Planar heating tool

Abstract

The object is to detect deterioration of a wire heater to stop energization. A planar heating tool (100) of the invention has a wire heater (30) in which a wire is arranged in a heating section (10), having a heater wire (32), a temperature detection wire (34), and an intermediate layer (33), and a control section (40) that alternately switches energization and energization stop of the heater wire (32) based on information on the temperature detected by the temperature detection wire (34) to control the temperature of the heating section (10). The control section (40) continues energization stop of the heater wire (32) based on information on at least one of energization and energization stop of the heater wire (32).

Description

Technical Field

[0001] This invention relates to surface heating tools. Background Technology

[0002] Previously known surface heating devices utilize a single-wire line heater that integrates the heater wire and temperature sensing wire (see Patent Document 1). Such surface heating devices control the heating of the heater wire based on temperature information detected by the temperature sensing wire, thereby achieving the desired temperature for the user.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 6-5175 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, if an object is placed on a surface heating appliance for an extended period, the heat dissipation of that location is impaired, resulting in localized insulation and continued high temperatures. If this high temperature persists, the interlayer between the heater wires and the temperature sensing wires gradually deteriorates, potentially causing a short circuit. Surface heating appliances typically include a temperature fuse as a safety device; a short circuit between the heater wires and the temperature sensing wires should trigger the fuse. However, depending on the degree of interlayer deterioration, the temperature fuse may not blow, or it may blow earlier than expected.

[0008] The purpose of this invention is to detect the deterioration of the wire heater and stop the power supply.

[0009] Methods used to solve problems

[0010] The present invention is a surface heating tool comprising: a wire heater, wired within a heating section, having a heater wire, a temperature detection wire, and an intermediate layer located between the heater wire and the temperature detection wire; and a control mechanism that, based on temperature information detected by the temperature detection wire, alternately switches between energizing and de-energizing the heater wire to control the temperature of the heating section; characterized in that the control mechanism continues to de-energize the heater wire based on information regarding at least one of energizing and de-energizing the heater wire.

[0011] Invention Effects

[0012] According to the present invention, it is possible to detect the deterioration of the wire heater and stop the power supply. Attached Figure Description

[0013] Figure 1 This is a diagram schematically illustrating the structure of a surface heating tool.

[0014] Figure 2 This is a diagram illustrating an example of the general structure of a wire heater.

[0015] Figure 3 This is a diagram illustrating an example of the internal structure of a surface heating tool.

[0016] Figure 4 This is a diagram illustrating an example of voltage changes in a temperature sensing line.

[0017] Figure 5 This is a diagram illustrating an example of temperature changes in a wire heater.

[0018] Figure 6 It is a diagram used to illustrate leakage current.

[0019] Figure 7 This is a diagram illustrating an example of the voltage change in a temperature sensing line when leakage current increases.

[0020] Figure 8 This is a diagram illustrating an example of voltage changes in a temperature sensing line under conditions of leakage current.

[0021] Figure 9 This is a flowchart illustrating an example of the processing in the first embodiment.

[0022] Figure 10 This is a flowchart illustrating an example of the processing in the second embodiment.

[0023] Figure 11 This is a flowchart illustrating an example of the processing in the third embodiment.

[0024] Figure 12 This is a diagram illustrating an example of the structure of the power-on control unit in the fourth embodiment.

[0025] Figure 13 This diagram illustrates the processing of the power-on control unit.

[0026] Figure 14 This is a flowchart illustrating an example of the processing in the fourth embodiment.

[0027] Figure 15 This is a diagram illustrating an example of the structure of the power-on control unit in the fifth embodiment.

[0028] Figure 16 This is a flowchart illustrating an example of the processing in the fifth embodiment.

[0029] Label Explanation

[0030] 100: Surface heating tool; 10: Heating unit; 20: Controller; 21: Temperature setting unit; 22: Reporting unit; 30: Line heater; 32: Heater line; 33: Intermediate layer; 34: Temperature detection line; 38: Smoothing circuit; 40: Control unit; 50: Power-on control unit; 60: Temperature control unit. Detailed Implementation

[0031] Hereinafter, the surface heating tool of this embodiment will be described with reference to the accompanying drawings. In this embodiment, it is assumed that an electric blanket is used as a surface heating tool.

[0032] Figure 1 This is a schematic diagram illustrating an example of the structure of a surface heating device 100. The surface heating device 100 is started by receiving electricity, for example, 100V AC power.

[0033] The surface heating tool 100 includes a heating element 10, a controller 20, and a wire heater 30.

[0034] The heating section 10 is a surface area that a user sits on for heating. Viewed from above, the heating section 10 is, for example, rectangular, with a large horizontal area. The heating section 10 is constructed by layering a surface layer, a padding layer, and an insulation layer sequentially from top to bottom. The surface layer is the part that comes into contact with the user and can be, for example, felt or polyvinyl chloride (PVC). The padding layer disperses the force acting on the heating section 10 when the user sits on it, providing elasticity to the user or insulating the heat generated by the coil heater 30. The padding layer can be, for example, polyurethane. Furthermore, the insulation layer provides insulation to prevent heat generated by the coil heater 30 from dissipating to the ground. The insulation layer can be, for example, felt.

[0035] The controller 20 alternately switches between energizing and de-energizing the heater wire 32 (described later) of the wire heater 30 to control the temperature of the heating unit 10. The controller 20 is located in the exposed portion relative to the heating unit 10. Electrically connected to the controller 20 are a temperature setting unit 21 for the user to set the temperature of the heating unit 10 to a desired temperature and a reporting unit 22 for reporting the operating status of the surface heating tool 100 to the user. The temperature setting unit 21, for example, is a switch that allows the user to set a desired temperature level (e.g., Lv1 to Lv5) by sliding a lever, inputting a voltage corresponding to the sliding position to the controller 20. Here, temperature level Lv1 corresponds to "weak" when the temperature of the heating unit 10 decreases, and temperature level Lv5 corresponds to "strong" when the temperature of the heating unit 10 increases. The reporting unit 22 is, for example, a light-emitting unit such as an LED, which reports the current operating status of the surface heating tool 100 to the user by varying the lighting and off times.

[0036] The wire heater 30 generates heat by converting electrical energy into heat when energized. The wire heater 30 is wired into the heating unit 10. Specifically, the wire heater 30 is wired along the surface direction between the underlayment and insulation layer within the heating unit 10. The wire heater 30 heats the heating unit 10 comprehensively by being wired in a meandering or spiral manner across its entire surface. Alternatively, units of the wire heater 30 can be pre-formed by sandwiching the wire heater 30 between the underlayment and insulation layer, and the wire heater 30 can be wired into the heating unit 10 by layering these units between the underlayment and insulation layer.

[0037] Figure 2 This is a diagram showing an example of the schematic structure of the wire heater 30.

[0038] The in-line heater 30 uses a so-called single-wire in-line heater. Specifically, the in-line heater 30 has a core 31, a heater wire 32, an intermediate layer 33, a temperature sensing wire 34, and an outer sheath 35. The core 31 is, for example, polyester resin, with the heater wire 32 arranged on its outer periphery. The heater wire 32 is a conductor such as copper alloy, and is arranged in a spiral wound on the outer periphery of the core 31. The intermediate layer 33 is a polymer layer such as nylon resin, with the temperature sensing wire 34 arranged on its outer periphery. The temperature sensing wire 34 is a conductor such as nickel, and is arranged in a spiral wound on the outer periphery of the intermediate layer 33. The temperature sensing wire 34 has the characteristic that its resistance increases with increasing temperature. The outer sheath 35 is, for example, polyvinyl chloride, and is arranged on the outermost periphery. Furthermore, the in-line heater 30 is not limited to the above-described structure and material. For example, the heater wire 32 and the temperature sensing wire 34 can be arranged in opposite directions, or other layers can be added, and the structure and material can be appropriately modified.

[0039] Figure 3 This is a diagram showing an example of the internal structure of a surface heating device 100.

[0040] like Figure 3 As shown, the surface heating tool 100, in addition to the aforementioned wire heater 30, also includes a control unit 40 and various components and circuits. The control unit 40 and the various components and circuits are arranged within the aforementioned controller 20.

[0041] Figure 3 In the wire heater 30 shown, resistor H1 is heater wire 32, with one end connected to contact h1 and the other end connected to contact h2 along its length. Similarly, resistor S1 is temperature sensing wire 34, with one end connected to contact s1 and the other end connected to contact s2 along its length. Furthermore, heater wire 32 and temperature sensing wire 34 are insulated from each other by an interlayer 33.

[0042] In addition, AC 100V power is supplied to contacts v1 and v2 to energize the heater wire 32. Between contacts v1 and v2, the heater wire 32 (resistor H1), switch SW, and thermal fuse TF1 are connected in series. The heater wire 32 is heated by energizing it, thus heating the heating unit 10. The heater wire 32 is energized when switch SW is open and de-energized when it is closed. Switch SW can be switched on and off via relay RL or the energizing control unit 50 described later. The thermal fuse TF1 is heated by resistor TF1-R, which is integrally formed with the thermal fuse TF1, and melts when it reaches a predetermined temperature. When the thermal fuse TF1 melts, the energizing of the heater wire 32 is cut off even if switch SW is open. Therefore, the heater wire 32 cannot heat the heating unit 10 until a new thermal fuse TF1 is installed.

[0043] Furthermore, a control power supply, such as DC 5V, for temperature control is supplied from contact u1 to contact u2. Here, the control power supply is supplied by converting AC 100V using a voltage conversion circuit (not shown). Between contact u1 and contact u2, a resistor R1, a variable resistor VR1, a temperature sensing line 34 (resistor S1), and a resistor R2 are connected in series. The temperature sensing line 34 supplies a DC voltage corresponding to the temperature to the control unit 40 by changing the resistance S1 according to the temperature. Resistors R1 and R2 are used to divide the voltage to make the voltage input to the control unit 40 an appropriate value, and the variable resistor VR1 is used to adjust the voltage according to the type (model) of the surface heating appliance. In addition, a smoothing circuit 38, consisting of resistor R3 and capacitor C1, is used to smooth the voltage input to the control unit 40.

[0044] Furthermore, the anodes of diodes D1 and D2 are connected to both ends of the temperature sensing line 34, and the cathodes of diodes D1 and D2 are connected together to one end of resistor TF1-R. Additionally, the anode of diode D3 is connected to the other end of resistor TF1-R, and the cathode of diode D3 is connected between the temperature fuse TF1 and switch SW.

[0045] The control unit 40 includes an energization control unit 50 and a temperature control unit 60.

[0046] The power supply control unit 50 controls the circuit to prevent power from being supplied to the heater wires 32 of the wire heater 30 when it detects deterioration of the wire heater 30. The processing performed by the power supply control unit 50 will be described later.

[0047] The temperature control unit 60 controls the temperature of the heating unit 10 by alternately switching the energization and de-energization of the heater line 32 based on the temperature information detected by the temperature detection line 34. The temperature control unit 60 includes an AD converter 61, an AD converter 62, a meter 63, a selector 64, an upper limit comparator 65a, a lower limit comparator 65b, and a relay switching unit 66.

[0048] The AD converter 61 converts the voltage corresponding to the temperature detected by the temperature detection line 34 into a digital signal and outputs it to the upper limit comparator 65a and the lower limit comparator 65b respectively. The AD converter 62 converts the voltage corresponding to the temperature level set by the temperature setting unit 21 into a digital signal and outputs it to the selector 64. Table 63 holds information on the upper limit threshold and lower limit threshold of each temperature level (Lv1 to Lv5) set by the temperature setting unit 21. Here, for example, if the upper limit threshold of temperature level Lv1 is set to Vrmax1, the lower limit threshold of temperature level Lv1 is set to Vrmin1, the upper limit threshold of temperature level Lv5 is set to Vrmax5, and the lower limit threshold of temperature level Lv5 is set to Vrmin5, then the relationships are Vrmax1>Vrmin1, Vrmax5>Vrmin5, Vrmax5>Vrmax1, and Vrmin5>Vrmin1.

[0049] Selector 64 extracts the upper and lower threshold values ​​corresponding to the temperature level set by temperature setting unit 21, and outputs them to upper limit comparator 65a and lower limit comparator 65b respectively.

[0050] The upper limit comparator 65a compares the voltage value input from the detection line input terminal (hereinafter referred to as the detection line input) based on the output of the temperature detection line 34 with the upper limit threshold, and outputs the comparison result to the relay switching unit 66. The lower limit comparator 65b compares the voltage value input from the detection line input with the lower limit threshold, and outputs the comparison result to the relay switching unit 66.

[0051] The relay switching unit 66 switches the relay RL on and off based on the comparison results from the upper limit comparator 65a and the lower limit comparator 65b. Specifically, the relay switching unit 66 sets the relay RL on when the voltage value input to the detection line is at or below the lower limit threshold. Furthermore, the relay switching unit 66 turns the relay RL on when the voltage value input to the detection line reaches the lower limit threshold and then moves into the range between the lower and upper limit thresholds. Conversely, the relay switching unit 66 turns the relay RL off when the voltage value input to the detection line is at or above the upper limit threshold. Furthermore, the relay switching unit 66 turns the relay RL off when the voltage value input to the detection line reaches the upper limit threshold and then moves into the range between the lower and upper limit thresholds.

[0052] When relay RL is turned on and switch SW is turned on, the heater line 32 is energized. Conversely, when relay RL is turned off and switch SW is turned off, the heater line 32 is de-energized.

[0053] Here, refer to Figure 4 The changes in voltage of the temperature detection line 34 corresponding to the aforementioned actions performed by the temperature control unit 60, the changes in the energization state of the heater line 32, and the changes in temperature of the line heater 30 will be explained. Furthermore, Figure 4 This diagram illustrates the operation under normal conditions without leakage current, in which the voltage of the temperature sensing line 34 is the same as the voltage input to the sensing line.

[0054] Figure 4 (a) is a graph showing the voltage change of the temperature sensing line 34. Figure 4 (b) is a diagram showing the change in the energization state of heater wire 32. Figure 4 (c) is a graph showing the temperature change of the wire heater 30. Furthermore, the voltage of the temperature detection line 34 here is a voltage value output to the control unit 40 after being smoothed by the smoothing circuit 38.

[0055] Figure 4 (a) The voltage value Va1 shown is the voltage value of the temperature detection line 34 when the temperature of the wire heater 30 is rising. Here, since the voltage value moves to the range between the lower and upper thresholds after reaching the lower threshold, the relay RL is turned on. Figure 4 (b) shows the state where heater line 32 is energized (on state). Therefore, as shown... Figure 4 As shown in (c), the temperature of the wire heater 30 also continues to rise. Additionally, Figure 4 (b) The time of the on-state shown is denoted by HHs. Then, the relay RL becomes off when the voltage value reaches the upper limit threshold, thus stopping the energization of the heater line 32 (off state). Furthermore, by stopping the energization of the heater line 32, the temperature of the line heater 30 decreases from Toff.

[0056] Figure 4 The voltage value Vb1 shown in (a) is the voltage value of the temperature detection line 34 when the temperature of the wire heater 30 drops after the power to the heater line 32 is stopped. Here, since the voltage value moves into the range between the lower and upper thresholds after reaching the upper threshold, the relay RL is closed, as shown in (a). Figure 4 (b) shows the state where the heater line 32 is de-energized (off state). Therefore, as shown... Figure 4 As shown in (c), the temperature of the wire heater 30 also continues to decrease. Additionally, Figure 4(b) The time of the off state shown is denoted by HLs. Then, the relay RL becomes on when the voltage value reaches the lower threshold, thus energizing the heater line 32 (on state). Furthermore, by energizing the heater line 32, the temperature of the line heater 30 rises from Ton.

[0057] Thus, as Figure 4 As shown in (a), the voltage value through temperature detection line 34 repeatedly rises and falls between the lower and upper threshold values, as... Figure 4 (b) shows the alternating switching of energizing and de-energizing the heater line 32, as shown. Figure 4 As shown in (c), the temperature of the wire heater 30 repeatedly rises and falls.

[0058] Furthermore, if the temperature level set by the temperature setting unit 21 increases, the lower and upper threshold values ​​compared in the upper limit comparator 65a and the lower limit comparator 65b respectively become larger. Therefore, the higher the temperature level set by the temperature setting unit 21, the higher the temperature of the wire heater 30 repeatedly rises and falls.

[0059] Figure 5 This diagram illustrates an example of the temperature changes of the coil heater 30 and the surface temperature of the heating element 10 after power is supplied to the surface heating appliance 100. Additionally, Figure 5 The cycle of temperature rise and fall of the wire heater 30 shown is related to Figure 4 (c) The temperature rise and fall periods of the wire heater 30 shown are the same. Figure 5 It sets the time on the horizontal axis to be more than Figure 4 (c) is a graph of the length of time on the horizontal axis. Figure 5 The horizontal axis shown is in hours [h (hour)].

[0060] like Figure 5 As shown, the surface temperature of the heating unit 10 also rises and falls repeatedly with approximately the same cycle as the temperature of the wire heater 30. At this time, the surface temperature of the heating unit 10, like the temperature of the wire heater 30, rises and falls repeatedly at a temperature corresponding to the temperature level set by the temperature setting unit 21. Furthermore, the temperature range between the upper and lower limits of the surface temperature of the heating unit 10 is smaller than the temperature range between the upper and lower limits of the temperature of the wire heater 30, resulting in a temperature change that is imperceptible to the user.

[0061] In this way, the temperature control unit 60 controls the temperature of the heating unit 10 by alternately switching the energization and de-energization of the heater line 32 based on the temperature information detected by the temperature detection line 34.

[0062] Next, the method for detecting the deterioration of the line heater 30 will be explained. Figure 6 This is a diagram illustrating the state of leakage current caused by the deterioration of the wire heater 30. Specifically, Figure 6 (a) is a diagram showing the leakage current when the AC power supply is in the positive half-wave condition. Figure 6 (b) is a diagram showing the leakage current when the AC power supply is in the negative half-wave condition.

[0063] The higher the temperature around the intermediate layer 33 of the wire heater 30, the more progressive the degradation, and the more progressive the degradation, the lower the insulation resistance. Due to the decrease in insulation resistance of the intermediate layer 33, the alternating current energizing the heater wire 32 leaks through the intermediate layer 33 to the temperature sensing wire 34.

[0064] In such Figure 6 (a) When the AC power supply is in the positive half-wave state, contact v1 is positive and contact v2 is negative. The leakage current from heater line 32 through intermediate layer 33 to temperature detection line 34 flows through contact s1 and branch point A to smoothing circuit 38, and through contact s2 to control GND. However, when the AC power supply is in the positive half-wave state, since the voltage on diodes D1 and D2 is higher than that on contacts s1 and s2, the leakage current does not flow from contacts s1 and s2 to diodes D1 and D2. The leakage current flows through contact s1 and branch point A to smoothing circuit 38, and a voltage corresponding to the leakage current is added to the voltage detected by temperature detection line 34, which is then input to control unit 40.

[0065] In such Figure 6 (b) When the AC power supply is in the negative half-wave condition, contact v1 is negative and contact v2 is positive. The leakage current from heater line 32 through intermediate layer 33 to temperature detection line 34 flows through contacts s1 and s2 from diodes D1 and D2 to resistor TF1-R and diode D3. However, in the negative half-wave condition, since the voltage at branch point A is higher than that at diodes D1 and D2, the leakage current does not flow to branch point A. Furthermore, if the intermediate layer 33 deteriorates further, the leakage current flows further into resistor TF1-R due to a short circuit between heater line 32 and temperature detection line 34. This causes resistor TF1-R to heat up and reach a high temperature, triggering the temperature fuse TF1. The melting of the temperature fuse TF1 disconnects the power supply to heater line 32 even when switch SW is open, functioning as a final protection circuit.

[0066] Here, if we focus on Figure 6 (a) and Figure 6 The voltage at branch point A shown in (b) indicates that at branch point A, the voltage corresponding to the leakage current occurs only during the positive half-wave of the AC power supply. On the other hand, if we consider the voltage at branch point A... Figure 6 (a) and Figure 6The voltage input to the control unit 40 of the circuit shown in (b) is smoothed by the smoothing circuit 38, which smooths the voltage corresponding to the leakage current that occurs only during the positive half-wave of the AC power supply.

[0067] Figure 7 This is a graph showing the voltage change detected based on leakage current. Here, we assume an AC power supply of 60Hz for illustration. Figure 7 As shown, when the leakage current is low, a voltage dv corresponding to the leakage current occurs at branch point A every 1 / 60th of a second, i.e., every half-wave of the AC circuit. This voltage dv corresponding to the leakage current is smoothed by smoothing circuit 38 to become voltage adv (see reference). Figure 7 (The "smoothing value" is shown). As a result, the control unit 40 inputs the voltage detected by the temperature detection line 34 plus the voltage advance corresponding to the leakage current.

[0068] Furthermore, if the leakage current increases and becomes higher, then at branch point A, a voltage dv+ higher than the voltage dv occurs every 1 / 60th of a second corresponding to the leakage current (see reference). Figure 7 (The dashed line is shown). The voltage dv+ corresponding to the leakage current is smoothed by the smoothing circuit 38 to become a voltage adv+ that is higher than the voltage adv. As a result, the control unit 40 inputs the voltage detected by the temperature detection line 34 plus the voltage adv+ corresponding to the leakage current.

[0069] Thus, if a voltage corresponding to the leakage current is input to the control unit 40, the change in voltage of the temperature detection line 34 will be different from the case where there is no leakage current and only the voltage detected by the temperature detection line 34 is input to the control unit 40. See details... Figure 8 This explains the changes in voltage of temperature detection line 34, changes in energization state of heater line 32, and changes in temperature of line heater 30, corresponding to the operation of temperature control unit 60 when a voltage corresponding to leakage current is input to control unit 40.

[0070] Figure 8 (a) is a graph showing the voltage change of the temperature sensing line 34. The voltage change of the temperature sensing line 34 with leakage current is represented by a solid line, and the voltage change of the temperature sensing line 34 without leakage current is represented by a dashed line. Furthermore, the voltage change of the temperature sensing line 34 without leakage current is compared with... Figure 4 The solid lines in (a) change in the same way. Figure 8 (b) is a diagram showing the changes in the energization state of heater wire 32. Solid lines represent changes in the energization state with leakage current, while dashed lines represent changes in the energization state without leakage current. Furthermore, the changes in the energization state without leakage current are related to... Figure 4 The solid line in (b) changes in the same way. Figure 8 (c) is a graph showing the temperature change of the wire heater 30. The temperature change of the wire heater 30 with leakage current is represented by a solid line, and the temperature change of the wire heater 30 without leakage current is represented by a dashed line. Furthermore, the temperature change of the wire heater 30 without leakage current is compared with... Figure 4 The solid lines in (c) change in the same way.

[0071] Figure 8 The voltage value Va2 shown in (a) is the voltage value of the temperature sensing line 34 when the temperature of the wire heater 30 rises. The voltage value Va2 is increased by a voltage Δv (offset Δv) compared to the voltage value Va1 without leakage current. Voltage Δv is equivalent to... Figure 7 The voltage adv or voltage adv+ is shown. Here, as... Figure 8 (b) shows the energized state (on state) of heater wire 32, as indicated. Figure 8 As shown in (c), the temperature of the line heater 30 continues to rise. Then, by rapidly reaching the upper threshold voltage corresponding to the applied voltage Δv, the relay RL turns off, stopping energization to the heater line 32 (off state). Therefore, as... Figure 8 As shown in (b), the on-state time HH corresponds to the voltage value reaching the upper threshold more quickly and the energizing of heater line 32 stopping more quickly, so the on-state time HHs is shorter compared to the case without leakage current. Furthermore, as... Figure 8 As shown in (c), the temperature of the wire heater 30 begins to drop faster than it would in the case of no leakage current because the power supply to the heater wire 32 is stopped more quickly. Furthermore, as... Figure 8 As shown in (a), if the voltage value reaches the upper limit threshold, the heater line 32 is de-energized, and there is no longer any leakage current. Therefore, the sum of the voltage Δv immediately disappears, and the voltage value of the temperature detection line 34 returns to the value under conditions without leakage current. Figure 8 The voltage value on the dashed line shown in (a) gradually decreases.

[0072] Figure 8 The voltage value Vb2 shown in (a) is the voltage value of the temperature detection line 34 when the temperature of the line heater 30 drops due to the cessation of energization to the heater line 32. Here, the relay RL is off, which is for... Figure 8 (b) The heater line 32 shown is de-energized (off state). Therefore, as Figure 8As shown in (c), the temperature of the line heater 30 continues to decrease. Then, as the voltage value corresponding to the disappearance of the voltage Δv increases, the lower threshold is reached relatively quickly, and the relay RL becomes active, energizing the heater line 32 (on state). Therefore, as... Figure 8 As shown in (b), the off-state time HL corresponds to the faster voltage value reaches the lower threshold and the faster energization of heater line 32, thus the off-state time HLs is shorter compared to the case without leakage current. Furthermore, as... Figure 8 As shown in (c), the temperature of the wire heater 30 begins to rise faster than in the case of no leakage current because the heater wire 32 is energized more quickly.

[0073] Similarly, due to the influence of voltage Δv applied to the voltage value of temperature sensing line 34, or the immediate disappearance of the applied voltage Δv, the on-state time HH and the off-state time HL of heater line 32 are shortened compared to the case without leakage current. Therefore, the energization and de-energization cycle of heater line 32 is shortened. Furthermore, the temperature rise and fall cycle of line heater 30 is also shortened, and since the temperature Toff under the condition of no leakage current is not reached, the temperature (average temperature) of line heater 30 decreases.

[0074] Furthermore, since the voltage Δv increases with increasing leakage current, the energization and de-energization cycle of heater wire 32 becomes shorter as the leakage current increases. Similarly, as the leakage current increases, the temperature rise and fall cycle of wire heater 30 also becomes shorter, and the temperature (average temperature) of wire heater 30 decreases.

[0075] In this embodiment, the power-on control unit 50 detects the deterioration of the wire heater 30 before the temperature fuse TF1 blows, based on the various changes mentioned above caused by the occurrence of leakage current. It then stops energizing the heater wire 32 and stops energizing it again. The specific processing performed by the power-on control unit 50 will be described below with reference to the flowchart.

[0076] (First Embodiment)

[0077] In the first embodiment, the power-on control unit 50 continues to power on and off the heater line 32 based on information about the power-on and power-off cycles of the heater line 32.

[0078] Figure 9 This is a flowchart illustrating an example of the processing performed by the power-on control unit 50 in the first embodiment. Additionally, in the case of... Figure 9 In subsequent flowcharts, this is achieved by the power-on control unit 50 executing the program stored in the memory within the power-on control unit 50.

[0079] In S10, the energization control unit 50 obtains the time HH of the on-state of energizing the heater wire 32 (refer to...). Figure 8 (b) The power-on control unit 50 obtains the time HH of the energized state for the heater line 32 by measuring the time when the relay switching unit 66 outputs an on signal to the relay RL. However, the power-on control unit 50 can also obtain the time HH of the energized state by measuring the time when the relay RL becomes on or the time when the switch SW becomes on.

[0080] In S11, the power-on control unit 50 obtains the time HL (refer to) when the heater line 32 is in a shut-off state where power has been stopped. Figure 8 (b) The power-on control unit 50 obtains the time HL of the off state, in which the heater line 32 is de-energized, by measuring the time when the relay switching unit 66 outputs a signal to the relay RL to turn off. However, the power-on control unit 50 may also obtain the time HL of the off state by measuring the time when the relay RL turns off or the time when the switch SW turns off.

[0081] In S12, the power-on control unit 50 obtains the power-on and power-off cycles. The power-on control unit 50 obtains the power-on and power-off cycles by adding the time HH of the on state to the time HL of the off state. As described above, as the leakage current increases, the power-on and power-off cycles for the heater line 32 become shorter.

[0082] In S13, the power-on control unit 50 calculates the difference between the obtained power-on and power-off cycles and the power-on and power-off cycles when there is no leakage current. Furthermore, the power-on and power-off cycles when there is no leakage current are equivalent to... Figure 4 (b) The time for adding the time HHs of the on state to the time HLs of the off state, as shown, is pre-stored in the memory within the power-on control unit 50. Furthermore, the power-on control unit 50 can repeat S10 to S13 multiple times to calculate the average of the differences.

[0083] In S14, the power-on control unit 50 determines whether the difference in cycles is above a predetermined value (threshold Ta). If it is above the predetermined value, it proceeds to S15; otherwise, it returns to S10. The predetermined value is pre-stored in the memory of the power-on control unit 50 and remains constant regardless of the temperature level set by the temperature setting unit 21. Furthermore, the predetermined value is set to be smaller than the difference between the power-on and power-off cycles before the temperature fuse TF1 blows and the power-on and power-off cycles when there is no leakage current. Alternatively, the difference in cycles can be an average value calculated by repeatedly performing S10 to S13 multiple times.

[0084] In step S15, the power-on control unit 50 determines that the wire heater 30 has deteriorated. Regardless of the temperature information detected by the temperature detection line 34, it stops energizing the heater wire 32. Specifically, the power-on control unit 50 stops energizing the heater wire 32 by turning off the relay RL or the switch SW via a safety circuit (not shown). The power-on stop process performed by the power-on control unit 50 takes precedence over the temperature control process performed by the temperature control unit 60. Furthermore, the power-on control unit 50 reports to the user that the power supply has been stopped due to the deterioration of the wire heater 30 by changing the lighting and off times of the reporting unit 22.

[0085] Thus, according to this embodiment, based on the energizing and de-energizing cycle, the degradation of the wire heater 30 can be detected earlier than the temperature fuse TF1 blows by continuously stopping and starting the energizing of the heater wire 32. Furthermore, since the energizing and de-energizing cycle is longer than the period of the AC power waveform, high-precision cycle measurement is not required, thus enabling low-cost detection of the degradation of the wire heater 30.

[0086] Furthermore, while the first embodiment described the use of a cycle for energizing and stopping the energizing process, it is also possible to continue energizing and stopping the heater line 32 if the difference between the time HH of the energized state and the time HHs of the energized state without leakage current is a predetermined value (threshold Tb). Similarly, if the difference between the time HL of the unenergized state and the time HLs of the unenergized state without leakage current is a predetermined value (threshold Tc), it is also possible to continue energizing and stopping the heater line 32.

[0087] Furthermore, the time HH during the energized state of heater line 32 can be compared with a predetermined time (threshold Td). If the time is less than the predetermined time, energizing heater line 32 can continue, but energizing can stop. Similarly, the time HL during the de-energized state of heater line 32 can be compared with a predetermined time (threshold Te). If the time is less than the predetermined time, energizing heater line 32 can continue, but energizing can stop. Additionally, the measured energizing and de-energizing cycles can be compared with a predetermined cycle (threshold Tf). If the cycle is less than the predetermined cycle, energizing heater line 32 can continue, but energizing can stop.

[0088] (Second Embodiment)

[0089] In the second embodiment, the power-on control unit 50 continues to stop powering on the heater line 32 based on information about the power-on and power-off of the heater line 32, specifically the number of times the heater line 32 is powered on and power-off is stopped. Figure 10This is a flowchart illustrating an example of the processing performed by the power-on control unit 50 of the second embodiment.

[0090] In S20, the energization control unit 50 counts the number of times the heater line 32 is energized and energized off, and adds the count to the first counter. The energization control unit 50 increments the first counter by "1" when energization is applied, and then increments the first counter by "1" when energization stops. The energization control unit 50 counts the number of times the relay RL is turned on and off, or the switch SW is turned on and off, by using either the relay RL or the switch SW. Since the energization and energization-stop cycle of the heater line 32 shortens as the leakage current increases, as the leakage current increases, the number of times the heater line is energized and energized off within a certain time period increases.

[0091] In step S21, the power-on control unit 50 determines whether the number of counts (first counter) during a certain period of time has reached a predetermined number (threshold N, for example, 10 times) or more. If it has reached the predetermined number, the second counter is incremented by "1", and the process proceeds to step S22. On the other hand, if it has not reached the predetermined number, the process returns to step S20 and continues counting the number of times power is turned on and off. The threshold N is pre-stored in the memory of the power-on control unit 50 and remains constant regardless of the temperature level set by the temperature setting unit 21. Furthermore, the threshold N is set to a number less than the number of times power is turned on and off on the heater line 32 when the temperature fuse blows.

[0092] In S22, the power-on control unit 50 determines whether the number of counts (first counter) during a certain period of time has exceeded a predetermined number of times (threshold M, for example, 3 times). That is, it determines whether the predetermined number of times (threshold M, for example, 3 times) has been reached by continuously adding the second counter. If the predetermined number of times has been reached, it proceeds to S23. On the other hand, if the predetermined number of times has not been reached, it returns to S20, resets the counted number of times (first counter, second counter), and continues counting the number of times power is turned on and off.

[0093] In S23, the power-on control unit 50 determines that the wire heater 30 has deteriorated, and regardless of the temperature information detected by the temperature detection line 34, it stops energizing the heater line 32 and stops energizing again. This process is the same as that described in S15 above.

[0094] Thus, according to this embodiment, by continuously stopping and starting the energization of the heater line 32 based on the number of times the energization is turned on and off, the deterioration of the line heater 30 can be detected earlier before the temperature fuse TF1 blows.

[0095] Furthermore, in the second embodiment, the counting of the number of times power was applied and power was stopped was described. However, it is also possible to only count the number of times power was applied and determine whether the number of times counted within a certain period of time has reached a predetermined number (threshold N / 2, for example, 5 times) or more. Alternatively, it is possible to only count the number of times power was stopped and determine whether the number of times counted within a certain period of time has reached a predetermined number (threshold N / 2, for example, 5 times) or more. Furthermore, if the number of times counted reaches the predetermined number before a certain period of time has elapsed, the count can be reset without waiting for the certain period of time to elapse, and the counting of the number of times power was applied and power was stopped can begin after the next certain period of time has elapsed. In this way, by not waiting for the next certain period of time to elapse before starting the next certain period of time, the deterioration of the wire heater 30 can be detected earlier.

[0096] (Third Embodiment)

[0097] In the third embodiment, the power-on control unit 50 continues to stop energizing the heater wire 32 based on information about the temperature of the wire heater 30, specifically based on the average temperature of the wire heater 30.

[0098] Figure 11 This is a flowchart illustrating an example of the processing performed by the power-on control unit 50 in the third embodiment. In the third embodiment, the surface heating tool 100 has a temperature sensor that measures the temperature of the line heater 30. Preferably, the temperature sensor is capable of measuring at multiple points on the line heater 30; for example, a multi-point membrane sensor that is separately attached to the line heater 30 can be used. The temperature information measured by the temperature sensor is input to the power-on control unit 50.

[0099] In S30, the power-on control unit 50 continuously acquires temperature information from multiple points of the wire heater 30 from the temperature sensor for a certain period of time. The power-on control unit 50 stores the acquired temperature information of the wire heater 30.

[0100] In step S31, the power-on control unit 50 calculates the average temperature of the wire heater 30 based on the acquired temperature information from multiple points. As described above, the average temperature of the wire heater 30 decreases as the leakage current increases.

[0101] In step S32, the power-on control unit 50 calculates the difference between the calculated average temperature of the wire heater 30 and the average temperature of the wire heater 30 when there is no leakage current. Furthermore, the average temperature of the wire heater 30 when there is no leakage current, which corresponds to the temperature level set by the temperature setting unit 21, is pre-stored in the memory of the power-on control unit 50. Additionally, the power-on control unit 50 can repeat steps S30 to S32 multiple times to calculate the average value of the difference.

[0102] In step S33, the power-on control unit 50 determines whether the temperature difference is above a predetermined value (threshold Tg). If it is above the predetermined value, it proceeds to step S33; otherwise, it returns to step S30. The predetermined value is pre-stored in the memory of the power-on control unit 50 and remains constant regardless of the temperature level set by the temperature setting unit 21. Furthermore, the predetermined value is set to be smaller than the difference between the average temperature of the wire heater 30 when the temperature fuse TF1 is blown and the average temperature of the wire heater 30 when there is no leakage current. Alternatively, the temperature difference can be an average value calculated by repeatedly performing steps S30 to S32 multiple times.

[0103] In S34, the power-on control unit 50 determines that the wire heater 30 has deteriorated, and regardless of the temperature information detected by the temperature detection line 34, it stops energizing the heater line 32 and stops energizing it again. This process is the same as that described in S15 above.

[0104] Thus, according to this embodiment, by continuing to stop energizing the heater wire 32 based on the temperature of the wire heater 30, the deterioration of the wire heater 30 can be detected earlier before the temperature fuse TF1 is blown.

[0105] In addition, in the third embodiment, the case of calculating the average temperature by frequently obtaining the temperature information of multiple points of the line heater 30 over a certain period of time is described. However, it is also possible to store the temperature at multiple points of the line heater 30 when the temperature changes from rising to falling (upper limit temperature) and when the temperature changes from falling to rising (lower limit temperature), and calculate the average temperature based on the upper limit temperature and lower limit temperature at multiple points.

[0106] Alternatively, the upper limit average temperature can be calculated by averaging the upper limit temperatures of multiple points over a certain period of time, and the difference between the upper limit average temperature of the line heater 30 when there is no leakage current can be calculated to determine whether it is above the specified value (threshold Th).

[0107] Alternatively, the average temperature at multiple points on the wire heater 30 can be compared with a predetermined temperature (threshold Ti), and if the temperature exceeds the predetermined temperature, the energization of the heater wire 32 can be stopped. Furthermore, the upper limit average temperature at multiple points on the wire heater 30 can be compared with a predetermined temperature (threshold Tj), and if the temperature exceeds the predetermined temperature, the energization of the heater wire 32 can be stopped.

[0108] In addition, the energizing and de-energizing cycle of the first embodiment can be replaced with the cycle when the temperature of the wire heater 30 switches from rising to falling, or the time HH of the energizing state of the heater wire 32 of the first embodiment can be replaced with the time when the temperature of the wire heater 30 rises, or the time HL of the de-energizing state of the heater wire 32 of the first embodiment can be replaced with the time when the temperature of the wire heater 30 falls, etc., to detect the deterioration of the wire heater 30.

[0109] (Example 4)

[0110] In the fourth embodiment, the power-on control unit 50 continues to stop powering on the heater line 32 based on information about the voltage applied corresponding to the leakage current detected by the temperature detection line 34.

[0111] Figure 12 This is a diagram showing an example of the internal structure of the surface heating tool 100 of the fourth embodiment.

[0112] Here, a block diagram of an electric control unit 50 is added to the surface heating tool 100.

[0113] The power-on control unit 50 includes a half-wave rectification and zero-crossing detection unit 121, a sampling pulse generation unit 122, a voltage detection unit 123, a subtractor 124, a comparator 125, and a smoothing circuit 38.

[0114] The half-wave rectification and zero-crossing detection unit 121 detects the timing of the negative half-wave of the AC power supply, even when there is leakage current, but no voltage corresponding to the leakage current occurs. The sampling pulse generation unit 122 generates a sampling pulse based on the timing of the negative half-wave detected by the half-wave rectification and zero-crossing detection unit 121.

[0115] Figure 13 This diagram illustrates the processing performed by the half-wave rectification & zero-crossing detection unit 121 and the sampling pulse generation unit 122.

[0116] Figure 13 (a) is a diagram showing the waveform of the AC power input to the half-wave rectification & zero-crossing detection unit 121. The half-wave rectification & zero-crossing detection unit 121 performs negative half-wave rectification based on the waveform of the input AC power.

[0117] Figure 13 (b) is a diagram showing the waveform after the negative half-wave is rectified. The half-wave rectification & zero-crossing detection unit 121 detects the timing of the voltage value crossing 0 [V] (zero crossing) based on the rectified waveform.

[0118] Figure 13(c) is a graph showing the waveform after the detected voltage value crosses 0 [V] (zero crossing). The sampling pulse generation unit 122 generates sampling pulses at predetermined intervals starting from the timing of the voltage generation.

[0119] Figure 13 (d) is a diagram showing the timing of generating the sampling pulse. The sampling pulse generation unit 122 outputs the generated sampling pulse to the voltage detection unit 123.

[0120] The voltage detection unit 123 receives the voltage value of the temperature detection line 34 before smoothing at branch point A. The voltage detection unit 123 measures the voltage value of the temperature detection line 34 at the timing of the sampling pulse output from the sampling pulse generation unit 122. Therefore, the voltage detection unit 123 can measure the voltage value Vso of the temperature detection line 34 when there is no leakage current, even in the case of leakage current.

[0121] The smoothing circuit 38 smooths the voltage value of the temperature sensing line 34 at branch point A. Therefore, when there is leakage current, the smoothing circuit 38 outputs a voltage value (Vso + ΔV) corresponding to the leakage current. Conversely, when there is no leakage current, the smoothing circuit 38 outputs the voltage value Vso of the temperature sensing line 34.

[0122] Subtractor 124 subtracts the voltage value measured by voltage detection unit 123 from the voltage value output by smoothing circuit 38, and outputs the subtracted value to comparator 125. For example, in the case of leakage current, subtractor 124 subtracts the voltage value Vso measured by voltage detection unit 123 from the voltage value (Vso+ΔV) output by smoothing circuit 38 corresponding to the leakage current, and outputs the voltage value ΔV to comparator 125.

[0123] Comparator 125 compares the voltage value output from subtractor 124 with a specified threshold. If the voltage value is above the specified threshold, the power supply to heater line 32 is stopped, and the power supply is stopped again.

[0124] Figure 14 This is a flowchart illustrating an example of the processing performed by the power-on control unit 50 in the fourth embodiment.

[0125] In S40, the power-on control unit 50 acquires the voltage value of the temperature detection line 34 after it has been smoothed by the smoothing circuit 38 during the time the heater line 32 is energized. Specifically, the power-on control unit 50 can acquire the voltage value of the temperature detection line 34 after it has been smoothed by measuring the voltage value input to the control unit 40. As described above, the voltage value of the temperature detection line 34 increases as the leakage current increases.

[0126] In step S41, the power-on control unit 50 calculates the difference between the voltage value of the temperature detection line 34 obtained and the voltage value of the temperature detection line 34 when there is no leakage current. Here, the voltage value of the temperature detection line 34 when there is no leakage current can be obtained by the voltage detection unit 123 measuring the voltage value of the temperature detection line 34 at the timing of the sampling pulse generated by the sampling pulse generation unit 122, as described above. Alternatively, the voltage value of the temperature detection line 34 when there is no leakage current can also be stored in the memory of the power-on control unit 50 in advance as a value corresponding to the temperature level set by the temperature setting unit 21. Furthermore, the power-on control unit 50 can repeat steps S40 to S41 multiple times to calculate the average value of the difference.

[0127] In step S42, the power-on control unit 50 determines whether the voltage difference is above a predetermined value (threshold Vc). If it is above the predetermined value, it proceeds to step S43; otherwise, it returns to step S40. The predetermined value is pre-stored in the memory of the power-on control unit 50 and remains constant regardless of the temperature level set by the temperature setting unit 21. Furthermore, the predetermined value is set to be smaller than the difference between the voltage value when the thermal fuse blows and the voltage value when there is no leakage current. Alternatively, the voltage difference can be the average value calculated by repeatedly performing steps S40 to S41 multiple times.

[0128] In step S43, the power-on control unit 50 determines that the wire heater 30 has deteriorated, stops energizing the heater wire 32, and stops energizing again. This process is the same as that described in step S15 above.

[0129] Thus, according to this embodiment, based on the temperature information of the temperature detection line 34 after it has been smoothed by the smoothing circuit 38, the deterioration of the line heater 30 can be detected as early as possible before the temperature fuse TF1 blows by continuing to stop energizing the heater line 32.

[0130] In addition, in the fourth embodiment, the case of calculating the difference between the voltage value of the smoothed temperature detection line 34 and the voltage value of the temperature detection line 34 when there is no leakage current was explained. However, it is also possible to compare the voltage value of the smoothed temperature detection line 34 during the time the heater line 32 is energized with a predetermined voltage value (threshold Vd), and stop energizing the heater line 32 if the voltage value is above the predetermined voltage value.

[0131] (5th embodiment)

[0132] In the fifth embodiment, the power-on control unit 50 continues to stop powering on the heater line 32 based on information about the voltage applied corresponding to the leakage current detected by the temperature detection line 34.

[0133] Figure 15This is a diagram showing an example of the internal structure of the surface heating tool 100 of the fifth embodiment.

[0134] Here, a block diagram of an electric control unit 50 is added to the surface heating tool 100. Additionally, with... Figure 12 The same structure is assigned the same labels, and the description is omitted. The power-on control unit 50 is located between branch point A and smoothing circuit 38.

[0135] The power-on control unit 50 includes a delay unit 126. The delay unit 126 receives the voltage value of the temperature detection line 34 before smoothing at branch point A. The delay unit 126 measures the peak voltage value of each half-wave output of the AC power supply in the input voltage value, causing the subtractor 124 to delay the output of the measured peak voltage value. This delay is to match the timing of the voltage value of the temperature detection line 34 measured by the voltage detection unit 123. Furthermore, the delay unit 126 outputs the measured voltage values ​​sequentially to the smoothing circuit 38, including the peak voltage values.

[0136] Subtractor 124 subtracts the voltage value measured by voltage detection unit 123 from the voltage value output by delay unit 126, and outputs the subtracted value to comparator 125. Comparator 125 compares the voltage value output from subtractor 124 with a predetermined threshold. If the voltage value is greater than the predetermined threshold, it stops energizing heater line 32 and continues to stop energizing.

[0137] Figure 16 This is a flowchart illustrating an example of the processing performed by the power-on control unit 50 of the fifth embodiment.

[0138] In S50, the power-on control unit 50 acquires the peak voltage value of the temperature detection line 34 before it is smoothed by the smoothing circuit 38 during the time the heater line 32 is energized. Specifically, the power-on control unit 50 measures... Figure 3 The voltage value at branch point A shown can be obtained from the voltage value of the temperature sensing line 34 before smoothing. As mentioned above, if there is leakage current, a voltage is generated in each half-wave of the AC circuit corresponding to the leakage current.

[0139] In step S51, the power-on control unit 50 calculates the difference between the peak voltage value of the temperature detection line 34 and the voltage value of the temperature detection line 34 when there is no leakage current. Here, the voltage value of the temperature detection line 34 when there is no leakage current can be obtained by the voltage detection unit 123 measuring the voltage value of the temperature detection line 34 at the timing of the sampling pulse generated by the sampling pulse generation unit 122. In addition, the voltage value of the temperature detection line 34 when there is no leakage current can also be stored in the memory of the power-on control unit 50 in advance as a value corresponding to the temperature level set by the temperature setting unit 21.

[0140] In step S52, the power-on control unit 50 determines whether the voltage difference is above a predetermined value (threshold Ve). If it is above the predetermined value, it proceeds to step S53; otherwise, it returns to step S50. The predetermined value is pre-stored in the memory of the power-on control unit 50 and remains constant regardless of the temperature level set by the temperature setting unit 21. Furthermore, the predetermined value is set to be smaller than the difference between the voltage value when the temperature fuse blows and the voltage value when there is no leakage current.

[0141] In S53, the power-on control unit 50 determines that the wire heater 30 has deteriorated, stops energizing the heater wire 32, and then stops energizing again. This process is the same as that described in S15 above.

[0142] Thus, according to this embodiment, based on the temperature information of the temperature detection line 34 before it is smoothed by the smoothing circuit 38, the deterioration of the line heater 30 can be detected earlier before the temperature fuse TF1 is blown by continuing to stop the power supply to the heater line 32.

[0143] In addition, in the fifth embodiment, the case of calculating the difference between the peak voltage value of the temperature detection line 34 before smoothing and the voltage value of the temperature detection line 34 when there is no leakage current was explained. However, it is also possible to compare the peak voltage value of the temperature detection line 34 before smoothing with a predetermined voltage value (threshold Vf), and stop energizing the heater line 32 if it is above the predetermined voltage value.

[0144] The present invention has been described above using the above-described embodiments and examples. However, the present invention is not limited to the above-described embodiments and examples. Modifications can be made within the scope of the present invention, and the embodiments and variations can be appropriately combined.

[0145] In the above embodiments, the case where the surface heating tool is an electric blanket has been described, but it is not limited to this case; it can also be applied to electric heating pads, electric blankets, etc. Furthermore, it is not limited to products with AC 100V; products with AC 200V can also be applied.

Claims

1. A surface heating tool having: a wire heater with a wire in a heating section, having a heater wire, a temperature detecting wire, and an intermediate layer between the heater wire and the temperature detecting wire; and a control mechanism that alternately switches energization and energization stop of the heater wire based on information of temperature detected by the temperature detecting wire, and controls temperature of the heating section, characterized in that the control mechanism continues energization stop of the heater wire based on information of at least one of energization and energization stop of the heater wire.

2. The surface heating tool according to claim 1, characterized in that the control mechanism continues energization stop of the heater wire regardless of information of temperature detected by the temperature detecting wire, in a case where the information of at least one of energization and energization stop of the heater wire is: information of a period of energization and energization stop of the heater wire; information of a time of energization of the heater wire; information of a time of energization stop of the heater wire; or information of a number of times of at least one of energization and energization stop of the heater wire.

3. The surface heating tool according to claim 1, characterized in that the control mechanism continues energization stop of the heater wire regardless of information of temperature detected by the temperature detecting wire, in a case where a difference between the period of energization and energization stop of the heater wire and the period of energization and energization stop of the heater wire in the absence of a leakage current is a threshold value or more, a difference between the time of energization of the heater wire and the time of energization of the heater wire in the absence of a leakage current is a threshold value or more, a difference between the time of energization stop of the heater wire and the time of energization stop of the heater wire in the absence of a leakage current is a threshold value or more.

4. The surface heating tool according to claim 3, characterized in that there is a temperature fuse that disconnects energization of the heater wire, and the threshold value is a value smaller than a difference between the period of energization and energization stop of the heater wire when the temperature fuse disconnects energization of the heater wire and the period of energization and energization stop of the heater wire in the absence of a leakage current.

5. The surface heating tool according to any one of claims 1 to 3, characterized in that there is a temperature fuse that disconnects energization of the heater wire, and the control mechanism continues energization stop of the heater wire earlier than the temperature fuse disconnects energization.

6. The surface heating tool according to any one of claims 1 to 3, characterized in that the control mechanism reports to a user, via a reporting section, a case where energization stop of the heater wire is continued. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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