JPS5810837B2 - induction heating cooker - Google Patents

Description

[Detailed description of the invention] The present invention relates to an induction heating cooker.

An induction heating cooker generates an alternating magnetic field by passing an alternating current through an induction coil, applies this alternating magnetic field to a cooking pot made of a magnetic material, and heats it using the eddy current loss generated inside the magnetic material. be.

In such a cooker, there is an output control circuit that controls the output by changing the frequency of the alternating current in the range of 20 to 40 KHz, detects the temperature of the pot, and compares this temperature with a given temperature. However, many are equipped with a temperature control circuit that prevents the temperature of the pot from rising above a certain level.

These output control circuits and temperature control circuits are normally driven independently by operating rotary knobs or slide knobs provided separately on the cooking device operating section.

However, in actual use, it is often preferable for these to be linked.

For example, high temperature and high output are desirable for tempura dishes, and low temperature and low output are preferable for stew dishes, which require simmering for a long time.

The present invention has been developed in view of these circumstances, and allows the output and temperature to be adjusted by operating a single operating knob.

Examples of the present invention will be described in detail below.

In FIG. 1, 1 is an induction heating cooker according to an embodiment,
A top plate 2 made of an insulating plate such as a ceramic plate is provided on the upper surface, and an operating section 3 is provided on one side.

Numeral 4 is a temperature/output selector switch, and 5 is a temperature/output setting knob that also serves to turn on and off the power, which can be formed by a rotary switch.

6 is a power indicator lamp that lights up when the power is turned on; 7 is a temperature operation indicator lamp that lights up when the temperature control circuit is operating;
8 is a temperature/output display device consisting of a plurality of light emitters for displaying the output level.

In Fig. 2, 9 is a commercial AC power supply, and Sl is the temperature above.
The power switch is driven by the output setting knob 5, and its closing activates the relay CR and switches the switch S1. S2 is closed and AC power supply 9 is energized to power supply circuit 10.

This power supply circuit 10 consists of a rectifier circuit that converts alternating current into pulsating current or direct current, and the power supply voltage rectified here is supplied to a high frequency inverter circuit 11.

The high frequency inverter circuit 11 includes an induction coil 12, a resonant capacitor (not shown), a switching element (not shown), and the like.

This high frequency inverter circuit 11 oscillates in synchronization with a high frequency pulse signal of about 20 to 40 KHz applied to the switching element, and causes a high frequency alternating current of the same frequency to flow through the induction coil 12.

This alternating current generates a magnetic field, and the magnetic cooking pot 13 placed within this magnetic field is heated.

Reference numeral 14 denotes an auxiliary power supply to which the AC power supply 9 is supplied via a step-down transformer T, which drives the temperature control circuit 15, the output control circuit 16, and the inverter drive circuit 17.

The inverter drive circuit 17 is a high frequency inverter circuit 1
It generates a drive pulse for controlling one switching element on and off, and an LED is provided as a power indicator lamp 6 on its input side.

CT is a current transformer installed in the power line.
Its output terminals A and B are input terminal A of the output control circuit 16.

B, and is taken out as an AC voltage signal across the resistor R1.

19 is a first comparator in which this input detection signal is converted into a DC voltage via a rectifier 18 and a smoothing capacitor C1 and a resistor R2, and is applied to the signal input terminal ■.The other reference signal input terminal ○ is connected to the auxiliary power supply 14 The voltage is divided by resistors R3, R4 and variable resistor VR1 and applied.

This variable resistor VR1 is linked to the switch S1, and the temperature
It is variably controlled by the output setting knob 5.

The output of the first comparator 19 is applied to the inverter 7 drive circuit 17 to control the frequency of the output pulse.

In other words, if the output IKw is set with the temperature/output setting knob 5, when the input voltage to the load reaches IKw, the voltage between terminals AB increases and the rectified and smoothed voltage exceeds the reference voltage and the first The output signal of comparator 19 changes to R level.

This signal increases the frequency of the output pulse of the inverter drive circuit 17, and reduces the output applied to the load.

On the other hand, if the input level is below IKw, the first comparator 19
The output of the inverter 1 drive circuit 17 is at L level, which lowers the frequency of the output pulse of the inverter 1 drive circuit 17 and increases the output applied to the load.

In this way the output is held at 1Kw.

Additionally, regarding the relationship between oscillation frequency and output, the decrease in oscillation frequency is due to increasing the time width of the pulse signal applied to the switching element of the inverter circuit 11, and by doing this, the current flowing through the switching element increases. The output will be larger.

Conversely, an increase in the oscillation frequency shortens the conduction time of the switching element or <1, so the current flowing decreases and the output decreases.

Next, the temperature control circuit 15 will be described. Reference numeral 20 denotes a heat-sensitive element, such as a thermistor, mounted below the steel device on the back surface of the top plate 2, and is a negative resistance characteristic element whose resistance value decreases as the temperature rises.

21 is the auxiliary power supply 14 voltage is connected to the thermistor 20 and resistor R
5, R6, R7 is the second comparator that divides the voltage and inputs it to the signal input terminal (■), and the reference signal input terminal (○) has a variable resistor (R2).
A voltage signal adjusted by is input.

This variable resistor R2 is configured to operate in conjunction with the switch S1, and is connected to the temperature via the resistor and diode D1.
It is connected to the temperature side terminal 22 of the output changeover switch S2 (indicated by reference numeral 4 in FIG. 1), and when this terminal 22 is selected, the auxiliary power supply 14 voltage is applied via the temperature/output changeover switch S2.

The temperature/output changeover switch S2 has an output terminal 23, and this terminal 23 is connected to one end of the variable resistor R2 via a resistor R9.

7 is an LED provided between the temperature side terminal 22 and ground, and serves as a temperature operation display lamp.

The output of the second comparator 21 is applied to the inverter/drive circuit 17 to turn on/off the oscillation drive of the inverter circuit 11.

The operation of this temperature control circuit 15 will be described in the case where the temperature/output changeover switch S2 is set to the temperature side terminal 22, and the heating temperature is set to 100° C. by rotating the temperature/output setting knob 5.

While the temperature of the pot 13 is below 100° C. after the start of heating, the voltage applied to the signal input terminal (3) of the second comparator 21 is higher than the reference voltage, and the output of the second comparator 21 is at H level.

Therefore, the impark drive circuit 17 operates and the high frequency inverter circuit 11 oscillates.

When the temperature of the pot 13 reaches 100° C., the resistance value of the thermistor 20 decreases, and the signal at the signal input end of the second comparator 21 becomes lower than the reference signal, and the output of the second comparator 21 changes to L level.

As a result, the inverter drive circuit 17 stops operating, and the high frequency inverter circuit 11 stops oscillating.

In this way, the temperature of the pot 13 is maintained at the set temperature.

When the temperature/output setting knob 5 is operated to set a desired temperature, the variable resistor VR is simultaneously driven and the reference signal of the first comparator 19 is changed.

An output proportional to the set temperature is selected, a low output is selected when the temperature is set to a low temperature, and a high output is selected when the temperature is set to a high temperature.

In addition, when the temperature/output selector switch S2 is set to the output side terminal 23, as described above, an arbitrary output is set by the variable resistor VR1 by rotating the temperature/output setting knob 5, but at this time, the second comparison At the reference signal input terminal θ of the device 21,
The auxiliary power supply 14 voltage is divided and applied by the resistor R9r Rho.

Since the value of these combined resistances is set to correspond to the maximum heating temperature (approximately 260° C.), the temperature of the pot 13 will not rise indefinitely even during output control operation.

Returning to Fig. 2 and continuing the explanation, 24 is a temperature/output display device, which includes a plurality of light emitting diodes LE arranged in parallel.
D1. LED 2 .
A signal voltage is input from the signal input terminal (2) of the second comparator 21 or the signal input terminal (2) of the second comparator 21 via the switch S3.

The switch S3 switches between the first comparator 19 and the second comparator 21, and is linked to the temperature/output changeover switch S2.

Therefore, when the temperature/output selector switch S2 is set to the output side, the input signal to the first comparator 19 is detected by the level detection circuit 25, and several light emitting diodes LED1 and LED2 corresponding to the level of this input signal are detected. ... lights up.

This light emitting diode LED1. LED2... lights up from the left end to the right side in the figure as the output increases.

Furthermore, when the temperature/output selector switch S2 is switched to the temperature side, the light emitting diode LED1.
LED2... lights up sequentially from the left end.

Note that whether the temperature/output display device 24 is displaying temperature or output can be easily determined by checking whether or not the temperature operation display lamp 7 is lit.

As explained above, the induction heating cooker of the present invention has a configuration in which one temperature/output setting knob serves both as a temperature control circuit and an output control circuit, and a changeover switch for temperature control and output control is provided to switch between them. When this changeover switch is set to the temperature side to adjust the temperature, the output is also adjusted at the same time, so the output is proportional to the heating temperature, that is, the output is low for low temperatures, and the output is adjusted at the same time. It becomes possible to obtain high output at high temperatures.

Therefore, it is possible to provide a cooking device that is easier to operate and easier to use than conventional cooking devices in which temperature and output are adjusted separately during actual cooking.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, and FIG. 2 is a circuit diagram of the same side. DESCRIPTION OF SYMBOLS 1...Induction heating cooker, 9...Power supply circuit, 11...High frequency inverter circuit, 15...Temperature control circuit, 16...Output control circuit, 24...Temperature/output display device.

Claims (1)

[Claims] 1. A high-frequency inverter circuit including an induction coil, an output control circuit that adjusts the output by controlling the oscillation frequency of the high-frequency inverter circuit, and a temperature detecting place for a cooking pot made of a magnetic material placed close to the induction coil. A temperature control circuit that adjusts the heating temperature of the pot in comparison with a given temperature, a temperature/output changeover switch that switches between the output control circuit and the temperature control circuit, and a temperature setting means that sets the heating temperature to an arbitrary value. An induction heating cooker, characterized in that the temperature setting means controls the output at the same time when the temperature/output changeover switch is in the temperature selection position.