| 摘要 |
PURPOSE:To lessen substantially an air gap between a second plunger and a magnetic stopper cap and thereby to speed up a motion, by putting a magnetic tubular body on the butting part of a non-magnetic second cylinder with the magnetic stopper cap. CONSTITUTION:When an overload current flows, a magnetomotive flux from a coil 12 flows to the left and right outer side plates 6 and 7 of a U-shaped yoke 5, a first plunger 3, a magnetic stopper cap 2 and a second plunger 9. Thereby the first plunger 3 is attracted and moved onto the side of the magnetic stopper cap 2, so as to compress an air gap with the second plunger 9 and finally to move the second plunger 9. At this time, a magnetic flux X of the yoke 5 is separated into a main magnetic flux X1 flowing from the right outer side plate 7 to the magnetic stopper cap 2 through a small-diameter part 11 and a large- diameter head part 10, and into a by-pass magnetic flux X3 flowing from the large-diameter head part 10 to the magnetic stopper cap 2 via a magnetic tubular member 18 interposed in the butting part of the second cylinder 13 with the magnetic stopper cap 2, and an air gap between the large-diameter head part 10 and the stopper cap 2 is lessened substantially by this by-pass magnetic flux X3. |
