JP2013165015A - Planar warmer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar warmer equipped with a controller of small size and low cost by reducing a current capacity of a power source circuit part.SOLUTION: A planer warmer includes an AC power source 20, a heating element 21 in which a heater wire 24, a soluble body 23, and a temperature detecting wire 22 are provided as one body, a temperature detection part 25 for outputting a temperature signal voltage Va, a control part 27 for driving a power control element 28, a power source circuit part 31 which supplies control power source, a temperature signal wire drive part 37 for driving the temperature detection wire 22, and a temperature detecting current drive part 45 which allows current to flow the temperature detection part 25. The temperature detecting current drive part 45 causes current to flow the temperature detection part 25 only a part of the period in which the temperature detection wire 22 is in a conductive state, thereby an average current flowing the temperature detection part is reduced and a current capacity of the power source circuit part is reduced. Thus, a planer warmer equipped with a controller of small size and low cost is provided.

Description

  The present invention relates to a surface warmer that heats a wide area such as an electric carpet or an electric blanket.

  Conventionally, this type of surface heating device performs temperature detection using the half cycle side of the AC power supply, and on the other half cycle side, when the heater wire is fully energized due to a failure of the control circuit, the heater wire and temperature are detected. A fusible body provided between the detection wires is blown and the heater wire and the temperature detection wire are in contact with each other, so that the thermal fuse is disconnected and the safety means for stopping energization of the heater wire is ensured (for example, Patent Documents) 1).

  6 to 7 show a conventional planar warming tool described in Patent Document 1. FIG. As shown in FIG. 7, the heating element 1 covers the heater wire 2 with a fusible body 3 that melts at a certain temperature, and is provided with a temperature detection wire 4 on the heater wire 2. Covered. This string-like heating element 1 is heated by wiring the sheet-like rug. As shown in FIG. 6, the transistor 8 of the temperature signal line drive unit 7 is turned off and the temperature detection line 4 is disconnected from GND on the positive cycle side where the P point side of the AC power supply 6 is at a high voltage. The reason why one end of the temperature detection line 4 is disconnected from the GND in this way is to ensure that the safety means operates, and the safety means is that the heater wire 2 is abnormally heated due to some failure and the fusible body 3 is melted. All of the short-circuit current that flows when the temperature detection line 4 comes into contact is sent to the heating resistor 9, and the thermal fuse 10 that is thermally coupled is heated by the heating resistor 9, and the temperature detection line 4 is connected to GND. If it is left as it is, the short-circuit current is diverted to the GND side and the heating resistor 9 is not sufficiently overheated. On the negative cycle side where the N point side of the AC power supply 6 is at a high voltage, the transistor 8 is turned on to connect the temperature detection line 4 to GND. When the temperature detection line 4 is connected to GND, a current flows from the power supply circuit unit 11 to the temperature detection unit 12, the temperature detection line 4, and GND, depending on the resistance 13 of the temperature detection unit 12 and the resistance value of the temperature detection line 4. A temperature signal voltage Va is generated by voltage division. The temperature signal voltage Va changes with a change in the resistance value of the temperature detection line 4, and the resistance value of the temperature detection line 4 changes with the temperature of the heater line 2. The temperature signal voltage Va is input to the control unit 14, and the control unit 14 controls the power control element 15 so that the heater wire 2 has a predetermined temperature. Then, when a failure occurs in which the transistor 8 of the temperature signal line driving unit 7 is turned on, the short-circuit current that flows when the heater wire 2 is abnormally overheated and the fusible body 3 melts and the heater wire 2 and the temperature detection wire 4 come into contact with the GND side. Since the overheating of the heating resistor 9 is not sufficient, the state of the transistor 8 is confirmed by the monitoring unit 16 and a signal indicating that the transistor 8 that should be turned off is input to the control unit 14. Then, the control unit 14 determines that it is abnormal and takes measures such as turning off the power control element 15 and stopping energization of the heater wire 2.

Japanese Patent No. 4710512

However, in the above-described conventional configuration, the temperature detection wire 4 becomes a path for a short current that heats the heating resistor 9 when the fusible body 3 melts due to abnormal heating of the heater wire 2 and the heater wire 2 contacts the temperature detection wire 4. . For example, when the current path when the heater wire 2 and the temperature detection line 4 are in contact with each other at the intermediate point a of the heating element 1 is seen, during the positive cycle in which the P point side of the AC power supply 6 becomes a high voltage, the temperature from the P point This is a path (path (1)) that flows from the fuse 10, the heater line 2, the contact point a, the temperature detection line 4 and the temperature detection line 4 to the diode 17, the heating resistor 9, the diode 18, and the N point of the AC power supply 6. .

  The resistance value of the temperature detection line 4 greatly affects the determination of the short-circuit current value, and the resistance value of the temperature detection line 4 is set to about 300Ω in order to secure the amount of heat generated by the heating resistor 9. When the temperature is in the control temperature range of 20 ° C. to 80 ° C., the resistance value is as low as about 200Ω.

  Further, since the temperature detection line 4 is a metal wire, the temperature coefficient is small, and the resistance value change in the control temperature range of 20 ° C. to 80 ° C. is several tens of Ω. Therefore, it is necessary to increase the voltage of the power supply circuit unit 11 so that the change of the temperature signal voltage Va is large.

  Here, assuming that the voltage of the power supply circuit unit 11 is 12V, the resistance 13 of the temperature detection unit 12 is 500Ω, and the resistance of the temperature detection line 4 is 200Ω, the current value is calculated to be 17 mA (12 ÷ (500 + 200) = Current of 0.017 A) flows.

  In general, a surface heating device is provided with a controller case with a hermetically sealed structure in a corner of a wide range of rugs where a long heating element 1 is installed so that water and the like do not enter as much as possible. In general, control components such as 11 are housed, and it is important to reduce the size of the control components and reduce heat generation, and the reduction of a slight current of 17 mA is also a priority issue.

  This 17 mA flows for a half cycle period on the negative cycle side in which the N point side of the AC power supply 6 in the state where the transistor 8 of the temperature signal line driving unit 7 is turned on becomes a high voltage. Since it is impossible to cover the current of the half cycle period with the smoothing capacitor provided in the power supply circuit unit 11 or a capacitor that supplements the instantaneous current, the power supply circuit unit 11 having a large current capacity is necessary, and the size of the components can be increased. It leads to cost increase.

  In addition, when an area switching function is added to the surface heating device, a plurality of temperature detection lines 4 and temperature detection units 12 are required, and a current flowing therethrough is multiplied by several times, and a power supply circuit unit 11 having a larger current capacity is required. Come. In addition, since a plurality of monitoring units 16 for detecting an abnormality of the transistor 8 of the temperature signal line driving unit 7 are necessary, and the number of parts and the number of signal lines to be input to the control unit are increased, it is necessary to use a microcomputer having a large number of ports. There was still room for improvement from the viewpoint of miniaturization of the controller and cost reduction.

  The present invention solves the above-described conventional problems, and provides a planar warmer having a small and low-cost controller that reduces the current capacity of the power supply circuit unit and the number of signal lines input to the control unit. The purpose is to provide.

In order to solve the above-mentioned conventional problems, the sheet heating device of the present invention is provided with an AC power source, a sheet heating device main body, and a heating element in which a heater wire, a fusible body, and a temperature detection line are integrally provided. A temperature detection unit that detects a change in the resistance value of the temperature detection line and converts it to a temperature signal voltage; and drives a power control element that processes the temperature signal voltage of the temperature detection unit to turn on and off the heater line. The control unit, the power supply circuit unit that supplies control power to at least the temperature detection unit and the control unit, and the heater wire and the temperature detection wire are short-circuited due to melting of the fusible body when the heater wire is abnormally heated, and heat is generated by the flowing current. A heating resistor, a thermal fuse that is melted by heating of the heating resistor and stops energization of the heater wire, and the temperature detection line is made conductive to obtain a temperature signal voltage during one half cycle of the AC power supply, and the other Half-cycle period A temperature signal line drive unit that brings the temperature detection line into a non-conductive state; and a temperature detection current drive unit that supplies a temperature detection current to the temperature detection unit. The temperature detection current drive unit is connected to the temperature detection line. It is characterized in that a current is passed through the temperature detector only during a part of the period that is in the state.

  As a result, the temperature signal voltage can be obtained in a shorter period of a half cycle of the AC power supply, the average current flowing through the temperature detection unit can be reduced, and the current flowing through the temperature detection unit is applied to the capacitor in the power supply circuit unit. Since the charged electric charge can be supplemented, the current capacity of the power supply circuit unit can be reduced, and a planar warming tool including a small and low-cost controller can be provided.

  The planar warmer of the present invention can reduce the current capacity of the power supply circuit unit, and can provide a planar warmer equipped with a small and low-cost controller.

The circuit diagram which shows the structure of the control system of the planar warming tool in Embodiment 1 of this invention Schematic diagram showing the configuration of the heating element according to Embodiment 1 of the present invention. Timing chart of planar warming tool in Embodiment 1 of the present invention The block diagram of the planar warming tool in Embodiment 2 of this invention Timing chart of planar warmer in embodiment 2 of the present invention Configuration diagram of a conventional surface heating device Schematic diagram showing the configuration of a conventional heating element

  1st invention is arrange | positioned in AC power supply and a planar warming tool main body, The heating element which integrally provided the heater wire, the soluble body, and the temperature detection line, and the resistance value change of the said temperature detection wire are detected. A temperature detection unit that converts the temperature signal voltage into a temperature signal voltage, a control unit that drives the power control element that processes the temperature signal voltage of the temperature detection unit to turn on and off energization of the heater wire, and at least the temperature detection unit A power supply circuit unit that supplies control power to the control unit, and a heating resistor that generates heat due to a current that flows when the heater wire and the temperature detection line are short-circuited due to melting of the fusible body during abnormal heating of the heater wire, A temperature fuse that is blown by heating of the heating resistor to stop energization of the heater wire, and the temperature detection line is made conductive so that the temperature signal voltage is obtained during one half cycle of the AC power supply; The other The cycle period includes a temperature signal line driving unit that brings the temperature detection line into a non-conductive state, and a temperature detection current driving unit that supplies a temperature detection current to the temperature detection unit, and the temperature detection current driving unit Is a planar warming tool characterized in that a current is passed through the temperature detection part only during a part of the period in which the temperature detection line is in a conductive state.

  As a result, the temperature signal voltage can be obtained in a shorter period of a half cycle of the AC power supply, the average current flowing through the temperature detection unit can be reduced, and the current flowing through the temperature detection unit is applied to the capacitor in the power supply circuit unit. Since the charged electric charge can be supplemented, the current capacity of the power supply circuit unit can be reduced, and a planar warming tool including a small and low-cost controller can be provided.

  In a second aspect of the invention, in particular, in the first aspect of the invention, the temperature signal voltage of the temperature detection unit is pulled up to the control power source of the control unit, and the temperature signal line driving unit sets the temperature detection line in a non-conductive state. In a certain period, the control unit monitors the temperature signal voltage and detects an abnormality of the temperature signal line driving unit.

  As a result, it is possible to detect a short circuit fault in the temperature signal line drive unit, and a dedicated detection circuit is not required. Therefore, it is possible to reduce the number of components and the number of signal lines input to the control unit. A planar warming tool having a low-cost controller can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a circuit diagram showing a configuration of a control system for a planar warmer in Embodiment 1, FIG. 2 is a schematic diagram showing a configuration of a heating element, and FIG. 3 is a timing of the planar warmer with respect to an AC power supply. It is a chart.

  A planar warming tool (not shown) in the present embodiment is formed by laminating a plurality of sheets, a planar planar warming tool main body containing a heating element, a controller installed at one end of the planar warming tool main body, It consists of a power cord that supplies AC power to the controller.

  The AC power source 20 shown in FIG. 1 is obtained by a power cord. A linear heating element 21 is provided in a meandering manner over substantially the entire surface of the surface warmer body.

  As shown in FIG. 2, the heating element 21 has a temperature detection line 22 that spirals around the center glass fiber 21a and spirally forms a fusible body 23 that is also an insulator made of nylon resin. The heater wire 24 is spirally wound around the outer periphery of the fusible body 23, and a PVC insulating layer 21b is formed on the outer periphery thereof.

  The temperature of the temperature detection line 22 increases as the temperature of the heater line 24 increases, and the resistance value of the temperature detection line 22 itself increases. Conversely, when the temperature of the heater wire 24 decreases, the resistance value of the temperature detection line 22 itself decreases. The temperature detection line 22 controls the temperature of the heating element 21 to a predetermined temperature by converting the change in the resistance value of the temperature detection line 22 into a change in voltage and detecting it.

  The temperature detection unit 25 outputs a voltage obtained by dividing the voltage of the control power supply by the resistor 26 and the temperature detection line 22 as the temperature signal voltage Va. The temperature signal voltage Va changes so as to increase as the resistance value of the temperature detection line 22 increases. This temperature signal voltage Va is input to the control unit 27.

  When the control unit 27 recognizes the temperature signal voltage Va value and determines that the temperature of the heating element 21 has not reached the set temperature, the relay coil unit 29 of the power control element 28 is driven to perform relaying. The contact part 30 is turned on. The AC power supply 20 is supplied to the heater wire 24 when the relay contact portion 30 is turned on.

  When it is determined that the temperature of the heating element 21 has reached the predetermined temperature, that is, the temperature signal voltage Va has reached the predetermined voltage, the control unit 27 stops driving the relay coil unit 29 of the power control element 28 and relays it. The contact part 30 is turned off.

  A control power supply for obtaining the temperature signal voltage Va is generated in the power supply circuit unit 31. The power supply circuit unit 31 supplies voltages of different control power sources to the temperature detection unit 25 and the control unit 27, respectively. The voltage of the different control power supply is supplied to the temperature detection unit 25 by supplying a high control power supply voltage (for example, 12V) in order to take out a small resistance value change of the temperature detection line 22 as a temperature signal voltage Va of a large change. This is because a control power supply voltage (for example, 5 V), which is an allowable operating voltage, is supplied to the control unit 27 including a microcomputer or the like. The power supply circuit unit 31 includes capacitors 32 and 33 for smoothing the voltage of the control power supply and supplying an instantaneous current.

Next, a diode 34 is connected in parallel to both ends of the temperature detection line 22, one end connected to the cathode of the diode 34 is connected to the temperature detection unit 25, and a heating resistor 35 is connected to the same one end. The heat generating resistor 35 is thermally coupled to the temperature fuse 36 and generates heat when the heater wire 24 is abnormally heated, so that the temperature fuse 36 is melted.

  A temperature signal line drive unit 37 is connected to the other end of the temperature detection line 22. In the temperature signal line drive unit 37, the transistor 40 is turned on by a current flowing from the diode 38 and the resistor 39 during a positive cycle period in which the P point side of the AC power supply 20 is at a high voltage. When the transistor 40 is turned on, all the current flowing from the power supply circuit unit 31 through the resistor 41 flows to the collector of the transistor 40, so that the transistor 42 is turned off and one end of the temperature detection line 22 is opened.

  One end of the temperature detection line 22 is opened during the positive cycle period in which the P-point side of the AC power supply 20 is at a high voltage in the transistor 42 because of a short circuit that flows from the heater line 24 to the temperature detection line 22 when the heater line 24 is abnormally heated. This is because all current flows through the heating resistor 35.

  For example, when the relay contact 30 of the power control element 28 causes a welding failure and the heater wire 24 is continuously energized, the temperature of the heating element 21 becomes abnormally high. In particular, the temperature rises quickly when there is a part kept warm by a cushion. When the temperature of the heating element 21 reaches about 170 ° C., the fusible body 23 melts, the heater wire 24 and the temperature detection wire 22 are short-circuited, and a short current flows.

  If a short circuit occurs at point s1, which is the central part of the entire length of the heating element 21 where the heat generation amount of the heat generating resistor 35 is small, the short current flowing at the point s1 turns off the transistor 42 of the temperature signal line driving unit 37. Therefore, a path flows from the point P to the temperature fuse 36, the heater wire 24, the short-circuit point s1, the temperature detection line 22 and the temperature detection line 22 to the diode 34, the heating resistor 35, the diode 43, and the N point of the AC power supply 20. All of the short-circuit current that flows only through (path sa) and flows to the point s1 flows through the heat generating resistor 35, so that the heat generation amount of the heat generating resistor 35 can be sufficiently secured.

  Further, the short-circuit current flowing to the point s1 also flows in the negative cycle period in which the voltage on the N-point side of the AC power supply 20 increases, and the path is from the N-point to the relay contact portion 30, the heater wire 24, the short-point s1 point, This is a path that flows from the temperature detection line 22 and the temperature detection line 22 to the diode 34, the heating resistor 35, the diode 44, the temperature fuse 36, and the point P of the AC power supply 20. The heating resistor 35 generates heat due to all short currents flowing to the point s1 in the positive cycle or the negative cycle, and the temperature fuse 36 can be sufficiently heated, so that the temperature fuse 36 is blown and the energization of the heater wire 24 is stopped.

  Further, the temperature signal line drive unit 37 has a resistance in the negative cycle period in which the N point side of the AC power supply 20 is at a high voltage, since the diode 38 is in the reverse direction and the base current does not flow to the transistor 40 and the transistor 40 is off. The current flowing through the transistor 41 flows to the base of the transistor 42 and the transistor 42 is turned on. When the transistor 42 is turned on, one end of the temperature detection line 22 is connected to the GND of the control unit 27.

  The temperature signal voltage Va is detected within a negative cycle period in which the N point side of the AC power supply 20 is at a high voltage, but the period for detecting the temperature signal voltage Va is further limited by the temperature detection current driver 45. The temperature detection current drive unit 45 operates with a signal from the control unit 27 only for a shorter period of the negative cycle period in which the N point side of the AC power supply 20 becomes a high voltage. The transistor 47 is turned on by the current flowing through the resistor 46 by the Lo signal from the control unit 27, and the current based on the voltage (12 V) of the control power supply of the power supply circuit unit 31 is supplied to the temperature detection unit 25.

Furthermore, the diode 48 and the diode 49 are respectively connected to the GND side and the HOT side of the power supply circuit unit 31 in order to prevent a circuit current during a negative cycle period in which the N point side of the AC power supply 20 becomes a high voltage.

  About the planar warming tool comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the resistance value of the temperature detection wire 22 is a short current that flows when the heater wire 24 is abnormally heated and the fusible body 23 melts and the heater wire 24 and the temperature detection wire 22 are short-circuited. Since it is necessary to obtain the amount of heat generated by the heat generating resistor 35 until the fuse 36 is blown, the resistance value of the temperature detection line 22 is determined.

  Since the heat generating resistor 35 needs to be insulated and thermally coupled to the temperature fuse 36, the heat generating resistor 35 has an integral structure filled with an insulating material. The resistance value of the heat generating resistor 35 is about 150Ω, and if a power consumption of about 5 W is applied, the temperature fuse A heat generation amount capable of fusing 36 is generated.

  And it is necessary to set the resistance value of the temperature detection line 22 to a resistance value that can secure about 170 ° C. that is the temperature when the fusible body 23 melts and the power consumption of the heating resistor 35 is about 5 W. Becomes around 300Ω at around 170 ° C.

  Moreover, since the temperature detection line 22 uses a metal wire, there is little change amount of the resistance which changes with temperature. Generally, the temperature coefficient is a positive coefficient of about 0.45 [% / ° C.]. For example, when the resistance value at 170 ° C. is set to 300Ω, when it is used at 20 ° C. to 80 ° C. used as temperature control, At 213Ω, the amount of change is 34Ω. Since it is necessary to detect this slight change amount, the control power supply of the temperature detection unit 25 connected in series with the temperature detection line 22 is set to a higher voltage than the control power supply of the control unit 27 that inputs the temperature signal voltage Va.

  Although the voltage change of the temperature signal voltage Va can be increased by increasing the voltage of the control power supply on the temperature detection unit 25 side, the upper limit of the temperature signal voltage Va is an allowable operating voltage of the control unit 27 including a microcomputer or the like. Generally, it is set to a voltage of the control power supply (5V) or less. Therefore, the resistor 26 of the temperature detection unit 25 is set to, for example, about 500Ω or more so that the temperature signal voltage Va is equal to or lower than the voltage (5V) of the control power source of the control unit 27.

  If the resistance 26 is 500Ω, the resistance of the temperature detection line 22 is 300Ω at 170 ° C., the voltage of the control power supply supplied to the temperature detection unit 25 is 12V, and the temperature signal voltage Va is simply calculated from the divided voltage of the resistor, it is 4.5V. The voltage (5 V), which is the control power source of the control unit 27, can be reduced.

  The other end of the temperature detection line 22 is connected to the GND of the control unit 27 during the negative cycle period in which the temperature signal line driving unit 37 is at a high voltage on the N point side of the AC power supply 20. The temperature detection unit 25 is also connected to the control power supply (12 V) of the power supply circuit unit 31 for a shorter period of the negative cycle period in which the N point side of the AC power supply 20 is a high voltage in the temperature detection current drive unit 45.

  FIG. 3 is a timing chart showing the functions and signal timings for the AC power supply 20. As shown in FIG. 3, the transistor 42 of the temperature signal line driver 37 is turned off during the positive cycle period of the AC power supply 20 and turned on during the negative cycle period of the AC power supply 20.

The transistor 47 of the temperature detection current drive unit 45 is turned on by a signal from the control unit 27 only during a shorter t1 period of the negative cycle period of the AC power supply 20, and the temperature detection current drive unit 45 is sent to the temperature detection unit 25. A current from the control power supply voltage (12 V) of the power supply circuit unit 31 is supplied. In this t1 period, the pulse voltage divided by the resistance value of the temperature detection line 22 and the resistor 26 of the temperature detection unit 25 is input to the control unit 27 as the temperature signal voltage Va, and the control unit 27 performs the t1 period. The temperature signal voltage Va is processed to control the temperature of the heater wire 24.

  As described above, the current from the control power supply voltage (12 V) of the power supply circuit unit 31 flows to the temperature detection unit 25 during the t1 period. The peak value of the current value is, for example, at 20 ° C. of the temperature detection line 22. Assuming that the resistance value is 179Ω, the resistance 26 of the temperature detection unit 25 is 500Ω, and the voltage of the control power source supplied to the temperature detection unit 25 is 12V, it is 17.7 mA.

  If the t1 period is set to 5% of one cycle period of the AC power supply 20, the average current is reduced to 0.885 mA, for smoothing the voltage of the control power supply provided in the power supply circuit unit 31 and supplying an instantaneous current. The current flowing to the temperature detection unit 25 can be supplemented by the capacitor 32.

  As described above, the planar warming tool in the present embodiment conducts one end of the temperature detection line 22 so that the temperature signal voltage Va is obtained in the negative cycle period in which the N point side of the AC power supply 20 is a high voltage, During the positive cycle period in which the P point side of the AC power supply 20 is at a high voltage, the temperature detection line 22 is provided with a temperature signal line drive unit 37 that is non-conductive so that the temperature signal line drive unit 37 can obtain the temperature signal voltage Va. Temperature detection current drive for supplying a current to the temperature detection section 25 only during a part of the negative cycle period in which the N point side of the AC power supply 20 that is conducting to connect one end of the temperature detection line 22 to the high voltage is high. The unit 45 is configured to be driven. By adopting such a configuration, during the positive cycle period in which the P point side of the AC power supply 20 is at a high voltage, the heater wire 24 and the temperature detection wire 22 are short-circuited by the melting of the fusible body 23 due to abnormal heating of the heater wire 24. Thus, since all the short-circuit current that flows can be passed through the heating resistor 35, a sufficient amount of heat generated by the heating resistor 35 can be secured even at a low temperature or under a low AC voltage, thus providing a safe means of stable operation.

  In addition, the current is supplied to the temperature detection unit 25 by the temperature detection current drive unit 45 only during a certain period of the negative cycle in which the N point side of the AC power supply 20 becomes a high voltage, thereby reducing the average current flowing to the temperature detection unit 25. Thus, the power supply circuit unit 31 is smoothed and compensated with the electric charge charged in the capacitor for supplying the instantaneous current, the current capacity of the power supply circuit unit 31 can be reduced, and the parts used can be reduced in size and inexpensive. .

(Embodiment 2)
FIG. 4 is a circuit diagram showing the configuration of the control system for the planar warmer in Embodiment 1, and FIG. 5 is a timing chart for the AC power source of the planar warmer.

  As shown in FIG. 4, the present embodiment is different from the first embodiment in that the temperature signal voltage Va of the temperature detection unit 25 is connected to the control power supply of the control unit 27 by the resistor 51 of the pull-up unit 50. It is the point which is set as the structure which improves.

  About the planar warming tool comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the resistance 51 of the pull-up unit 50 is set to a large resistance value, for example, about 100 kΩ, with respect to a resistance value of about 300 Ω around 170 ° C. of the temperature detection line 22, thereby affecting the temperature signal voltage Va. Can not be given.

  The temperature signal voltage Va becomes the voltage (5 V) of the control power supply of the control unit 27 in synchronization with the AC power supply 20 except when the transistor 47 of the temperature detection current drive unit 45 is turned on by the pull-up unit 50. The voltage changes on the GND side.

The timing for this AC power supply 20 is shown in FIG. As shown in FIG. 5, when the transistor 42 of the temperature signal line drive unit 37 is off in the positive cycle period in which the P point side of the AC power supply 20 is at a high voltage, the resistor 51 of the pull-up unit 50 causes the control unit 27 to Current detection for temperature detection in a negative cycle period in which the voltage (5V) side which is a control power supply is shown and the N point side of the AC power supply 20 is a high voltage while the transistor 42 of the temperature signal line drive unit 37 is on. Except for the t1 period when the transistor 47 of the section 45 is on, the temperature signal voltage Va becomes a voltage determined by the divided voltage of the resistance 51 of the pull-up section 50 and the resistance of the temperature detection line 22, so that the temperature detection line 22 The voltage value on the GND side is shown because the resistance value is much smaller than the resistance value of the resistor 51 of the pull-up unit 50.

  During the t1 period when the transistor 47 of the temperature detection current drive unit 45 is on, the temperature signal voltage Va determined by the resistance 26 of the temperature detection unit 25 and the resistance of the temperature detection line 22 is input to the control unit 27. The temperature of the heater wire 24 is controlled.

  Next, detection when the transistor 42 of the temperature signal line driving unit 37 causes a short circuit failure will be described.

  When the transistor 42 causes a short-circuit failure, when the fusible body 23 is melted due to abnormal heating of the heater wire 24, a short-circuit current flowing due to a short circuit between the heater wire 24 and the temperature detection wire 22 causes a short-circuit failure from the temperature detection wire 22. The current flows to the GND of the power supply circuit section 31 through the transistor 42 and to the diode 48 by another path, the short current to the heat generating resistor 35 is reduced, the amount of heat generation becomes insufficient, and the temperature fuse 36 is not blown and the heater wire is not blown. An unsafe event occurs in which 24 continues to be energized. In order to prevent this unsafe event, the control unit 27 monitors the temperature signal voltage Va in the positive cycle period in which the P point side of the AC power supply 20 becomes a high voltage.

  The temperature signal voltage Va indicates a Hi signal that is on the voltage (5 V) side that is the control power source of the control unit 27 in the positive cycle period in which the P point side of the AC power source 20 is a high voltage if the transistor 42 is normal. When a short circuit failure occurs in the transistor 42, the voltage is determined by the divided voltage of the resistance 51 of the pull-up unit 50 and the resistance of the temperature detection line 22, so that the resistance value of the temperature detection line 22 is the resistance of the resistance 51 of the pull-up unit 50. Since it is much smaller than the value, it indicates the Lo signal on the GND side.

  When the temperature signal voltage Va indicates the Lo signal, the control unit 27 determines that the transistor 42 has caused a short circuit failure, stops the driving of the relay coil unit 29 of the power control element 28, and stops energization of the heater wire 24. Alternatively, the temperature fuse 36 may be blown by another circuit (not shown) that blows the temperature fuse 36 with a signal from the control unit 27.

  As described above, in the present embodiment, the temperature signal voltage Va is connected to the control power supply of the control unit 27 by the pull-up unit 50 and pulled up, and the temperature detection voltage 22 is monitored by monitoring the temperature signal voltage Va. Therefore, it is possible to detect a short-circuit failure of the transistor 42 on the same signal line as that for detecting the temperature of the transistor 42. Therefore, a dedicated circuit is not required for detecting the short-circuit of the transistor 42, and the number of parts is reduced and the signal line to be input to the control unit 27 is used. The number of can be reduced.

  As described above, the planar warming device according to the present invention can be miniaturized by reducing the current capacity of the power supply circuit unit, and therefore can be applied to other heating devices using a heater.

DESCRIPTION OF SYMBOLS 20 AC power supply 21 Heating element 22 Temperature detection line 23 Soluble body 24 Heater line 25 Temperature detection part 27 Control part 28 Power control element 31 Power supply circuit part 35 Heat generation resistor 36 Temperature fuse 37 Temperature signal line drive part 45 Temperature detection current drive part 45 Va Temperature signal voltage

Claims (2)

AC power supply,
A heating element that is disposed on the surface warming tool main body, and integrally includes a heater wire, a fusible body, and a temperature detection line;
A temperature detection unit that detects a change in resistance value of the temperature detection line and converts it into a temperature signal voltage; and
A controller that drives the power control element that processes the temperature signal voltage of the temperature detector to turn on and off the heater wire;
A power supply circuit unit for supplying control power to at least the temperature detection unit and the control unit;
A heating resistor that generates heat due to a current flowing when the heater wire and the temperature detection wire are short-circuited due to melting of the fusible body during abnormal heating of the heater wire,
A thermal fuse that blows off by heating of the heating resistor and stops energization of the heater wire;
The temperature signal line drive in which the temperature detection line is turned on so that the temperature signal voltage is obtained during one half cycle of the AC power supply, and the temperature detection line is turned off during the other half cycle And
A temperature detection current drive unit for supplying a temperature detection current to the temperature detection unit,
The temperature detection current drive unit is configured to flow a current to the temperature detection unit only during a part of a period in which the temperature detection line is in a conductive state.
Planar warmer. The temperature signal voltage of the temperature detection unit is pulled up to the control power source of the control unit, and the control unit monitors the temperature signal voltage during a period in which the temperature signal line driving unit makes the temperature detection line non-conductive. And detecting an abnormality of the temperature signal line drive unit,
The planar warming tool according to claim 1.