JP2011023163A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rice cooker capable of enlarging a fluctuated allowable range of a power supply voltage and surely determining existence or nonexistence of a pan at an unstable area of the power supply voltage. <P>SOLUTION: The rice cooker has an inverter circuit 10 formed with a heating coil 6, a resonance capacitor 7, and a power element 8, a current detection section 2 for detecting AC current circulating in a diode bridge 3 and outputting voltage in proportion to detection current, an inverter voltage detection section 5 for detecting voltage in the inverter circuit 10 and outputting voltage in proportion to detection voltage, a power source voltage detection circuit 12 for detecting voltage of a commercial power source, and a pan detection section 9 for determining that the pan is not located at a designated position when output voltage of the inverter voltage section 5 becomes designated threshold voltage or more rather than output voltage of the current detection section 2. When the detected voltage of the power source voltage detection section 12 is higher than rated voltage, the threshold voltage is set up to be higher than the predetermined threshold voltage. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a means for detecting whether or not a pan in which rice and water are preliminarily placed before cooking rice is installed in a pan accommodating portion of a rice cooker body in a general household or commercial rice cooker.

  Conventionally, this type of rice cooker has a detection circuit that detects the input current and the inverter voltage, and compares the detection current of each detection circuit and the circuit output according to the detection voltage, and the output of the inverter voltage detection circuit is input. When it becomes larger than the output of an electric current detection circuit, it is judged that the pan is not installed in the predetermined position (the pan accommodating part of the rice cooker main body) (for example, refer patent document 1). FIG. 4 shows a conventional rice cooker described in Patent Document 1. As shown in FIG. As shown in FIG. 4, the heating coil 6, the resonance capacitor 7, the inverter composed of the power element 8, the current detection means 2, the inverter voltage detection means 3, the pan detection means 9, and the inverter control circuit 10. It is composed of

Japanese Patent Laid-Open No. 2-95315

However, in the conventional configuration, when the output of the inverter voltage detection circuit becomes larger than the output of the input current detection circuit, it is determined that the pan is not installed. Is higher than the input current, the inverter voltage is relatively higher than the input current (that is, when the commercial power supply voltage is the rated voltage, the detection current of the input current detection circuit is I ₁ and the detection voltage of the inverter voltage detection circuit is When V _{1 is} a commercial power supply voltage higher than the rated voltage and the detection current of the input current detection circuit is I ₂ and the detection voltage of the inverter voltage detection circuit is V ₂ , I ₁ = I ₂ , V ₁ <V ₂ It may be judged that there is no pan even if there is a pan. In general design, the judgment level of the pan detector is considered in consideration of a certain level of voltage fluctuation, but in the case of voltage fluctuation exceeding the assumption, it is temporarily assumed in areas where commercial power supply is unstable. It was not uncommon for overvoltage exceeding 1 to be applied, and there was a problem that the pan detector was erroneously determined.

  The present invention solves the above-mentioned conventional problems, expands the allowable range of fluctuations in the power supply voltage, and reliably determines the presence or absence of a pan even in an unstable power supply voltage area (a pot accommodating portion of the rice cooker main body before cooking rice) The purpose is to provide a rice cooker that can determine whether or not a pan is installed.

  In order to solve the conventional problems, the rice cooker of the present invention detects an alternating current flowing through a diode bridge, detects a voltage in the inverter circuit, and a current detection unit that outputs a voltage proportional to the detection current, Inverter voltage detection unit that outputs a voltage proportional to the detection voltage, power supply voltage detection circuit that detects the voltage of the commercial power supply, and the output voltage of the inverter voltage detection unit is a predetermined threshold voltage or higher than the output voltage of the current detection unit And a pan detection unit that determines that a pan is not installed at a predetermined position when the detected voltage of the power source voltage detection circuit is higher than the rated voltage. It is something to raise.

  This makes it possible to change the judgment level of the pan detection unit according to fluctuations in the power supply voltage, expand the allowable range of fluctuations in the power supply voltage, and reliably determine the presence or absence of the pan even in areas where the power supply voltage is unstable (before cooking rice It is possible to determine whether or not a pot is installed in the pot accommodating portion of the rice cooker body.

  In the rice cooker of the present invention, the allowable range of fluctuations in the power supply voltage is expanded, and a reliable pan presence / absence determination is made even in regions where the power supply voltage is unstable (whether the pan is installed in the pan housing part of the rice cooker body before rice cooking) Can be determined).

The block diagram of the rice cooker in Embodiment 1 of this invention. The figure which shows the example of no pot determination in Embodiment 1 of this invention Block diagram of using another inverter in the first embodiment of the present invention Block diagram of a conventional rice cooker

  1st invention detects the alternating current which flows into a diode bridge, the current detection part which outputs the voltage proportional to a detection current, and the inverter voltage which detects the voltage in an inverter circuit and outputs the voltage proportional to a detection voltage A pan is installed at a predetermined position when the output voltage of the detection unit, the power supply voltage detection circuit for detecting the voltage of the commercial power source, and the output voltage of the inverter voltage detection unit is higher than the output voltage of the current detection unit. If the detection voltage of the power supply voltage detection circuit is higher than the rated voltage, the threshold voltage is set higher than the preset threshold voltage to respond to fluctuations in the power supply voltage. Can change the judgment level of the pan detector, expand the allowable range of fluctuations in the power supply voltage, and reliably determine the presence or absence of a pan even in areas where the power supply voltage is unstable (before the rice cooker The pot receiving part to determine whether the installed) becomes possible.

(Embodiment 1)
FIG. 1: shows the block diagram of the rice cooker in the 1st Embodiment of this invention. In FIG. 1, a commercial power source 1 is converted into a DC voltage by a diode bridge 3, and high-frequency power generated by an inverter circuit composed of a heating coil 6, a resonance capacitor 7, and a power element 8 is disposed above the heating coil 6. The rice cooker 13 is supplied as a high frequency magnetic field, an eddy current is generated in the rice cooker 13, and the rice cooker is heated by the Joule heat.

  Further, the current detector 2 constituted by the current transformer 2 a and the current-voltage conversion circuit 2 b generates a voltage proportional to the alternating current value flowing into the diode bridge 3. Further, the inverter voltage detector 5 detects a voltage generated in the inverter circuit, and in FIG. 1, the voltage applied to the power element 8 is detected. Furthermore, the power supply voltage detection circuit 12 detects the fluctuation range of the commercial power supply voltage with respect to the rated voltage.

  The outputs of the current detection unit 2 and the inverter voltage detection unit 5 are compared by the comparison circuit 9a that constitutes the pan detection unit 9, and the comparison result is output to the pan presence / absence determination circuit 9b. The pan presence / absence determination circuit 9b calculates a correction value from the output of the power supply voltage detection circuit 12, and determines that there is no pan when the output of the inverter voltage detection is larger than the value obtained by adding the correction value to the output of the current detection unit.

  FIG. 2 shows the way of thinking of the pan detector. The pot detection unit sets the correction value A from the output of the power supply voltage detection unit, compares the value obtained by adding the correction value to the output of the input current detection unit and the output of the inverter voltage detection unit, and exceeds the no pan determination level. When the inverter voltage rises, it is determined that there is no pan.

  The correction value is set to satisfy A1 <A2 when the correction value at the rated voltage is A1 and the correction value at the excessive voltage is A2.

  First, when the detected value of the input current at the rated voltage is Iin1, and the detected value of the inverter voltage is Vin1, the operating point is at a position indicated by 31. When the power supply voltage rises above the rated voltage, the operating point shifts to 32 because the inverter voltage rises. The operating point at this time is at the positions of Iin1 and Vin2. If the input current is not corrected, the operating point 32 may reach the no pan determination level, and even if there is a pan, it may be erroneously determined that there is no pan.

  In this embodiment, Iin2 obtained by adding the correction value A2 at the time of excessive voltage to Iin1 is calculated, a correction value is set based on Iin2 and the output of the power supply voltage detection circuit, and is compared with Vin2.

  By adding a correction value, the pan detection circuit determines that the operating point is 33, and there is sufficient margin for the panless determination level, expanding the allowable range of fluctuations in the power supply voltage, and ensuring even in regions where the power supply voltage is unstable. The presence or absence of a hot pot can be determined.

  In the present embodiment, the idea of correcting the input current is shown, but the same effect can be obtained even when correction for the inverter voltage or correction for the panless determination level is performed.

  FIG. 3 shows an example applied to a two-stone inverter.

  The same effect can be obtained by applying a portion where the voltage rises according to the operation of the inverter as the detection voltage of the inverter voltage.

  As described above, the rice cooker according to the present invention expands the allowable range of fluctuations in the power supply voltage and enables reliable pan presence determination even in areas where the power supply voltage is unstable. It can also be applied to uses such as rice cookers.

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Current detection part 2a Current transformer 2b Current-voltage conversion circuit 3 Diode bridge 4 Smoothing capacitor 5 Inverter voltage detection part 6 Heating coil 7 Resonance capacitor 8 Power element 9 Pan detection part 9a Comparison circuit 9b Pan presence determination circuit 10 Inverter Control circuit 11 Power element drive circuit 12 Power supply voltage detection circuit 13 Rice cooker

Claims (1)

A diode bridge that converts commercial power into DC voltage;
A heating coil that supplies a high frequency magnetic field to the pan;
An inverter circuit composed of the heating coil, a resonant capacitor, and a power element;
Detecting an alternating current flowing through the diode bridge and outputting a voltage proportional to the detected current; and
An inverter voltage detector that detects a voltage in the inverter circuit and outputs a voltage proportional to the detected voltage;
A power supply voltage detection circuit for detecting the voltage of the commercial power supply;
A pan detection unit that determines that a pan is not installed at a predetermined position when the output voltage of the inverter voltage detection unit is greater than or equal to a predetermined threshold voltage than the output voltage of the current detection unit;
The rice cooker which makes the threshold voltage higher than a preset threshold voltage when the detection voltage of the power supply voltage detection circuit is higher than a rated voltage.

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