JP4113507B2 - Heating tool - Google Patents

Description

  The present invention relates to a warming tool such as an electric carpet or an electric blanket using resistance heating of a heating wire, and more particularly to temperature control for abnormal heat generation.

  There are various types of heating devices used at home, including electric carpets, electric blankets, electric mattresses, electric cushions, and floor heating panels. For example, in a surface heating device such as an electric carpet, a general structure is to sandwich a heating element between a front fabric and a back fabric. The heating element is composed of a metal heating wire.

  By the way, an electromagnetic wave is generated from the heating element by the current flowing through the heating wire. Patent Document 1 discloses a heating element that suppresses the generation of electromagnetic waves. As shown in FIG. 3, the heating element 1 has a heating wire 2 covered with a heat-resistant insulator 3, and the heating wire 4 is wrapped around the insulator 3 and further covered with a covering material 5 such as nylon. 5 is a structure in which a temperature detection wire is wound as a heat sensitive body 6 and covered with a vinyl chloride insulating sheath 7.

  The two heating wires 2 and 4 are wired coaxially or in parallel via the insulator 3. As shown in FIG. 4, one end of each heating wire 2, 4 is connected to the control device 8, and the other end of each heating wire 2, 4 is connected to each other. As a result, reverse currents flow through the heating lines 2 and 4, the magnetic fields generated by the currents cancel each other, and electromagnetic waves generated from the heating element 1 are suppressed. In the figure, 9 is a control circuit, 10 is a relay contact, 11 is a current fuse, and 12 is a power supply.

As described above, the two heating wires are provided via the insulator. However, when insulation failure occurs due to pinholes or thermal degradation, the two heating wires are short-circuited, increasing the current flowing through the heating element and causing abnormal heat generation. Therefore, a current fuse is provided, or as described in Patent Document 2, a current detector is provided in series with the heating element to detect an abnormal current when a short circuit occurs and cut off the current supply. .
JP-A-4-278125 JP-A-11-191480

  The current detector may malfunction due to fluctuations in power supply voltage or external noise even when the heating element is in a normal state. In addition, the closer the location where the heating wire is short-circuited to the power supply side, the larger the value of the current that flows through the detector when an abnormality occurs, and the shorter the time from when the abnormality occurs until operation is performed. Conversely, the further away from the power supply side, the smaller the value of the current flowing through the detector. As a result, it takes time until the detector operates after an abnormality occurs, or the detector may not operate depending on the current at the time of a short circuit, which causes a problem in safety.

  In view of the above, an object of the present invention is to provide a warming tool that can reliably and quickly detect a short circuit in a heating element.

  The present invention relates to a heating element in which two heating wires are connected to each other so that two heating wires are adjacent to each other through an insulator and the directions of flowing currents are opposite to each other, and control for controlling energization to the heating element A first current detector that detects a current flowing through the heating element, a second current detector that detects a current flowing through one of the heating lines, and the control The device controls on / off of energization based on the output of each current detector.

  The first current detector is provided in series with the heating element. The second current detector is provided at a connection point between the two heating wires. Specifically, one end of each heating wire is connected to the power source, and the first current detector is interposed between one of the heating wires and the power source. Also, the other ends of the heating lines are connected to each other, and the second current detector is interposed between the other ends of the heating lines. Thus, by arranging the current detector, it is possible to detect even a small change in the current in the heating element relative to the current flowing through the entire heating element.

  Then, the control device compares the output of the first current detector and the output of the second current detector, and determines whether or not a short circuit has occurred. When the insulation abnormality of the insulator occurs, the two heating wires are short-circuited, so that the output of the second current detector is reduced. When the output of the first current detector becomes larger than the output of the second current detector, the control device determines that a short circuit has occurred and immediately turns off the power supply to the heating element. Thereby, abnormal heat generation of the heating element is prevented.

  According to the present invention, when an insulation abnormality occurs in the insulator in the heating element, a short circuit due to the insulation abnormality can be reliably detected by causing a current difference between the inside and outside of the heating element. Therefore, power supply to the heating element can be stopped immediately, abnormal heat generation can be prevented, and safety can be improved.

  FIG. 1 shows an electric carpet that is a heating tool of the present embodiment. A control device 8 that controls energization of the heating element 1 is attached to a corner portion of the carpet body 20 in which the heating element 1 is sandwiched between the front fabric and the back fabric. The structure of the heating element 1 is the same as that of the two heating lines 2 and 4 shown in FIG. 3 adjacent to each other through the insulator 3, and the heating lines 2 and 4 and the heat sensitive element 6 of the heating element 1 are , Connected to the control device 8.

  The control device 8 is connected to the power source 12 via a power cord 21 and has a control circuit 9 composed of a microcomputer and a relay (not shown) controlled by the control circuit 9 as shown in FIG. In the control device 8, one end of each heating wire 2, 4 is connected to the lead wire 22 connected to the power cord 21, and the other end of each heating wire 2, 4 is connected to the other via a lead wire 23. A relay contact 10 and a current fuse 11 are interposed in a lead wire 22 connected to one heating wire 2, and the current fuse 11 is connected to the AC 1 side of the power source 12. The control circuit 9 operates the relay to open and close the relay contact 10 to turn on and off the energization.

  And in order to detect the insulation abnormality of the insulator 3, the 1st current detector 24 which detects the electric current which flows into the heat generating body 1, and the electric current which flows into the one exothermic line of the two exothermic lines 2 and 4 are used. A second current detector 25 for detection is provided. Each of the current detectors 24 and 25 includes a current transformer. The first current detector 24 is interposed between one end of one heating wire 2 and the relay contact 10 and is connected in series with the heating element 1. The second current detector 25 is interposed in a lead wire 23 that connects the other ends of the two heating wires 2 and 4. That is, it is arranged at a connection point between the two heating wires 2 and 4.

  Each of the current detectors 24 and 25 outputs a voltage corresponding to the current flowing through the detection point to the control circuit 9. The control circuit 9 compares the outputs of the current detectors 24 and 25 to determine whether a short circuit has occurred between the two heating lines 2 and 4. Based on the determination result, the relay contact 10 is opened and closed to control on / off of energization.

  Normally, when the relay contact 10 is closed and energization is started, a current flows through the heating element 1 and the temperature rises. Accordingly, an output voltage corresponding to the temperature rise is input from the heat sensitive body 6 to the control circuit 9. Based on the output of the heat sensitive body 6, the control circuit 9 controls the opening and closing of the relay contact 10 to keep the surface temperature of the carpet body 20 constant.

  At this time, each of the current detectors 24 and 25 detects a current flowing through the heating element 1, and the control circuit 9 outputs the output voltage Va of the first current detector 24 and the output voltage Vb of the second current detector 25. Compare the size with. In normal times, the total current flowing through the heating element 1 is equal to the current flowing through the heating wires 2 and 4, so Va = Vb, and the control circuit 9 determines that it is normal.

  Here, when an abnormality occurs in the insulator 3, a short circuit such as a rare short occurs between the two heating wires 2 and 4. Then, the current flowing through the second current detector 25 decreases or disappears, and the output voltage Vb of the second current detector 25 decreases.

  The control circuit 9 detects that Va> Vb and determines that an abnormality has occurred. Then, the control circuit 9 operates the relay to open the relay contact 10. The energization to the heating element 1 is turned off. Therefore, even if an insulation abnormality of the insulator 3 occurs at any location in the heating element 1, this can be reliably detected, and the energization to the heating element 1 can be stopped to prevent abnormal heating. In addition, when said abnormality generate | occur | produces, it is good to alert | report by a sound, a display, etc.

  By the way, the current detectors 24 and 25 are arranged in the control device 8. The control device 8 has a structure in which a control circuit 9 and the like are mounted on a circuit board and are housed in a case. Therefore, the current detectors 24 and 25 are mounted in the case. If the current detectors 24 and 25 can be mounted, the current detectors 24 and 25 can be mounted on the circuit board, and the control device 8 can be downsized.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. As the current detector, a resistance element, a Hall element, or the like that can be surface-mounted may be used.

  The warming tool may have a structure in which a plurality of heating elements are arranged in parallel. In this case, the first and second current detectors are provided for each heating element. The control device monitors the presence or absence of a short circuit for each heating element.

Top view of the electric carpet of the present invention Electrical diagram of the control device Diagram showing structure of heating element Electric circuit diagram of conventional control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating body 2, 4 Heating wire 3 Insulator 8 Control apparatus 9 Control circuit 10 Relay contact 24 1st current detector 25 2nd current detector

Claims (4)

A heating element in which two heating wires are arranged adjacent to each other via an insulator and a control device for controlling energization to the heating element are provided, and the directions of currents flowing through the heating lines are opposite to each other. As described above, one end of each heating wire is connected to a power source, the other end of each heating wire is connected to each other, and a first current detector for detecting a current flowing through the heating element is between one heating wire and the power source. provided, the second current detector for detecting a current flowing in the other heating wire is provided between the other ends of the other of the heating wire of one of the heating wire, wherein the control device, the current detecting A heating tool characterized by controlling on / off of energization based on the output of the vessel. Controller, when the output of the first current detector becomes larger than the output of the second current detector, Todan device according to claim 1, wherein turning off the power supply to the heating element. The first current detector and a second current detector according to claim 1 or 2, characterized in that provided in the casing to form a circuit board or the controller constituting the control device
The listed warming tool. The warming tool according to any one of claims 1 to 3 , wherein a plurality of heating elements are provided, and a first current detector and a second current detector are provided for each heating element.

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