JPS61128029A - electric stove - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an electric stove for heating.

Conventional configuration and its problems Conventional stoves have an unprotected structure even if objects such as curtains or other flammable cloth are placed close to the front of the electric stove, sometimes covering the electric stove. The temperature of the pieces of cloth rose, causing them to burn or even ignite or cause a fire.

Purpose of the Invention It is an object to realize an electric stove for home use that can quickly detect such an abnormal situation and turn off the power to ensure safety.

In order to achieve the structure and the above-mentioned object of the invention, two heat-sensitive elements having different heat capacities are provided at different locations to ensure safe operation.

DESCRIPTION OF EMBODIMENTS One embodiment will be described below based on the drawings. As shown in FIG. 1, several metal safety grids 3 are provided on the front of the stove for safety purposes.

As shown in FIG. 2, two thermistors 5 and 6 are built into a portion 3' of a safety grate made of pipes arranged in the center of the stove. The safety grid 3 has a diameter of 1
It is generally constructed of stainless steel or nickel-plated iron rods at the front and back of the throat, and in this example,
All the grids, except the central safety grid 3' - wood, are made of nickel-plated iron with a diameter of 1+a. The safety grid 31 in the center is made of a stainless steel pipe, and an opening 9 is formed approximately in the center of the pipe, and a thermistor 5 is disposed near the opening. Another thermistor 6 is fixed to the inner surface of the safety grid 3' with adhesive in the vicinity of the thermistor 6, and detects the temperature of the safety grid 3'. In other words, the thermistor 6 has the heat capacity of a single element, and the other thermistor 6 can be regarded as a thermally responsive large heat-sensitive element with a heat capacity approximately equal to the heat capacity of the safety grid 3' (the heat capacity of the stainless steel pipe). can.

Therefore, as shown in the graph of FIG. 6(a), the temperatures of the thermistors 6 and 6 after the stove is turned on are 5' and 6.
It responds as shown by the line . That is, the thermistor 6 reaches almost the saturation temperature in the time T1 due to the radiant heat from the heating element 2 of the stove, while the thermistor 6 reaches the saturation temperature a little later.
The saturation temperature is reached in 2 hours. In a steady state, there is no temperature difference and the temperatures are almost the same, but as shown in Figure 2, when a piece of flammable cloth 80, etc. approaches the front of the stove, the temperature near the safety grids 3 and 3' rises rapidly. , the temperature of the thermistor 5 rises rapidly during a short period of time T3 as shown at 5" in FIG. As shown, the temperature rises slowly.The difference in temperature between the two thermistors 6 and θ is shown in Figure 6 (Φ).Figure 3 is an electrical circuit diagram that constitutes the control section of the stove. The two heating elements 2 are connected in series with the contacts 8 driven by the control circuit A.
The figure is a functional diagram of the control circuit A. Series resistors 2!5 and 26 are connected to the thermistors 6 and 6, respectively, and a DC voltage is applied by a DC power source 1o. The voltage across the thermistor 6 and θ is amplified by a differential amplifier 11, and the differential voltage is differentiated by a differentiating circuit 12 to obtain a voltage VD as shown in FIG. 5(C). The voltage difference VD is compared with the reference voltage vth, and when it becomes higher than vth, an output voltage V□ is generated in the comparator 13 as shown in FIG. Turn off. Note that the reference voltage is a divided voltage of the resistor 27 and the variable resistor 28, and has an adjustable configuration.

Note that the relay drive circuit 14 has a self-holding function,
Self-holding until manually reset.

In the figure, 1 is the main body, and 4 is the main switch.

Effects of the Invention The present invention makes it possible to detect an abnormal situation by utilizing the difference in response characteristics of two heat-sensitive elements having different heat capacities, and to ensure safety by cutting off the current supply to the heating element.

[Brief explanation of drawings]

Fig. 1 is an external view of an electric stove according to one embodiment of the present invention;
The figure is a cross-sectional view of the electric stove, Figure 3. FIG. 4 is an electric circuit diagram of the control section, and FIG. 5 is an output waveform diagram of the control section. 2... Heating element, 5, 6... Thermistor (heat sensitive element), 7... Control circuit (control unit), 1
1...Differential amplifier, 12...Differential circuit, 13...Comparator, 14...Relay drive unit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4

Claims (2)

[Claims] (1) An electric stove that includes two heat-sensitive elements having different heat capacities disposed near a heat-generating element and a safety grid, and a control unit that energizes the heat-generating element by the outputs of these heat-sensitive elements. (2) The control unit includes a circuit that differentiates the output of the differential amplifier, a comparator that compares the differential output voltage with a reference voltage, and a relay drive unit that drives the relay using the output voltage of this comparator. The electric stove according to claim 1, further comprising a heating element connected in series with the contacts of the relay.