JP2714168B2 - Induction heating cooker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an induction heating cooker with a built-in timer for heating a cookware by supplying an alternating magnetic flux to the cookware mounted on a top plate by an inverter. About.

<Problems to be solved by the conventional technology and the invention> Conventionally, a metal cooker is placed on a ceramic top plate, and high-frequency current is applied to an induction heating coil arranged close to the top plate for cooking. There is provided an induction heating cooker that generates an eddy current in a utensil and uses the Joule heat generated by the eddy current as a heat source for cooking.

As this induction heating cooker, for example, Japanese Utility Model Laid-Open No. 60-149097
As disclosed in Japanese Unexamined Patent Publication (Kokai) No. HEI 10-203, there is known an apparatus with a built-in timer. According to this, the heating operation is performed for a preset time, and the heating can be automatically terminated when the timer is up. Therefore, the cook can perform desired cooking only by setting the timer according to the content of the food.

However, in actual cooking, a so-called pre-program cooking in which a cooking utensil (for example, a pan) is removed and a new content is replaced and placed again, or a heating operation is performed for a predetermined time and then heating is performed again for a predetermined time. In such a case, if you want to continue cooking, turn off the power once,
I had to set the timer again and turn it on.

However, it is complicated to perform the power-off operation and the timer reset operation, and there is a problem that the efficiency of cooking is reduced particularly when the operation is manually reset such as when performing preprogrammed cooking for business use.

Therefore, an object of the present invention is to provide an induction heating cooker that can save the trouble by automatically resetting a timer circuit when removal of a cooking appliance is detected.

<Means for Solving the Problems> In order to achieve the above object, an induction heating cooker according to the present invention comprises a detecting means for detecting a current input to an inverter, and a current detected by the current detecting means being a predetermined value. A load discriminating means for outputting a proper load output when the current value is not less than the reference value, and outputting an improper load output when the current detected by the current detecting means is smaller than the reference value.
A timer means configured to start measurement of the set cooking time when an appropriate load output is output from the load determination means, and to be reset when the measurement of the cooking time is completed; and During the period in which the cooking time is measured by the timer means, heating control means for supplying an electric current to the inverter to generate an alternating magnetic flux,
Reset means for forcibly resetting the timer means when an improper load output is output from the load determining means during the measurement of the cooking time by the timer means.

<Operation> When the cookware 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, if the current input to the inverter is detected, and the current detected is smaller than the reference value during the measurement of the cooking time by the timer, the timer is reset. When the cooking utensils are placed on the kitchen, cooking can be performed again full time.

<Example> Hereinafter, the present invention will be described with reference to the accompanying drawings.

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

The main body of the induction heating cooker includes a DC power supply circuit A and an inverter circuit B for switching a DC current to generate a high frequency.
A control circuit C for controlling ON / OFF of the inverter circuit B;
Current sensor (current transformer) that detects power supply current 11
And a timer circuit E that sends a heating stop signal to the control circuit C when its own time is up based on the load detection circuit D that determines whether the load (the cooking utensil 14 in this case) is appropriate based on the detected current. I have.

The DC power supply circuit A is connected to a commercial AC power supply 1a by a power switch.
1c, a full-wave rectifier 1b is connected via a fuse 1d, and an output of the full-wave rectifier 1b is connected to a choke coil 1e and a smoothing capacitor 1f.

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

The control circuit C starts heating when it detects that the cooking utensil 14 is placed, and controls ON / OFF of the switching element 2c to cook at the set temperature.

The timer circuit E operates at the same time when the power is turned on, and sends an operation signal to the control circuit C during time measurement. The timer is reset in any case when the timer is up or when an improper load output is received from the load determination circuit D. When a non-suitable load output is received, the start of the next time measurement operation is suspended until the next proper load output is received. Therefore, when the load is removed, the timer circuit E is always in a reset state.

The load discriminating circuit D has a current transformer with a predetermined time constant.
By detecting the detected current of the current transformer 11 and comparing it with a reference value by a comparator (not shown), when it is determined that the detected current of the current transformer 11 is smaller than the reference value, a non-suitable load output is output, and When it is determined that there is more, an 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 determination circuit D outputs an inappropriate load output. Thereby, the timer is reset, and the switching element 2c is turned off to stop the oscillation.

Thereafter, at regular intervals (about one second), the control circuit C controls the switching element 2c to repeat intermittent oscillation for a very short time, and continues to detect the input current. When the cooking utensil 14 is placed again, the current transformer
Since a large amount of current flows through 11, the control circuit C automatically detects this and restarts continuous oscillation. At the same time, the load determination circuit D outputs an appropriate load output, and the timer restarts. Therefore, the time set by the timer (full time)
Cooking can be started, and it becomes very convenient especially for business use.

Although not shown, the control circuit C generally includes an overvoltage detection circuit, a temperature protection circuit, and the like. For example, the induction heating cooker is not for general household use, but the power supply state is often poor under conditions used for business use, and instantaneous fluctuations in the power supply voltage are common everyday, in such a case,
Due to the instantaneous fluctuation of the power supply voltage, the inverter circuit B temporarily stops oscillating. However, since the timer circuit E is not reset even if the oscillation is stopped, when the power returns to normal, heating for the remaining time is continuously performed, so that the quality of cooking does not change.

<Effects of the Invention> According to the invention described above, the timer means is set and reset in response to the operation of placing and removing the load (cooking utensil). This eliminates the need for repetitive operations, improving usability.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an induction heating cooker according to the present invention. B: Inverter circuit, D: Load discriminating circuit, E: Timer circuit, 11: Current transformer

Claims (1)

(57) [Claims] 1. An induction heating cooker for heating a cooking utensil by supplying an alternating magnetic flux by an inverter, a detecting means for detecting a current inputted to the inverter, and a current detected by the current detecting means being a predetermined reference. A load discriminating means for outputting an appropriate load output when the current value is equal to or more than the reference value, and outputting an improper load output when the current detected by the current detecting means is smaller than the reference value; When the load output is output, the measurement of the set cooking time is started, and when the measurement of the cooking time is finished, the timer is configured to be reset. A heating control unit for supplying an electric current to the inverter to generate an alternating magnetic flux during a period in which the measurement is being performed; and the cooking time by the timer unit. In the course measurement, if the non proper load output from the load determining means is outputted, the induction heating cooker, characterized in that it comprises a reset means for forcibly resetting said timer means.