JPH0418680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an induction heating cooker for general household or commercial use, which cooks food by generating heat in an object to be heated, such as a pot made of magnetic material, based on the principle of induction heating. It is something.

Conventional structure and its problems Conventionally, this type of induction heating cooker has been used for temperature control such as constant oil temperature control in deep-frying dishes.
Since the temperature of the heated object was indirectly detected and controlled through the pot and the top plate using a temperature sensing element such as a thermistor installed in contact with the bottom surface of the top plate, responsiveness and control accuracy were improved. The error was large, and only rough control was possible.

In addition, in order to improve control accuracy, it is possible to insert a temperature sensor with a temperature sensing element into the pot and directly detect the temperature of the food being cooked, but if you forget to insert this temperature sensor by mistake, When cooking with oil, the oil can reach high temperatures and can be extremely dangerous.

Purpose of the Invention The present invention solves such conventional problems, improves the responsiveness of temperature detection of heated objects, improves temperature control accuracy, and provides an induction heating cooker that takes safety into account. It is something.

Composition of the Invention The induction heating cooker of the present invention includes an inverter device that converts commercial power into a high-frequency power source, an oscillation control device that controls oscillation of the inverter device, and an immersion temperature sensor that detects the temperature of the food being cooked. , a temperature control device that controls the operation of the oscillation control device based on the output of the immersion type temperature sensor, and an alarm notification device that detects forgetting to insert the immersion type temperature sensor into the object to be heated and generates an alarm. and has
The alarm notification device includes an input detection device that detects the input state of the inverter device, a change detection device that detects the temperature change of the heated object from the output of the immersion temperature sensor, the output of the input detection device, and the change detection device. This system consists of an output of In addition to controlling the oscillation of the inverter device, the device also detects the insertion of the temperature sensor into the object to be heated and issues an alarm.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram schematically showing the present invention, in which 1 is an inverter device that converts a commercial power source into a high-frequency power source, 2 is an oscillation control device that controls oscillation of the inverter device 1, and 3 is a temperature control device for the object to be heated. 4 is a temperature control device that controls the operation of the oscillation control device 2 based on the output of the immersion temperature sensor 3; 5 is a temperature control device for controlling the operation of the oscillation control device 2 by the output of the immersion temperature sensor 3; This is an alarm notification device that detects if you forget to insert the battery and issues an alarm.

FIG. 2 is a block diagram showing the outline of the alarm notification device 5, in which 6 is an input detection device that detects the input state of the inverter device 1, and 7 is a differential signal from the output of the immersion temperature sensor 3 to extract the differential signal from the heated object. A differentiator 8 detects changes in the temperature of an object, and detects forgetting to insert the immersion type temperature sensor 3 into the object to be heated using the output of the input detection device 6 and the output of the differentiator 7, and issues an alarm. It is an alarm driving device.

FIG. 3 is a circuit diagram showing a specific embodiment of the present invention.
4, a commutating capacitor 15, a power transistor 16, and a damper diode 17. The oscillation control device 2 includes a programmable union transistor 18 (hereinafter referred to as
(abbreviated as PUT), a comparator 19, etc. The immersion type temperature sensor 3 is inserted into the pot 20 which is the object to be heated.
A negative characteristic thermistor 3' is incorporated therein. The temperature control device 4 includes a reference temperature setting volume 2
0', a comparator 21, and the like.
The alarm notification device 5 is composed of an input detection device 6, a differentiator 7, and an alarm drive device 8. The input detection device 6 is composed of a current transformer 22, a full-wave rectifier 23, a comparator 24, etc., and the differentiator 7 is It is composed of a differentiator circuit including a capacitor 25 and a resistor 26, a comparator 27, a thyristor 28, and the like. In addition, the alarm driving device 8 includes a PUT 29,
It is comprised of a timer circuit consisting of thyristors 30 and 31, an unstable multivibrator circuit consisting of transistors 32, 33 and 34, a piezoelectric buzzer 35, and the like.

The operation in the above configuration will be explained. When the immersion type temperature sensor 3 is thrown into the pot 20 and the power switch 10 is turned on, the inverter device 1 oscillates by switching the power transistor 16.
The oscillation frequency at this time is determined by the on/off cycle of the PUT 18, since the output of the comparator 21 is high until the temperature reaches the temperature set by the reference temperature setting volume 20' of the temperature control device 4. . The comparator 19 is for generating a square wave to ensure the switching of the power transistor 16. As the temperature of the object to be heated increases, the resistance value of the negative characteristic thermistor 3' decreases. When the inverting input terminal voltage of the comparator 21 reaches the voltage set by the reference temperature setting volume 20' (hereinafter referred to as the reference temperature setting voltage), the output of the comparator 21 is inverted and the inverter device 1 stops oscillating. . When the inverter device 1 stops oscillating, the pot 20 starts to cool down and the resistance value of the negative characteristic thermistor 3' increases again, so the inverting input terminal voltage of the comparator 21 falls below the reference temperature setting voltage and the output of the comparator 21 is inverted again. Then, the inverter device 1 starts oscillating. In this way, the object to be heated responds extremely quickly to the set temperature by the direct temperature detection method using the immersion type temperature sensor 3, and is precisely controlled to a constant temperature.

Here, a case where the immersion type temperature sensor 3 is forgotten to be inserted into the object to be heated will be explained.

When the power switch 10 is turned on, the inverter device 1 starts oscillating. And input current to alternator 2
2, the voltage is taken out and converted into a DC voltage by a full-wave rectifier 23. Therefore, when the inverter device 1 is oscillating with a predetermined input power, the output of the comparator 24 becomes a high output, and the timer circuit constituted by the PUT 29 starts operating. On the other hand, the transistor 32 is normally turned on, and the transistor 33 is turned off via the diode 36. When the timer circuit ends its operation and the PUT 29 is turned on, the thyristor 30 is turned on and the transistor 32 is turned off. Then, the transistors 33 and 34 are turned on and off alternately, the unstable multivibrator circuit starts operating, and the piezoelectric buzzer 35 emits an intermittent sound. At the same time, since the thyristor 31 is also turned on, the power transistor 16 is turned off via the diode 37 and the oscillation of the inverter device 1 is stopped. When the inverter device 1 stops oscillating, the output of the comparator 24 is inverted and the PUT 29 is turned off, but the thyristor 3
Since the numbers 0 and 31 have a racking effect, the inverter device 1 will not return to its original state unless the power switch 10 is turned off, and the piezoelectric buzzer 35 will continue to emit intermittent sounds, causing the user to experience an immersion temperature warning. This is to ensure that the forgetting to insert the sensor 3 is communicated.

Further, the case where the immersion type temperature sensor 3 is thrown into the object to be heated and the power switch 10 is turned on will be explained again. In this case, as the object to be heated is heated, the resistance value of the negative characteristic thermistor 3' decreases, and the time change of this terminal voltage is sent to the comparator 27 via a differentiating circuit consisting of a capacitor 25 and a resistor 26. input. If this time-varying voltage exceeds a predetermined value, it is determined that the immersion type temperature sensor 3 is inside the object to be heated, and the output of the comparator 27 is inverted, turning on the thyristor 28, and the timer circuit ends its operation. Even if PUT 29 is turned on, the thyristors 30 and 31 cannot be turned on. In other words, the temperature of the heated object can be controlled under normal conditions. In this embodiment, as a change detection device for detecting the temperature change of the object to be heated from the output of the immersion type temperature sensor 3, a change in the terminal voltage of the negative characteristic thermistor 3' is detected by a differentiating circuit consisting of a capacitor 25 and a resistor 26. I explained the detection method, but
This terminal voltage change detection can also be realized by a method in which a microprocessor reads and calculates the terminal voltage at regular time intervals.

Also, if you forget to insert the temperature sensor 3,
We have explained the configuration that not only issues an alarm but also stops the oscillation of the inverter device 1, but the overheating protection device works by the action of a temperature sensing element (thermistor, bimetal, etc.) built into the product body (usually installed on the bottom of the top plate). By providing this, a configuration may be adopted in which only an alarm is notified if the user forgets to insert the battery.

Furthermore, although the piezoelectric buzzer has been described as an alarm notification means, it goes without saying that it is also possible to replace it with a light emitting diode or use it in combination with the piezoelectric buzzer.

Effects of the Invention As is clear from the above embodiments, since the induction heating cooker of the present invention employs an immersion type temperature sensor, the temperature detection response is quick and the temperature control accuracy is extremely good. In addition, it has an alarm function that detects if you forget to insert the temperature sensor and issues an alarm, so even if you forget to insert the temperature sensor when cooking fried foods, the oil will not reach high temperatures. It is highly safe as it issues a warning to the user without causing any damage.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of the present invention, FIG. 2 is a block diagram schematically showing the same alarm notification device, and FIG. 3 is a circuit diagram showing a specific embodiment of the same. 1... Inverter device, 2... Oscillation control device,
3... Immersion type temperature sensor, 4... Temperature control device, 5... Alarm notification device.

Claims (1)

[Claims] 1. An inverter device that converts a commercial power source into a high-frequency power source, an oscillation control device that controls oscillation of the inverter device, an immersion type temperature sensor that detects the temperature of the food to be cooked, and an immersion type temperature sensor that uses the output of the immersion type temperature sensor to It has a temperature control device that controls the operation of the oscillation control device, and an alarm notification device that detects forgetting to insert the immersion type temperature sensor into the object to be heated and generates an alarm. An input detection device that detects the input state of the device, a change detection device that detects temperature changes of the heated object from the output of the immersion type temperature sensor, and an output of the input detection device and an output of the change detection device. An induction heating cooker comprising an alarm driving device that detects forgetting to insert a type temperature sensor into an object to be heated and generates an alarm.