JPH0295315A - Rice cooker - Google Patents

Abstract

PURPOSE:To prevent the misuse by a user and to improve performance and safety by providing a control part to control the action of an inverter circuit part to supply a high frequency current to a heating coil and a load detector to detect the heated condition of a pot. CONSTITUTION:When a pot 3 is made of a material to be improper to induction heating such as an aluminum, glass and pottery, or it is in an improper shape that it has a large recessed part in a bottom part and that an outer diameter size is small, a load detector 16 inputs and compares the output signal of an input detecting circuit 19 and the output signal of a voltage detecting circuit 28, the fact that the pot 3 is a container improper for cooking is detected, and a heating stop signal is outputted to a control part 13 by a small article detecting circuit 30. Then, the control part 13 inhibits a base driving signal to a power switching semiconductor 26 at the time of receiving the output signal of the load detector 16, and an inverter circuit part 8 stops the supply of the high frequency current to heating coils 4 and 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rice cooker using induction heating, particularly a small pot,
This invention relates to a load detection device that detects an aluminum pot or the like and stops the operation of an inverter circuit section.

BACKGROUND OF THE INVENTION In conventional rice cookers, a load detection device is provided at the center of the bottom of the pot to mechanically detect whether or not the pot has a lid.

Problems to be Solved by the Invention With such a conventional configuration, rice can be cooked in any shape and material of the pot as long as it operates the load detection device. However, there is a problem in that even if a user mistakenly uses an inappropriate pot as described above, rice can still be cooked, resulting in unpalatable rice, which is undesirable in terms of performance.

The present invention solves this problem by detecting the heating state of the pot and stopping the operation of the inverter circuit when heating is done with an inappropriate pot.For example, when cooking in an aluminum pot, etc. Utilizing the unique characteristics of induction heating, when heated with an inappropriate pot, the input current is lower than when heated with a regular pot, and the voltage between the terminals of the power switching semiconductor in the inverter circuit becomes considerably large. The object of the present invention is to detect whether the pot is suitable for cooking and to control the operation of the inverter circuit section.

Means for Solving the Problems The rice cooker of the present invention comprises a pot for cooking, a storage section for storing the pot, a heating coil for inductively heating the pot, an inverter circuit section for supplying high-frequency current to the heating coil, and an inverter. The apparatus is equipped with a control section that controls the operation of the circuit section, and a load detection device that detects the heating state of the pot.

Function: In the rice cooker of the present invention, when a high frequency current is supplied from the inverter circuit section to the heating coil, and the pot is induction heated and rice cooking starts, the input detection circuit detects the magnitude of the input current to the inverter circuit section. A signal is output to the small object detection circuit, and the voltage detection circuit also detects the magnitude of the voltage between the terminals of the power switching semiconductor in the inverter circuit section and outputs a signal to the small object detection circuit. Here, the small object detection circuit compares the signal output of the input detection circuit and the signal output of the voltage detection circuit, and if the signal output of the input detection circuit is smaller than the signal output of the voltage detection circuit, the pot is unable to cook. When it is determined that the inverter circuit is appropriate, the inverter circuit unit outputs a signal to the control unit to stop supplying high-frequency current to the heating coil, and the rice cooking operation is stopped.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a rice cooker body using induction heating, which is an embodiment of the present invention, and is provided with a storage part 2 for storing a pot 3 for storing food therein, and the upper part of the body 1 is covered with a top lid 9. It has a cover structure that can be opened and closed freely, and the pot 3 can be taken out by opening and closing the upper cover 9. 4 and 6 are heating coils for inductively heating the pot 3, which are placed on a support base e, and a plurality of ferrite cores 7 are provided radially below the support base 6 to absorb leakage magnetic flux. . 10 is a pot detection device that moves up and down to mechanically detect the presence or absence of pot 3;
If there is a pot 3 provided on the bottom of the control unit 13
Outputs a signal to start heating.

The control unit 13 receives the output signal of the load detection device 16, and
It controls the oscillation of an inverter circuit section 8 provided at the bottom of the main body 1 that supplies high-frequency current to the heating coils 4 and 5, and also controls the operation display section 11 provided at the top of the main body 1. Reference numeral 12 is a cooling fan that cools inverter circuit components, etc., 14 and 16 are heaters for keeping the pot 3 warm; The power supply to the cooling fan 12 and the heat-retaining heaters 14 and 16 is controlled by the control unit 13.

Next, in FIG. 2, 21 is a commercial AC power source, 22 is a rectifier circuit that rectifies the commercial AC power source 21 into a DC power source, 8 is an inverter circuit unit that converts the DC power source of the rectifier circuit 22 into a high frequency power source, and 13 is an inverter circuit. This is a control section that controls the operation of the circuit section 8. 16 is a load detection device that detects the heating state of the pot 3 and outputs a signal to the control section 13.

The inverter circuit section 8 includes a capacitor 23 connected between the output terminals of the rectifier circuit 22, a series circuit of heating coils 4 and 6 and a power switching semiconductor 26 connected between the output terminals, and the heating coils 4 and 5. A resonance capacitor 24 and a power switching semiconductor 26 connected in parallel to
A damper diode 26 is connected in parallel so as to be in the opposite direction.

The load detection device 16 includes an input detection circuit 29 that receives a signal from a current transformer 27 for detecting the magnitude of the input current of the inverter circuit section 8 and outputs an output signal proportional to the input current, and a power switching semiconductor. A voltage detection circuit 28 detects the magnitude of the terminal voltage of 26 and outputs an output signal proportional to the magnitude of this terminal voltage, and inputs the output signals of these input detection circuits 29 and the output signal of the voltage detection circuit 28. If the output signal of the input detection circuit 29 is smaller than the output signal of the voltage detection circuit 28, a signal is output to the control unit 13 to prohibit the supply of the pace drive signal from the control unit 13 to the power switching semiconductor 26. The small object detection circuit 30 is configured to include a small object detection circuit 30.

In FIG. 3, the relationship between the input current and the terminal voltage of the power switching semiconductor 26 is shown for a normal standard pot and an aluminum pot. Here, for example, if the terminal voltage of the power switching semiconductor 26 is constant and compared, the input current of a normal standard pot is necessarily larger than the input current of an aluminum pot. Therefore, power switching semiconductor 2
By comparing the terminal voltage of 6 and the input current, it is possible to detect whether the pot is inappropriate for cooking, such as an aluminum pot or a small pot.

In the above configuration, when the pot is induction heated, the pot 3
For example, the material may be unsuitable for induction heating, such as aluminum, glass, or ceramics, or the material may have an irregular shape, such as a large dent on the bottom or a small outer diameter. If it is inappropriate, the load detection device 16 inputs and compares the output signal of the input detection circuit 29 and the output signal of the voltage detection circuit 28, and as described above with reference to FIG. It is detected that the container is inappropriate for cooking, and the small object detection circuit 3o outputs a heating stop signal to the control section 13. Then, the control unit 13
Upon receiving the output signal from the load detection device 1e, the inverter circuit section 13 inhibits the bead drive signal to the power switching semiconductor 2e, and stops the supply of high frequency current to the heating coils 4 and 6.

In the above embodiment, the load detection device compares the input current from the current transformer with the terminal voltage of the power switching semiconductor to detect whether or not the pot is appropriate. However, the present invention is not limited to this. For current detection, for example, a signal corresponding to a resistance or input power may be detected, and the terminal voltage of the power switching semiconductor can also be used as the voltage of the heating coil to achieve the effects of the present invention.

In addition, in order to judge whether the pot is suitable or not based on the magnitude of the input current, by changing the comparison setting value in proportion to the voltage of the power switching semiconductor, the pot can be determined with even higher precision. can be judged.

FIG. 4 is a circuit diagram showing another embodiment of the present invention, in which an input voltage detection circuit 31 is added to the load detection device 16, and the input voltage detection circuit detects the voltage of the AC power supply 21. 31 indicates that the voltage of the AC power supply 21 is outside the predetermined voltage range;
For example, if it is outside the range of 85 to 115V, a signal is output to the control unit 13 so that the inverter circuit unit 8 stops outputting the pace drive signal to the power switching semiconductor 26. Here, when the voltage of the input AC power supply 21 fluctuates, for example, if it becomes 100V or more, the voltage detection circuit 28 detects the υ power switching semiconductor 2
Control is applied to keep the voltage between the terminals of 6 constant, and the input voltage is maintained at a nearly constant value despite the rise in the voltage of the input AC power supply 21, and conversely, when it falls below 100V The input current is controlled by the input detection circuit 29 to be constant, and decreases linearly as the voltage of the input AC power supply 21 decreases. therefore.

Compared to conventional rice cookers heated with heaters, it is possible to significantly suppress fluctuations in input power in response to fluctuations in power supply voltage.

Effects of the Invention As is clear from the description of the embodiments above, the present invention provides the following effects.

(1) A signal proportional to the input current of the inverter circuit section is compared with a signal proportional to the terminal voltage of the power switching semiconductor that makes up the inverter circuit section, so it can be determined whether the pot is suitable for cooking. It is possible to judge with high precision.

(2) Since it determines with high precision whether the pot is suitable for cooking, it is possible to stop cooking rice in an inappropriate pot, preventing users from using the pot incorrectly, and greatly improving performance and safety. It is something.

(3) Since input power is controlled by the load detection device, fluctuations in input power can be suppressed to a minimum with respect to power supply voltage fluctuations, and a constant rice cooking performance can always be maintained even when power supply voltage fluctuations occur.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a rice cooker showing an embodiment of the present invention, Fig. 2 is a circuit diagram of the rice cooker, and Fig. 3 shows the relationship between input current and power switching semiconductor voltage of the rice cooker. The characteristic diagram, FIG. 4, is another circuit diagram of the same rice cooker. 2... Storage section, 3... Pot, 4, 5...
... Heating coil, 8 ... Inverter circuit section, 13 ... Control section. 16...Load detection device. Name of agent Patent attorney Shigetaka Awano and one other person

Claims (1)

[Scope of Claims] A pot for cooking, a storage section for storing the pot, a heating coil for inductively heating the pot, an inverter circuit section for supplying high-frequency current to the heating coil, and a control for controlling the operation of the inverter circuit section. 1. A rice cooker comprising a load detection device for detecting a heating state of the pot.