JP2006134628A - Induction heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating device constituted so that a current flowing in a coil heating a pot is controlled by an energizing control element by connecting a resonance capacitor in parallel and having no large peak at a fixed frequency by dispersing a spectrum of radiation noises. <P>SOLUTION: The pot 1 is attachably/detachably housed in a body of a rice cooker, and the bottom part of the pot 1 is heated by induction heating with the coil 2, The resonance capacitor 3 is connected with the coil 2 in parallel. A feedback diode 6 is provided in parallel with the energizing control element 5 controlling the current flowing in the coil 2. The energizing control element 5 is energized for a set times Ton with a timer means 7. If a detected current value Iin of a current value detection means 9 detecting a current value supplied to a DC power supply exceeds a threshold Iin3 of a third current value set by a third current value setting means 15 and equal to or larger than Iin2 and equal to or less than Iin1, the set time Ton of the timer means 7 is periodically increased and decreased by a Ton changing means 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an induction heating apparatus configured to connect a resonance capacitor in parallel and control a current flowing in a coil for heating a pan by an energization control element.

  Conventionally, this type of induction heating apparatus is configured as shown in FIG. Hereinafter, the configuration will be described.

  As shown in FIG. 7, the pan 1 is detachably housed in a rice cooker body (not shown), and the bottom of the pan 1 is heated by induction heating with a coil 2. A resonance capacitor 3 is connected in parallel to the coil 2 so that a current is supplied from the DC power source 4 to the coil 2 and the current flowing through the coil 2 is controlled by the energization control element 5. A reflux diode 6 is installed in parallel with the energization control element 5, and the timer means 7 makes the energization control element 5 conductive for a set time Ton. The trigger means 8 monitors the coil 2 voltage and starts counting the set time Ton. The current value detection means 9 detects the current value Iin supplied to the DC power supply 4.

  When the detected current value Iin of the current value detecting means 9 has not reached the threshold value Iin1 of the first current value set by the first current value setting means 10, the soft start means 11 sets the set time Ton of the timer means 7 The threshold value Iin2 of the second current value is set by the second current value setting means 12, and the timer setting time Ton is set even though the detected current value Iin of the current value detection means 9 is equal to or less than Iin2. Is over the timer time threshold value Ton1 set by the first timer time setting means 13, the accessory detection means 14 stops the drive signal to the energization control element 5 of the timer means 7.

  In the above configuration, when the oscillation of the induction heating device is started, the soft start means 11 gradually increases the set time Ton of the timer means 7 and increases the conduction time of the energization control element 5. As the conduction time of the energization control element 5 increases, the detected current value Iin of the current value detecting means 9 increases, and after reaching the first current value threshold value Iin1 set by the first current value setting means 10 The soft start means 11 stops the increase of the set time Ton, and then the energization control element 5 repeats conduction for a fixed set time Ton (conduction time). Therefore, the oscillation frequency is constant.

  The trigger means 8 monitors the voltage on one side or both ends of the coil 2, generates a trigger signal, and starts the Ton count of the timer means 7. The timer means 7 starts counting the set time Ton and outputs a drive signal to the energization control element 5, the energization control element 5 becomes conductive, and a current flows through the coil 2.

Although the detected current value Iin of the current value detecting means 9 is not more than the threshold value Iin2 of the second current value set by the second current value setting means 12, the timer setting time Ton is set to the first timer time setting. When the timer time threshold value Ton1 set by the means 13 is exceeded, it is determined that it is not the pot 1 but the small thing other than the pot, and the drive signal to the energization control element 5 of the timer means 7 is determined. Is stopped, and energization of the coil 2 is stopped (see, for example, Patent Document 1).
JP 2000-166757 A

  However, such a conventional configuration has a problem that the oscillation frequency of the induction heating device is substantially fixed, and the spectrum of the radiation noise is fixed at a constant frequency and has a large peak.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an induction heating apparatus that disperses the spectrum of radiation noise and does not have a large peak at a constant frequency.

  In order to achieve the above object, the present invention detachably stores a pot in the rice cooker body, heats the bottom of the pot by induction heating with a coil, and connects a resonance capacitor in parallel to the coil. A free-wheeling diode is installed in parallel with the energization control element that controls the current flowing through the coil, the energization control element is made conductive for the set time Ton by the timer means, the coil voltage is monitored by the trigger means, and the timing of the set time Ton is started. When the detected current value Iin of the current value detecting means for detecting the current value Iin supplied to the DC power supply has not reached the first current value threshold value Iin1 set by the first current value setting means, soft start is performed. The set time Ton of the timer means is gradually increased by the means, and the detected current value Iin of the current value detecting means is set to the second current set by the second current value setting means. When the set time Ton of the timer means exceeds the threshold time Ton1 set by the first timer time setting means even though the threshold value Iin2 is less than or equal to the threshold value Iin2, the accessory detection means drives the energization control element of the timer means. When the signal is stopped and the detected current value Iin of the current value detecting means exceeds the threshold value Iin3 of the third current value not less than Iin2 and not more than Iin1 set by the third current value setting means, the Ton changing means The set time Ton of the timer means is periodically increased or decreased.

  As a result, the oscillation frequency of the induction heating device constantly varies periodically, and the spectrum of the radiation noise can be dispersed so as not to have a large peak at a constant frequency. During startup, during the soft start, while the detection current Iin of the current value detection means is lower than Iin3 set larger than Iin2, the fluctuation of Iin is suppressed by prohibiting the fluctuation of Ton. Small object detection that is performed when the detected current value Iin is equal to or smaller than Iin2 and that is determined as a small object when the set time Ton of the timer exceeds the threshold value Ton1 can be accurately performed.

  The induction heating apparatus of the present invention can vary the oscillation frequency to disperse the spectrum of radiation noise so that it does not have a large peak at a certain frequency, and also occurs during the soft start at the time of startup, which occurs as a negative effect of oscillation frequency fluctuations. It is possible to prevent the detection accuracy of the small object detection performed in step 1 from being lowered.

  A first invention is a pot that is detachably stored in a rice cooker body, a coil that heats the bottom of the pot by induction heating, a resonance capacitor connected in parallel to the coil, and the coil A direct current power source for supplying current, an energization control element for controlling the current flowing in the coil, a free wheel diode installed in parallel to the energization control element, and a timer means for energizing the energization control element for a set time Ton Trigger means for monitoring the coil voltage and starting timing of the set time Ton; current value detecting means for detecting the current value Iin supplied to the DC power supply; and a first current value threshold value Iin1 Current value setting means, and when the detected current value Iin of the current value detection means has not reached the first current value threshold value Iin1, the set time Ton of the timer means is gradually increased. Soft-start means for setting, second current value setting means for setting a second current value threshold value Iin2, first timer time setting means for setting a timer time threshold value Ton1, and detection by the current value detection means The drive signal to the energization control element of the timer means is stopped when the set time Ton of the timer means exceeds the threshold time Ton1 of the timer means even though the current value Iin is less than or equal to the second current value threshold Iin2. An accessory detection means; a third current value setting means for setting a third current value threshold value Iin3 between Iin2 and Iin1; and a detected current value Iin of the current value detection means is a third current value threshold value Iin3. And a Ton fluctuation means for periodically increasing or decreasing the set time Ton of the timer means, the oscillation frequency of the induction heating device is always set to the frequency. It is possible to change the spectrum of the radiation noise so that it does not have a large peak at a certain frequency, and the current detection means is detected during the soft start at the start of oscillation of the induction heating device. While the current Iin is lower than Iin3 which is set to be larger than Iin2, the variation of Iin is suppressed by prohibiting the variation of Ton, and the timer is operated when the detected current value Iin of the current detection means is equal to or smaller than Iin2. It is possible to accurately detect an accessory that is determined to be an accessory when the set time Ton exceeds the threshold value Ton1.

  In a second aspect based on the first aspect, the Ton changing means is configured to change randomly when the detected current value Iin of the current value detecting means exceeds the threshold value Iin3 of the third current value. The set time Ton of the timer means is increased or decreased at all times, and the oscillation frequency of the induction heating device constantly varies at random, disperses the spectrum of radiation noise, and does not have a large peak at a constant frequency. In addition, during the soft start at the start of the oscillation of the induction heating device, the variation of Ton is prohibited while the detected current value Iin of the current detecting means is lower than Iin3 set larger than Iin2. Thus, the variation in Iin is suppressed, and the timer setting time Ton that is performed when the detected current value Iin of the current detecting means is equal to or smaller than Iin2 is the threshold value Ton1. It can be accurately small sensing to determine that small when exceeded.

  According to a third aspect of the present invention, in the first or second aspect of the invention, there is provided zero volt detection means for detecting zero volt of the AC power supply, and the Ton fluctuation means is a timer synchronized with a zero volt detection signal output from the zero volt detection means. The setting time Ton of the means is changed, and the setting time Ton of the timer means is changed near zero volts of the AC power supply. Originally, in the vicinity of zero volts of this AC power supply, the voltage of the DC power supply is low, the current flowing through the coil is small, and the repulsive force against the coil of the pan is small, so there is little difference in the repulsive force applied to the pan before and after Ton fluctuation, It is possible to prevent abnormal noise from being produced from the pan.

  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 partial block circuit diagram of the induction heating apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the pan 1 is detachably housed in a rice cooker body (not shown), and the bottom of the pan 1 is heated by induction heating with a coil 2. A resonance capacitor 3 is connected in parallel to the coil 2 so that a current is supplied from the DC power source 4 to the coil 2 and the current flowing through the coil 2 is controlled by the energization control element 5. A reflux diode 6 is installed in parallel with the energization control element 5, and the timer means 7 makes the energization control element 5 conductive for a set time Ton. The trigger means 8 monitors the coil 2 voltage and starts counting the set time Ton. The current value detection means 9 detects the current value Iin supplied to the DC power supply 4.

  When the detected current value Iin of the current value detecting means 9 has not reached the threshold value Iin1 of the first current value set by the first current value setting means 10, the soft start means 11 sets the set time Ton of the timer means 7 The threshold value Iin2 of the second current value is set by the second current value setting means 12, and the timer setting time Ton is set even though the detected current value Iin of the current value detection means 9 is equal to or less than Iin2. Is over the timer time threshold value Ton1 set by the first timer time setting means 13, the accessory detection means 14 stops the drive signal to the energization control element 5 of the timer means 7.

  The third current value setting means 15 sets a third current value threshold value Iin3 between Iin2 and Iin1, and the detected current value Iin of the current value detection means 9 exceeds the third current value threshold value Iin3. In this case, the set time Ton of the timer means 7 is periodically increased or decreased by the Ton changing means 16.

  The operation and action of the above configuration will be described. When induction heating is started, the timer means 7 receives the trigger pulse of the trigger means 8 that monitors the voltage across the coil 2 and generates a trigger signal, and starts counting time until the count time reaches the set time Ton. During this time, a drive signal is output to the energization control element 5, and during that time, the energization control element 5 is conducted and the coil 2 is energized. The soft start means 11 gradually increases the set time Ton of the timer means 7, whereby the conduction time Ton of the energization control element 5 is gradually increased to realize soft start.

  As the conduction time Ton of the energization control element 5 increases, the detected current value Iin of the current value detecting means 9 increases. At this time, until the detected current value Iin exceeds the second current value threshold Iin2 set by the second current value setting means 12, the set time Ton is set by the first timer time setting means 13. If the set timer time threshold value Ton1 is exceeded, it is determined that an accessory other than the pan 1 is being heated, and the accessory detection means 14 immediately goes to the energization control element 5 of the timer means 7. The driving signal is stopped, the energization of the coil 2 is stopped, and heating is stopped.

  If the set time Ton does not exceed the timer time threshold value Ton1 until the detected current value Iin of the current value detection means 9 exceeds the second current value threshold value Iin2, the set time Ton continues to increase further. After the detected current value Iin of the value detecting means 9 exceeds the third current value threshold value Iin3 set by the third current value setting means 15, Ton determined by the soft start means 11 by the Ton changing means 16 Change the value periodically.

  FIG. 2 is a conceptual diagram of the periodic variation of the set time Ton. The timer unit 7 superimposes the periodic variation of the set time Ton by the Ton varying unit 16 on the increase of the set time Ton by the soft start unit 11. The determined Ton drive signal is output to the energization control element 5.

  After the detected current value Iin of the current value detecting means 9 reaches the first current value threshold value Iin1 set by the first current value setting means 10, the soft start means 11 stops increasing the set time Ton. The timer means 7 outputs to the energization control element 5 a drive signal of the set time Ton determined by superimposing the periodic fluctuation by the Ton fluctuation means 16 on this constant value. That is, in this state, the change in Ton is only a periodic change by the Ton changing means 16.

  FIG. 3 shows the period from when the induction heating device is started until the detected current value Iin of the current value detecting means 9 reaches the first current value threshold Iin1 and the increase of Ton by the soft start means 11 is stopped. , Ton value graph.

  Induction heating is started at time 0, and until the detected current value Iin of the current value detecting means 9 reaches the third current value threshold value Iin3, the set time Ton increases linearly, and the detected current value Iin Also increases linearly. After the detected current value Iin by the current value detecting means 9 reaches the threshold value Iin3 of the third current value, it becomes Ton obtained by adding the periodic fluctuation of Ton shown in FIG. The current value Iin detected by the current value detection means 9 varies slightly. After the detected current value Iin by the current value detecting means 9 reaches the first current value threshold value Iin1, the linear rise of Ton disappears, and only the periodic variation of Ton shown in FIG. The detected current value Iin obtained by the means 9 also varies finely with the first current value threshold Iin1 as a peak.

  From the start of induction heating until the current value Iin detected by the current value detection means 9 reaches the threshold value Iin2 of the second current value, the accessory detection means 14 does not exceed the first timer time set value Ton1. Monitor that.

  In the case of a small object, the detected current value Iin and the set time Ton of the current value detecting means 9 are as indicated by dotted lines, and the set time Ton is reduced before the detected current value Iin reaches the second current value threshold Iin2. The first timer time set value Ton1 is exceeded, and the accessory detection means 14 detects the accessory there, stops the drive signal output from the timer means 7 to the energization control element 5, and the induction overheating is stopped.

  As described above, in the present embodiment, the detected current value Iin of the current value detecting means 9 exceeds the threshold value Iin3 of the third current value not less than Iin2 and not more than Iin1 set by the third current value setting means 15. In this case, since the setting time Ton of the timer means 7 is periodically increased / decreased by the Ton fluctuation means 16, the periodic fluctuation of the conduction time Ton of the energization control element 5 and consequently the oscillation frequency of the induction heating device is By fluctuating, it is possible to disperse the spectrum of the radiation noise so that it does not have a large peak at a certain frequency, and during the soft start at the time of starting the induction heating device, during small object detection, To prevent periodic fluctuations in the conduction time Ton oscillation frequency of the energization control element 5 and to eliminate small fluctuations in Iin and to detect small objects with high accuracy. Kill.

  In the present embodiment, the detected current value Iin of the current value detecting means 9 exceeds the threshold value Iin3 of the third current value not less than Iin2 and not more than Iin1 set by the third current value setting means 15. In this case, the setting time Ton of the timer means 7 is periodically increased or decreased by the Ton changing means 16, but the setting time Ton of the timer means 7 may be randomly increased or decreased by the Ton changing means 16. The same effect can be obtained.

(Embodiment 2)
FIG. 4 is a circuit diagram in which the induction heating apparatus according to Embodiment 2 of the present invention is partially blocked.

  As shown in FIG. 4, the zero volt detection means 17 detects zero volt of the AC power supply, and the Ton fluctuation means 16 sets the timer means 7 in synchronization with the zero volt detection signal output from the zero volt detection means 17. By changing the time Ton, the change of Ton is performed near zero volts of the AC power supply. 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 and action of the above configuration will be described. Note that the basic operation of induction heating is the same as that of the first embodiment, and thus the description thereof is omitted.

  FIG. 5 is an envelope waveform of the detected current value Iin of the current value detecting means 9 of the present embodiment. This waveform corresponds to the voltage waveform of the AC power supply, and is almost 0 amperes at the zero point t0 of the AC power supply. The change of the set time Ton is performed near the zero point of the AC power supply, and the height of the envelope of the detected current value Iin is different before and after the zero point because the set time Ton is different.

  FIG. 6 shows a case where the set time Ton is changed at a point other than the zero point of the AC power supply, and the Iin waveform suddenly changes vertically as indicated by Iin0 before and after the Ton change.

  During induction heating, the induction current flowing through the bottom of the pan 1 and the current flowing through the coil 2 generate a repulsive magnetic field, and the pan 1 is subjected to a levitating force. In this state, if the Iin waveform suddenly changes vertically, the buoyancy applied to the pan 1 also changes abruptly, causing abnormal noise in the viewable area.

  When the set time Ton is changed near the zero point of the AC power supply as in the present embodiment, there is no sudden change in the buoyancy applied to the pan 1, and no abnormal noise is generated in the viewable area. .

  As described above, in the present embodiment, the Ton changing means 16 changes the set time Ton of the timer means 7 in synchronization with the zero volt detection signal output from the zero volt detecting means 17. 7 is changed in the vicinity of zero volts of the AC power supply. Originally, in the vicinity of zero volts of this AC power supply, the voltage of the DC power supply is low, the current flowing through the coil is small, and the repulsive force against the coil of the pan is small, so there is little difference in the repulsive force applied to the pan before and after Ton fluctuation, It is possible to prevent abnormal noise from being produced from the pan.

  As described above, the induction heating device according to the present invention disperses the spectrum of the radiation noise by changing the oscillation frequency so as not to have a large peak at a constant frequency, and occurs as an adverse effect of the fluctuation of the oscillation frequency. Since it is possible to prevent the detection accuracy of the small object detection performed during the soft start at the start-up, it is possible to control the current flowing through the coil for connecting the resonance capacitor in parallel and heating the pan with the energization control element. It is useful as a configured induction heating device.

Circuit diagram in which the induction heating apparatus according to Embodiment 1 of the present invention is partially blocked The figure which shows an example of the periodic fluctuation | variation of the setting time Ton of the same induction heating apparatus Time chart showing changes in set time Ton and detected current value Iin of the induction heating device Circuit diagram in which the induction heating apparatus according to Embodiment 2 of the present invention is partially blocked Envelope waveform diagram of detected current value Iin of the same induction heating device Envelope waveform diagram of detected current value Iin when Ton is changed except near zero volt of AC power supply A partial block diagram of a conventional induction heating device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pan 2 Coil 3 Resonance capacitor 4 DC power supply 5 Energization control element 6 Reflux diode 7 Timer means 8 Trigger means 9 Current value detection means 10 First current value setting means 11 Soft start means 12 Second current value setting means 13 First timer time setting means 14 Small object detection means 15 Third current value setting means 16 Ton fluctuation means

Claims (3)

A pot that is detachably stored in the rice cooker body, a coil that heats the bottom of the pot by induction heating, a resonance capacitor connected in parallel to the coil, and a DC power source that supplies current to the coil A current-carrying control element that controls a current flowing through the coil, a reflux diode installed in parallel with the current-carrying control element, timer means for conducting the current-carrying control element for a set time Ton, and monitoring a coil voltage. Trigger means for starting timing of the set time Ton, current value detection means for detecting a current value Iin supplied to the DC power supply, and first current value setting means for setting a first current value threshold value Iin1 And software for gradually increasing the set time Ton of the timer means when the detected current value Iin of the current value detection means does not reach the first current value threshold value Iin1. , A second current value setting means for setting a second current value threshold value Iin2, a first timer time setting means for setting a timer time threshold value Ton1, and a detection current of the current value detection means A small item that stops the drive signal to the energization control element of the timer means when the set time Ton of the timer means exceeds the timer time threshold Ton1 even though the value Iin is equal to or less than the second current value threshold Iin2. Detecting means; third current value setting means for setting a third current value threshold value Iin3 not less than Iin2 and not more than Iin1; and a detected current value Iin of the current value detecting means means a threshold value Iin3 for the third current value. An induction heating apparatus comprising: a Ton changing unit that periodically increases or decreases the set time Ton of the timer unit when the time exceeds. The Ton changing means randomly increases or decreases the set time Ton of the timer means instead of periodically when the detected current value Iin of the current value detecting means exceeds the third current value threshold Iin3. The induction heating apparatus according to claim 1. 3. A zero volt detecting means for detecting zero volt of an AC power supply, wherein the Ton changing means changes a set time Ton of the timer means in synchronization with a zero volt detection signal output from the zero volt detecting means. The induction heating apparatus described.

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