JPH0121364Y2 - - Google Patents

Description

[Detailed description of the invention] This invention detects the temperature inside the control unit and cuts off the power to the control unit and the kotatsu heater when the electronic control unit of the electric kotatsu is accidentally placed inside the kotatsu. The present invention also relates to a control device for an electric kotatsu whose purpose is to alert the user to proper use by activating an alarm device.

Generally, in an electric kotatsu as shown in FIG. 1, an electronic control unit 3 is inserted in the middle of the power cord 17 between the kotatsu tower 1 and the power outlet 2. As shown in the figure. In the temperature control circuit 4 of FIG. 2,
When the power switch 5 is closed, a closed circuit of the commercial power supply 6, heater 7, bidirectional three-terminal thyristor 8, and coil 9 is formed, and by controlling the firing angle of the three-terminal thyristor 8, the power consumption is controlled. The firing angle of this three-terminal thyristor 8 is determined by the temperature detection thermistor 1 inside the tower kotatsu.
0, a variable resistor 11 for setting the kotatsu temperature, a capacitor 12 and a negative resistance oscillation element 13. The above operation will be explained in more detail based on FIG. In FIG. 3, a shows the waveform of the voltage of the power supply 6, b shows the waveform of the voltage of the thyristor 8, c shows the waveform of the voltage of the heater 7, and d shows the waveform of the voltage of the capacitor 12. First, it is assumed that the variable resistor 11 is set so that the inside of the kotatsu reaches a desired temperature, and the switch 5 is closed at time _t0 . At this time, during the half cycle from _t0 to _t2 , the capacitor 12 is gradually charged through the thermistor 10 and variable resistor 11 as shown in FIG. 3d. This charging voltage increases, and at t ₁ , the negative resistance oscillation element 13
When the oscillation region v ₀ of is reached, the negative resistance oscillation element 13 oscillates and applies a gate drive pulse to the gate of the thyristor 8. Then, the thyristor 8 is ignited and power is supplied to the heater 7 as shown by diagonal lines in FIG. 3c. When the oscillation element 13 oscillates, the capacitor 12 discharges and prepares for charging in the next half cycle. Next, at time _t2 , when the voltage of the power supply 6 becomes a negative half cycle, the thyristor 8 is cut off and the supply of power to the heater 7 is stopped.

Next, when the voltage of the power supply 6 becomes a negative half cycle at time _t2 , the capacitor 12 is charged in the negative direction as before, and the negative resistance oscillation element 13 applies a gate drive pulse to the thyristor 8 at time _t3 , and the thyristor 8 is ignited again to supply power to the heater 7 as shown by diagonal lines in FIG. 3c. This is repeated in the same manner.

Here, since the thermistor 8 has a positive characteristic, the resistance value increases as the temperature inside the kotatsu increases, and the charging time of the capacitor 12 increases.

Therefore, the time required for the charged voltage of the capacitor 12 to reach the oscillation region v ₀ of the negative resistance oscillation element 13 becomes longer, and as a result, the firing of the thyristor 8 is delayed, so that the firing angle becomes larger. As a result, the shaded area in FIG. 3c becomes narrower, the power supplied to the heater 7 decreases, and the temperature inside the kotatsu falls.

On the other hand, when the temperature inside the kotatsu decreases, the resistance value of the thermistor 8 decreases, which acts in the opposite manner to the above, the firing angle decreases, the power supplied to the heater 7 increases, and the temperature inside the kotatsu rises. In this way, the temperature inside the kotatsu is always kept constant.

The resistors 14 and 15 and the capacitor 16 are used to replenish the charge to the capacitor 12 after the capacitor 12 is discharged when the ignition angle is small, thereby ensuring smooth control.

In the temperature control circuit as described above, if the electronic control unit 3 is used with it inside the futon 18 or placed near a stove etc., the semiconductor elements inside the electronic control unit 3 may be destroyed due to the temperature rise. or malfunction. Therefore, a method has already been proposed in which a thermostat is housed in the unit and the temperature inside the unit is detected to reduce the power to the heater 7 or turn off the power. However, since there was no way to notify the user of this, the user did not notice that the situation was abnormal, and if left unattended, the overheat prevention device would activate and return to its original state repeatedly. There was no control.

The present invention was developed to improve the above-mentioned drawbacks. A temperature-sensitive resistance element is provided in the control unit, and changes in voltage are detected in accordance with changes in resistance value due to changes in temperature. Depending on the change, the switching element is opened or closed, reducing the power to the kotatsu heater, cutting off the power, and activating the alarm device.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 4, the temperature control circuit 4 is substantially the same as that in FIG. 2, and in the present invention, an alarm device 19 and a temperature detection device 20, which are surrounded by chain lines, are further added to the control unit 3.

The alarm device 19 is a device that generates a sound such as a buzzer, but may also be a device that emits light or a combination of sound and light.

The detection circuit 28 of the temperature detection device 20 is mainly composed of a temperature-sensitive resistance element 21 whose resistance value increases rapidly when the temperature exceeds a certain temperature.
This temperature-sensitive resistance element 21 is connected in series with the thermistor 10 and between the power source 6 and the heater 7. In addition to this temperature-sensitive resistance element 21, the detection circuit 28 is further comprised of voltage dividing resistors 22, 23, a reverse current blocking diode 24, a smoothing capacitor 25, a discharge resistor 26, and a resistor 27. Further, a reference voltage generation circuit 34 is constituted by a diode 29, resistors 30, 31, 32, and a capacitor 33, and this reference voltage generation circuit 34 and detection circuit 28 are connected to a comparator 35, and further, resistors 36, 37,
It is coupled to a driving transistor 39 via 38 .

Next, the operation of the present invention will be explained.

Assume that the control unit 3 is now inside the kotatsu and the temperature of the control unit 3 has risen above a predetermined temperature. Then, the resistance value of the temperature-sensitive resistance element 21 increases rapidly, and as mentioned above, the voltage of the capacitor 16 decreases, and the charging time becomes longer, so that the negative resistance oscillation element 13 continues until it reaches its oscillation region _v0 . time becomes longer, the ignition of the thyristor 8 is delayed, and the power supply to the kotatsu heater 7 gradually decreases. In some cases, the negative resistance element 13 is outside the operating range, and the thyristor 8 is turned off without producing any output, stopping the power supply to the kotatsu heater 7. After that, when the temperature inside the kotatsu decreases and the temperature inside the control unit 3 also decreases, the temperature-sensitive resistance element 21 and thermistor 10 return to a low resistance value, the capacitor 16 is charged again, and the kotatsu heater 7 is turned on again. Become. However, as long as the control unit 3 is inside the kotatsu, the above operations are repeated, which not only prevents normal temperature control of the kotatsu but also causes damage to the semiconductor device or malfunction. Therefore, in the present invention, the temperature inside the control unit 3 is further detected by the temperature sensitive resistance element 21, so if the control unit 3 is placed inside the kotatsu and the temperature rises abnormally, the resistance of the temperature sensitive resistance element 21 will be detected. The value increases and the divided voltage decreases. When the voltage becomes lower than the reference voltage, an output appears from the comparator 35 and turns on the transistor 39. Therefore, an alarm device 19 such as a buzzer is activated to notify the user of the abnormality. At this point, if the control unit 3 is removed from the kotatsu and cooled with outside air, or the power switch 5 is turned off, the alarm device 19 will stop.

Since the present invention is configured as described above, when the temperature inside the control unit rises, it is detected by the temperature-sensitive resistance element, and it not only turns off the kotatsu heater, but also
The alarm device is activated to notify the user that there is an abnormality. Therefore, abnormal conditions can be noticed immediately,
Can be used correctly and safely at all times.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an electric kotatsu, Fig. 2 is an electric circuit diagram of a conventional control device, Fig. 3 is an output waveform diagram of each part, and Fig. 4 is an electric circuit showing an embodiment of the control device according to the present invention. It is a diagram. 1... Kotatsu tower, 3... Control unit, 4
... Control circuit, 5 ... Power switch, 6 ... Power supply, 7 ... Kotatsu heater, 8 ... Bidirectional 3-terminal thyristor, 10 ... Temperature detection thermistor, 1
1... variable resistor for temperature setting, 13... negative resistance oscillation element, 17... power cord, 18... futon,
19...Alarm device, 20...Temperature detection device, 21
... Temperature-sensitive resistance element, 28 ... Detection circuit, 35 ...
Comparator, 39...drive transistor.

Claims (1)

[Scope of utility model registration request] A kotatsu temperature control unit is connected in the middle of the power cord of the kotatsu heater, and the thyristor firing angle control circuit consisting of the temperature sensing element in the kotatsu and the negative resistance oscillation element, resistor, and capacitor in the control unit controls both temperatures. In an electric kotatsu that controls the power of the kotatsu heater by controlling the firing angle of a tropic three-terminal thyristor, a temperature-sensitive resistance element that is housed in the control unit and whose resistance value changes rapidly when a certain temperature is reached is used. A temperature detection device is constructed by connecting the thyristor firing angle control circuit in series and connecting it in series to a voltage detection circuit consisting of a voltage dividing resistor, and connecting this voltage detection circuit and a reference voltage generation circuit to a comparator. A control device for an electric kotatsu is formed by connecting an alarm device to the output side of the temperature detection device via a transistor.