JPH0377295A - Induction heating cooking unit - Google Patents

Abstract

PURPOSE:To obviate the repeated operation of a timer and improve conveniences for operation by controlling a cooking unit in such a way that when a cooking utensil is again placed on a top plate, much current flows to a current transformer during intermittent oscillation for causing the restart of continuous oscillation. CONSTITUTION:When a cooking utensil 14 is removed from a top plate during cooking, the detection current of a current transformer 11 drops below a reference value and a load judgement circuit D outputs a non optimum load signal. As a result, a timer E is reset and a switching element 2c is turned off, thereby stopping oscillation. Thereafter, a control circuit C controls the switching element 2c at constant intervals, and causes the repetition of intermittent oscillation for a very short time, thereby continuing the detection of input current. In this case, when the cooking utensil 14 is again placed on the top plate, much current flows to the current transformer 11 during the intermittent oscillation and, therefore, the control circuit C automatically detects the current, thereby causing the restart of the continuous oscillation. At the same time, the load judgement circuit D outputs an optimum load signal and the timer E is restarted. It is possible, therefore, to start cooking according to the time set with the timer E.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides an induction heating cooker with a built-in timer that heats cooking utensils by supplying alternating magnetic flux to the cooking utensils placed on a top plate using an inverter. Regarding.

<Conventional technology and invention! The problem to be solved> Conventionally, metal cooking utensils were placed on a ceramic top plate, and a high-frequency current was passed through an induction heating coil placed close to the top plate to generate eddy currents in the cooking utensil. ,
There has been provided an induction heating cooker that utilizes Joule heat generated by this eddy current as a heat source for cooking.

As this induction heating cooker, for example,
As disclosed in Japanese Patent No. 097, a built-in timer type is known. According to this, the heating operation can be performed for a preset time, and when the timer goes up, the heating can be automatically ended. Therefore, the cook can perform desired cooking by simply setting the timer according to the contents of the food to be cooked.

However, in actual cooking, cooking utensils (such as a pot)
If you want to continue cooking, when you remove the container, replace the contents, and place it again, or when you want to continue cooking, you may want to continue cooking. I had to turn the power off and turn it off again, set the timer seven times, and turn it back on.

However, performing the above-mentioned power-off operation and timer reset operation is complicated, and in particular, if the reset is done manually, such as when performing pre-programmed cooking for commercial use, there is a problem that cooking efficiency decreases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an induction heating cooker that can eliminate the above-mentioned trouble by automatically resetting a timer circuit when the removal of a cooking utensil is detected.

Means for Confronting the Problems> The induction heating cooker of the present invention for achieving the above object includes a timer means for setting cooking time, a detection means for detecting the current input to the inverter, and a detection means. and reset means for resetting the timer means when the detected current is smaller than a reference value.

Effect> When the cooking utensil is removed, that is, when there is no load or a load smaller than a predetermined value, the current input to the inverter is small. Therefore, when the current input to the inverter is detected and is smaller than the reference value,
By resetting the timer means, the next time the cooking utensils are placed on the machine, full-time cooking will be possible again.

<Example> The present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an embodiment of an induction heating cooker according to the present invention.

The induction heating cooker body includes a DC power supply circuit A, an inverter circuit B that switches the DC current to generate high frequency, and a control circuit C that controls the inverter circuit B in 0N10FF.
Based on the current detected by the current sensor (current transformer) 11 that detects the power supply current, the load (in this case, the cooking utensil 1
4) A load determination circuit that determines whether or not the load is appropriate;
The timer circuit E is provided with a timer circuit E which sends a heating stop signal to the control circuit C when its own time-up occurs.

Is DC power supply circuit A commercial AC? A full-wave rectifier 1b is connected to the tS source 1a via a power switch IC1 fuse 1d, and a choke coil 1e and a smoothing capacitor 1f are connected to the output of the full-wave rectifier 1b.

The inverter circuit B has an induction heating coil 2a connected to the choke coil 1e, and a resonant capacitor 2b and a switching element 2c connected to the induction heating coil 2a. As the switching element 2C, a Darlington connection transistor with a built-in diode is used. When this switching element 2C is ONL, current flows from the DC power supply circuit A to the induction heating coil 2a and the resonant capacitor 2.
b, and a high frequency alternating magnetic flux is applied to the cooking utensil 7.

When the control circuit C detects that the cooking utensil 14 is placed on the cooking utensil 14, it starts heating the cooking utensil 14, and also controls the switching element 2c to 0N10FF so as to cook at a set temperature.

The timer circuit E operates at the same time as the power is turned on, and sends an operation signal to the control circuit C during time measurement. The timer is reset in either case when the timer is up or when an unsuitable load output is being received from the load discrimination circuit. When an inappropriate load output is received, the next time measurement operation is suspended until the next appropriate load output is received, so the timer circuit E is always in a reset state when the load is removed.

The load discrimination circuit uses current transformer 1 with a predetermined time constant.
By detecting the detected current of current transformer 11 and comparing it with a reference value using a comparator (not shown), when it is determined that the detected current of current transformer 11 is less than the reference value, an unsuitable load output is output and the reference value is When it is determined that the load is higher than that, the appropriate load output is output.

According to the above configuration, when the cooking utensil 14 is removed from the top plate during cooking, the detected current of the current transformer 11 becomes lower than the reference value, and the load discrimination circuit outputs an inappropriate load output. This resets the timer and
The switching element 2C is turned off and oscillation stops.

After that, the control circuit C controls the switching element 2c at regular intervals (about 1 second) to repeat intermittent oscillation for a very short time, and continues to detect the input terminal. Cookware 14
When placed again, a large amount of current flows through the current transformer 11 during the intermittent oscillation, so the control circuit C automatically detects this and restarts continuous oscillation. At the same time, the load discrimination circuit outputs an appropriate load output and the timer restarts. Therefore, cooking can be started for the time set by the timer (full time), making it extremely convenient to use, especially for commercial use.

Although not shown, the control circuit C generally includes an overvoltage detection circuit, a temperature protection circuit, and the like.

For example, when an induction heating cooker is used for commercial purposes rather than for general household use, the power supply condition is often poor, and instantaneous fluctuations in the power supply voltage are common in everyday life. Due to the instantaneous fluctuation in , inverter circuit B temporarily stops oscillating. However, even if the oscillation stops, the timer circuit E is not reset, so when the power is restored to normal, the remaining heating will continue, so the quality of the cooking will not change.

<Effects of the Invention> According to the above invention, since the timer means is set and reset in response to the operation of placing and removing the load (cooking utensils), the timer means can Repeat 1. No operation is required, improving usability.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of the induction heating cooker of the present invention.

Claims (1)

[Scope of Claims] 1. In an induction heating cooker that heats cooking utensils by supplying alternating magnetic flux using an inverter, there is provided a timer means for setting a cooking time, a detection means for detecting a current input to the inverter, and a detection means for detecting current input to the inverter. An induction heating cooker comprising reset means for resetting the timer means when the current detected by the means is smaller than a reference value.