| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive shut-off device capable of reliably preventing ignition of an electric wire and capable of being used for a long period of time.SOLUTION: In a CPU 63, the temperature difference between ambient temperature of an electric wire 4 and temperature of the electric wire 4 are repeatedly calculated with passage of time. When the temperature obtained by adding the temperature difference calculated by the CPU 63 to the ambient temperature is equal to or higher than a predetermined temperature, a control circuit 53 shuts off the current flowing through the electric wire 4 by turning off an FET 51. The CPU 63 sets an initial temperature difference which is a positive value on the basis of the ambient temperature. In the CPU 63, the set initial temperature difference is used in calculation of the initial temperature difference, and a previously calculated temperature difference is used in the calculation of the later temperature difference. |
