JP4507930B2 - Surface heating device - Google Patents

Description

  The present invention relates to a sheet heating device such as an electric carpet, an electric blanket, and a panel heater.

  In a conventional sheet heating device such as an electric carpet, a magnetic field having a commercial frequency is generated by a current flowing through a heating element. Therefore, the heating element is divided into a first heating line and a second heating line, currents in opposite phases are passed through the heating lines, and both the first heating line and the second heating line are brought close to each other. There is known a configuration in which leakage of a magnetic field to the outside is prevented by canceling out a magnetic field generated by.

  In the above configuration, when adjacent heating wires are short-circuited, a configuration is generally used in which a current fuse provided in a device is used and the current fuse is blown by a current generated at the time of a short-circuit. However, when a short circuit occurs at an unspecified part of the heating wire and the device current does not reach the fusing point of the current fuse at the time of the short circuit, for example, in the case of an electric carpet, the heating wire reaches several tens of meters, so the short circuiting part Depending on the case, it is conceivable that the heating wires are short-circuited while leaving a certain resistance value. In this case, the current fuse is not blown. If the current fuse is held without being blown, there is a risk that the power cord may generate heat due to heat generation of the power cord or abnormal heating of the heating wire itself.

Therefore, as a countermeasure, a configuration shown in FIG. According to this document, a heating element composed of a first heating wire 1 and a second heating wire 2 is arranged in the heating device body, the heating element is energized and heated by the commercial power source 3, and the commercial power source 3 is melted by an overcurrent. The current fuse 4, the first heating wire 1, the current breaker 5 that opens and closes according to the temperature of the heating element, and the second heating wire 2 and the temperature fuse 6 that blows when heated from the outside are connected in series. A heat generating resistor 7 that heats and melts the temperature fuse 6 and a switching element (triac) 8 that turns on and off the heat generating resistor 7 are connected in series between both ends of the temperature fuse 6, and the first heat generating wire is connected. When the current breaker 5 is used as a turning point so that current flows through the first and second heating wires 2 in opposite directions, and the heating element is short-circuited at an unspecified location, the temperature fuse 6 is blown to generate heat from circuit components and the like.・ Safety against ignition It is Mel possible.
JP 2004-293932 A

  However, the conventional configuration does not directly detect a short circuit between the first and second heating wires. That is, when the temperature of the heating wire is controlled by opening / closing the current breaker 5, the heating resistor 7 is energized through the triac 8 because the heating wire is short-circuited when the current breaker 5 is open, and the temperature fuse 6 is melted and the short circuit state is not maintained, so that when the current breaker 5 is closed, the short circuit is detected and the device cannot be stopped. For this reason, there is a problem that a delay occurs in detection of a short circuit, and heat generation / ignition cannot be completely prevented.

  The present invention solves the above-mentioned conventional problems, and dramatically improves safety against heat generation and ignition by detecting a short circuit between heating wires in an unspecified part and immediately cutting off the current supply to the heating element. An object of the present invention is to provide a sheet heating device.

In order to solve the above conventional problems, a planar heating device of the present invention includes a heating element in which a first heating wire and a second heating wire are connected in series, and a control unit that controls energization to the heating element. Current detecting means for detecting the current of the heating element, and current interrupting means for interrupting energization of the heating element, and current detection at a connection point of the first heating wire and the second heating wire. The control unit is configured to shut off the current supply to the heating element when the current value detected by the current detection means becomes equal to or less than a predetermined value .

  As a result, when the heating wire is short-circuited at an unspecified part, there is no current passing through the current detection means. Therefore, when the output of the current detection means falls below a predetermined value, it detects that the heating wire is short-circuited and opens the current interruption means Thus, the current supply to the heating wire can be stopped.

According to the planar heating device of the present invention, the current detection provided at the connection point of the first heating wire and the second heating wire that the first heating wire and the second heating wire are short-circuited at an unspecified part. Detecting when the current value detected by the means is less than or equal to a predetermined value, and by turning off the current interrupting means, the current supply to the heating element can be interrupted, so when the heating wire is short-circuited, the device Can be stopped.

According to a first aspect of the present invention, there is provided a heating element in which a first heating line and a second heating line are connected in series, a control unit that controls energization of the heating element, and current detection means that detects a current of the heating element. Current interrupting means for interrupting energization to the heating element, provided with a current detection means at a connection point between the first heating wire and the second heating wire, and a current value detected by the current detection device When the current becomes less than a predetermined value, the control unit opens the current interrupting means and cuts off the current supply to the heating element, whereby the heating wire is short-circuited at an unspecified part. When there is no current passing through the current detection means, when the output of the current detection means falls below a predetermined value, the heating wire is detected as a short circuit and the current interrupting means is opened to cut off the current supply to the heating element. Safety against overheating and ignition It is possible to thermocline improved.

In the second invention, in particular, the current detection means of the first invention has a current transformer, a rectifier, and an averaging circuit, the rectifier rectifies the output of the current transformer, and the averaging circuit By configuring the output of the rectifying unit to be averaged, when the heating wire is short-circuited at an unspecified part, there is no current passing through the current detection device. It is possible to cut off the current supply to the heating element by detecting the short circuit and opening the current interruption means, so that it is possible to dramatically improve the safety against heat generation and ignition.

According to a third aspect of the invention, in particular, the current detection means of the first aspect of the invention has a current transformer and pulse output means for outputting a pulse when the output of the current transformer is positive or negative, and a control unit is the pulse output means. When the output pulse is not output for a predetermined time or longer, the current interrupting means is opened and the current supply to the heating element is interrupted. Since there is no current to pass, the pulse output means will not output a pulse due to the detected current, and if no pulse is output for a predetermined time, it will detect a short circuit of the heating wire and open the current interrupting means to generate heat. Since the current supply to the body can be cut off, the safety against heat generation and ignition can be dramatically improved.

  Reference embodiments and embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Reference form 1 )
Reference Embodiment 1 of the present invention will be described with reference to the drawings as an application example to an electric carpet.
FIG. 1 is a schematic external view of an electric carpet according to the present invention.

  The carpet body has a heating element 11 that generates heat when energized on a backing cloth 10 made of a material having excellent heat insulation properties (for example, a polyester felt cloth). The outer fabric 12 is bonded and fixed. Further, the outer peripheral portion is formed by overlock sewing. A controller 13 having a temperature adjustment function and a safety protection function is connected to the peripheral edge of the carpet body to control the amount of electricity supplied to the heating element 11, and a plug 14 for supplying power from the commercial power supply 3 is connected to the controller 13. It is connected.

  In the heating element 11, a first heating wire 15 made of a copper alloy is spirally wound around a core, the first heating wire 15 is covered with a heat-resistant insulator such as polyester or polyamide, and the outer periphery thereof is further covered. A second heating wire 16 similar to the first heating wire 15 is spirally wound, and the first heating wire 15 and the second heating wire 16 are arranged on the same axis that is covered with a heat-resistant insulator again. The first heating wire 15 made of a copper alloy is spirally wound around a structure in which both heating wires are arranged adjacent to each other or the core material, and the first heating wire 15 is heat-resistant such as polyester or polyamide. The configuration is such that the second heating wire 16 having the same configuration is disposed adjacently and in parallel with each other, or is disposed adjacently by twisting both heating wires.

FIG. 2 is a main part circuit diagram of the electric carpet according to the first embodiment of the present invention. As shown here, the first heating wire 15, the second heating wire 16, and the current interrupting device 18 are sequentially connected in series to the commercial power source 3, and the first heating wire 15 or the second heating wire 16 is connected. Current detecting means 17 for detecting the passing current of is provided. The controller 19 controls on / off of the current interrupting means 18 in order to control the heat generation amount of the heating element 11 composed of the first heating wire 15 and the second heating wire, and when the current detecting means 17 detects an overcurrent, the current interrupting means 18 It works to forcibly shut off the means 18. The display unit 20 displays this state when the control unit 19 detects a short circuit of the heating element 11 and forcibly cuts off the current interruption unit 18.

  FIG. 3 is a waveform diagram showing the current detected by the current detection means 17. A predetermined current value determined by the resistance value of each heating wire is observed until time T1 when both the first heating wire 1 and the second heating wire 16 are operating in a normal state. For example, when the heating wires are short-circuited between A1 and A2 in FIG. 1 at time T1, a current is generated because the resistance value of the heating element 11 as viewed from the commercial power supply 3 side is reduced. The peak value rises to I2.

This is because, for example, the heating wires 15 and 16 are partially heated due to some abnormality, and the insulation interposed between the heating wires melts or the user accidentally penetrates the push pin or the like into the electric carpet. This is a phenomenon that may occur when the heating wires are accidentally short-circuited. Usually, as a protective measure against overcurrent, a current fuse (not shown) is connected to the heating element 11 in series, but in the case of an electric carpet, the entire length of the heating element 11 reaches several tens of meters. Depending on the part that is short-circuited, the fusing current of the current fuse may not be reached. In this case, since the short-circuit state of the heating wire is kept indefinitely by the protection by the current fuse, there is a problem in safety. However, by providing the current detection means 17 for detecting overcurrent as in the first embodiment, the current is detected. Even if the short-circuit current does not reach the fusing current of the fuse, the abnormality can be detected, so that the overheating of the heating element 11 can be prevented. At the same time, it is possible to notify the user that an abnormality has been detected by the display means 20 and forcibly stopped by the current interrupting means 18, and the user can be prevented from misuse.

FIG. 4 is a circuit example showing a more specific configuration of the current detection means 17. A load transformer 22 is connected to the output of the current transformer 21 and the current transformer 21 for detecting the current of the heating wire, and the output of the current transformer 21 is temporarily converted to a direct current via a rectifier 23 that rectifies the output of the current transformer 21. The averaged voltage output is averaged by the averaging circuit 24. The comparator 26 compares the reference voltage 25 with the output of the averaging circuit 24, and does not output in a normal state. However, if the detection output of the current transformer 21 increases due to a short circuit of the heating wire 11, the reference voltage 25 (Vref). A signal is generated by exceeding. The control unit 19 opens the current interrupting means 18 by this signal, and interrupts the current supply to the heating element 11. For this reason, since the short circuit in the heating element 11 can be detected in a short time and the current supply from the commercial power source 3 can be cut off, the heating element 11 does not become abnormally hot and the safety of the electric carpet is improved. Is possible.

Further, this preferred embodiment 1, although not any restrictions on the resistance values of the first and second heating wire 15 and 16, for example, in the case of two of the heating wire are substantially equal resistance to each other, the resistance value of the two heating wire Is unbalanced, only the one heating wire generates heat and the other heating wire does not generate heat, so that the effect of the present embodiment can be exhibited.

( Reference form 2 )
Reference Embodiment 2 of the present invention will be described with reference to FIGS. FIG. 6 is a circuit diagram of a main part of the hot carpet according to the present invention. As shown here, the first heating wire 15, the second heating wire 16, and the current interrupting device 18 are sequentially connected in series to the commercial power source 3, and the second heating wire 16 is connected to the commercial power source 3 side. One current detection means 27 is provided, and a second current detection means 28 is provided on the other terminal side. The first and second current detection means 27 and 28 are input to the comparator 29, and the comparator 29 transmits a signal to the control unit 19 when there is a difference between the detection outputs of the two current detection means. The control unit 19 controls on / off of the current interrupting means 18 in order to control the heat generation amount of the heating element 11 composed of the first heating line 15 and the second heating line, and the comparison air 29 has a difference between the two current detection means. When it is detected that the current exceeds a certain level, the current interrupting means 18 is forcibly interrupted. Further, when the control unit 19 detects a short circuit of the heating element 11 and forcibly cuts off the current interrupting unit 18, the reporting unit 20 notifies the user of this state by voice.

  FIG. 6 is a waveform diagram showing the detected currents of the first current detection means 27 and the second current detection means 28. The state is shown in which the first heating wire 15 and the second heating wire 16 are short-circuited between B1 and B2 for some reason at time T2. In a normal state in which the heating lines are not short-circuited with each other, the currents flowing through the first current detection unit 27 and the second current detection unit 28 are equal to each other. However, when a short circuit occurs between B1 and B2 at time T2, the current flowing from the commercial power supply 3 into the first heating wire 15 is short-circuited at B1 and B2 and does not pass through the second current detection means. It flows into the heating wire 16. Then, a current flows through a path that returns to the commercial power supply 3 through the first current detection means 27.

  Accordingly, since the resistance value of the heating element 11 in the path through which the current flows decreases, the current I detected by the first current detection means 27 is detected to be a value I3 that is larger than the normal state. The rate of increase in current varies depending on the position at which the heating wires are short-circuited, and the rate of increase is large when short-circuited closer to the commercial power supply 3, and conversely the connection between the first heating wire 15 and the second heating wire 16. The rate of increase in current decreases as it approaches the part. On the other hand, the detection current of the second current detection means 28 becomes zero when a short circuit occurs. This occurs even if the heating wires are short-circuited at any location.

  Therefore, when a short circuit occurs between the heating wires, a large difference occurs in the detected current values of the first current detection means 27 and the second current detection means 28, and a large difference also occurs in the output. The comparator 29 detects this difference to determine whether the heating wire is short-circuited, and transmits a signal that detects the heating wire short-circuit to the control unit 19. Upon receiving this signal, the control unit 19 forcibly interrupts the current interrupting means 18 and prevents the current from being continuously supplied from the commercial power source 3 while the heating wire 11 is short-circuited.

For this reason, it is possible to prevent an abnormal temperature rise due to a short circuit at an unspecified part of the heating wire 11 and to dramatically improve the safety of the electric carpet. At the same time, it is possible to notify the user that the abnormality has been detected by the reporting means 30 and forcibly stopped by the current interrupting means 18 by voice or the like, and it is possible to prevent misuse of the user more reliably. it can.

(Embodiment 1 )
A first embodiment of the present invention FIG. 7 will be described with reference to FIGS. FIG. 7 is a main part circuit diagram in the first embodiment of the present invention. As shown here, the first heating wire 15, the second heating wire 16, and the current interrupting device 18 are sequentially connected to the commercial power source 3 in series, and the current detection device 31 is connected to the first heating wire 15 and the first heating wire 15. It is arranged at the connection point of the two heating wires 16. The current detection means 31 transmits a signal to the control unit 19 when the detected current becomes a predetermined value or less. The control unit 19 controls the on / off of the current interrupting means 18 to control the heat generation amount of the heat generating element 11 composed of the first heat generating line 15 and the second heat generating line, and confirms that the detected current has become a predetermined value or less. When the current detection means 31 detects, it works to forcibly cut off the current cutoff means 18.

  For example, if the first and second heating wires 15 and 16 are short-circuited for some reason at a certain time from the state where current is flowing normally, the current flowing into the first heating wire 15 from the commercial power supply 3 is short-circuited. As a shortcut, the current flows into the second heating wire 16 without passing through the current detection means 31. For this reason, if a short circuit occurs in any part of the heating wire 11, the current detection means 31 cannot detect the current, and this state is determined as the occurrence of a short circuit. The specific circuit configuration is a signal that rectifies the output of the current transformer 21 in the configuration of FIG. 4 described in the first embodiment, averages the rectified output, and determines that a short circuit occurs when the average value falls below a predetermined value. As shown in FIG. 9, the output of the current transformer 21 is simply rectified by a rectifier 32 (diode), and this output is compared by a comparator 26. When the output exceeds a predetermined value, a Hi signal is output. You may comprise so that it may output. In this case, when the heating element 11 is operating normally, the current transformer 21 detects a current, so the comparator 26 outputs a pulse train having the frequency of the commercial power source 3. If a short circuit occurs at an arbitrary position of the heating element 11, no current flows through the current transformer 21, so that the output of the current transformer 21 is always at a low level and does not exceed the reference voltage 24Vref. Therefore, the comparator 26 does not output a pulse train. The controller 19 determines that a short circuit has occurred when the state in which the pulse train does not come from the comparator 26 continues for a predetermined time, and operates to forcibly interrupt the current interrupting means 18. For this reason, it is possible to prevent an abnormal temperature rise due to a short circuit at an unspecified part of the heating wire 11 and to dramatically improve the safety of the electric carpet.

( Reference form 3)
Reference Embodiment 3 of the present invention will be described with reference to FIGS. FIG. 7 is a main part circuit diagram in Reference Embodiment 3 of the present invention. As shown here, the first heating wire 15, the second heating wire 16, and the current interrupting device 18 are sequentially connected in series to the commercial power source 3, and the first power source 3 is connected from the commercial power source 3 by the unbalanced current detection unit 33. The current flowing into the heating line 15 and the current flowing from the first heating line 15 into the second heating line 16 are detected. In the drawing, the current unbalance of the first heating wire 15 is described as being detected. However, it should be understood that the configuration of detecting the current unbalance of the second heating wire 16 is not different. . The unbalanced current detection means 33 transmits a signal to the control unit 19 when the detected current imbalance exceeds a predetermined value. When the control unit 19 controls the on / off of the current interrupting means 18 to control the heat generation amount of the heating element 11 composed of the first heating line 15 and the second heating line, and detects the output from the unbalanced current detection means 33, It works to forcibly interrupt the current interrupting means 18.

The unbalanced current detecting means 33 that functions in this way can be realized by the configuration shown in FIG. A detection winding 35 is wound around the annular magnetic core 34, and current lines 36 and 37 for detecting current are passed through the annular core 34. At this time, the directions of current flow in the current lines 36 and 37 must be opposite to each other. With this configuration, when current flows in the direction of current lines 36 and 37 as shown in the figure and the condition of I1 = I2 is established, magnetic fields generated by the current lines cancel each other, so that magnetic flux is generated in the magnetic core 34. do not do. For this reason, the output of the detection winding 35 is zero. However, when I1 ≠ I2, magnetic flux is generated in the magnetic core 34, and a voltage is output to the detection winding 35. When an output voltage is generated in the detection winding 35, the control unit 19 forcibly interrupts the current interrupting means 18 and stops the device.

  Considering the case where the first heating wire 15 and the second heating wire 16 are short-circuited at an arbitrary position at a certain time, the current flowing from the commercial power supply 3 to the first heating wire 15 is once an unbalanced current. It flows into the first heating wire 15 through the detection means 33, flows into the second heating wire 16 through the short-circuited portion, and flows again on the path returning to the commercial power source 3. Therefore, no current flows through one of the current lines of the unbalanced current detecting means 33. For this reason, unbalance occurs in the current lines 36 and 37 of the unbalanced current detecting means 33, and magnetic flux is generated in the magnetic core 34, so that an output voltage is generated in the detection winding 35. Since this phenomenon always occurs no matter where the short circuit between the heating wires occurs, in this embodiment, the short circuit between the heating wires can be reliably detected by the unbalanced current detecting means 33. For this reason, it is possible to prevent an abnormal temperature rise due to a short circuit at an unspecified part of the heating wire 11 and to dramatically improve the safety of the electric carpet.

  As described above, since the sheet heating device according to the present invention can reliably detect a short circuit between heating lines, a sheet heating device such as an electric carpet, an electric blanket, a panel heater, or other heating wire heating is applied. It can also be applied to short circuit detection of equipment.

External view of electric carpet in reference embodiment of the present invention Main circuit diagram of the electric carpet Current detection waveform diagram of current detection means 17 of the electric carpet The circuit diagram which shows the specific example of the electric current detection means 17 of the electric carpet 1 is a circuit diagram of a main part of an electric carpet according to a first embodiment of the present invention. Detected current waveform diagram of first and second current detecting means 27, 28 of the same electric carpet Circuit diagram of main parts of electric carpet in second embodiment of the present invention The circuit diagram which shows the specific example of the electric current detection means 31 of the electric carpet Circuit diagram of main parts of electric carpet according to third embodiment of the present invention The figure which shows the specific structural example of the unbalanced electric current detection means 34 of the same electric carpet. Main circuit diagram of a conventional surface heating device

DESCRIPTION OF SYMBOLS 3 Commercial power supply 15 1st heating wire 16 2nd heating wire 17 Current detection means 18 Current interruption means 19 Control part 20 Display means 21 Current transformer 23 Rectifier 24 Averaging circuit 27 1st current detection means 28 2nd electric current Detection means 30 Notification means 31 Current detection means 33 Unbalanced current detection means 34 Magnetic body 35 Detection winding

Claims (3)

A heating element in which a first heating wire and a second heating wire are connected in series;
A control unit for controlling energization to the heating element;
Current detection means for detecting the current of the heating element;
Current interrupting means for interrupting energization to the heating element,
A current detecting means is provided at a connection point between the first heating wire and the second heating wire;
When the current value detected by the current detecting means becomes a predetermined value or less, the control unit opens the current interrupting means and interrupts the current supply to the heating element. The current detection means is a current transformer,
A rectifying unit;
An averaging circuit,
The rectification unit rectifies the output of the current transformer,
The planar heating device according to claim 1 , wherein the averaging circuit is configured to average the output of the rectifying unit. The current detection means is a current transformer,
Pulse output means for outputting a pulse when the output of the current transformer is positive or negative,
2. The sheet heating device according to claim 1 , wherein the control unit is configured to open the current interrupting unit when the output pulse of the pulse output unit is not output for a predetermined time or more and to interrupt the current supply to the heating element.

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