PROBLEM TO BE SOLVED: To prevent a case storing a PTC(positive resistance temperature coefficient) resistor element from being acutely broken due to the rise of a case internal pressure during operation. ;SOLUTION: Case 1 is made of an upper case 2 having an opening portion 2a and a sealed end portion 2b and a lower case 3 having an opening portion 3 and a sealed end portion 3b. A PTC resistance element 4 is housed inside this case 1. An atmosphere release portion 6 with its thickness that is thicker than the sealed end portion 3b is formed at the sealed end portion 3b of the lower case 3. Here, when gas pressure is effected in the case 1, an atmosphere release portion 6 is broken, gas escapes into atmosphere, and the internal pressure is lowered.;COPYRIGHT: (C)1998,JPO
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