JPH0232237Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an improvement in an electric iron using a bidirectional three-terminal switching element to control energization of a heater that heats an iron base.

[Technical Background of the Invention] Electric irons generally incorporate a temperature control device to maintain a substantially constant temperature of the iron base in direct contact with the fabric being ironed. Such electric irons are, for example,
It has the circuit configuration shown in the figure. That is, 1 in the figure is an AC power supply that supplies 100 volt AC power to this temperature control device via an outlet or plug, for example, and a heater 2 attached to an iron base (not shown) is connected to this AC power supply 1 in a bidirectional manner. They are connected via a triax 3 as a three-terminal switching element. A gate signal for energization control outputted from a temperature control circuit 4 made up of, for example, an IC circuit element is input to the gate terminal of the triac 3. A variable resistor 5 for temperature setting and a thermistor 6 as a temperature detection element attached to the iron base are connected in series between a pair of output terminals A ₁ and A ₀ from which the reference voltage of the temperature control circuit 4 is output. ing. Then, the potential at the connection point between the variable resistor 5 and thermistor 6 is inputted to the input terminal T as a temperature signal. Further, the temperature control circuit 4 is supplied with a circuit driving voltage Vc from the AC power supply 1 via a voltage drop resistor 7 and a rectifying diode 8.

With an electric iron configured like this,
When the power is turned on, the temperature of the iron base is the set temperature Ts set by variable resistor 5.
, the resistance value of the thermistor 6 is large, and the voltage level of the temperature signal input to the input terminal T is high. As a result, the gate signal sent from the temperature control circuit 4 to the gate terminal of the triax 3 becomes H level, the triax 3 becomes conductive, and an alternating current flows from the alternating current power supply 1 to the heater 2.

When the iron base is heated by the heater 2 and the temperature of the iron base rises above the set temperature Ts set by the variable resistor 5, the resistance of the thermistor 6 decreases and the temperature signal input to the input terminal T decreases. The voltage level decreases, and the voltage level of the gate signal output from temperature control circuit 4 changes to L level. As a result, the triax 3 is cut off and the current supply to the heater 2 is also cut off. In this way, the iron base is always maintained at approximately the set temperature Ts.

[Problems with Background Art] However, the electric iron using the bidirectional three-terminal switching element to control the energization of the heater as described above has the following problems. In other words, when ironing clothes that have been washed and dried, the temperature of the ironed cloth is above a certain temperature.
Only a small amount of electric power is required to maintain the temperature of the iron base at the set temperature Ts once it reaches the set temperature Ts. However, when it is necessary to iron wet cloth, such as when drying wet clothes or ironing immediately after washing, the amount of heat released from the iron base increases. In such a case, the gate signal output from the temperature control circuit 4 continues to maintain the H level in order to maintain the temperature of the iron base at the set temperature Ts. Therefore, since the triac 3 continues to conduct, the triac 3 itself generates heat due to its internal resistance, and if the heating state continues for a long time, there is a risk that the element itself may be thermally damaged.

In order to eliminate the above-mentioned inconvenience, it has been proposed to attach a heat sink to the triax 3 itself, but in order to completely dissipate the heat generated by the triax 3, the heat dissipation area of the heat sink should be set to a certain value or more. There is a need. Therefore, there is a problem in that the volume required to house electronic components such as the triax 3 to which the heat sink is attached increases, resulting in an increase in the size of the electric iron as a whole.

[Purpose of the invention] This invention was made based on the above circumstances, and its purpose is to
By connecting a thermoswitch in parallel to the terminal switching element, the storage volume of the electronic circuit components including the bidirectional three-terminal switching element can be maintained almost at the current level, even when ironing wet cloth. It is an object of the present invention to provide an electric iron that can suppress the temperature rise of a bidirectional three-terminal switching element even if the heater is energized for a long time, and can be small and improve reliability.

[Summary of the invention] The electric iron of the invention is inserted between a heater that heats the iron base and an AC power supply that supplies power to the heater, and an energization control signal is input to the gate terminal from the temperature control circuit. A thermoswitch is connected in parallel to the bidirectional three-terminal switching element, which shorts both terminals of the bidirectional three-terminal switching element when the temperature of the bidirectional three-terminal switching element rises above a predetermined permissible limit. In addition, this thermoswitch can be
It is thermally integrated with the terminal switching element.

[Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing the electric iron of the embodiment. In the figure, reference numeral 11 denotes an iron base that comes into direct contact with the cloth to be ironed, and a heater 2 is cast into this iron base 11. The upper surface of this iron base 11 is covered with a cover 13, and a cassette-type water tank 1 is installed on the front end side of the upper surface of this cover 13.
4 is removably attached. This water tank 1
4 contains water for steam injection. Furthermore, a handle body 15 is attached to the rear end side of the upper surface of the cover 13. As shown in the figure, the handle body 15 includes a base 16 and a grip portion 1 made of synthetic resin or the like.
7, and a base 16 and an electronic component storage section 18 attached to the rear end of the grip section 17. Note that the electronic component storage section 18 is fixed to the end surface of the grip section 17 with screws 19.

Bidirectional 3 is provided on the bottom wall inside the electronic component storage section
A circuit board 21 on which electronic components 20 such as terminal switching elements and a temperature control circuit are attached is fixed. Furthermore, a conductive plate 22 is connected to the heater 2 cast into the iron base 11, which passes through a through hole 23 formed in the upper wall of the cover 13 and the bottom wall of the electronic component storage section 18. This conductive plate 22 is connected to the circuit board 21 by a lead wire.

FIG. 1 shows a circuit board 21 inside the electronic component storage section 18.
5 is a configuration diagram of an electronic circuit formed in FIG. 5, and the same parts as in FIG. Therefore, the explanation of the overlapping parts will be omitted. In this embodiment, a heater 2 cast into an iron base 11 is connected to a 100 volt AC power supply 1 via a triax 3 as a bidirectional three-terminal switching element. A gate signal for energization control outputted from a temperature control circuit 4 made up of, for example, an IC circuit element is input to the gate terminal of the triac 3. A variable resistor 5 for temperature setting and a thermistor 6 as a temperature detection element attached to the iron base 11 are connected in series between a pair of output terminals A ₁ and A ₀ from which the reference voltage of the temperature control circuit 4 is output. has been done. Note that a capacitor 24 for voltage stabilization is connected between the pair of output terminals A ₁ and A ₀ . Then, the potential at the connection point between the variable resistor 5 and thermistor 6 is input to the input terminal T as a temperature signal.
is input to. Further, the temperature control circuit 4 is supplied with a circuit driving voltage Vc from the AC power supply 1 via a voltage drop resistor 7 and a rectifying diode 8.

Further, a thermoswitch 25 is connected between both terminals of the triax 3. The thermoswitch 25 is attached to the surface of the triax 3 with an adhesive or the like, as shown in FIG. 3, for example, and opens and closes in response to the temperature of the triax 3. In other words, when the triax 3 rises above the preset allowable limit temperature Tc, the thermo switch 25
is closed, and both terminals of the triac 3 are short-circuited. In addition, in the figure, 26a, 26b, and 26c are connection terminals for attaching to the circuit board 21.

In the electric iron configured in this way,
When the power is turned on, the temperature of the iron base 11 is the set temperature set by the variable resistor 5.
Since Ts has not been reached, the resistance value of the thermistor 6 is large, and the voltage level of the temperature signal input to the input terminal T is high. As a result, the gate signal sent from the temperature control circuit 4 to the gate terminal of the triac 3 becomes H level, the triac 3 becomes conductive, and current flows from the AC power supply 1 to the heater 2. Note that in this state, the temperature of the triac 3 is low, so naturally the thermoswitch 25 is in an open state. Then, the iron base 11 is heated by the heater 2, and the temperature of the iron base 11 is changed by the variable resistor 5.
When the temperature rises above the set temperature Ts set in
The resistance value of the thermistor 6 decreases, the voltage level of the temperature signal input to the input terminal T decreases, and the voltage level of the gate signal output from the temperature control circuit 4 changes to L level. As a result, the triax 3 is cut off and the current supply to the heater 2 is also cut off. In this way, the iron base 11 is always maintained at approximately the set temperature Ts.

In addition, once the iron base 11 has reached the set temperature Ts
In a state in which the triax 3 is controlled on and off in response to temperature fluctuations caused by normal ironing operations after the ironing temperature has reached 100, the temperature rises to the above-mentioned allowable limit temperature Tc because the amount of heat generated by the triax 3 is small. Never.

With such an electric iron, when it is necessary to iron wet cloth, such as when drying clothes that have gotten wet in the rain or when ironing them immediately after washing, as mentioned above,
The amount of heat released from the iron base 11 increases. In such a case, the gate signal output from the temperature control circuit 4 continues to maintain the H level in order to maintain the temperature of the iron base 11 at the set temperature Ts.
Since the triax 3 continues to conduct, the temperature of the triax 3 increases. However, tryack 3
When the temperature rises above the allowable limit temperature Tc, the thermoswitch 25 attached to the surface of the triax 3 closes. As a result, both terminals of the triax 3 become short-circuited, and the triax 3 becomes short-circuited.
becomes blocked. Therefore, tryack 3
will stop generating heat, so the temperature will reach the allowable limit temperature Tc
A rise above this level is suppressed. Furthermore, even if the triac 3 is cut off, the current flowing through the heater 2 flows through the thermoswitch 25, so the heater 2 will not be cut off.

When the cut-off state of the triax 3 continues for a certain period of time and the temperature of the triax 3 falls below the permissible limit temperature Tc, the thermoswitch 25 is opened again.
At this point, if the temperature of the iron base 11 is lower than the set temperature Ts, an H level gate signal is applied from the temperature control circuit 4 to the triac 3, and the triac 3 becomes conductive. On the other hand, if the temperature of the iron base 11 is equal to or higher than the set temperature Ts, the gate signal sent from the temperature control circuit 4 becomes L level, so the triac 3 continues to be cut off.

In this way, by attaching the thermoswitch 25 to the triax 3, which is controlled to open and close in response to the temperature of the triax 3, it is possible to prevent the triax 3 from rising above a predetermined allowable limit temperature Tc. Therefore, thermal damage caused by a rise in temperature of the triax 3 can be prevented, and the reliability of the electric iron as a whole can be improved.

Further, unlike the conventional electric iron, there is no need to attach a large heat sink to the triax 3 itself, so the volume of the electronic component storage section 18 that stores the electronic components 20 including the triac 3 can be reduced. As a result, the entire electric iron can be made smaller and lighter.

Note that the present invention is not limited to the embodiments described above. In the embodiment, as shown in FIG.
However, if the conduction time of the triax 3 is relatively long even during normal ironing operation, a medium-sized heat sink may be used as shown in Figure 4. 27 to the surface of the triax 3 with, for example, bolts 28,
A similar effect can be obtained by attaching the thermoswitch 25 to the heat sink 27.

[Effects of the invention] As explained above, according to the invention, a thermoswitch that shorts both terminals of the triax in response to a rise in temperature of the triax is connected in parallel to the triax as a bidirectional three-terminal switching element. ing. Therefore, even if the heater is energized for a long time, such as when ironing a wet cloth, the rise in temperature of the triax can be suppressed while maintaining the storage volume of the electronic circuit components including the triax at almost the current level. This makes it possible to downsize the entire electric iron and improve its reliability.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an electric iron according to an embodiment of the present invention, Fig. 2 is a sectional view showing the same electric iron, and Fig. 3 is a perspective view showing the triax and thermoswitch of the same embodiment. FIG. 4 is a perspective view showing the triax and thermoswitch of an electric iron according to another embodiment of the present invention;
FIG. 5 is a circuit diagram showing a conventional electric iron. 1... AC power supply, 2... Heater, 3... Triack, 4... Temperature control circuit, 5... Variable resistance,
6...Thermistor, 11...Iron base, 1
3... Cover, 14... Water tank, 15... Handle body, 18... Electronic component storage section, 20... Electronic component, 21... Circuit board, 22... Conductive plate, 25...
...thermo switch, 27...heat sink.

Claims (1)

[Scope of utility model registration request] Bidirectional 3 interposed between an iron base, a heater that heats this iron base, and an AC power supply that supplies power to this heater and this heater
a terminal switching element, a temperature detection element that detects the temperature of the iron base, and the bidirectional 3 based on the temperature detected by the temperature detection element.
A temperature control circuit that sends an energization control signal to the gate terminal of the terminal switching element, and a temperature control circuit that is connected in parallel to the bidirectional three-terminal switching element and thermally integrally attached to the bidirectional three-terminal switching element; An electric iron comprising: a thermoswitch that shorts both terminals of the bidirectional three-terminal switching element when the temperature of the bidirectional three-terminal switching element rises above a predetermined permissible limit.