means for heating the pan.

Main part block diagram of rice cooker in Embodiment 1 of this invention Cross section of the rice cooker Main part block diagram of rice cooker in Embodiment 2 of this invention Main part block diagram of rice cooker in Embodiment 3 of this invention Flow chart of disconnection judgment of the rice cooker Main part block diagram of rice cooker in Embodiment 4 of this invention Main part block diagram of rice cooker in Embodiment 5 of this invention Flow chart of disconnection judgment of the rice cooker

1 Heater (heating means)
2 switching means 3 control means 10 disconnection judging means 11 abnormality notifying means 25 pan

Claims (1)

A heating means for heating the pan, a capacitor constituting a parallel resonance circuit with the heating means, a switching means connected in series to the heating means, cutting off a current path of the heating means, and energizing the heating means, and turning on and off the switching means Control means, first disconnection determination means for determining disconnection of the heating means, abnormality notification means for informing about disconnection of the heating means, rectification means for rectifying an alternating current, and dividing the power supply voltage of the AC power supply A power supply voltage detection means for detecting the detected voltage, and a both-end voltage detection means for detecting a voltage obtained by dividing the voltage at the connection between the heating means and the switching means, and the disconnection determination means is configured to output the power supply voltage detection means. The output of the both-end voltage detection means is compared, and when the output value of the power supply voltage detection means is larger, the heating means is determined to be disconnected, and the abnormality notification means corresponds to disconnection. It performs abnormality notification,
The rectifying means includes low-frequency magnetic field canceling means composed of a winding having the same frequency component as the low-frequency component of the current flowing through the heating coil, and the low-frequency magnetic field canceling means is the low-frequency magnetic field canceling means. The low-frequency magnetic field and the low-frequency magnetic field generated by the heating coil are arranged in the vicinity of the heating coil so as to cancel each other, and the output voltage of the power supply voltage detection means and the output voltage of the rectification means are compared, A rice cooker comprising second disconnection determining means for determining disconnection of the low frequency magnetic field canceling means when the output voltage of the voltage detecting means is large .