JPH08145388A - Surface heating tool - Google Patents

Abstract

(57) [Summary] [Purpose] A planar heating tool that uses a single-line temperature-sensitive heater.
Overheat is prevented by reliably detecting disconnection of the signal line that also functions as a temperature detector and safety device and controlling the energization of the heating line. [Structure] The polymer temperature sensor 7 is provided between the heating line 6 and the signal line 8.
A heat-sensitive heater wire 16 with a power supply 1 interposed therebetween, a temperature fuse 2 on one side of a power source 1, a resistor 4 and a diode 5 thermally coupled to the temperature fuse 2.
A temperature detection circuit 11 connected from the series circuit via a signal line 8, a switching element 9 connected between a connection point between the series circuit and the signal line and circuit ground, and a switching element. 9, timer means for outputting an ON signal for a certain time at a certain timing, a disconnection detection circuit 10 for receiving the signal and monitoring a signal at a connection point of the temperature detection circuit 11 to detect a disconnection of the signal line 8, and a temperature detection circuit. The heating wire 6 is generated by the signal from the signal line 11 and the signal from the disconnection detection circuit 10.
Control energization to.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a surface heating and collecting tool such as an electric carpet.

[0002]

2. Description of the Related Art A two-wire system in which a heating wire and a temperature detection wire are separately wired is the mainstream of a surface heating tool mainly for electric carpets. The development of a surface heating tool with a one-wire configuration as a heater wire is in progress. With the one-wire configuration, it is not necessary to separately wire the heating wire and the temperature detection wire, and the temperature can be controlled simply by wiring the integrated temperature sensitive heater wire. Therefore, the material cost of the temperature detection wire and the wiring man-hours can be reduced. It can reduce the cost and reduce the cost. Further, since the heat generating portion and the temperature detecting portion are integrated, the temperature of the heat generating wire can be directly controlled, so that the temperature rise can be suppressed even if the heat is locally maintained, and the safety is enhanced.

The temperature-sensitive heater wire used in the one-wire system is
A polymer temperature sensor is placed between the heat generation line and the signal line, and the temperature characteristics of the impedance of this temperature sensor change the current flowing between the lines. I do. In the unlikely event that the signal line is broken, the current flowing through the temperature sensitive material will decrease, and the temperature will not be able to be measured normally, which may result in an unsafe condition.

Further, the signal line is used as a safety device for stopping energization to the heating wire in case of excessive temperature rise due to external heating or local heating. This is because, for example, a heat-melting resin such as nylon is used as the temperature-sensitive material, and the resin is melted by local overheating, resulting in conduction between the signal line and the heating line, and the current flowing therethrough causes a resistor to flow. Is made to generate heat, the thermal fuse thermally coupled to the resistor is cut, and the power supply to the heating wire is stopped. Therefore, if the signal line is broken, this safety device will not work depending on the location.

As described above, the disconnection of the signal line in the one-wire system cannot detect the temperature, and the safety device will not work in case of emergency. Therefore, the method for surely detecting this is the one-wire system. It is an indispensable technology.

Therefore, a conventional one-line type sheet heating device has a structure as shown in FIG. 10, for example. A temperature sensitive heater wire 16 in which a polymer temperature sensitive body 7 is interposed between a heat generating wire 6 and a signal wire 8, a temperature fuse 2 and a temperature fuse 2 in a power source 1.
A diode 5 whose anode is connected via a resistor 4 which is thermally coupled to the temperature detection circuit 11 connected from the cathode of the diode 5 via a signal line 8; and a connection point between the signal line 8 and the temperature detection circuit 11. Disconnection detection circuit 10 connected,
It is composed of a relay 13 for controlling energization to the heating wire 6 and its drive circuit 12, and the disconnection detection circuit 10, the temperature detection circuit 11 and the relay drive circuit 12 are connected to the microcomputer 3 and a program in the microcomputer 3 is connected. Together with this, a disconnection detecting means, a temperature detecting means, and a power control means are respectively configured. FIG. 10 shows a flowchart of the program in the microcomputer 3.

This configuration operates as follows. Power supply 1
In a negative cycle, a current flows from the base of the transistor of the temperature detection circuit 11 to the emitter, and a current proportional to this flows from the collector to the base. Since the base current of the transistor changes due to the line impedance of the temperature sensitive heater wire 16, the collector current changes in proportion to this, and the output voltage of the temperature detection circuit 11 that smooths this also changes.
The output to the relay drive circuit 12 is controlled so that the magnitude of this voltage becomes the set temperature by the microcomputer 3, and the temperature of the planar warming tool is controlled to a constant temperature.

Next, the operation of detecting the disconnection of the signal line 8 will be described. FIG. 12 shows operation waveforms. As described above, the temperature signal is generated by using the current flowing during the negative cycle of the power supply 1. When the power supply 1 is in the negative cycle, disconnection of the signal line 8,
The transistors of the disconnection detection circuit 10 are reverse-biased and turned off regardless of whether or not they are disconnected.
The output signal of becomes H level.

With the signal line 8 normally connected,
In the cycle in which the power supply 1 is positive, current flows through the transistor of the disconnection detection circuit 10 through the resistor 4, the diode 5, and the signal line 8, the transistor is turned on, and the output signal of the disconnection detection circuit 10 becomes L as shown in FIG. It becomes a level.

Therefore, when the signal line 8 is normally connected, the pulse signal becomes L level in the positive cycle of the power source 1 and H level in the negative cycle, as indicated by a in FIG.

On the other hand, when the signal line 8 is disconnected, even in the positive cycle of the power supply 1, the current flowing through the resistor 4 and the diode 5 is disconnected due to the disconnection of the signal line 8 and the disconnection detection circuit 1
The transistor of 0 is not reached. Therefore, even in the positive cycle of the power supply 1, the transistor of the disconnection detection circuit 10 does not turn on, so that the output signal of the disconnection detection circuit 10 is as shown in FIG.
As shown in, the waveform has a waveform that maintains the H level state in both the positive and negative cycles of the power supply 1.

These disconnection and non-disconnection disconnection detection circuits 10
The microcomputer 3 determines the change in the waveform according to the flowchart shown in FIG. 10. In the case of disconnection, the relay 13 is turned off to stop energizing the heating wire 6 to ensure safety.

Further, when the temperature of the temperature-sensitive heater wire 16 locally rises due to local heat retention or external overheating, the polymer temperature sensor 7 is melted and conduction is generated between the heating wire 6 and the signal wire 8. The current from the power source 1 flows from the resistor 4, the diode 5 and the signal line 8 to the heat generating line 6 so that the resistor 4 generates heat and the thermal fuse 2 is cut to stop the power supply to the heat generating line 6. It also has a device.

[0014]

However, in such a conventional configuration, the disconnection detection circuit 10 is provided through the signal line 8.
Since the disconnection or non-disconnection of the signal line 8 is detected by the change in the output waveform of the disconnection detection circuit 10 depending on the presence or absence of the current flowing in the circuit, there are the following problems.

When the resistance value of the signal line 8 is sufficiently smaller than the impedance of the polymer temperature sensitive body 7, the conventional configuration can sufficiently cope. However, for example, when the carpet has a large area, the length of the temperature-sensitive heater wire 16 used for this also becomes long. This means that the impedance of the polymer temperature sensor 7 decreases and the resistance value of the signal line 8 increases at the same time, and the difference therebetween decreases. In general, the polymer temperature sensor 7 used for the temperature-sensitive heater wire 16 is inexpensive and has stable characteristics, but its impedance is lowered as the temperature rises. When the temperature rises and the impedance decreases, the difference between the resistance value of the signal line 8 and the impedance is further reduced.

As described above, when the difference in impedance between the polymer temperature sensor 7 and the signal line 8 becomes small, the transistor of the disconnection detection circuit 10 is sufficiently turned on at the positive cycle of the power supply 1 when the disconnection occurs as shown in FIG. Current 1
7 will flow. As described in the above description of the operation, in this configuration, the disconnection of the signal line 8 is detected by utilizing the fact that the disconnection detection transistor does not turn on in the positive cycle when the signal line 8 is disconnected. The transistor is turned on, resulting in a pulse waveform as shown in FIG. 12C, and it is impossible to distinguish between disconnection and non-disconnection.

In addition, it is very difficult to select a circuit constant that does not turn on the transistor even in the above-mentioned state. Even if it is possible, the lower limit of the impedance of the polymer temperature sensing element 7 is severely limited, and the sensor sensitivity is limited. There is a problem in that it cannot be dealt with when the usage length of the heater wire 16 becomes long or the impedance characteristic of the polymer temperature sensor 7 is changed and becomes low.

Some of these polymer temperature-sensing bodies 7 include a reactance component in addition to a resistance component as impedance. For example, a waveform including a capacitance component is as shown in FIG. 12d. At 90 °, a maximum phase lead of 90 ° occurs. The phase thereof is not constant and constantly changes depending on the temperature and the characteristics of the polymer temperature sensor 7. Therefore, not only the signal processing for determining the disconnection or non-disconnection becomes complicated, but also the determination becomes impossible depending on the temperature range.

Depending on the structure of the temperature sensitive heater wire 16, even if the signal wire 8 is once broken, the wires may come into contact with each other and the break may not be detected. In the conventional configuration, since the relay 13 is turned off when the disconnection is detected, the user has a chance to reuse the relay 13 even in such a state, and the danger cannot be prevented.

Further, in such a surface warming tool, when a failure occurs in which the heating wire 6 is energized regardless of temperature detection, such as contact welding of the relay 13, short-circuit failure of the power control element, etc. It is usual to detect and turn off the thermal fuse 2 to stop the energization of the heating wire 6, but it is necessary to separately attach a thermal fuse, a switching element and the like as parts for that purpose. Further, the circuit failure of these safety circuits cannot be detected, and there is a possibility that the safety circuits may be used in a failed state.

The present invention solves the above-mentioned problems and enhances safety without causing erroneous detection of disconnection of the signal line 8 due to the line length of the temperature sensitive heater wire 16, the impedance characteristic of the polymer temperature sensor 7 and its temperature change. A first object is to provide a surface heating tool.

A second object of the present invention is to prevent an erroneous detection of disconnection of the signal line 8 even when the polymer temperature sensor 7 is used in which the impedance of the temperature sensitive layer has a reactance component, which changes. It is to provide a sheet heating device with improved safety.

A third object of the present invention is to prevent the erroneous detection of the disconnection of the signal line 8 even when using the polymer temperature sensor 7 in which the impedance of the temperature sensitive layer has a capacitive component and the impedance of the capacitive component changes. The object is to provide a sheet-shaped warming tool with improved performance.

[0024] A fourth object of the present invention is to provide a planar warming tool with enhanced safety by making sure the disconnection of the signal line 8 cannot be reused by the user. is there.

Further, a fifth object of the present invention is to stop the power supply to the heat generating wire 6 when the power is continuously supplied to the heat generating wire 6 due to a component failure when it is not necessary to supply the power, thereby improving the safety. An object of the present invention is to provide a surface heating device with improved safety capable of detecting disconnection and detecting a circuit failure of a safety circuit while suppressing cost increase.

[0026]

In order to achieve the above-mentioned object, a sheet heating device of the present invention comprises a temperature-sensitive heater wire having a polymer intercalator interposed between a heating wire and a signal wire, and a power supply. A temperature fuse connected to one side of a series circuit of a resistor and a diode thermally coupled to the temperature fuse, a temperature detecting means connected from the series circuit through a signal line, a connection point between the series circuit and the signal line, and a circuit. A switching element connected between the ground, a timer means that outputs an ON signal to the switching element at a constant timing for a fixed time, and a signal from the connection point of the temperature detecting means by monitoring the signal from the timer means. It comprises a disconnection detecting means for detecting a disconnection of the signal line, and a power control means for controlling energization to the heating wire by a signal from the temperature detecting means and a signal from the disconnection detecting means.

In order to achieve the second object, a power supply synchronizing means for outputting a signal synchronized with a waveform of a power supply, and a delay means for outputting a delay signal after receiving a signal from the power supply synchronizing means for a predetermined time. The switching element is driven by receiving the ON signal from the timer means and the delay signal from the delay means, and the disconnection detecting means from receiving the signal from the power supply synchronizing means to outputting the delay signal. The signal at the connection point between the signal line and the temperature detecting means is monitored to detect disconnection of the signal line while the delay signal is output.

In order to achieve the third object, the delay means delays the signal within 90 degrees in the power supply phase and within 90 degrees in the power supply phase after the polarity of the power supply is inverted from negative to positive by the signal of the power supply synchronizing means. Is configured to output.

In order to achieve the fourth object, a disconnection continuous ON means for outputting an ON signal continuously to the switching element when the disconnection detection means detects a disconnection is provided.

In order to achieve the fifth object, an energization state detecting means for detecting the energization state of the heating wire is provided, and the heating wire is energized even though the power control means is in the energization disapproval state. In this case, the switching element is provided with continuous ON means for continuously outputting an ON signal when the energizing circuit fails.

[0031]

According to the present invention, with the above-described structure, the timer means turns on the switching element for a certain period of time and at a certain timing to drop the series circuit side of the resistor and the diode of the signal line to the ground potential. Whether or not it is transmitted to the connection point between the temperature detection means and the disconnection detection means through the wire is detected by the disconnection detection means, and the power control means is controlled by the result of the disconnection and non-disconnection and the temperature detection means, and the heating wire is energized. Turn on and off.

The switching element is turned on by the signal of a constant time generated by the timer means at a constant time and the signal of the power supply synchronizing means by the delay means and delayed for a predetermined time. The series circuit side of is dropped to the ground potential, and the disconnection detection means detects whether or not this is transmitted to the connection point of the temperature detection means and the disconnection detection means through the signal line. The control means is controlled to turn on / off the power supply to the heating wire.

Within 90 degrees in the power supply phase, 90 degrees in the power supply phase after the polarity of the power supply is inverted from negative to positive by the power supply synchronization means.
The delay signal is output for up to 60 degrees, the switching element is turned on by this signal, and the series circuit side of the resistor and diode of the signal line is dropped to the ground potential, which is the connection point between the temperature detecting means and the disconnection detecting means through the signal line. Whether or not the power is transmitted is detected by the disconnection detecting means, and the power control means is controlled by the result of disconnection and non-disconnection and the temperature detecting means to turn on / off the power supply to the heating wire.

When disconnection is detected by the disconnection detecting means, an ON signal is continuously output to the switching element to generate heat in the resistor to disconnect the thermal fuse thermally coupled thereto, thereby cutting off the power supply to the heat generating line.

Further, when the energization state detecting means detects the energization state to the heating wire, and the power control means is energizing the heating wire even though the energization state is not permitted, the energization circuit fails. The ON signal is continuously output to the switching element by the continuous ON means to heat the resistor, and the thermal fuse thermally coupled to the resistor is blown to cut off the energization.

[0036]

An embodiment of the present invention will be described below with reference to the drawings. The same configurations as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

The first embodiment is shown in FIG. Reference numeral 16 is a temperature-sensitive heater wire, 6 is a heating wire, 8 is a signal wire, 7 is an interpolymer high temperature body,
1 is a power supply, 2 is a thermal fuse, 4 is a resistor, 5 is a diode, 11 is a temperature detection circuit, 10 is a disconnection detection circuit, 13
Is a relay and 12 is a relay drive circuit. Reference numeral 9 is a thyristor as a switching element connected to the microcomputer 3. Similar to the conventional example, the disconnection detection circuit 10, the temperature detection circuit 11, and the relay drive circuit 12 are connected to the microcomputer 3, and together with the program in the microcomputer 3, constitute disconnection detection means, temperature detection means, and power control means, respectively. ing. Further, a timer in the microcomputer 3 is used to configure a timer means. FIG. 2 shows a flowchart of the program in the microcomputer 3.

The operation of the above configuration is exactly the same as that of the conventional configuration with respect to the temperature detection, and the description thereof will be omitted. Next, regarding disconnection detection, this operation is as follows according to the flowchart shown in FIG. The output waveform of the disconnection detection circuit 10 during operation is as shown in FIG.

When the operation is started, the microcomputer 3
The timer inside starts. In this embodiment, the initial value is set to 3 minutes. While the timer is not up, the relay 13 is turned on / off according to the temperature without detecting the disconnection.

When three minutes have elapsed and the timer times out, the timer is restarted and then the thyristor is turned on. At this time, a waiting time of 1 ms is inserted to wait for signal stabilization, and then the signal of the disconnection detection circuit 10 is input. After inputting a signal, it is determined whether the wire is open or not. If the wire is open, the relay 13 is turned off. If the wire is not open, the normal temperature control is performed. At this time, the signal given to the gate of the thyristor becomes a pulse having a width of about 1 ms, like the trigger signal of FIG.

When the trigger signal of FIG. 3 is at H level, that is, when the timer times out, the potential of the signal line 8 is dropped to the circuit ground. As a result, all the current that should originally flow through the resistor 4 and the diode 5 in the positive cycle of the power supply 1 flows toward the thyristor, and as a result, the transistor of the disconnection detection circuit 10 is turned off. Therefore, the output signal of the disconnection detection circuit 10 when there is no disconnection is at the L level in the positive cycle of the power supply when the timer has not timed up and the signal line 8 is not disconnected as shown in FIG. In the negative cycle, the pulse becomes H level, and the timer is timed up, and becomes H level only in the positive cycle when the switching element is turned on.

Next, the operation when the signal line 8 is broken will be described. In this case, two cases are conceivable. The first case is a case where no current flows through the transistor of the disconnection detection circuit 10 regardless of the ON / OFF state of the switching element 9. In this case, the conventional disconnection detection waveform is used. Similarly to the above, the power supply 1 is at the H level regardless of whether the power supply 1 is negative or positive.
The waveform becomes like b. The second case is a case where the impedance of the polymer temperature sensor 7 is low. In this case, in the positive cycle of the power supply 1, even if the wire is broken, a current flows through the polymer temperature sensor 7, and the transistor of the wire breakage detection circuit 10 is turned on. Therefore, even if the timer times out, the switching element is turned on, and the potential of the signal line 8 on the power supply 1 side is dropped to the ground, the signal line 8 is disconnected, so the transistor of the disconnection detection circuit 10 is not turned off. . Therefore, the output of the disconnection detection circuit becomes L level even in the positive cycle when the thyristor is turned on.
The waveform becomes like c in the figure.

As described above, when the signal line 8 is not disconnected, when the timer times out and the switching element is turned on, the output of the disconnection detection circuit 10 becomes H level even in the positive cycle of the power supply 1. On the other hand, when the signal line 8 is disconnected, the output waveform of the disconnection detection circuit 10 may be at the H level regardless of the positive or negative cycle of the power source 1 in FIG. 3b, or may be at the L level in the positive cycle of the power source 1 in FIG. 3c. In each case, the waveform is different from that when there is no disconnection. Utilizing this, disconnection of the signal line 8 is detected, and when the disconnection is detected, the relay 13 is turned off to stop the power supply to the heating wire 6.

Further, FIG. 4 shows the second and third embodiments.
This will be described with reference to FIG. In the second and third embodiments shown in FIG. 4, the power supply synchronizing circuit 15 is added to the first embodiment. The power supply synchronizing circuit 15 has a pulse waveform that becomes L level in a positive cycle of the power supply 1 and becomes H level in a negative cycle, as indicated by a in FIG. The flowchart of the microcomputer 3 is different from that of the first embodiment, and this is shown in FIG. As shown in FIG. 5, the delay means is realized as a delay timer of the microcomputer 3. The other structure is similar to that of the first embodiment.

Next, the operation will be described. 3 when the operation starts
The minute timer starts. Subsequently, the start of the positive cycle of the power supply 1 is determined, which is detected by the point where the output of the power supply synchronizing circuit 15 changes from H to L. While not at the start point of the positive cycle, the temperature is adjusted according to the temperature signal from the temperature detection circuit 11. When the start point of the positive cycle of the power supply 1 is detected, it is determined whether the 3-minute timer is up. If the time is not up, adjust the temperature as it is. If the timer is up, restart the timer and start the delay timer. This delay timer has a power supply frequency of 50 Hz and a phase angle of 45 °, which corresponds to 5 ms.
Is set to. When 5 ms has elapsed and the delay timer times out, the signal from the disconnection detection circuit 10 is input for the first time to turn on the thyristor. After the signal stabilization wait time of 1 ms, the signal from the disconnection detection circuit 10 is input a second time to turn off the trigger signal of the thyristor to determine the disconnection. When the disconnection occurs, the relay 13 is turned off, and when not disconnected, the normal temperature control is performed. I do.

This operation waveform is shown in FIG. The trigger signal is the disconnection detection circuit 1 after the first signal input of the disconnection detection circuit 10 and the signal stabilization wait time after the delay time by the delay timer from the point that the output signal of the power supply synchronization circuit 15 changes from H to L.
Only the pulse width during the second detection of the 0 signal input is detected.
It is output as shown in the middle b. This is only a delay of the trigger signal when viewed from the first embodiment, and the other circuit operations are the same as in the first embodiment.

That is, when the signal line 8 is not disconnected, the output waveform of the disconnection detection circuit 10 turns on the thyristor at the timing when the trigger signal is output, and the potential at one end of the signal line 8 becomes the circuit ground. The transistor of the disconnection detection circuit 10 is turned off, and its output has a waveform such as c in FIG.

When the signal line 8 is broken, as in the first embodiment, the signal is at the H level regardless of the power source polarity as shown by d in FIG. 6 and the pulse as shown by e in FIG. May be However, this embodiment shows the case where the impedance of the polymer temperature sensor 7 has a capacitive component, and the signal of the disconnection detection circuit 10 is advanced by 90 degrees.

As described above, when the signal line 8 is not disconnected, the output signal of the disconnection detection circuit 10 is at the L level before the delayed trigger signal as shown by c in FIG. 6 and at the H level after the output of the trigger signal. It becomes a level. Further, in the case of disconnection, when the signal is fixed to H as shown by d in FIG. 6, both are set to H level by the detection before and after the trigger signal. Further, when the waveform becomes a pulse at the time of disconnection, even if there is a capacitive component in the impedance and there is a change in the phase as shown by e in FIG. 6, the advance is up to 90 degrees, and the value of the delay timer If L is set within 90 degrees in the power supply phase, both L can be detected before and after the trigger signal, so that disconnection and non-disconnection can be reliably detected. Therefore, based on this result, the relay 13 can be turned off and the device can be safely stopped.

Next, a fourth embodiment will be described with reference to FIG. The configuration of the fourth embodiment is the same as that of the first embodiment shown in FIG. The different point is the flowchart of FIG. 7 of the microcomputer 3. Although FIG. 7 is almost the same as the flowchart of the first embodiment, a point corresponding to the continuous ON means at the time of disconnection is added. Therefore, the signal line 8
Since the operation up to the point of detecting the disconnection is completely the same as that of the first embodiment, detailed description will be omitted. When the disconnection of the signal line 8 is detected by this configuration, the trigger signal of the thyristor is kept on. Therefore, once the disconnection of the signal line 8 is detected, the thyristor is continuously turned on, and the thermal fuse 2 thermally coupled by the heat generation of the resistor 4 is melted and the power supply to the heating line 6 is interrupted. You can

In this embodiment, reuse is impossible unless the temperature fuse 2 is replaced. Therefore, once the signal line 8 is broken, it cannot be reused by the user even if it is brought into contact again. Therefore, safety can be secured.

Next, a fifth embodiment is shown in FIGS. FIG.
In the first embodiment, the contact state detection circuit 14 is provided as the energization state detection means. As for the output of the contact state detection circuit 14, when the contact of the relay 13 is open, an L level signal is output in the positive cycle of the power supply 1 and an H level signal is output in the negative cycle. On the other hand, when the contact of the relay 13 is closed, the transistor remains off and the signal remains L.
Further, FIG. 9 shows a flowchart of the microcomputer 3. This structure is almost the same as that of the first embodiment,
A part corresponding to the continuous ON means at the time of failure of the energizing circuit is added.

As for the operation of this configuration, as shown in FIG. 9, the operation of detecting the disconnection of the signal line 8 is exactly the same as that of the first embodiment, and therefore its explanation is omitted.

When the relay 13 is turned off by the disconnection or the temperature detection signal, the contact state detection circuit 14 detects the contact state. At this time, if the signal from the contact state detection circuit 14 is a pulse as described above, the contact is considered to be open and normal, and the processing is continued. If the signal from the contact state detection circuit 14 is at L level, the contact is closed and the contact should be off, so it is determined that the contact of the relay 13 is in a welded state and the thyristor is continuously turned on to generate resistance. Let
The thermal fuse 2 that is thermally coupled to this is melted and the heating wire 6
The power supply to the power supply can be cut off.

[0055]

As is apparent from the above description, the surface heating device of the present invention drops the potential at one end of the signal line to the circuit ground by the switching element which is turned on / off by the signal from the timer means which outputs a signal at regular intervals. The following effects can be obtained because the disconnection detection of the signal line is performed by detecting that this is transmitted to the disconnection detection means connected to the other end of the signal line.

(1) Since the disconnection can be reliably detected regardless of the impedance change of the polymer temperature sensing element used for the temperature sensitive heater wire, it is stable even at the high temperature when the characteristic change of the temperature sensor and the impedance decrease. Since the disconnection of the signal line can be detected, it is possible to provide a highly safe sheet heating device.

(2) Not a fixed level signal,
Since the disconnection is determined by the pulse signal, it is possible to detect the failure of the circuit component such as the disconnection of the resistor used for the disconnection detection and the short circuit open failure of the switching element.
It is possible to provide a surface heating device with higher safety.

(3) Since the disconnection can be stably detected regardless of the energization state of the heating wire, the planar heating tool with high safety can be obtained.

Further, since the continuous ON means at the time of disconnection for continuously outputting the ON signal to the switching element when the disconnection is detected is provided, the temperature fuse is melted when the disconnection of the signal line is detected. Since it is possible to prevent reuse in an unstable state where the broken wire comes into contact again, it is possible to provide a highly safe planar heating device.

An energization state detecting means and an energization circuit continuous ON means are provided, and a switching device used for disconnection detection is a safety device when the power control means fails and the energization state to the heating wire continues. Since it can be used for both purposes, it is possible to provide a highly safe surface heating device while suppressing cost increase. Further, this makes it possible to detect the open circuit failure of the resistor for melting the temperature fuse and the diode connected in series with it, and the failure of the switching element, which cannot be detected conventionally.

[Brief description of drawings]

FIG. 1 is a block diagram of a planar heating tool according to a first embodiment of the present invention.

FIG. 2 is an operation flowchart of the surface heating device.

FIG. 3 is an operation explanatory view of the surface heating device.

FIG. 4 is a block diagram of a planar heating tool according to a second embodiment of the present invention.

FIG. 5 is an operation flowchart of the surface heating device.

FIG. 6 is an operation explanatory view of the surface heating device.

FIG. 7 is an operation flowchart of the planar heating tool according to the fourth embodiment of the present invention.

FIG. 8 is a block diagram of a sheet heating device according to a fifth embodiment of the present invention.

FIG. 9 is an operation flowchart of the surface heating device.

FIG. 10 is a block diagram of a conventional surface heating tool.

FIG. 11 is an operation flowchart of the surface heating device.

FIG. 12 is an explanatory diagram of the operation of the surface heating device.

FIG. 13 is an operation explanatory view of the surface heating device.

[Explanation of symbols]

 1 Power Supply 2 Thermal Fuse 4 Resistor 5 Diode 6 Heating Wire 7 Polymer Thermosensitive Body 8 Signal Wire 9 Thyristor 10 Disconnection Detection Circuit 11 Temperature Detection Circuit 16 Temperature Sensitive Heater Wire

Claims (5)

[Claims] 1. A temperature-sensitive heater wire having a polymer temperature-sensing body interposed between a heating wire and a signal wire, a temperature fuse on one side of a power supply, a resistor thermally coupled to the temperature fuse, and a diode in series. A circuit is connected to the temperature detection means connected from the series circuit via the signal line, a switching element connected between a connection point of the series circuit and the signal line and circuit ground, and the switching element. A timer means for outputting an ON signal at a constant timing for a constant time and a disconnection detecting means for receiving a signal from the timer means and monitoring a signal at a connection point of the temperature detecting means to detect disconnection of the signal line. And a surface warming tool including electric power control means for controlling energization to the heating wire by a signal from the temperature detecting means and a signal from the disconnection detecting means. 2. A power supply synchronizing means for outputting a signal synchronized with a power supply waveform, and a delay means for outputting a delayed signal after delaying a predetermined time after receiving the signal from the power supply synchronizing means, wherein the switching element is the timer. To be driven by receiving the ON signal from the means and the delay signal from the delay means,
The disconnection detecting means monitors the signal at the connection point between the signal line and the temperature detecting means from the time when the signal from the power supply synchronizing means is received until the delay signal is output, and while the delay signal is being output, The planar warming tool according to claim 1, wherein the disconnection detection of the signal line is performed. 3. The delay means outputs the delay signal within 90 degrees in the power phase and within 90 degrees in the power phase after the polarity of the power source is inverted from negative to positive by the signal of the power synchronization means. Item 2. The surface heating tool according to item 2. 4. The planar heating according to any one of claims 1, 2 and 3, wherein continuous disconnection means for outputting a continuous ON signal is provided to the switching element when disconnection is detected by the disconnection detection means. Ingredient 5. A switching element is provided when an energization state is detected by the energization state detecting means for detecting the energization state of the heating wire and the power control means is not energized. The planar warming tool according to any one of claims 1, 2, 3 and 4, further comprising: a continuous ON means at the time of a failure of an energizing circuit that continuously outputs an ON signal to the.