JPH0518018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electric stove mainly used at home.

Prior Art A conventional example is shown in FIG. In Figure 5, 12
13 is a casing, 13 is a heater, 14 is a reflector, and 15 is a guard. As is well known, when electricity is applied to the heater 13, the heater 13 becomes red hot, and the reflection effect of the reflector 14 can collect heat.

In general, electric stoves are widely used because they are light and easy to carry, can be used anywhere as long as there is an electrical outlet, can be used immediately with a switch, and are hygienic.

Problems to be Solved by the Invention However, because of its simplicity, it is often used near combustible materials in small rooms, and as a result, combustible materials may fall onto electric stoves, or combustible materials may fall onto electric stoves. There was a risk of fire due to abnormally approaching the guard surface of the machine.

The problem with the prior art is that it is completely defenseless against falling or abnormally approaching flammable materials, and cannot prevent fires from occurring due to user carelessness.

The present invention solves the above-mentioned problems of the prior art, and aims to prevent fires from occurring due to falling or abnormally approaching flammable materials.

Means for Solving the Problems The electric stove of the present invention includes a heater, a switch for turning on or reducing the amount of electricity supplied to the heater, a guard in front of the heater, a reflector plate behind the heater, and the guard. A temperature sensor that is installed near the guard in a space surrounded by a reflector and whose electrical signal changes continuously depending on the temperature, a reference signal setting section, and a comparison of the reference signal of the reference signal setting section and the signal of the temperature sensor. the comparison section compares the signal of the temperature sensor with the reference signal, and the reference signal is the temperature and the temperature increase rate, and the comparison section compares the temperature of the temperature sensor mounting part or the temperature increase rate with the reference signal. The switch is configured to operate when a signal is reached.

Since the electric stove of the present invention has the above-described configuration, there is a danger that flammable materials may fall onto the electric stove and cover the guard surface, or combustible materials may abnormally approach the guard surface and cause a fire. When a fire occurs, the temperature sensor quickly detects the abnormal condition from the temperature and temperature rise, turns off the power to the heater, and prevents the fire from occurring.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 is a front view of an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the center of FIG.

In Figures 1 and 2, 1 is a housing, 2 is a heater, 3 is a reflector, 4 is a guard in front of the heater 2, and 5
is the power switch, 6 is the thermistor (temperature sensor)
It protrudes from the center of the reflecting plate 3 and is provided close to the guard 4. 7 is the start switch,
8 is a controller.

FIG. 3 shows a block diagram of the controller and other components. The controller 8 includes a reference signal setting section 9, a correction signal generation section 10, and a comparison section 11, and the reference signal setting section sets the reference temperature to To and the reference temperature increase rate dT/dt.
is set, and the correction signal generating section generates a signal for correcting the reference signal using the room temperature T _R and the voltage E. The comparator 11 compares the temperature signal from the thermistor 6 with a reference signal set by the reference signal setting section 9, and sends a signal to turn off the start switch 6, thereby turning off the heater 2.

Next, the operation of this embodiment will be explained with reference to FIG.

First, when the power supply voltage is relatively high, when the power switch 5 is turned on and the start switch 7 is turned on, the temperature T detected by the thermistor 6 starts to rise from _T1 , and under normal usage conditions _T2 and _T3. and changes. At this time, the room temperature T _R also gradually rises as shown in the figure. Reference signal T ₀ set by reference signal setting section 9
T ₀₁ , T 02 , and T ₀₂ are also corrected for supply voltage and room temperature.
Changes to T ₀₃ . Another signal set by the reference signal setting section 9, the reference temperature increase rate dT/dt, is
The rate is set to be greater than the rate of temperature rise of the thermistor 6 at the start of use of the electric stove. Therefore, under normal operating conditions, the temperature T of the thermistor 6 does not exceed the reference temperature _T0 , and the temperature increase rate of the thermistor 6 does not exceed the reference temperature increase rate, so the electric stove continues to be energized normally. do.
Next, at time _t2 , in an abnormal situation when combustible material such as clothing falls onto the electric stove and covers the guard 4, the temperature T of the thermistor 6 rises rapidly and passes from _T2 to _T02 .
Trying to ascend to T ₀₄ . However, thermistor 6
If the temperature increase rate exceeds the reference temperature increase rate,
The comparator 11 immediately sends a signal to turn off the start switch 7, and the power to the heater 2 is turned off. Also, depending on the conditions of the abnormal state, thermistor 6
Even if the temperature increase rate does not exceed the reference temperature increase rate, the power to the heater 2 is similarly turned off at T ₀₂ when the temperature T of the thermistor 6 exceeds the reference temperature T ₀ . In other words, in response to the occurrence of various abnormal conditions, changes in the two characteristic values of temperature and temperature rise rate are detected, and the power supply to the heater 2 is cut off more quickly.

Next, when the power supply voltage is relatively low, the temperature of the thermistor 6 rises from T ₁ , and under normal conditions it reaches T' ₂ and T' ₃ .
It changes along the curve of T′. The reference temperature is subjected to voltage correction and changes from T' ₀₁ , which is lower than T _01, to T' ₀₂ and T' ₀₃ as the room temperature rises and is subjected to room temperature correction. The reference temperature increase rate is also corrected to be slightly smaller than when the voltage is high. Hereinafter, in the same way as when the voltage is high, the current is maintained normally during normal times, and the current is immediately turned off to the heater 2 during abnormal times to prevent the occurrence of a fire. Furthermore, the action of the correction signal generating section 10 prevents delays in detecting abnormalities due to voltage fluctuations and room temperature fluctuations, and improves the reliability of operation as a safety device.

Effects of the Invention As described above, the present invention provides the following effects.

(i) If a combustible object approaches the guard abnormally and the temperature rises abnormally, the temperature sensor is located in a position that receives heat radiation from the combustible object, so there will be a large difference between the signals between the abnormal state and the normal state. The switch can be operated reliably in the event of an abnormality without causing any malfunction.

(ii) Furthermore, since a temperature sensor has an electrical signal (e.g. electrical resistance) that continuously changes depending on the temperature, the rate of temperature rise can be detected, making it easy to distinguish between abnormal and normal states, and to prevent malfunctions. can be prevented and activated reliably in the event of an abnormality.

(iii) Furthermore, since the temperature sensor has a signal that changes continuously and operates by comparing it with a reference signal, malfunctions due to changes in room temperature or voltage can be prevented.

[Brief explanation of drawings]

Fig. 1 is a front view of an electric stove according to an embodiment of the present invention, Fig. 2 is a central sectional view of Fig. 1, Fig. 3 is a signal block diagram, and Fig. 4 is an operation explanation showing the relationship between temperature and time. FIG. 5 is a sectional view of a conventional electric stove. 2... Heater, 4... Guard, 5... Power switch, 6... Thermistor (temperature sensor), 7
...Start switch, 8...Controller, 9...
Reference signal setting section, 10... Correction signal generation section, 1
1... Comparison section.

Claims (1)

[Scope of Claims] 1. A heater, a switch that turns off or reduces the amount of electricity supplied to the heater, a guard in front of the heater, a reflector behind the heater, and a space surrounded by the guard and the reflector. Installed near the inner guard,
The temperature sensor includes a temperature sensor whose electrical signal changes continuously depending on the temperature, a reference signal setting section, and a comparison section that compares the reference signal of the reference signal setting section with the signal of the temperature sensor, and the reference signal is determined by the temperature. The temperature rising rate is set as the temperature rising rate, and the signal of the temperature sensor is compared with the reference signal in the comparing section, and when the temperature of the temperature sensor mounting part or the temperature rising rate reaches the reference signal, the switch is actuated. electric stove. 2. The electric stove according to claim 1, comprising a correction signal generation section that corrects the reference signal based on room temperature or voltage, or room temperature and voltage.