Adjusting screw structure of oil immersed solenoid and oil immersed solenoid including the same

1. An adjusting screw structure of an oil immersed solenoid comprising:

a movable core provided in a space of a case so as to be movable in an axial direction, the movable core being biased by an adjusting spring in a direction in which the movable core is pulled by a fixed magnetic pole portion or in an opposite direction thereof; and

an adjusting screw structure capable of adjusting biasing force of the adjusting spring, the adjusting screw structure comprising an air-bleeding plug configured to be detachably attached to and seal an opening end portion of the case, the opening end portion communicating with the space of the case;

wherein the air-bleeding plug includes an internal screw portion with which the adjusting screw structure threadedly engages, and a detachable mechanism configured to attach the air-bleeding plug to the opening end portion of the case such that the air-bleeding plug is located at a predetermined attachment position in a movement direction of the adjusting screw structure, and

wherein the detachable mechanism includes:

a detachable screw portion configured to attach the air-bleeding plug to the opening end portion of the case such that the air-bleeding plug threadedly engages with the opening end portion;

an annular sealing portion configured to be attached to an annular groove formed on an outer peripheral surface of the air-bleeding plug;

a sealing inclined surface configured to be formed in an annular shape on an inner peripheral surface of the opening end portion of the case, have an inner diameter increasing in size toward the opening, and tightly contact the annular sealing portion when the air-bleeding plug is attached at an attachment position of the opening end portion; and

an air-bleeding hole configured to be formed on the air-bleeding plug and allow the space of the case and an outside of the oil immersed solenoid to communicate with each other when the air-bleeding plug is loosened.

2. The adjusting screw structure according to claim 1 , wherein:

the adjusting spring is a coil spring;

a base end portion of the adjusting spring fits and is attached to a first spring seat formed at a tip end portion of the adjusting screw structure;

a tip end portion of the adjusting spring fits and is attached to a second spring seat; and

each of the first and second spring seats includes a convex stop portion configured to stop a movement in a direction in which the base end portion or tip end portion of the adjusting spring is detached therefrom.

3. An oil immersed solenoid comprising the adjusting screw structure according to claim 1 .

4. The adjusting screw structure according to claim 1 , wherein the detachable mechanism further includes a pressing inclined surface configured to be formed in an annular shape on the inner peripheral surface of the opening end portion of the case, have an inner diameter increasing in size toward the opening, be located on an opening side of the sealing inclined surface, and press the annular sealing portion into the annular groove when the air-bleeding plug threadedly engages with the opening end portion of the case to be tightened into the opening end portion.

5. The adjusting screw structure according to claim 4 , wherein the detachable mechanism further includes a seal supporting surface configured to be formed in an annular shape on the inner peripheral surface of the opening end portion of the case, be located between the pressing inclined surface and the sealing inclined surface, and extend substantially in parallel with a center axis of the air-bleeding plug.