JP3051386U - Safety device for sheet heating element - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention is to reduce the risk of fire when the predetermined wattage (current consumption) of a sheet heating element changes, that is, when a crack or aging occurs. They try to prevent them before they happen. SOLUTION: In a carbon sheet heating element provided with electrode strips on both side edges, a power supply line 3 to the electrode strips is provided with a current sensor-4 and a switch interposed therebetween.
A control circuit for generating a signal according to a change in current to the sheet heating element is provided on the secondary side, and the power to the carbon sheet heating element can be cut off by an off signal generated by the control circuit 8. Things.

Description

[Detailed description of the invention]

[0001]

[Industrial applications]

 The present invention relates to a safety device for a carbon sheet heating element.

[0002]

[Prior art]

 Conventionally, this type of planar heating element has an electrode band for power supply along both side edges, and a means for temperature control such as a thermistor is provided between them.

[0003]

[Disadvantages of conventional technology]

 However, sheet heating elements such as carbon sheet heating elements have disadvantages in safety in the event of an abnormality compared to wire heating elements such as nichrome wire heating elements. In other words, when the wire heating element is disconnected, the energization stops at that point and there is no danger, but the planar heating element bypasses the current even if a part of it is cracked. However, current concentration occurs in the detour, causing partial heating, which is dangerous.

A sheet heating element made by applying a conductive paint obtained by kneading a resin and carbon to a cloth provided with an electrode band on both sides, such as a carbon sheet heating element, has a part thereof. If the temperature becomes high and the temperature becomes high, the resistance becomes high, causing heat spots, which is dangerous.

[0005] Furthermore, even when the planar heating element is changed over time due to long-term use, the resistance changes and the initial wattage changes (current changes).

[0006]

[Problems to be solved by the invention]

 The present invention has been developed to solve these drawbacks. When a predetermined wattage (consumption current) of the sheet heating element changes, that is, when a crack or aging occurs, the current is cut off and ignition occurs. This is to try to prevent the danger of this.

[0007]

[Means for Solving the Problems] Therefore, when the change in the current value due to cracks, aging, etc. is captured by the current sensor, the current value rises above a certain level or lower than the current flowing in normal times. This is to turn off the power when it drops.

[0008]

【Example】

 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. Reference numeral 1 denotes a carbon sheet heating element which is formed by, for example, applying a conductive paint obtained by kneading a resin and carbon to a cloth, and applying a power supply along both side edges. Supply electrode strips 2 and 2 are provided. A power supply line 3 drawn from one of the power supply electrode bands 2 is wound around a primary side of a core 5 constituting a current sensor 4 and a magnet switch 6 is interposed therebetween. A current smoothing circuit 7 is provided on the secondary side of the core 5 constituting the rent sensor-4, and a control circuit that emits a signal according to a change in heater current (for example, an off signal at 0.8 A or less and an off signal at 1.5 A or more) The control unit or the relay operation circuit is cut off by an off signal generated by the control circuit 8 via the control circuit 8, and the magnet switch 6 is turned off.

In FIG. 1, reference numeral 9 denotes a power supply circuit, and reference numeral 10 denotes a temperature controller circuit, which is connected to a temperature sensor 11 such as a thermistor attached to the sheet heating element 1. In this embodiment, the temperature controller circuit 10 is used, but a circuit which does not require a temperature controller can be used.

An electronic switch (SSR) can be used instead of the magnet switch 6.

[0011]

[Action]

 The present invention is embodied as described above. In the unlikely event that a part of the planar heating element 1 is in a heating state and becomes high in temperature, the resistance becomes high, and a current change occurs in the power supply line 3 (for example, 0.8 A or less; 5A or more), which is detected by a change in the excitation voltage of the current sensor 4, and the magnet switch 6 is turned off by the off signal of the control circuit 8.

[0012]

【effect】

 As described above, the present invention catches a change in the current value due to cracks and aging, etc., using a current sensor, and when the current value rises or falls below a certain level as compared with the current flowing under normal conditions. Since the power is turned off, it is safe to prevent a burn accident due to heating or the like.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a safety device according to the present invention.

[Description of Signs] 1 Sheet heating element 2 Electrode strip 3 Power line 4 Current sensor 5 Core 6 Magnet switch 8 Control circuit 9 Power circuit 10 Temperature controller 11 Temperature sensor

Claims (1)

[Utility model registration claims] 1. In a carbon sheet heating element having electrode bands on both side edges, a power supply line 3 to an electrode band is provided with a current sensor-4 and a switch interposed therebetween.
Is provided on the secondary side thereof with a control circuit 8 for generating a signal according to a change in current to the planar heating element, and the off-signal generated by the control circuit 8 allows the current to be cut off via a switch. Safety equipment.