JPH08219450A - Safety device for cooker - Google Patents

Abstract

PURPOSE: To achieve a simplification and a lower cost of a safety device which is operated accurately with no effect on the intrinsic performance by a thermosensitive element. CONSTITUTION: A magnet solenoid valve 10 is provided with two coils 14 and 15 within the body thereof. One coil 14 is connected in series to a thermocouple 1 arranged near a burner head, the other coil 15 is connected to an energization control circuit 2 being wound opposite to the direction of winding the coil 14 to allow excitation opposite to the coil 14. Moreover, the energization control circuit 2 has the coil 15 and a PTC thermistor 4 adapted to increase an electric resistance value sharply under a set temperature connected in parallel to a dry battery 3. A drain source DS of an FET5 is connected in series to the coil 15 while a gate source GS of the FET5 is connected thereto in parallel with the PTC thermistor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device used in cookers such as table hobs and rice cookers.

[0002]

2. Description of the Related Art As the above-mentioned safety device, JP-A-6-26 is known.
As disclosed in Japanese Patent No. 653, a thermocouple disposed near the burner head, a solenoid valve that shuts off the gas flow passage by closing the valve,
There is known an invention of a gas control circuit in which a temperature-sensitive element having a positive characteristic, which is arranged on the bottom of a pan and whose electric resistance value increases as the temperature rises, is connected in series. This is because the electromotive force of the thermocouple normally keeps the solenoid valve adsorbed and open, and when it goes out, the solenoid valve closes due to the decrease in thermoelectromotive force, shuts off gas supply, and the pot bottom is overheated. When the temperature element reaches the set temperature, the electrical resistance value suddenly increases and the energization amount decreases, so that the solenoid valve is closed. On the other hand, the same thermocouple, temperature-sensitive element, and solenoid valve are separately connected to an electronic circuit for monitoring, and an electronic circuit that detects the thermoelectromotive force of the thermocouple and the electric resistance value of the temperature-sensitive element is used. There is also a configuration in which energization to the solenoid valve is turned off when the set value is reached.

[0003]

In the former gas control circuit, if the room temperature resistance value of the temperature sensitive element is not less than about 30 mΩ, the solenoid valve is held open with a low thermoelectromotive force obtained by low heat or low heat cooking. Can not be. However, the current performance of the temperature sensitive element does not satisfy the above requirements, resulting in problems such as ignition failure and deterioration of the throttle characteristic, which is not preferable in practical use. Further, the latter electronic circuit requires a large manufacturing cost for the control board and the like, which leads to an increase in the cost of the entire cooking device.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention provides a safety device for a cooking device that is low in cost and highly reliable without being affected by the performance of the temperature sensitive element.
An electromagnetic valve in which two coils are wound around the same iron core is arranged in the gas supply path, one coil is connected to a thermoelectric element arranged in the vicinity of the burner, and forced by the thermoelectromotive force of the thermoelectric element. The electromagnetic valve that is opened to hold the adsorption valve open, and the other coil is equipped with a temperature sensitive element and a power source whose electric resistance value rapidly increases at a set temperature due to a rise in the temperature of the bottom of the pan, and the other coil when energized. An energization control circuit that excites the coil in the opposite direction to that of the one coil and controls the energization amount to the other coil to almost 0 before reaching the set temperature of the temperature-sensitive element and to rapidly increase after reaching the set temperature. It is characterized by being connected to. Further, it is desirable that the energization control circuit is composed of a field effect transistor having a gate connected to the input side of the temperature sensitive element and a drain / source connected to the other coil.

[0005]

The solenoid valve forcibly opened at the time of ignition is adsorbed and held open by energizing one coil by the thermoelectromotive force of the thermoelectric element heated by the burner. At the same time, in the energization control circuit,
When the coil is energized, the other coil is energized to excite in the direction opposite to that of the one coil. However, since the energization amount is controlled to almost 0 before the set temperature of the temperature sensing element is reached, the adsorption by the excitation of one coil The valve opening is maintained. When the pot bottom temperature rises and reaches the set temperature of the temperature sensitive element, the amount of electricity to the other coil that is reverse-excited sharply increases, the combined magnetomotive force decreases and the adsorption force decreases, so the solenoid valve closes. Then, the gas supply is cut off. When the field effect transistor is used in the energization control circuit, the gate voltage decreases and the resistance value between the drain and source increases while the electric resistance value of the temperature sensitive element is small. Becomes almost 0, and when the electric resistance value rapidly increases due to reaching the set temperature of the temperature sensitive element, the gate voltage also increases and the resistance value between the drain and the source decreases, so that the amount of electricity supplied to the other coil increases. The resultant magnetomotive force is reduced, and the adsorption force is reduced.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of a safety device applied to a table stove. A magnet solenoid valve 10 here has two coils 14 and 15 in a main body, and one coil 14 Is connected in series to a thermocouple 1 arranged in the vicinity of the burner head, and the other coil 15 is connected to an energization control circuit 2 that can be excited in the opposite direction to the excitation by the coil 14. In this energization control circuit 2, a dry battery 3 as a power source is connected in parallel with the coil 15 and a PTC thermistor 4 whose electric resistance value rapidly increases depending on a set temperature.
-Type field effect transistor 5 (hereinafter abbreviated as FET5) is connected in series with the drain and source DS, and
The gate / source GS of the FET 5 is connected to the input side of the PTC thermistor 4. Reference numeral 6 is a switch that is turned on in conjunction with the ON operation of the burner ignition switch, and 7 is a resistor. As shown in FIG. 2, the magnet solenoid valve 10 adopted here has a base body 12 fitted to one side of a casing 11, and a U-shaped fixed iron core 13 is attached to the base body 12.
The coil 14 is wound around the one end of the fixed iron core 13, and the coil 15 reversely wound with the coil 14 is wound around the other end of the fixed iron core 13. The coil terminal fittings 16a and 16b are joined together. Further, on the right side of the fixed iron core 13 of FIG.
A valve shaft 18 connected to the adsorption piece 17 and a valve body 19 connected to the valve shaft 18 and protruding to the outside of the casing 11. These are provided between the valve body 19 and the casing 11. It is biased to the right by the spring 20. Therefore, in the blinker main body 21 in which the magnet electromagnetic valve 10 is incorporated, the valve body 19 is forcibly pushed to the casing 11 side by the forward movement of the spindle 23 accompanying the ignition switch ON operation, and the attraction piece 17 is fixed.
Pressed to 3. When the coil 14 is energized,
By the excitation, the adsorption piece 17 is held as it is, the valve open state is maintained, and when the coil 15 is energized, the coil 1
When the magnetomotive force in the coil 14 decreases due to the excitation in the direction opposite to the direction of 4, and the lower limit value of the adsorption is exceeded, the compression spring 20
The attraction piece 17 separates from the fixed iron core 13 by the bias of
The valve element 19 projects to close the valve seat 22.

Therefore, in the safety device having such a structure, when the ignition switch is turned on, the valve body 19 of the magnet solenoid valve 10 is forcibly opened and the burner is ignited. An adsorption current flows to the coil 14 due to the thermoelectromotive force of (1) and attracts the adsorption piece 17 as described above, so that the magnet solenoid valve 10 is held open.
Simultaneously with this ignition operation, the switch 6 is turned on in the energization control circuit 2 as well, and a current flows through the PTC thermistor 4.
At this time, the electric resistance value of the PTC thermistor 4 is still small, and the gate voltage obtained by the FET 5 is small.
The electric resistance value between the drain and source DS of T5 is very large. Therefore, the counter magnetomotive force A generated in the coil 15 in the opposite direction is
T ₂ remains almost 0 (FIG. 3), and the magnetomotive force A of the coil 14 is
It does not affect the holding of the adsorption valve by T ₁ . When the extinguishing occurs, the thermoelectromotive force of the thermocouple 1 decreases,
The energization amount to the coil 14 is reduced, the excitation by the coil 14 is released, and the solenoid valve 10 is closed. On the other hand, when the pot bottom temperature rises and the PTC thermistor 4 reaches the set temperature (here, 250 ° C.), the electrical resistance value suddenly increases and the FE
As the voltage of T5 to the gate G increases, the electrical resistance value between the drain and source DS decreases, and the amount of electricity supplied to the coil 15 increases rapidly. Then, the counter magnetomotive force AT _{2 of the} coil 15
There - increases to the side, the magnetomotive force AT ₁ coil 14 for adsorbing the adsorption piece 17, because the synthetic magnetomotive force AT ₃ with counter electromotive force AT ₂ coil 15 is decreased, this synthetic magnetomotive force AT _3,
When the value falls below the lower limit value L _{O of the} magnetomotive force with which the attracting piece 17 can be maintained in the attracted state, the attracting piece 17 separates from the fixed iron core 13,
The valve body 19 closes the valve seat 22. In addition, here
The heat capacity of such PTC thermistor 4 and the sensor case for accommodating it, the lower limit value L _O composite magnetomotive force AT ₃ below which we passed the lower limit -L _O adsorption state sustainable counter electromotive force AT ₂ in the opposite Since the time t _O is required by the time, the adsorbing piece 17 can be reliably separated from the fixed iron core 13 by the bias of the compression spring 20 before the time t _O elapses, and the valve can be closed. This time t
_O is also relatively short, synthetic magnetomotive force AT ₃ by setting the counter electromotive force AT ₂ coil 15 so as not to exceed the opposite lower limit -L _O, no adsorption maintained by synthesis magnetomotive force AT ₃ . As described above, in the present embodiment, the thermocouple for holding the magnet solenoid valve in the adsorption open state and the PTC thermistor for detecting the pan bottom temperature are respectively adopted in different circuits, and these are combined with the magnet solenoid valve to form a safety device. I configured it, so P
The normal temperature resistance value of the TC thermistor does not affect the throttling characteristics of the cooking device, and the ignition failure does not occur.

If the field effect transistor 5 is used in the energization control circuit 2, the energization control can be suitably performed by the switching operation of the field effect transistor 5 and the circuit can be simply constructed. However, these configurations are not limited to the above embodiments. The design can be arbitrarily changed by adopting another circuit configuration. Similarly, the structure of the magnet solenoid valve may be changed in various ways such as the shape of the fixed iron core and the winding position of the coil.

[0009]

As described above, according to the present invention, the thermoelectric element and the temperature sensitive element are connected to separate circuits and combined with a single solenoid valve, so that the room temperature resistance value of the temperature sensitive element is 30 mΩ.
Even if it is more than a certain level, there is no problem such as the influence of the thermal power on the throttling characteristics, and a safety device that can operate reliably can be configured easily and at low cost. Further, when the field effect transistor is used for the energization control circuit, the energization control circuit can be simply constructed and the amount of energization to the coil can be suitably controlled.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a safety device.

FIG. 2 is an explanatory diagram of a magnet solenoid valve.

FIG. 3 is an explanatory diagram showing a change in magnetomotive force due to two coils.

[Explanation of symbols]

1 ... Thermocouple, 2 ... Energization control circuit, 3 ... Dry battery, 4
..PTC thermistors, 5..Field effect transistors,
6 ・ ・ Switch, 7 ・ ・ Resistance, 10 ・ ・ Magnet solenoid valve, 11 ・ ・ Casing, 12 ・ ・ Base body, 13 ・ ・ Fixed iron core, 14 ・ ・, 15 ・ ・ Coil, 17 ・ ・ Suction piece, 1
8 ... Valve shaft, 19 ... Valve element.

Claims (2)

[Claims] 1. A solenoid valve, in which two coils are wound around the same iron core, is arranged in a gas supply path, and one coil is connected to a thermoelectric element arranged in the vicinity of a burner to generate a thermoelectric element. By the electric power, the electromagnetic valve forcibly opened is held by adsorption and opened, and the other coil is provided with a temperature sensitive element and a power source whose electric resistance value rapidly increases at a set temperature due to a temperature rise of the bottom of the pan, Energizing the other coil in the opposite direction to that of the one coil by energization, and controlling the energization amount so that it is almost 0 before reaching the set temperature of the temperature sensing element and increases rapidly after reaching the set temperature. A cooker safety device that is connected to a control circuit. 2. The cooker according to claim 1, wherein the energization control circuit includes a field effect transistor having a gate and source connected to the temperature sensitive element and a drain and source connected to the other coil. Safety device.