JPS6146822A - Electric stove - Google Patents

Abstract

PURPOSE:To improve safety of an electric stove by a method wherein a self- holding characteristic is released when an automatic return contact point type off-switch for a heat generating unit is operated or an abnormal increase of temperature of a combustible material is sensed and then the heat generating body is turned off. CONSTITUTION:When a temperature sensor 10 arranged at the central part of a reflector plate shows an increased temperature and reaches to an operating temperature, a two-way thyristor Tr2 is turned off, a relay coil Re is turned off, a contact point Cr is opened, a heat generating body 6 is turned off and an alarm lamp 12 is lit. Even if the temperature is decreased, reenergization is not carried out until the turned-on switch 11 is turned again. When an operating part not shown is operated due to a drop of combustible material or the like and an off-switch 9 is turned off, the relay Re is turned off, the contact point Cr is opened to release the self-holding condition, a heat generating body 6 is turned off and an alarm lamp 12 is lit. With this arrangement, it is possible to improve safety of the unit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electric stoves, and in particular to fire prevention and safety devices thereof.

Conventional Structures and Problems Traditionally, electric heaters are equipped with guards to prevent people's hands, objects, etc. from easily touching the heat generating part.

However, if there is flammable material close to the front of the guard, the heat from the heating element will heat the combustible material and it will reach a high temperature, which could lead to charcoal burning of the combustible material in the vicinity and even a fire in the house. was there.

Hereinafter, the conventional electric stove as described above will be explained with reference to the drawings.

FIG. 1 shows a cross section of a conventional electric stove, and FIG. 2 shows its electric circuit diagram.

1 is a stove housing, 2 is a reflective plate that reflects heat forward, 3 is a heating element located in front of the reflective plate 2, and 4 is located on the back of the reflective plate 2, inside the stove housing 1. A thermostand detects the temperature rise inside the stove housing and turns off the electricity to the heating element 3.

The operation of the electric stove configured as described above will be explained below.

Is the temperature inside the stove i? ;When the temperature rises abnormally, the thermostat stops energizing the heating element 3.

However, with the above configuration, the thermostat does not operate unless the temperature inside the stove casing 1 rises, so if flammable materials fall onto the electric stove, the response is slow, and the stove If there is a flammable object in front of the device, it will not work as a safety device because the temperature inside the casing will not rise, and it will not be suitable as a safety device for fire prevention.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and aims to prevent fires from occurring due to falling flammable materials or abnormal approach.

Structure of the Invention In order to achieve the above object, the electric stove of the present invention includes a heating element, a temperature sensor that directly or indirectly detects a temperature rise of an object heated by the heating element, and a temperature sensor that detects whether the heating element is turned on or off. An automatic return contact type ON switch and an OFF switch that turn OFF, and an electric circuit that turns OFF the heating element according to a signal from the temperature sensor, and the electric circuit is provided with a self-holding circuit, and when the OFF switch is activated. , or when the temperature of the object rises abnormally, the heating element is turned off by canceling the self-holding circuit.
This is a configuration that performs F.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a front view of one embodiment of the present invention, and FIG. 4 is a central cross-section of FIG. 3.

In FIGS. 3 and 4, 5 is a housing, 6 is a heating element, 7 is a reflector, 8 is a guard, and 9 is an OFF switch, which is operated by an operating portion 13 that rotates around a fulcrum Ha.

A temperature sensor (thermistor) 10 protrudes from the center of the reflecting plate 7 and is provided close to the guard 8. 11 is a ○N switch, and 12 is an indicator lamp.

Figure 6 shows the electrical circuit. 10 is a thermistor, Ra is a variable resistor that adjusts the operating temperature, T r 1 is a bidirectional thyristor that turns on and off the circuit of Tr2 + Mari relay Re, Cr is a contact of relay Re, 11 is O
N switch, 9 is OFF switch, 12 is indicator lamp,
6 is a heater, R1-R4 are resistors, Ec is a DC power supply for the control circuit, and 14 is a plug for a 100V AC power supply.

The operation of the above configuration will be explained below.

Figure 5 shows the curtain surface temperature when the distance between the electric stove and the curtain rod is 50cm and 15cm. The relationship between degree T/ and temperature Ta of temperature sensor 0 is shown. As is clear from the figure, in the normal state of L-50cm, the curtain surface temperature TI is saturated at 75°C and there is no worry of smoke or ignition, and the temperature Ts of temperature sensor 0 at this time is 60°C. It is.

Next, when the spacing is brought closer to 15cm, curtains appear! The surface temperature Tl and the temperature Ts of the temperature sensor 0 rise suddenly, and if the heating element 6 continues to be energized, the curtain surface temperature Tf rises to 190°C, and the temperature Ts of the temperature sensor 10 rises.
temperature Ts rises to 100°C. At this time, the condition of the curtains was only a little discolored, and there was no smoke or ignition yet.
The situation is quite dangerous.

The electric stove according to one embodiment of the present invention turns off the heating element 6 when the temperature of the temperature sensor 10 reaches the operating temperature Tso.

At this time, the curtain surface temperature Tl is 120° C., and there is no fear of ignition or smoke generation.

Next, the operation of the electric circuit will be explained. In FIG. 6, when the plug 14 is inserted into the power outlet, the indicator lamp 12 lights up, and then when the ON switch (automatic return contact) 11 is turned on, the thermistor 10 is lower than the operating temperature, so the bidirectional thyristor T r 2 is activated. is in the ON state, the coil Re of the relay is ONL, the contact Cr of the relay is ONL, etc.
While forming a self-holding circuit, the heating element 6 turns ON and the indicator lamp 12 turns off. Then gradually the temperature sensor 10
temperature rises, but as mentioned above, under normal conditions it is 60'
It is saturated at about C. Next, when a flammable substance approaches abnormally, the temperature of the temperature sensor 10 rises rapidly, and when it reaches the operating temperature Tso (Fig. 5) set by the variable resistor Ra,
The bidirectional thyristor T r 2 is turned OFF, the relay coil Re is turned OFF 1, the contact Cr is opened, the heating element 6 is 0FFL, and the indicator lamp 12 is lit to notify the operation of the safety device due to an abnormal temperature rise. . Heating element 6 is 0F
FL/, when the temperature of the temperature sensor 10 decreases, the bidirectional thyrisk T r 2 is turned on again, but the ○N switch 1
Since the contact Cr between the relay 1 and the relay is OFF, the heating element 6 is not energized again. When using it again, turn on the ○N switch 11 after the temperature sensor 10 has cooled down sufficiently.
This is possible by doing the following.

Next, a case will be described in which a combustible material or the like falls onto an electric stove.

When a combustible object or the like falls and pushes the operating section 13 downward, the operating section 13 rotates around its fulcrum 13a and activates the normally closed automatic return contact type OFF switch 9 to turn it off. . Then, as shown in FIG. 6, the relay Re becomes ○FFL, its contact Cr opens, and the heating element 6 becomes
FF. If combustible material, etc. further slips on the operating part 13 and falls onto the floor, and the OFF switch is turned ON again, the heating element 6 will not be turned ON again, and in this case, the safety device is activated, and the indicator lamp 12 lights up to inform you that this is the case. In other words, when the ON switch 11 is turned ON, the relay Re is self-held at its contact point, and when the bidirectional thyristor T r 2 or the OFF switch 9 is turned OFF, the self-holding is released. is turned on and off by its self-holding circuit.
be done.

As described above, according to this embodiment, (1) The temperature sensor 0 installed near the guard of the electric stove sensitively detects the temperature rise of the object heated by the electric stove, and detects the temperature rise of the object heated by the electric stove. Since the heating element 6 is turned off, it is possible to prevent a fire from occurring due to abnormal approach of flammable materials or the like.

(2) Since the abnormal temperature detection method is based on the temperature sensor 0, malfunctions do not occur, unlike the abnormal approach detection method using ultrasonic waves, for example.

(3) The system releases the self-holding circuit in the event of an abnormality, so
- Once the repulsion heating element 6 is turned off, it will not be automatically turned on again, making it safe.

2) If flammable materials or the like fall onto the electric stove, the heating element 6 can be turned off as soon as possible. Since it is an OFF switch with an automatic return contact, light operation is possible.

It has this effect.

By replacing the indicator lamp 12 with an alarm buzzer, it is possible to notice an abnormality even if you are one step away from the electric heater.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) It is possible to prevent discoloration, scorching, and burnout due to abnormal temperature rise of any object heated by an electric stove.

(2) Abnormality is detected by a temperature sensor, so there is no malfunction.

(3) Since the abnormality is detected by a temperature sensor (for example, a thermistor), it can be realized at low cost.

(4) Safety is high because the self-holding circuit is released in the event of an abnormality.

(f) If flammable materials fall onto the electric stove, the heating element can be turned off as soon as possible.

(6) If an indicator lamp or alarm buzzer is provided, it will be possible to know when the safety device is activated.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional electric stove, Fig. 2 is an electric circuit diagram of Fig. 1, Fig. 3 is a front view of an electric stove according to an embodiment of the present invention, and Fig. 4 is the center of Fig. 3. Cross-sectional view, Figure 5 is an illustration of temperature rise depending on the distance between the electric stove and the curtain,
FIG. 6 is an electrical circuit diagram of FIG. 3. 6... Heating element, 7-... Reflector, 8... Guard, 9... OFF switch, 10... Temperature sensor, 11... ON switch, 12... Display Lamp (or alarm buzzer), 13...Operation unit. Name of agent: Patent attorney Toshi Nakao, Idiot 1
figure? Figure 2 Figure 3

Claims (2)

[Claims] (1) A heating element, a temperature sensor that directly or indirectly detects the temperature rise of the object heated by the heating element, and an automatic return contact type ON that turns the heating element ON and OFF.
A switch, an OFF switch, and an electric circuit that turns off the heating element according to a signal from the temperature sensor, and the electric circuit is provided with a self-holding circuit, and when the OFF switch is activated or the temperature of the object is An electric stove configured to turn off a heating element by releasing the self-holding circuit when the temperature rises abnormally. (2) The electric stove according to claim 1, wherein the operating part of the OFF switch is made to protrude from the upper surface of the electric stove.