| 摘要 |
<p>A self-holding type thermal protector incorporates a polymer PTC in a safe state where no hot spots occur even in the event of volume expansion caused due to thermal expansion during the heating time. When a bimetal (74) of a thermal protector (70) performs inverting operation at specified temperature, a movable contact (77) of a movable plate (75) moves upward to separate from a fixed contact (78), resulting in the current flowing between the contacts, that is, the current flowing between a movable contact-side terminal (76) and a fixed contact-side terminal (79-1) is shut off. This shutoff current flows through a polymer PTC (61), heating the polymer PTC (61) to cause thermal expansion of the polymer PTC (61), resulting in increased resistance. A second terminal member (64) on the side opposite to a first terminal member (63) on which the polymer PTC (61) is fixed in position forms a flexural part, and makes a clearance h between the top-side inner wall of a housing (73). Consequently, incremental volume caused by thermal expansion in the thickness direction of the polymer PTC (61) is absorbed by the flexural part on the second terminal member (64), which ensures that the degree of freedom in volume expansion of the polymer PTC (61) is never disturbed by external pressure.</p> |
